


Power-Frequency Fields & Cancer FAQ

   The Power-Frequency Fields and Cancer FAQ maintained by John Moulder
   addresses questions about the biological effects of EM fields. This
   FAQ does an excellent job of keeping up with current studies and their
   findings.
   
     _________________________________________________________________
                                      
      How to get the FAQ
      
   Usenet:
   
   This 6-part FAQ sheet is posted to sci.med.physics, sci.answers, and
   news.answers on a regular basis.
   
   Anonymous FTP:
   
   cdmas.crc.mcw.edu/pub/powerlines_and_cancer
   
   This archive contains both the posted 6-part version and a complete 1-
   part version.
   
   E-mail server:
   
   mail-server@rtfm.mit.edu

-To get the current FAQ you would send the following message:

   send /pub/usenet-by-group/news.answers/powerlines-cancer-FAQ/part1
   . . .
   send /pub/usenet-by-group/news.answers/powerlines-cancer-FAQ/part6

   World Wide Web:
   
   http://www.cis.ohio-state.edu/hypertext/faq/usenet/powerlines-cancer-FAQ
   
     _________________________________________________________________


                                  USENET FAQs
                                       
Powerlines Cancer FAQ

     * Powerlines & Cancer FAQs 1/8: Intro
     * Powerlines & Cancer FAQs 2/8: FAQ 1
     * Powerlines & Cancer FAQs 3/8: FAQ 2
     * Powerlines & Cancer FAQs 4/8: FAQ 3
     * Powerlines & Cancer FAQs 5/8: FAQ 4
     * Powerlines & Cancer FAQs 6/8: Biblio 1
     * Powerlines & Cancer FAQs 7/8: Biblio 2
     * Powerlines & Cancer FAQs 8/8: Biblio 3


    --------------------------------------------------------------------


                      Powerlines & Cancer FAQs 1/8: Intro
                                       

Archive-name: powerlines-cancer-FAQ/part1
Last-modified: 1996/2/20
Version: 3.4.1
Maintainer: jmoulder@its.mcw.edu
Keywords: powerlines, magnetic fields, cancer, EMF, non-ionizing
  radiation, EMR, ELF, FAQ

Frequently Asked Questions (FAQs) on Power-Frequency Fields (EMF) and
Cancer -- Introduction

** TABLE OF CONTENTS **

* Part2 *
Questions and Answers
1) Why is there a concern about power lines and cancer?
2) What is the difference between the electromagnetic (EM) energy
associated with power lines and other forms of EM energy such as
microwaves or x-rays?
3) Why do different types of EM sources produce different biological effects?
4) What is difference between EM radiation and EM fields?
5) Do power lines produce EM radiation?
6) How do ionizing EM sources cause biological effects?
7) How do RF and MW sources cause biological effects?
8) How do the power-frequency EM fields cause biological effects?
9) Do non-ionizing EM sources cause non-thermal as well as thermal effects?
10) What sort of power-frequency fields are common in residences and
workplaces?
11) Can power-frequency fields in homes and workplaces be reduced?
12) What is known about the relationship between power line corridors and
cancer rates?
13) How big is the "cancer risk" associated with living next to a power line?
14) How close do you have to be to a power line to be considered exposed
to power-frequency magnetic fields?
15) What is known about the relationship between "electrical occupations"
and cancer rates?

* Part3 *
16) Do laboratory studies indicate that power-frequency fields can
cause cancer?
    16A) Are power-frequency fields genotoxic?
    16B) Are power-frequency magnetic fields cancer promoters?
    16C) Do power-frequency magnetic fields enhance the effects of other
    genotoxic agents?
17) Do laboratory studies indicate that power-frequency fields have any
biological effects that might be relevant to cancer?
    17A) How do laboratory studies of the effects of power-frequency
    fields on cell growth relate to the question of cancer risk?
    17B) How do laboratory studies of the effects of power-frequency
    fields on immune function relate to the question of cancer risk?
    17C) How do laboratory studies of the effects of power-frequency
    fields on the pineal gland and melatonin relate to the question of
    cancer risk?
18) Do power-frequency fields show any reproducible biological effects in
laboratory studies?
    18A) Do power-frequency fields of the intensity encountered in
    occupational and residential settings show reproducible biological
    effects?
    18B) Are there known mechanisms by which power-frequency fields of
    the intensity encountered in occupational and residential settings
    could cause biological effects?
    18C) Haven't some new mechanisms been proposed that could explain
    how power-frequency magnetic fields could cause biological effects?
    18D) Could the presence of transients or higher-order harmonics in
    power-frequency fields provide a biophysical mechanism for
    biological effects?
19) What about the "new studies" showing a link between power-frequency
fields and cancer?
    19A) What about the new "Swedish" study showing a link between power
    lines and cancer?
    19B) What about the new studies showing a link between occupational
    exposure to power-frequency fields and cancer?
    19C) What about the new studies showing a link between electrical
    occupation and breast cancer?
    19D) What about the new studies showing a link between pulsed
    electric fields and lung cancer?
    19E) What about the new studies linking the use of electrical
    appliances with cancer?
    19F) What about Sweden's/Denmark's decision to regulate fields
    power line fields?
    19G) What about the new study showing that it is the interaction
    between power-frequency fields and the Earth's static field that
    causes cancer?

* Part4 *
20) What criteria do scientists use to evaluate all the laboratory and
epidemiologic studies of power-frequency magnetic fields and cancer?
    20A) Criterion One: How strong is the association between exposure
    to power-frequency fields and the risk of cancer?
    20B) Criterion Two: How consistent are the studies of associations
    between exposure to power-frequency fields and the risk of cancer?
    20C) Criterion Three: Is there a dose-response relationship between
    exposure to power-frequency fields and the risk of cancer?
    20D) Criterion Four: Is there laboratory evidence for an association
    between exposure to power-frequency fields and the risk of cancer?
    20E) Criterion Five: Are there plausible biological mechanisms that
    suggest an association between exposure to power-frequency fields
    and the risk of cancer?
21) If exposure to power-frequency magnetic fields does not explain the
residential and occupations studies which show increased cancer incidence,
what other factors could?
    21A) Could problems with dose assessment affect the validity of the
    epidemiologic studies of power-frequency fields and cancer?
    21B) Are there other cancer risk factors that could be causing a
    false association between exposure to power-frequency fields and
    cancer?
    21C) Could the epidemiologic studies of power-frequency fields and
    cancer be biased by the methods used to select control groups?
    21D) Could analysis of the epidemiologic studies of power-
    frequency fields and cancer be skewed by publication bias?
    21E) Could analysis of the epidemiologic studies of power-
    frequency fields and cancer be biased by multiple-comparison
    artifacts?

* Part5 *
22) What is the strongest evidence for a connection between
power-frequency fields and cancer?
23) What is the strongest evidence against a connection between
power-frequency fields and cancer?
24) What studies are needed to resolve the cancer-EMF issue?
25) Is there any evidence that power-frequency fields cause any human
health hazards, such as miscarriages, birth defects or Alzheimer's
disease?
26) What are some good overview articles?
27) Are there exposure guidelines for power-frequency fields?
     27A) What about the report that a US government agency (the NCRP)
     is about to recommend strict limits on occupational and residential
     exposure to power-frequency fields.
28) What effect do power lines have on property values?
29) What equipment do you need to measure power-frequency magnetic fields?
30) How are power-frequency magnetic fields measured?
31) Do the issues discussed in this FAQ sheet apply to EM fields other
than power-frequency fields?
    31A) Low-frequency fields other than sinusoidal power-frequency
    fields
    31B) Static electric and magnetic fields
    31C) Radiofrequency and microwave frequencies
32) What about the new study claiming that radon exposure is increased
    by the presence of electromagnetic fields.
33) Should I buy a house next to a power line?

* Part6 *
Annotated Bibliography
A) Recent Reviews of the Biological and Health Effects of Power-Frequency
   Fields
B) Reviews of the Epidemiology of Exposure to Power-Frequency Fields
C) Epidemiology of Residential Exposure to Power-Frequency Fields
D) Epidemiology of Occupational Exposure to Power-Frequency Fields

* Part7 *
E) Human Studies Related to Power-Frequency Exposure and Cancer
F) Biophysics and Dosimetry of Power-Frequency Fields
G) Laboratory Studies of Power-Frequency Fields and Cancer

* Part8 *
H) Laboratory Studies Indirectly Related to Power-Frequency Fields and Cancer
J) Studies of Power-Frequency Fields and Reproductive Toxicity
K) Reviews of Laboratory Studies of Power-Frequency Fields
L) Miscellaneous Items
M) Regulations and Standards for Ionizing and Non-ionizing EM Sources.


** SOURCES **
* Note: This FAQ sheet is posted monthly to sci.med.physics, sci.answers
and news.answers.  The FAQ sheet is archived at many sites, but not all
archives are up-to-date.

* The primary anonymous FTP archive is:
ftp://ftp.mcw.edu/pub/emf-and-cancer
This archive contains a 1-part version of the posted 8-part FAQ sheet.
It may also contain an updated, but not yet posted version; a BinHex
version (.hqx) of the Mac Word master; and other related documents.

* A secondary anonymous FTP archive is:
cdmas.crc.mcw.edu/pub/powerlines_and_cancer
This archive always contains a 1-part version of the currently posted
FAQ sheet.

The current FAQ sheet is archived in the following places:

* Anonymous FTP and Gopher:
rtfm.mit.edu/pub/usenet-by-group/news.answers/powerlines-cancer-FAQ
Files: part1, part2,... part8

* E-mail server:
mail-server@rtfm.mit.edu
-To get the current FAQ you would send the following message
   send /pub/usenet-by-group/news.answers/powerlines-cancer-FAQ/part1
   . . .
   send /pub/usenet-by-group/news.answers/powerlines-cancer-FAQ/part8

* On World Wide Web in the US at:
http://www.cis.ohio-state.edu/hypertext/faq/usenet/powerlines-cancer-FAQ
*On World Wide Web in Europe at:
http://www.cs.ruu.nl/wais/html/na-dir/powerlines-cancer-FAQ/.html
http://src.doc.ic.ac.uk/usenet/usenet-by-hierarchy/sci/med/physics
http://www.lib.ox.ac.uk/internet/news/faq/sci.med.physics.html

** Revision notes **
(v3.4.1, 20-Feb-96):  Citation cross-reference errors affecting the latest
occupations epidemiology studies were corrected.  Keywords were added to
auxiliary headers, and "EMF" added to mesh better with search engine
tactics. Two new epidemiology reviews were added, one general [B9] and one
specifically on brain cancer in electrical occupations [B8].  Two new
studies on childhood brain cancer and residence near powerlines, both
showing no association, were added [C28,C29].  Discussion of the "Henshaw
thesis" that powerlines cause cancer by concentrating alpha-emitting radon
daughters [H22] added as Q32.  A number of older reviews were deleted.

** Acknowledgments **
This FAQ sheet owes much to the many readers of USENET who have sent me
comments and suggestions, including:
kfoster@eniac.seas.upenn.edu
gary%ke4zv.uucp@mathcs.emory.edu
aa2h@virginia.edu
p.farrell@trl.oz.au
drchambe@tekig5.pen.tek.com
gemyers@anl.gov
spencer@radonc.duke.edu
hitch@vnet.ibm.com
krista_j_kotur@ue.com

** Notice **
This FAQ is Copyright (C) by John Moulder and the Medical College of
Wisconsin, and is made available as a service to the Internet community.
Permission is granted to copy and redistribute this document
electronically as long as it is unmodified.  Notification of such
redistribution would be appreciated.  This FAQ may not be sold in any
medium, including electronic, CD-ROM, or database, or published in print,
without the explicit, written permission of John Moulder.

end: powerlines-cancer-FAQ/part1

    ------------------------------------------------------------


                      Powerlines & Cancer FAQs 2/8: FAQ 1
                                       

Archive-name: powerlines-cancer-FAQ/part2
Last-modified: 1996/2/20
Version: 3.4.1
Maintainer: jmoulder@its.mcw.edu


FAQs on Power-Frequency Fields (EMF) and Cancer (Q&A, Part 1 of 4)


Organizational notes:

Cross references to other questions are indicated by the letter Q followed
by the question number;  for example, (Q16A) indicates that further
information is found in Question 16A.

Bibliographic references are shown in brackets, for example [M2] is a
reference to the second entry in section M of the annotated bibliography.


1) Why is there a concern about power lines and cancer?

Most of the concern about power lines and cancer stems from studies of
people living near power lines (Q12,Q13,Q14,Q19) and people working in
"electrical occupations" (Q15,Q19).  Some of these studies appear to show
a relationship between exposure to power-frequency magnetic fields and the
incidence of cancer.  Laboratory studies have shown little evidence of a
link between power-frequency fields and cancer (Q16,Q17,Q18), and a
connection between power line fields and cancer is biophysically
implausible (Q8,Q18).


2) What is the difference between the electromagnetic (EM) energy
associated with power lines and other forms of EM energy such as
microwaves or x-rays?

X-rays, ultraviolet (UV) light, visible light, infrared light (IR),
microwaves (MW), radiowaves (RF), and EM fields from electrical power
systems are all parts of the EM spectrum.  The parts of the EM spectrum
are characterized by their frequency or wavelength.  The frequency and
wavelength are related, and as the frequency rises the wavelength gets
shorter.  The frequency is the rate at which the EM field changes
direction and is usually given in Hertz (Hz), where one Hz is one cycle
per second.

Power-frequency fields in the US vary 60 times per second (60 Hz), and
have a wavelength of 5,000 km.  Power in most of the rest of the world is
at 50 Hz.  Broadcast AM radio has a frequency of around 10^6 (1,000,000)
Hz and a wavelength of around 300 m. Microwave ovens have a frequency of
about 2.5 x 10^9 Hz, and a wavelength of about 12 cm.  X-rays have
frequencies above 10^15 Hz, and wavelengths of less than 100 nm.

This FAQ sheet will use the term "power frequency" to refer to both the
50- and 60-Hz alternating current (AC) frequencies used in electric power
systems, and the term "power frequency field" to refer to the sinusoidal
electric and magnetic fields produced by 50- and 60-Hz lines and devices.
The phrase "EMF" will be avoided since it is an imprecise term that could
apply to many very different types of fields, and because the term has a
long-standing usage in physics to refer to an entirely different quantity,
electromotive force.  The terms "electromagnetic radiation" and
"nonionizing radiation" will be avoided since power-frequency sources
produce no appreciable radiation (Q5).

Power-frequency fields are also properly referred to as extremely low
frequency (or ELF) fields.  In strict electrical engineering terms, ELF
refers to frequencies between 30 and 300 Hz, but the term is often used in
the biological and occupational health literature to cover the range from
>0 Hz to 3000 Hz (everything above static fields and below RF).


3) Why do different types of EM sources produce different biological effects?

The interaction of biological material with an EM source depends on the
frequency of the source.  We usually talk about the EM spectrum as though
it produced waves of energy.  However, sometimes EM energy acts like
particles rather than waves, particularly at high frequencies.  The
particle nature of EM energy is important because it is the energy per
particle (or photons, as these particles are called) that determines what
biological effects EM energy will have [A5].

At the very high frequencies characteristic of hard UV and X-rays, EM
particles (photons) have sufficient energy to break chemical bonds.  This
breaking of bonds is termed ionization, and this part of the EM spectrum
is termed ionizing. The well-known biological effects of X-rays are
associated with the ionization of molecules.  At lower frequencies, such
as those characteristic of visible light, RF, and MW, the energy of a
photon is very much below those needed to disrupt chemical bonds.  This
part of the EM spectrum is termed non-ionizing. Because non-ionizing EM
energy cannot break chemical bonds there is no analogy between the
biological effects of ionizing and nonionizing EM energy [A5].

Non-ionizing EM sources can produce biological effects.  Many of the
biological effects of soft UV, visible, and IR frequencies depend on the
photon energy, but they involve electronic excitation rather than
ionization, and do not occur at frequencies below that of IR (below 3 x
10^11 Hz).  RF and MW sources can cause effects by inducing electric
currents in tissues, which cause heating.  The efficiency with which a
nonionizing EM source can induce electric currents, and thus produce
heating, depends on the frequency of the source, and the size and
orientation of the object being heated.  At frequencies below that used
for broadcast AM radio (about 10^6 Hz), EM sources couple poorly with the
bodies of humans and animals, and thus are very inefficient at inducing
electric currents and causing heating [A5].

Thus in terms of potential biological effects the EM spectrum can be
divided into four portions:
1) The ionizing radiation portion, where direct chemical damage can occur
(X-rays, hard UV).
2) The non-ionizing portion of the spectrum, which can be subdivided into:
  2a) The optical radiation portion, were electron excitation can occur
(soft UV, visible light, IR)
  2b) The portion where the wavelength is smaller than the body, and
heating via induced currents can occur (MW and higher-frequency RF).
  2c) The portion where the wavelength is much larger than the body, and
heating via induced currents seldom occurs (lower-frequency RF and power
frequencies).


4) What is difference between EM radiation and EM fields?

In general, EM sources produce both radiant energy (radiation) and
non-radiant fields.  Radiation travels away from its source, and continues
to exist even if the source is turned off.  In contrast, some electric and
magnetic fields exist near an EM source that are not projected into space,
and that cease to exist when the energy source is turned off.

The fact that exposure to power-frequency fields occurs at distances that
are much shorter than the wavelength of 50/60-Hz radiation has important
implications, because under such conditions (called "near-field"), the
electric and magnetic fields can be considered to be independent
entities.  This is in contrast to EM radiation, in which the electric and
magnetic fields are inextricably linked.


5) Do power lines produce EM radiation?

To be an effective radiation source an antenna must have a length
comparable to its wavelength.  Power-frequency sources are clearly too
short compared to their wavelength (5,000 km) to be effective radiation
sources.  Calculations show that the typical maximum power radiated by a
power line would be less than 0.0001 microWatts/cm^2, compared to the 0.2
microWatts/cm^2 that a full moon delivers to the Earths surface on a
clear night.  The issue of whether power lines could produced ionizing
radiation is covered in Q21B.

This is not to say that there is no loss of power during transmission.
There are sources of loss in transmission lines that have nothing to do
with "radiation" (in the sense as it is used in EM theory).  Much of the
loss of energy is a result of resistive heating; this is in sharp contrast
to RF antennas, which "lose" energy to space by radiation.  Likewise,
there are many ways of transmitting energy that do not involve radiation;
electric circuits do it all the time.


6) How do ionizing EM sources cause biological effects?

Ionizing EM radiation carries enough energy per photon to break bonds in
the genetic material of the cell, the DNA.  Severe damage to DNA can kill
cells, resulting in tissue damage or death.  Lesser damage to DNA can
result in permanent changes which may lead to cancer.  If these changes
occur in reproductive cells, they can also lead to inherited changes
(mutation).  All of the known human health hazards from exposure to the
ionizing portion of the EM spectrum are the result of the breaking of
chemical bonds in DNA.  For frequencies below that of hard UV, DNA damage
does not occur because the photons do not have enough energy to break
chemical bonds.  Well-accepted safety standards exist to prevent
significant damage to the genetic material of persons exposed to ionizing
EM radiation [M2].


7) How do RF and MW sources cause biological effects?

A principal mechanism by which RF and MW sources cause biological effects
is by heating (thermal effects).  This heating can kill cells.  If enough
cells are killed, burns and other forms of long-term, and possibly
permanent tissue damage can occur.  Cells which are not killed by heating
gradually return to normal after the heating ceases; permanent non-lethal
cellular damage is not known to occur.  At the whole-animal level, tissue
injury and other thermally-induced effects can be expected when the amount
of power absorbed by the animal is similar to or exceeds the amount of
heat generated by normal body processes.  Some of these thermal effects
are very subtle, and do not represent biological hazards [A5].

It is possible to produce thermal effects even with very low levels of
absorbed power.  One example is the "microwave hearing" phenomenon; these
are auditory sensations that a person experiences when his head is exposed
to pulsed microwaves such as those produced by radar.  The "microwave
hearing" effects is a thermal effect, but it can be observed at very low
average power levels.

Since thermal effects are produced by induced currents, not by the
electric or magnetic fields directly, they can be produced by fields at
many different frequencies.  Well-accepted safety standards exist to
prevent significant thermal damage to persons exposed to MW and RFs [M1]
and also for persons exposed to lasers, IR and UV light [M3].


8) How do the power-frequency EM fields cause biological effects?

The electric fields associated with the power-frequency fields exist
whenever voltage is present, and regardless of whether current is
flowing.  These electric fields have very little ability to penetrate
buildings or even skin.  The magnetic fields associated with
power-frequency fields exist only when current is flowing.  These magnetic
fields are difficult to shield, and easily penetrate buildings and
people.  Because power-frequency electric fields do not penetrate the
body, it is generally assumed that any biologic effect from routine
exposure to power-frequency fields must be due to the magnetic component
of the field, or to the electric fields and currents that these magnetic
fields induce in the body [A5].

At power frequencies the photon energy is a factor of 10^-10 smaller than
that needed to break even the weakest chemical bond, but there are
possible mechanisms of direct interaction.  Electric fields could exert
direct mechanical forces on charges or cellular structures within a
tissue, orient dipolar molecules, and depolarize cell membranes. Magnetic
fields could also directly exert forces, but since biological materials
are largely nonmagnetic these forces are very weak (see Q18C).  These
direct electric and magnetic effects are generally far weaker than those
produced by random thermal agitation (thermal noise), and to cause
significant changes in a biological system generally require fields that
far exceed those that exist in ordinary environments [F3].

Another mechanism by which power-frequency fields could cause biological
effects is by inducing electric currents.  If these currents are
sufficiently intense, they can cause heating, nerve excitation and other
effects [F3,K1].  However, at power frequencies, the body is poorly
coupled to external fields, and the induced currents are usually too small
to produce effects.  It requires a power-frequency magnetic field in
excess 500 microT (see Q10 for typical exposures) to induce electric
currents of a magnitude similar to those that occur naturally in the
body.  Well-accepted safety standards exist to protect persons from
exposure to power-frequency fields that would induce such currents (Q27).
The well-known direct hazards of electric power, shock and burns,
generally required that the subject directly contact a charged surface
allowing current to pass directly into the body.


9) Do non-ionizing EM sources cause non-thermal as well as thermal effects?

One distinction that is often made in discussions of the biological
effects of non-ionizing EM sources is between "nonthermal" and "thermal"
effects.  This refers to the mechanism for the effect: non-thermal effects
are a result of a direct interaction between the field and the organism
(for example, photochemical events like vision and photosynthesis); and
thermal effects are a result of heating (for example, heating with
microwave ovens or IR light). There are many reported biological effects
of non-ionizing EM sources whose mechanisms are totally unknown, and it is
difficult (and not very useful) to try to draw a distinction between
"thermal" and "nonthermal" mechanisms for such effects [A5].


10) What sort of power-frequency fields are common in residences and workplaces
?

In the US magnetic fields are often still measured in Gauss (G) or
milliGauss (mG), where 1,000 mG = 1 G.  In the rest of the world and in
the scientific community, magnetic fields are measured in Tesla (T), were
10,000 G equals 1 T (1 G = 100 microT; 1 microT = 10 mG).  In the FAQ
magnetic fields will generally be specified in microT; to convert microT
to milliG, just multiply by 10.  Electric fields are measured in
volts/meter (V/m).  Measurement techniques are discussed in Q29 & Q30.

Within the right-of-way (ROW) of a high-voltage (115-765 kV,
115,000-765,000 volt) transmission line, fields can approach 10 microT and
10,000 V/m.  At the edge of a high-voltage transmission ROW, the fields
will be 0.1-1.0 microT and 100-1,000 V/m.  Ten meters from a 12 kV (12,000
volt) distribution line fields will be 0.2-1.0 microT and 2-20 V/m.
Actual magnetic fields depend on distance, voltage, design and current;
actual electric fields are affected only by distance, voltage and design
(not by current flow) [F7].
Fields within residences vary from over 100 microT and 200 V/m a few cm
from certain appliances to less than 0.02 microT and 2 V/m in the center
of many rooms.  Appliances that have the highest magnetic fields are those
with high currents (e.g., toasters, electric blankets) or high-speed
electric motors (e.g., vacuum cleaners, electric clocks, blenders, power
tools).  Appliance fields decrease rapidly with distance [F7].

Because electric fields from powerlines do not penetrate buildings, there
is little correlation between electric and magnetic fields within homes
[C11,C12].  In particular, while magnetic fields are elevated inside
buildings near powerlines, electric fields are not [C11,C12].

Occupational exposures in excess of 100 microT and 5,000 V/m have been
reported (e.g., in arc welders and electrical cable splicers).  In
"electrical" occupations typical mean exposures range from 0.5 to 4 microT
and 100-2,000 V/m [F7,F11,F16,D23].  Exposure to power-frequency electric
and magnetic fields are poorly correlated in occupational settings [F16].


11) Can power-frequency fields in homes and workplaces be reduced?

There are engineering techniques that can be used to decrease the magnetic
fields produced by power lines, substations, transformers and even
household wiring and appliances.  Once the fields are produced, however,
shielding is very difficult.  Small areas can be shielded by the use of Mu
metal (a nickel-iron-copper alloy) but Mu metal shields are very
expensive.  Larger area can be shielded with less expensive metals, but
such shielding is still expensive, and generally requires considerable
technical knowledge.

Increasing the height of towers, and thus the height of the conductors
above the ground, will reduce the field intensity at the edge of a power
line ROW.  The size, spacing and configuration of conductors can be
modified to reduce magnetic fields, but this approach is limited by
electrical safety considerations.  Placing multiple circuits on the same
set of towers can also lower the field intensity at the edge of the ROW,
although it generally requires higher towers.  Replacing lower voltage
lines with higher voltage ones can also lower the magnetic fields.

Burying transmission lines greatly reduces their magnetic fields.  The
reduction occurs because the underground lines use rubber, plastic or oil
for insulation rather than air.  This allows the conductors to be placed
much closer together and allows greater phase cancellation.  Placing high
voltage lines underground is very expensive, adding costs that may exceed
one million US dollars per mile.

Different methods of household wiring can greatly affect magnetic fields
inside houses.  For example, the tube-and-knob method of wiring older
houses produces higher fields than modern methods that use conduit or
other methods that put the wires very close together; the fields are lower
because the conductors are closer together and there is greater phase
cancellation.  Other strategies for reducing fields from household wiring
include avoidance of ground loops, and care in how circuits with multiple
switches are wired.  In general conformance with modern electrical wiring
codes will result in decreased magnetic fields.


12) What is known about the relationship between power line corridors and
cancer rates?

Some studies have reported that children living near certain types of
power lines (high current distribution and transmission lines) have higher
than average rates of leukemia [C1,C6,C12,C19], brain cancers [C1,C6]
and/or overall cancer [C5,C17].  The correlations are not strong, and the
studies have generally not shown dose-response relationships.  When
power-frequency fields are actually measured, the correlation vanishes
[C6,C12,C19].  Many other studies have shown no correlations between
residence near power lines and risks of childhood leukemia
[C3,C5,C7,C9,C10,C16,C17], childhood brain cancer [C5,C9,C16,C17,C19], or
overall childhood cancer [C16,C19].  With one exception [C2] all studies
of correlations between adult cancer and residence near power lines have
been negative [C4,C9,C10,C13,C18,C21].


13) How big is the "cancer risk" associated with living next to a power line?

The excess cancer found in epidemiologic studies is usually quantified in
a number called the relative risk (RR).  This is the risk of an "exposed"
person getting cancer divided by the risk of an "unexposed" person getting
cancer.  Since no one is unexposed to power-frequency fields, the
comparison is actually "high exposure" versus "low exposure".  A RR of 1.0
means no effect, a RR of less the 1.0 means a decreased risk in exposed
groups, and a RR of greater than one means an increased risk in exposed
groups.  Relative risks are generally given with 95% confidence
intervals.  These 95% confidence intervals are almost never adjusted for
multiple comparisons (see Q21E) even when multiple types of cancer and
multiple indices of exposure are studied (see Olsen et al, [C17], Fig. 2
for an example of a multiple-comparison adjustment).

An simple overview of the epidemiology is impossible to achieve because
the epidemiologic techniques and the exposure assessment in the various
studies are so different.  Meta-analysis, a method for combining studies
[L13], has been attempted [B3,B4,B7], but the results are problematical.
The following table summarizes the relative risks (RR, see above) for the
studies of residential exposure.

     Type of cancer       Number of    Median      Range of
                           Studies       RR          RRs
  childhood leukemia:        16         1.5        0.9-2.5
  childhood brain cancer:     9         1.6        0.8-2.7
  childhood lymphoma:         6         2.0        0.8-5.0
  all childhood cancer:       4         1.5        0.9-2.5
  adult leukemia:             5         1.1        0.8-1.6
  adult brain cancer:         2         0.8        0.6-1.4
  all adult cancer:           3         1.1        0.9-1.3

As a base-line for comparison, the age-adjusted cancer incidence rate for
adults in the United States is 3 per 1,000 per year for all cancer (that
is, 0.3% of the population gets cancer in a given year),and 1 per 10,000
per year for leukemia.


14) How close do you have to be to a power line to be considered exposed
to power-frequency magnetic fields?

The studies that show a relationship between cancer and power lines do not
provide any consistent guidance as to what distance or exposure level is
associated with increased cancer incidence.  The studies have used a wide
variety of techniques to measure exposure, and they differ in the type of
lines that are studied.  The US studies have been based predominantly on
neighborhood distribution lines, whereas the European studies have been
based strictly on high-voltage transmission lines and/or transformers.

Field measurements: Several studies have measured power-frequency fields
in residences [C6,C7,C12,C19,C21].  Both one-time (spot), peak, and
24-hour average measurements have been made; none of the studies using
measured fields have shown a relationship between exposure and cancer.
Depending of the type of line and its current, magnetic fields from power
lines become less than those produced by the typical residence at a
distance of 20-50 meters.

Proximity to lines: Several studies have used the distance from the power
line corridor to the residence as a measure of power-frequency fields
[C4,C5,C9,C10,C13,C19,C21].  When something we can measure (distance to
the line), is used as an index of what we really want to measure (the
magnetic field), it is called a surrogate (or proxy) measure.  With two
exceptions [C5,C19], studies that have used distance from power lines as a
surrogate measure of exposure have shown no relationship between proximity
and cancer.  The major exception is a childhood leukemia study [C19] that
showed an increase in leukemia incidence for residence within 50 m of
high-voltage transmission lines.  This same study [C19,C21] showed no
elevation of child leukemia rates at 51-100 m, and no increase in
childhood brain cancer, overall childhood cancer, or any types of adult
cancer at any distance.

Wirecodes: The original US power line studies used a combination of the
type of wiring (distribution vs transmission, number and thickness of
wires) and the distance from the wiring to the residence as a surrogate
measure of exposure [C1,C2,C3,C6,C7,C12].  This technique is known as
"wirecoding".  Three studies using wirecodes [C1,C6,C12] have reported a
relationship between childhood cancer and "high-current configuration"
wirecodes.  Two of these studies [C6,C12] failed to show a relationship
between exposure and cancer when actual measurements were made, the third
study [C1] made no actual measurements.  Wirecodes are stable over time
[F6], but correlate poorly with measured fields [F6,F7,F10].  The wirecode
scheme was developed for urban areas in the U.S., and is not readily
applicable elsewhere.

Calculated Historic Fields: The recent European studies have used utility
records and maps to calculate what fields would have been produced by high
voltage power lines in the past [C16,C17,C19,C21].  Typically, the
calculated field at the time of diagnosis or the average field for a
number of years prior to diagnosis are used as a measure of exposure
(Q19).  These calculated exposures explicitly exclude contributions from
other sources such as distribution lines, household wiring, or
appliances.  There is no way to check the accuracy of the calculated
historic fields.


15) What is known about the relationship between "electrical occupations"
and cancer rates?

Several studies have reported that people who work in some electrical
occupations have higher than expected cancer rates.  The original studies
[D1,D2] were only of leukemia.  Some later studies also implicated brain,
lymphoma and/or breast cancer [A1,B3,B4].  As with the residential
studies, there are many negative studies, weak correlations, and no
consistent dose-response relationships.  Additionally, many these studies
are based on job titles, not on measured exposures.

Meta-analysis [L13] of the occupational studies is even more difficult
than for the residential studies.  First, a variety of epidemiologic
techniques are used, and studies using different techniques should not be
combined.  Second, a wide range of definitions of "electrical occupations"
are used, and very few studies actually measured exposure.  Lastly, there
is little consensus as to the appropriate exposure metric.  The following
table summarizes the relative risks (RR, see Q13) for the studies of
occupational exposure.

   Type of cancer     Number of    Median      Range of
                       Studies       RR          RRs
     leukemia:           30+        1.2        0.9-1.7
     brain:              25+        1.2        0.9-1.5
     lymphoma:            7+        1.20       0.9-1.7
     all cancer:          8+        1.05       0.9-1.15

See Q19 for a more detailed discussion of the recent studies.

Copyright (C) by John Moulder
End: powerlines-cancer-FAQ/part2

    ----------------------------------------------------------------


                      Powerlines & Cancer FAQs 3/8: FAQ 2
                                       

Archive-name: powerlines-cancer-FAQ/part3
Last-modified: 1996/2/20
Version: 3.4.1
Maintainer: jmoulder@its.mcw.edu


FAQs on Power-Frequency Fields and Cancer (Q&A, Part 3 of 4)


16) Do laboratory studies indicate that power-frequency fields can cause cancer
?

Carcinogens, agents that cause cancer, can be either genotoxic or
epigenetic (in older terminology these were initiators and promoters).
Genotoxic agents (genotoxins) can directly damage the genetic material of
cells.  Genotoxins often affect many types of cells, and may cause more
than one kind of cancer. Genotoxins generally do not have thresholds for
their effect; so as the dose of the genotoxin is lowered the risk gets
smaller, but it may never go away.  Thus evidence for genotoxicity at any
field intensity would be relevant to assessing carcinogenic potential
[A5].

An epigenetic agent is something that increases the probability that a
genotoxin will damage the genetic material of cells or that a genotoxin
will cause cancer.  Promoters are a particular kind of epigenetic agent
that increase the cancer risk in animals already exposed to a genotoxic
carcinogen.  Epigenetic agents (including promoters) may affect only
certain types of cancer.  Epigenetic agents generally have thresholds for
their effect; so as the dose of an epigenetic agent is lowered a level is
reached at which there is no risk.  Thus evidence for epigenetic activity
at field intensities far above those actually encountered in residential
and occupation settings would not be clearly relevant to assessing
carcinogenic potential.


16A) Are power-frequency fields genotoxic?

A broad range of whole organism and cellular genotoxicity studies of
power-frequency fields have been carried out.  Together these studies
offer convincing evidence that power-frequency magnetic fields are not
genotoxic.

There are many approaches to measuring genotoxicity.  Whole-organism
exposure studies can be used to see whether exposure causes cancer,
mutations or chromosomal injury.  Cellular studies can be done to detect
DNA or chromosomal damage.

Relatively few whole-organism exposure studies have been published (see
Loscher & Mevissen [K6] for some of the unpublished work).  Bellossi et al
[G14] exposed leukemia-prone mice to pulsed 12- and 460-Hz fields for 5
generations and found no effect on leukemia.  Otaka et al [G22] showed
that power-frequency magnetic fields did not cause mutations in fruit
flies.  Rannug et al [G23] showed that power-frequency magnetic fields did
not significantly increase the incidence of skin tumors or leukemia in
mice.  Benz et al [G4], in a multi-generation mouse exposure study, showed
that power-frequency fields had no effect on mutation rates, fertility, or
chromosomal injury.  Kowalczuk et al [G43] reported that 8 weeks of
exposure to a 10,000 microT 50-Hz field did not cause mutations in mice.
Beniashvili et al [G16] reported that exposure of mice to a 50-Hz field at
20 microT resulted in an increased incidence of mammary tumors.

A number of studies of chromosome aberrations in occupationally-exposed
workers have been published [E2,E3,E5,E11,E12,E13,E14]; some of which have
reported "positive" effects.  However, all of the studies examine multiple
endpoints and subgroups, raising a massive multiple comparison problem
(Q21E).  Skyberg et al [E12], for example, reports "significant"
chromosomal damage in exposed workers; but this increase is found in only
one subgroup, and has a p-value of only 0.04.  With any adjustment for
multiple comparison, the statistical significance of the observation
vanishes.  The multiple comparison problem also applies to the "positive"
findings reported by Valjus et al [E11] and Ciccone et al [E13]. The
"positive" effects that are reported are predominantly in smokers and
former smokers, groups in which excess chromosomal abnormalities are
expected.  The effects are also seen predominantly in workers exposed to
spark discharges[E5].  The body current at the point of a spark discharge
can reach several amps [E5], and electrical currents of this magnitude
have been associated with chromosomal injuries in other studies [K3].

Cellular genotoxicity studies have been massive in scope.  The results of
the cellular genotoxicity studies have been overwhelmingly negative.
Published laboratory studies have reported that power-frequency magnetic
fields do not cause DNA strand breaks [G6,G20,G37], chromosome aberrations
[G1,G8,G34,G38,G40,G41], sister chromatid exchanges (SCEs)
[G2,G8,G12,G24,G40,G42], micronuclei formation [G12,G15,G38,G40],
mutations [G3,G21,G19], or cell transformation [G29].

There are three published reports of genotoxicity in in vitro systems.
Khalil & Qassem [G17] reported that a 1050 microT pulsed field caused
chromosome aberrations; but Scarf et al [G38] and Takahashi et al [G5]
found no effect in similar studies.  Nordenson et al [G34] reported that
intermittent exposures of human cells to a 300 microT field caused
increased chromosomal aberrations.  However continuous exposure in the
same model had no effects [G34,G41], and the intermittent study has never
been replicated.  Tofani et al [G45] reported that exposure of human
lymphocytes to a 32-Hz field at 75 or 150 microT caused an increase in
micronucleus formation, but only if a parallel 42 microT static field was
also present.  The study has not been replicated.


16B) Are power-frequency magnetic fields cancer promoters?

Epigenetic agents are agents that influence the development of cancer
without directly damaging the genetic material.  Promoters are a specific
class of such epigenetic agents.  In a promotion test, animals are exposed
to a known genotoxin at a dose that will cause cancer in some, but not all
animals.  Another set of animals are exposed to the genotoxin, plus
another agent.  If the agent plus the genotoxin results in more cancers
than are seen for the genotoxin alone, then that agent is a promoter.

Four published studies have reported that 50-2000 microT power-frequency
fields do not promote chemically-induced skin cancer [G11,G23,G18,G31].
However, a recent study [G44] reports promotion of chemically-induced skin
cancer after exposure at 2000 microT.  Published studies of
chemically-induced liver cancer promotion by 0.5 to 500 microT fields have
been negative [G28,G25], and a negative lymphoma promotion study has been
reported [G36].

The literature on promotion of chemically induced breast cancer is
confusing.  One study [G26] reported that a 100 microT could promote
DMBA-induced mammary cancer in rats, but three similar studies using
higher and lower [G27,G32,G39] field intensities have shown no such
effect.  Beniashvili et al [G16] reported promotion of NMU-induced breast
cancer at 20 microT.

It has been suggested that power-frequency fields might be co-promoters;
that is, that they could enhance the activity of other promoters, even
though they have no genotoxic or promotional activity on their own.
Published studies of co-promotion have both shown little evidence for such
activity [G11,G25,G30].

Interpretation of the tumor promotion studies is complicated by the
observation in several studies [G17,G39] that exposure to power-frequency
fields appears to speed the growth of chemically-induced tumors, rather
than increase the actual number of tumors.  Such an effect on growth would
be of interest if it occurred at the field intensities to which people
were actually exposed, but it would not be evidence for promotion.


16C) Do power-frequency magnetic fields enhance the effects of other
genotoxic agents?

There are some types of studies that are relevant to the carcinogenic
potential of agents, but that are neither classic genotoxicity nor
promotion tests. The most common of these are cellular studies that test
whether an agent enhances the genotoxic activity of a known genotoxin;
these studies of "epigenetic activity" are the cellular equivalents of
promotion studies.

Published studies have reported that power-frequency magnetic fields do
not enhance the mutagenic effects of known genotoxins [G3,G21], and do not
inhibit the repair of DNA damage induced by ionizing [G9,G10] or UV [G19]
radiation.  One study [G8] has reported that power-frequency fields may
increase the frequency of sister chromatid exchanges induced by known
genotoxins.


17) Do laboratory studies indicate that power-frequency fields have any
biological effects that might be relevant to cancer?

There are biological effects other than genotoxicity and promotion that
might be related to cancer.  In particular, agents that have dramatic
effects of cell growth, on the function of the immune system, or on
hormone balances might contribute to cancer without meeting the classic
definitions of genotoxicity or promotion [A5].


17A) How do laboratory studies of the effects of power-frequency fields on
cell growth relate to the question of cancer risk?

There have been scattered reports that power-frequency fields can enhance
cell proliferation or tumor growth, but most studies have shown no
effect.  Many essentially harmless agents (e.g., temperature, pH,
nutrients) affect the growth rates of cells and tumors, so effects of cell
growth, by themselves, are not evidence for hazards (L16).  However, the
presence of certain types of effects on cell growth would be relevant to
an evaluation of carcinogenic potential.  It would be of particular
relevance to cancer if an agent caused previously non-dividing normal (as
opposed to tumor or transformed) cells to begin to divide, if the growth
stimulation effect persisted after the agent was removed, and/or if the
effect occurred at levels to which people were actually exposed.

Most studies of the effects of power-frequency magnetic fields on tumor
growth have shown no effect [G7,G11,G25,G27,G28,G31,G32,H3]; but three
studies have reported enhanced tumor growth after exposure to fields of
100-2000 microT [G18,G26,G39].

Most studies of effects of power-frequency magnetic fields on cell growth
have also shown no effect [G1,G2,G12,G20,G24,G40,H2,H8,H9]; but some have
shown increased [G8,G42] or decreased [G13] cell growth after exposure to
intense (greater than 1,000 microT) fields.  Recently Kwee & Rasmark [G46]
reported increased mammalian cell growth after 30 minutes of exposure to
80-130 microT fields; but higher or lower field intensities, and longer or
shorter exposure times, gave no effect.  With one controversial exception
[H1] there have been no reported effects on proliferation or progression
for fields below 80 microT.


17B) How do laboratory studies of the effects of power-frequency fields on
immune function relate to the question of cancer risk?

In the early 1970's there was speculation that the immune system had a
major role in preventing the development of cancer; this theory was known
as the "immune surveillance hypothesis" [E4,E8].  If this hypothesis were
true, then damage to the immune system could effectively cause cancer.
Subsequent studies have shown that this hypothesis is not generally valid
[E4,E7,E8].  Suppression of the immune system in animals and humans is
associated with increased rates of only certain types of cancer,
particularly lymphomas [E7,E8].  Immune suppression has not been
associated with an excess incidence of leukemia, except for viral-induced
leukemia in animals; and has not been associated with brain or breast
cancer in either animals or humans [E4,E7,E8].

Some studies have shown that power-frequency fields can have effects on
cells of the immune system [K2], but no studies have shown the type or
magnitude of immune suppression that is associated with an increased
incidence of lymphomas.


17C) How do laboratory studies of the effects of power-frequency fields on
the pineal gland and melatonin relate to the question of cancer risk?

It has also been suggested that power-frequency EM fields might suppress
the production of the hormone melatonin, and that melatonin has
"cancer-preventive" activity [H7,H8,L4].  This is still speculative.

There have been reports that electric fields and static magnetic fields
can affect melatonin production [H7], but studies using power-frequency
magnetic fields have not shown reproducible effects.  Kato et al [H10]
reported that exposure to circularly-polarized power-frequency fields of
1-250 microT caused a small decrease in melatonin production in rats, but
that lower-intensity fields [H10] and vertically- or
horizontally-polarized power-frequency fields [H13] had no effect.
Loscher et al [G32] reported that 0.3-1.0 microT power-frequency fields
caused a small decrease in melatonin production in mice, but that this
decrease did not lead to promotion of chemically-induced mammary tumors.
Lee et al [H11,H19] reported that exposure to a 500 kV transmission line
field (4 microT, 6 kV/m) had no effect on melatonin levels in sheep.
Yellon [H16] found that exposure to a 100 microT field reduced night-time
melatonin in Djungarian hamsters in one experiment, but the effect largely
vanished in replicates.

In 1993, it was reported that exposure to a 60-Hz field at 20 microT
suppressed nocturnal melatonin in some humans [E15].  A replication study
by the same group in 1994 [E15], found no evidence for the effect.

The second component of the hypothesis, that a decrease in melatonin
levels will lead to an increase in cancer, is also unproven.  While there
is some evidence that melatonin has activity against transplanted and
chemically-induced breast tumors in rats, there is little evidence that
melatonin affects other types of cancer in animals, or that it has any
effect on breast or other types of cancer in humans.


18) Do power-frequency fields show any reproducible biological effects in
laboratory studies?

While the laboratory evidence does not suggest a link between
power-frequency magnetic fields and cancer, numerous studies have reported
that these fields do have "bioeffects", particularly at high field
strength [K1,K2,M4,M6].  Power-frequency fields intense enough to induce
electric currents in excess of those that occur naturally (above 500
microT, see Q8) have shown reproducible effects, including effects on
humans [K1,M4,M6].


18A)  Do power-frequency fields of the intensity encountered in
occupational and residential settings show reproducible biological
effects?

If a reproducible biological effect is defined as one that has been
reported in the peer-reviewed literature by more than one laboratory,
without contradictory data appearing elsewhere; then there may be no
reproducible effects below about 200 microT.  While there are reports of
effects for fields as low as about 0.5 microT, none of these reports have
been validated.

The lack of validation of many of the "positive" bioeffect studies is due
to many factors.  First, many reports on the biological effects of
power-frequency fields have never been published in the peer-reviewed
literature, and cannot be scientifically evaluated or replicated.  Second,
no attempts have ever been made to replicate many of the published reports
of biological effects; and one positive report, standing in isolation, is
hard to evaluate.  Third, when attempts have been made to replicate some
of the published studies, these replications have often failed to show the
effect [H2,H5,H12,H16].  Lastly, the investigators in this field use a
wide variety of biological systems, endpoints, and exposure conditions,
which makes studies extremely hard to compare and evaluate.


18B)  Are there known mechanisms by which power-frequency fields of the
intensity encountered in occupational and residential settings could cause
biological effects?

The known biological mechanisms through which intense (greater than 500
microT) sinusoidal power-frequency magnetic fields cause biological
effects are not relevant to fields below about 50 microT.  The currents
induced in the body by fields of less than 50 microT are qualitatively
similar to, but much weaker than, the currents that occur naturally [F3].
In fact, the currents induced by a 5 microT power-frequency field are less
than those induced in the body by walking through the Earth's static field
[F3].

Power-frequency magnetic fields could also directly exert forces, but
since biological materials are largely nonmagnetic these forces are very
weak, and these direct effects are generally far weaker than those
produced by random thermal agitation (thermal noise) [F3,F12].

If sinusoidal power-frequency fields below 5 microT do actually have
biological effects, the mechanisms must be found, in Adair's [F3,F12]
words: "outside the scope of conventional physics".


18C) Haven't some new mechanisms been proposed that could explain how
power-frequency magnetic fields could cause biological effects.

The considerations discussed in Q18B show that the interactions of
sinusoidal power-frequency fields with the human body are very weak at
typical environmental field levels.  Numerous investigators have
speculated about how power-frequency fields might overcome signal-to-noise
problems via resonance or signal amplification mechanisms [F2,F4,H15,H14].

- Magnetic Biological Material:  Small magnetic particles (magnetite,
Fe3O4) have been found in bacteria that orient in the Earth's static
magnetic field, and these particles may also exist in fish, honeybees and
birds [F4].  The presence of magnetite in mammalian cells is still
unproven.  Kirschvink [F4] has suggested that power-frequency magnetic
fields could cause biological effects by acting directly on such
particles.  However, calculations show that this would require 50/60 HZ
fields of 2-5 microT or above [F4,F12,H13].

- Free Radical Reactions:  Static (DC) magnetic fields can affect the
reaction rates of chemical reactions that involve free radical pairs
[F14].  Since the radicals involved have lifetimes in the microsecond
range, and power-frequency fields have a cycle time in the millisecond
range, a power-frequency field acts like a static field during the time
scale in which these reactions occur.  The effects of the power-frequency
field would be additive with the Earth static field (30-70 microT), so no
detectable biological effects would be expected below about 50 microT
[F14].

- Resonance Theories:  Some of the biophysical constraints could be
overcome if there were resonance mechanisms that could make cells (or
organisms) uniquely sensitive to power-frequency fields.  Several such
resonance mechanisms have been proposed, most recently by Blanchard and
Blackman [H14].  So far, none of these theories have survived scientific
scrutiny [F3,F1,F5,F8], and much of the experimental evidence that
prompted the speculations cannot be independently reproduced
[H2,H5,H12,H20].  There are also severe incompatibilities between known
biophysical characteristics of cells and the conditions required for such
resonances [F3,F1,F5,F8].  Note also that resonance theories would predict
that biological effects would be different in the US (60 Hz) than in the
rest of the world (50 Hz).


18D) Could the presence of transients or higher-order harmonics in
power-frequency fields provide a biophysical mechanism for biological
effects?

The biophysical barriers to biological effects discussed in Q18C and Q18D
presume that 50 or 60 Hz sinusoidal power-frequency fields are the only
time-varying EM fields found in conjunction with the transmission,
distribution, and use of electric power.  If this presumption is not true,
and large transients and/or significant higher-order harmonics are
present, then it is possible that electric currents stronger than those
that occur naturally in the body could be induced at field levels that are
present in residential and occupational settings.  Such large currents
might provide a route to biological effects.


19) What about the "new studies" showing a link between power frequency
fields and cancer?

New studies, particularly epidemiologic studies, appear frequently.  When
these studies show "positive" effects they generate considerable media
coverage.  When they fail to show "positive" effects they are generally
ignored.  This section will cover the more recent (1993 to present)
studies in some detail.


19A) What about the new "Swedish" study showing a link between power lines
and cancer?

In 1993 five new residential exposure studies were released
[C16,C17,C18,C19,C21]. The childhood study from Sweden [C19] showed the
highest risk factors, and drew the most attention.  In contrast to the
earlier US studies which assessed exposure from both distribution and
transmission lines, these new studies were restricted to high voltage
power lines and substations.  Exposure was assessed by spot measurements
[C19,C21], calculated retrospective assessments[C16,C17,C19,C21], and
distance from power lines [C18,C19,C21].

The authors of the new childhood cancer studies [C16,C17,C19] have
produced a combined analysis (called a meta-analysis) of their data [B5].
The meta-analysis is based on retrospective calculated fields, the only
measure of exposure common to all three studies.  The range of RRs (Q13)
from this meta-analysis are shown below in comparison to meta-analysis of
the prior studies [B3,B4].

   Type of Cancer         Range of RRs in     Range of RRs in
                         the 3 new studies     prior studies
  Childhood leukemia         1.1-4.1              0.8-2.1
  Childhood lymphoma         0.3-3.7               none
  Childhood CNS cancer       0.7-3.2              1.7-3.5
  All childhood cancer       0.9-2.1              1.3-1.9

The two latest studies of childhood brain cancer and residence near
powerlines show no evidence for an association for either measured fields
[C29] or wirecodes [C28,C29].

The studies of adults living near high voltage lines showed no increases
in overall cancer, leukemia, or brain cancer [C18,C21].


19B) What about the new studies showing a link between occupational
exposure to power-frequency fields and cancer?

In 1993-1995 12 major new occupational studies were published.  Most of
these studies deal with leukemia [D11,D12,D13,D14,D15,D16,D22,D23,D24,D25]
and brain cancer [D12,D13,D14,D15,D16,D22,D24,D25]; but some also covered
breast cancer [D14,D15,D17,D18,D20,D22,D26,D24], lymphoma
[D13,D14,D15,D22,D24] and other cancers as well [D14,D15,D20,D22].  Four
studies also looked at overall cancer rates [D13,D15,D22,D25]. The studies
of breast and lung cancer are covered separately in Q19C and Q19D.

Unlike earlier studies that were based on job titles as listed on death
certificates, many of the latest studies have used job descriptions
supplemented by data from workers doing those jobs.  No studies to date
have performed dosimetry on the actual subjects of the study; and even if
such dosimetry were available, there is no consensus as to the appropriate
exposure metric, since arguments have been made for time-weighted average
fields, peak fields, rate of change of fields, or even transients.

Of the 10 studies of leukemia, four [D12,D14,D15,D23] showed some evidence
for a statistically significant increase in at least one "exposed" group.
For the studies as a whole the median RR was 1.35, but values as high as
2.0 or as low as 0.8 (protection) are compatible with the data.

Of the five studies of lymphoma, only one [D24] showed some evidence for a
statistically significant increase in at least one "exposed" group.

Of the 8 studies of brain cancer, only one [D25] showed evidence for a
statistically significant increase in at least one "exposed" group.  For
the studies as a whole the median RR was 0.95, but values as high as 1.9
or as low as 0.7 (protection) are compatible with the data.

A recent meta-analysis [B8] of the occupational brain cancer studies found
an overall RR of 1.2.  The meta-analysis shows a number of odd features.
First, while the US studies show an elevated RR, the studies done in
Nordic countries do not.  Second, the studies rated as having better
designs showed lower RRs than those judged to have weaker designs.  Third,
the occupational group with the highest RR was electrical engineers, a
group shown in other studies [D23]to have very low occupational exposures
to power-frequency magnetic fields.

Of the 4 studies of overall cancer, only one [D25] showed evidence for
increase in overall cancer in at least one "exposed" group.  For the
studies as a whole the median RR was 1.03, but values as high as 1.2 or as
low as 0.9 (protection) are compatible with the data.


19C) What about the new studies showing a link between electrical
occupation and breast cancer?

There are some laboratory studies [G16,G26] that suggest that
power-frequency fields might promote chemically-induced breast cancer (see
Q16B), and a biological mechanism has been proposed that could explain
such a connection (see Q17C).

McDowall et al [C4] found no excess female breast cancer (and no male
breast cancer at all) in adults living near transmission lines or
substations.  Vena et al [C23] found no excess breast cancer in women who
used electric blankets.  A number of studies have reported an elevated
incidence of male breast cancer in electrical workers.[D4,D5,D6,D7,D24];
but other studies have found no such excess [D15,D17,D14,D22].

Recently, Loomis et al [D18] reported an elevated incidence of female
breast cancer in occupations with presumed exposure to power-frequency
fields.  The occupations that showed an excess incidence of breast cancer
were "male-dominated".  Breast cancer mortality is known to be elevated
among women in professional and technical jobs in general; this is because
women working in male-dominated jobs tend to have reproductive histories
(for example, no pregnancies, delayed child-bearing, not breast-feeding)
that increase their risk for breast cancer. Cantor et al [D26], analyzing
the same database, found no evidence for an elevated incidence of female
breast cancer in occupations with presumed exposure to power-frequency or
radio-frequency fields.


19D) What about the new studies showing a link between pulsed electric
fields and lung cancer?

Armstrong et al [D20] reported that utility workers exposed to
short-duration pulsed EM fields (PEMFs) had increased lung cancer.  The
association of lung cancer with PEMF is moderately strong, and there is
evidence for a dose-response relationship.  The workers with the highest
exposure to PEMFs have an elevated lung cancer risk compared to workers
with lower levels of exposure, but they have a lower lung cancer rate than
members of the general public.  No relationships were found between PEMF
exposure and any other type of cancer.

Previous studies of power-frequency fields and lung cancer have found no
association.  In a summary of pre-1992 occupational studies, Hutchison
[B3] reports a summary relative risk of 0.8 (0.7-0.9), indicating that
workers with exposure to power-frequency fields have less lung cancer than
expected.  Similarly, Theriault et al [D15] reported a RR of 1.0 (0.7-1.5)
for lung cancer in electrical workers with the highest magnetic field
exposure.

The most difficult issue with the Armstrong report [D20], is the
definition of "PEMF" exposure.  The dosimetry is based on readings from a
dosimeter that was designed to respond to signals having an electric field
component greater than 200 V/m at 2-20 MHz, but this isn't what the
dosimeter actually responds to [D21]. In the utility environment this
dosimeter is exquisitely sensitive to radio transmissions near 150 MHz, a
band that is now (but only recently) used for portable radio communication
in the utility industry [D21].  So the job categories in which the
Armstrong report [D20] is finding excess lung cancer, are actually the
jobs that involve proximity to the use of portable radios.  Keep in mind
that the vast majority of the reported excess lung cancer occurred before
the use of these radios became common.


19E) What about the new studies linking the use of electrical appliances
with cancer?

The fields close to appliances that contain AC electric motors can exceed
100 microT and 2 V/cm.  If these appliances are used very close to the
body, as electric razors and hair dryers are, there can be large exposures
of small parts of the body.  There have been epidemiologic studies that
have looked at the relationship between the use of electrical appliances
and cancer [C6,C8,C11,C12,C22,C23,C28,C29].  These studies have shown
little consistent association between the use of electrical appliances and
cancer incidence, although the most recent of these studies [C22] has
actually shown a decrease in adult leukemia among users of personal
electrical appliances.


19F) What about Sweden's/Denmark's decision to regulate power line fields?

We frequently hear that Sweden or Denmark have decided to regulate the
magnetic fields produced by power lines, or have decided to move power
lines away from schools.  However, recent statements from officials in
both countries [L9,L10,L17] clearly indicate that they are neither
regulating fields from the lines or ordering lines to be moved away from
schools.


19G) What about the new study showing that it is the interaction between
power-frequency fields and the Earth's static field that causes cancer?

The inherent biophysical problems with explaining how power-frequency
magnetic fields of the magnitude encountered in residential and most
occupational settings could cause biological effects (Q18B) might be
overcome if a biological mechanism for amplifying power-frequency fields
could be identified.  A number of such amplification models have been
proposed (Q18C), most of which are based on some type of resonance between
the power-frequency field and the Earth's static geomagnetic field.

Bowman et al [C27] hypothesized that the risk of childhood leukemia might
be related to specific combinations of static (geomagnetic) and
power-frequency fields. Childhood leukemia data from the Los Angeles were
analyzed on the basis of these combinations.  No correlation between
measured static or power-frequency fields were found, but the authors do
claim a positive trend for the combined power-frequency and static data.
An issue not addressed by the authors is that all resonance theories
require a specific orientation between the AC and the DC field; thus it
should not be the total static field that matters, but only the component
of the static field that has the right orientation to the power-frequency
field.


Copyright (C) by John Moulder
End: powerlines-cancer-FAQ/part3

     ------------------------------------------------------------


                      Powerlines & Cancer FAQs 4/8: FAQ 3
                                       

Archive-name: powerlines-cancer-FAQ/part4
Last-modified: 1996/2/20
Version: 3.4.1
Maintainer: jmoulder@its.mcw.edu


FAQs on Power-Frequency Fields and Cancer (Q&A, Part 3 of 4)


20) What criteria do scientists use to evaluate all the laboratory and
epidemiologic studies of power-frequency magnetic fields and cancer?

There are certain widely accepted criteria that are weighed when assessing
epidemiologic and laboratory studies of agents that may pose human health
risks.  These are often called the "Hill criteria" [E1].  Under the Hill
criteria one examines the strength (Q20A) and consistency (Q20B) of the
association between exposure and risk, the evidence for a dose-response
relationship (Q20C), the laboratory evidence (Q20D), and the biological
plausibility (Q20E).

The Hill criteria must be applied with caution.  First, when employing the
Hill criteria it is necessary to examine the entire published literature;
it is not acceptable to pick out only those reports that support the
existence of a health hazard.  Second, it is necessary to directly review
the important source documents; it is not safe to base judgments solely on
academic or regulatory reviews.  Third, satisfying the individual criteria
is not a yes-no matter; support for a criterion can be strong, moderate,
weak, or non-existent.  Lastly, the Hill criteria must be viewed as a
whole; no individual criterion is either necessary or sufficient for
concluding that there is a causal relationship between exposure to an
agent and a disease.

Overall, application of the Hill criteria shows that the current evidence
for a connection between power-frequency fields and cancer is weak.  A
detailed evaluation of the criteria follows.


20A) Criterion One: How strong is the association between exposure to
power-frequency fields and the risk of cancer?

The first Hill criterion is the *strength of the association* between
exposure and risk.  That is, is there a clear risk associated with
exposure?  A strong association is one with a RR (Q13) of 5 or more.
Tobacco smoking, for example, shows a RR for lung cancer 10-30 times that
of non-smokers.

Most of the positive power-frequency studies have RRs of less than two.
The leukemia studies as a group have RRs of 1.2-1.7, while the brain
cancer studies as a group have RRs of about 1.1-1.9.  This is only a weak
association.  Interestingly, as the sophistication of the studies has
increased, the RRs have not (See Q19).


20B) Criterion Two: How consistent are the studies of associations between
exposure to power-frequency fields and the risk of cancer?

The second Hill criterion is the *consistency* of the studies.  That is,
do most studies show about the same risk for the same disease?  Using the
same smoking example, essentially all studies of smoking and cancer showed
an increased risk for lung and head-and-neck cancers.

Many power-frequency studies show increased incidence of some types of
cancers and some types of exposures, but many do not.  Even the positive
studies are inconsistent with each other.  For example, while a recent
Swedish study [C19] shows an increased incidence of childhood leukemia for
one measure of exposure, it contradicts prior studies that showed an
increase in brain cancer [B3,B4], and a parallel Danish study [C17] shows
an increase in childhood lymphomas, but not in leukemia.

Many of the studies are internally inconsistent.  For example, where a
recent Swedish study [C19] shows a positive association of childhood
leukemia with calculated retrospective fields, it shows a negative
association with measured fields.  This study also shows no overall
increase in childhood cancer.  Since leukemia accounts for about one-third
of all childhood cancer, this implies that the rates of other types of
cancer were decreased; an examination of the data indicates that this is
true.


20C) Criterion Three: Is there a dose-response relationship between
exposure to power-frequency fields and the risk of cancer?

The third Hill criterion is the evidence for a *dose-response
relationship*.  That is, does risk increase when the exposure increases?
Again, the more a person smokes, the higher the risk of lung cancer.

No published power-frequency exposure study has shown a dose-response
relationship between measured fields and cancer rates, or between
distances from transmission lines and cancer rates.  The lack of a
relationship between exposure and increased cancer incidence is a major
reason why most scientists are skeptical about the significance of the
epidemiology.

Not all relationships between dose and risk can be described by simple
linear no-threshold dose-response curves where risk is strictly
proportional to dose.  There are known examples of dose-response
relationships that have thresholds, that are non-linear, or that have
plateaus.  For example, the incidence of cancer induced by ionizing
radiation in rodents rises with dose, but only up to a certain point;
beyond that point, the incidence plateaus or even drops.  Without an
understanding of the mechanisms connecting dose and effect it is
impossible to predict the shape, let alone the magnitude of the
dose-response relationship.


20D) Criterion Four: Is there laboratory evidence for an association
between exposure to power-frequency fields and the risk of cancer?

The fourth Hill criterion is whether there is *laboratory evidence*
suggesting that there is a risk associated with such exposure.
Epidemiologic associations are greatly strengthened when there is
laboratory evidence for a risk.

Power-frequency fields show little evidence of the type of effects on
cells, tissues or animals that point towards their being a cause of
cancer, or to their contributing to cancer (see Q16,Q17,Q18).


20E) Criterion Five: Are there plausible biological mechanisms that
suggest an association between exposure to power-frequency fields and the
risk of cancer?

The fifth Hill criterion is whether there are *plausible biological
mechanisms* that suggest that there should be a risk.  When it is
understood how something causes disease, it is much easier to interpret
ambiguous epidemiology.  For smoking, while the direct laboratory evidence
connecting smoking and cancer was weak at the time of the Surgeon Generals
report, the association was highly plausible because there were known
cancer-causing agents in tobacco smoke.

From what is known of power-frequency fields and their effects on
biological systems there is no reason to even suspect that they pose a
risk to people at the exposure levels associated with the generation and
distribution of electricity (see Q16,Q17,Q18).


21) If exposure to power-frequency magnetic fields does not explain the
residential and occupations studies which show increased cancer incidence,
what other factors could?

There are basically five factors that can result in false associations in
the epidemiologic studies: inadequate dose assessment (Q21A), confounders
(Q21B), inappropriate controls (Q21C), publication bias (Q21D), and
multiple comparison artifacts (Q21E).


21A) Could problems with dose assessment affect the validity of the
epidemiologic studies of power-frequency fields and cancer?

If power-frequency fields are associated with cancer, we do not know what
aspect of the field is involved.  At a minimum, risk could be related to
the peak field, the average field, or the rate of change of the field.
The duration of exposure could also be a factor.  It has even been
suggested that harmonics, transients, and/or interactions with the Earth's
static magnetic fields are involved.  If we do not know who is really
exposed, and who is not, we will usually (but not always) underestimate
the true risk [C15].


21B) Are there other cancer risk factors that could be causing a false
association between exposure to power-frequency fields and cancer?

Associations between things are not always evidence for causality.  Power
lines (or electrical occupations) might be associated with a cancer risk
other than magnetic fields.  If such an associated cancer risk were
identified it would be called a "confounder" of the epidemiologic studies
of power lines and cancer.  An essential part of epidemiologic studies is
to identify and eliminate possible confounders.  Many possible confounders
of the power line studies have been suggested, including PCBs, herbicides,
ozone and nitrogen oxides, traffic density, and socioeconomic class.

- PCBs: Many transformers contain polychlorinated biphenyls (PCBs) and it
has been suggested that PCB contamination of power-line corridors might be
the cause of the excess cancer.  This is unlikely.  First, there is little
evidence for widespread PCB contamination of power line corridors.
Second, transformers are found along distribution lines, but not
high-voltage transmission lines, so PCBs could not account for the linkage
of childhood leukemia with transmission corridors [B5]. Three, the
evidence that PCB exposure causes or promotes cancer in people is weak
[E10,L2].  Lastly, PCBs predominantly cause and promote liver cancer in
animals; leukemia, brain and breast cancer have not been reported.

- Herbicides: It has been suggested that herbicides sprayed on the power
line corridors might be a cause of cancer.  This is also an unlikely
explanation.  First, herbicide spraying would not affect distribution
systems in urban areas (where 3 of 5 positive childhood cancer studies
have been done), and would not explain the reported increase in cancers in
electrical occupations. Second, evidence that herbicides are carcinogens
in humans is weak [L7].  Third, the epidemiology which suggests that the
phenoxy herbicides might be carcinogens suggests that the increased risk
is for lymphomas and soft-tissue sarcomas [L7]; only one study implicates
leukemia [D3], and none implicate brain cancer.

- Ozone and nitrogen oxides:  It has been suggested that ozone and
nitrogen oxides created when high voltage lines arc might be responsible
for the increased cancer along power line corridors.  This is another
unlikely explanation.  First, while ozone is a cellular genotoxin, there
is no evidence that it causes cancer in humans, and only ambiguous
evidence that it causes lung cancer in rats [L6].  There is essentially no
evidence that the nitrogen oxides are carcinogens.  Second, this potential
confounder would apply only to corridors containing high-voltage lines and
would not explain reports of excess cancer along distribution systems or
in electrical occupations.

- Traffic density: Transmission lines frequently run along busy roads, and
the "high current configurations" associated with excess childhood
leukemia in the US studies [C1,C6,C12] are associated with busy roads.  It
has been suggested that power lines might be a surrogate for exposure to
cancer-causing substances in traffic exhaust.  This may be a serious
confounder of the residential exposure studies, since traffic exhaust
contains known carcinogens, and traffic density has been shown to
correlate with childhood leukemia incidence [E6].  Note that this would
explain only the reported increase in cancer along power-lines; it would
not explain the reports of increased cancer in electrical occupations.

- Socioeconomic class: Socioeconomic class may be an issue in both the
residential and occupational studies, as socioeconomic class is clearly
associated with cancer risk, and "exposed" and "unexposed" groups in many
studies are of different socioeconomic classes [C15].  This is of
particular concern in the US residential exposure studies that are based
on "wirecodes", since the types of wirecodes that are correlated with
childhood cancer are found predominantly in older, poorer neighborhoods,
and/or in neighborhoods with a high proportion of rental housing
[C20,C25].

- Ionizing radiation from corona:  Recently it was suggested on the net
that corona discharges produce ionizing radiation, and that this could
explain the association between power lines and cancer.  Corona discharges
are electrical discharges that occur between two conductors of the same
high voltage line.  They are often luminous, they occur only on very high
voltage lines, and they are more common in certain weather conditions.
There is no evidence that these discharges produce ionizing radiation, and
strong physical arguments to suggest that they could not.  The issue is
complicated by the fact that corona discharges can produce ionization of
the surrounding air, and that corona and spark discharges (a related
phenomena) can produce genotoxic damage [E5,K3].  An added complication is
that many types of ionizing radiation monitors produce erratic readings in
the presence of strong electric and magnetic fields.  This explanation,
even if valid, would do nothing to explain the majority of the positive
epidemiologic studies, as these studies involve exposure conditions where
corona discharges do not occur.

- An infectious basis for leukemia:  It has been suggested that childhood
leukemia might be the result of infection [L14].  If so, the socioeconomic
differences between children living near and far from "high current
configurations" [C15,C20,C25] could confound studies of powerlines and
childhood leukemia [C24].  Even is this confounder turns out to be real,
it would not probably not be applicable to studies of adult leukemia, or
to studies of other types of cancer.

- Other factors: If "other" factors exist that increase the incidence of
cancer they need to be controlled for in studies.  In other words, you
have to make sure that the "exposed" and "unexposed" groups have the same
risk factors.  Every time a new risk factor is discovered, previous
studies need to be reexamined.


21C) Could the epidemiologic studies of power-frequency fields and cancer
be biased by the methods used to select control groups?

An inherent problem with many epidemiologic studies is the difficulty of
obtaining a "control" group that is identical to the "exposed" group for
all characteristics related to the disease except the exposure.  This is
very difficult to do for diseases such as leukemia and brain cancer where
the risk factors are poorly known.  An additional complication is that
often people must consent to be included in the control arm of a study,
and participation in studies is known to depend on factors (such as
socioeconomic class, race and occupation) that are linked to differences
in cancer rates.  See Jones et al [C20] and Gurney et al [C25] for example
of how selection bias could affect a power line study.


21D) Could analysis of the epidemiologic studies of power-frequency fields
and cancer be skewed by publication bias?

It is known that positive studies in many fields are more likely to be
published than negative studies.  This can severely bias meta-analysis
studies such as those discussed in Q13 and Q15.  Such publication bias
will increase apparent risks.  This is a bigger problem for the
occupational studies than the residential ones.

Several specific examples of publication bias are known in the studies of
electrical occupations and cancer.  In their review Coleman and Beral [B1]
report the results of a Canadian study that found a RR of 2.4 for leukemia
in electrical workers.  The British NRPB review [B4] found that further
followup of the Canadian workers showed a deficiency of leukemia (a RR of
0.6), but that this followup study has never been published.  This is an
anecdotal report, but publication bias, by its very nature, is usually
anecdotal.

It is also a clear problem for laboratory studies -- it is much easier to
publish studies that report effects than studies that report no effects.
An example of this can be seen in work by Cain and colleagues.  In a 1993
they published a report [G29] that 60-Hz fields were a co-promoter in a
cell transformation system.  But in 1993 and 1994 the same authors
reported at meetings that they could not replicate the co-promotion, and
that subsequent experiments showed a decrease in transformation when 60-Hz
magnetic fields were present.  However, the report of failure to replicate
is not published, so that only the positive report is currently in the
peer-reviewed literature.

A similar phenomena occurred recently over the issue of whether exposure
to power-frequency magnetic fields affected gene transcription.  There
were published reports of gene transcription effects (for example,
[H4,H6]); but there are also meeting reports that these studies could not
be replicated.  While the issue has not been resolved, the negative
reports have now been published in the peer-reviewed literature [H17,H18]

There is also "reporting bias", which refers to situations where multiple
studies are done but only some are reported, and to situations where
abstracts and/or press reports emphasize unrepresentative subsets of the
actual study.  The "Swedish" studies [C19,C21] provide an example.  The
original unpublished report used a number of different definitions of
"exposure", and studied both children and adults.  Of all the comparisons,
the strongest associations were found for childhood leukemia and
calculated fields.  The first published English language version omitted
the adult data, and the abstract emphasized the groups, exposure
definitions and cancer types for which the associations were the
strongest; the press reports were based largely on that abstract.  The
recent publication of the adult portion of the study [C19], which shows no
relationship between exposure and cancer incidence in adults has received
virtually no press coverage.  The result is that a handful of positive
associations have been emphasized from a much larger group of
overwhelmingly non-significant associations.


21E) Could analysis of the epidemiologic studies of power-frequency fields
and cancer be biased by multiple-comparison artifacts?

Interpretation of the epidemiologic studies is complicated by multiple
comparison issues.  When studies include multiple exposure metrics and/or
multiple types of cancer, the investigator can compare many different
subgroups.  Each comparison (by commonly accepted statistical criteria)
has a 5% probability of yielding a "statistically significant" difference,
even if there were no real differences.  A related problem arises when the
investigator groups subjects into categories based on arbitrarily chosen
exposure cutpoints.  Between multiple exposure metrics, multiple
cutpoints, multiple cancer sites, and subgroup analysis, a study may
contain 50 or more calculations of RR, each individually analyzed for
significance at 5%.  A high incidence of "false positive" associations
would be expected from such a study.

An illustrative example is the study by Feychting & Ahlbom [C19,C21],
which looked at 12 cancer types (4 in children and 8 in adults), and 3
different exposure metrics (measured fields, calculated historic fields,
and distances from lines).  Within each exposure metric were further
sub-definitions (such as different cutpoints for separating unexposed from
exposed).  Solely because of the multiple cancer types and exposure
metrics, 228 RRs were calculated (due to other subgroup analysis the
actual total is over 700), with values ranging from 0.0 (no cancer in
exposed groups) to 5.5 (more cancer in exposed groups).  Each RR was
separately analyzed to calculate 95% confidence intervals.  Eleven of the
228 RR's had lower confidence intervals of 1.0 or above (a crude
indication of statistical significance), but even if there were no
relationship between power lines and cancer, 5% (or 11.5) of the 288 RRs
would been expected to be "significant" by this standard.  Similarly, if
there were no relationship between power lines and cancer, some
"significantly" decreased rates of cancer would be expected, and such
examples can be found.

As a result, we are left not knowing whether the "significant correlation"
of childhood leukemia with calculated historic fields is an indicator of a
real association or a piece of statistical noise.  The inability of this
type of epidemiologic study to prove "statistical significance" is
explicitly acknowledged by  Feychting & Ahlbom [C26], who point out that
they do not even use the term "statistically significant" in their papers.

The multiple comparison issues is a particular problem for
"hypothesis-generating" studies of the type that have dominated the
epidemiology of power-frequency fields.  Because of the large number of
variables, it is almost impossible for such studies to show true
"statistical significance".  What such studies can do is generate ideas
that can be tested in subsequent "hypothesis-testing" studies.  The
hallmarks of such "hypothesis-testing" is a small set of hypotheses
(usually only one) that are stated in advance, and an experimental design
that avoids the multiple comparison issue by limiting the comparisons to
just those that could disprove the hypothesis.

The multiple comparison problem is not unique to this type of
epidemiology.  It is also a pervasive problem in clinical trials, and
issues such as multiple endpoints, multiple cutpoints, subgroup analysis,
and selection of results for summaries have been extensively discussed in
the biomedical literature [L1,L11,L12].  Three things are very clear:
- Ignoring these issues can lead to a dramatic increase in reports that
something is statistically significant when it is, in fact noise.
- Statistical techniques exist for correcting these problems, but it is
better to avoid the problems by using proper experimental designs.
- The need for multiple comparison corrections is not accepted by many
practicing epidemiologist [L15].

Copyright (C) by John Moulder
end: powerlines-cancer-FAQ/part4

     -------------------------------------------------------------


                      Powerlines & Cancer FAQs 5/8: FAQ 4
                                       

Archive-name: powerlines-cancer-FAQ/part5
Last-modified: 1996/2/20
Version: 3.4.1
Maintainer: jmoulder@its.mcw.edu
Keywords: powerlines, magnetic fields, cancer, EMF, non-ionizing
  radiation, EMR, ELF, FAQ


FAQs on Power-Frequency Fields and Cancer (Q&A, Part 4 of 4)


22) What is the strongest evidence for a connection between
power-frequency fields and cancer?

The best evidence for a connection between cancer and power-frequency
fields is probably:
a) The four epidemiologic studies that show a correlation between
childhood cancer and proximity to high-current wiring [C1,C6,C12,C19],
plus the meta-analysis of the Scandinavian studies [B5].
b) The epidemiologic studies that show a correlation between work in
electrical occupations and cancer, particularly leukemia and brain cancer
[A1,B3,B4,D12,D14,D25].
c) The lab studies that show that power-frequency fields do produce
bioeffects.  One of the most interesting, but also currently one of the
most controversial of the lab studies are the ones claiming increased
transcription of oncogenes at fields of 100-500 microT [H4,H6].  Be aware,
however, that there are reports [H17,H18] that these gene transcription
effects cannot be independently replicated.
d) The three laboratory studies that provide evidence that power-frequency
magnetic fields can promote chemically-induced cancer [G16,G26,G44].
e) The studies reporting that intense fields can enhance tumor
[G18,G26,G39] and cell [G8,G35,G42] growth rates.


23) What is the strongest evidence against a connection between
power-frequency fields and cancer?

The best evidence that there is not a connection between cancer and
power-frequency fields is probably:
a) Application of the Hill criteria (Q20) to the entire body of
epidemiologic and laboratory studies.
b) The fact that the lab studies of genotoxicity have been overwhelmingly
negative (Q16A).
c) The fact that most lab studies of epigenetic activity have been
negative, and that the few positive studies have used fields far more
intense than those to which people are actually exposed (Q16B & Q16C).
d) Adair's [F3,F12] biophysical analyses that indicates that "any
biological effects of weak (less than 4 microT) ELF fields on the cellular
level must be found outside of the scope of conventional physics"
e) The fact that multiple comparison problems call into question the
statistical significance of essentially all of the "positive"
epidemiologic studies (Q21E).

Note:  Jackson [E9] and Olsen [C17] argue that a connection between cancer
and power lines is unlikely because childhood and adult leukemia rates
have been stable over a period of time when per capita power consumption
has risen dramatically.  This argument presumes that "exposure" has risen
in parallel with "consumption"; there is little relevant historical data,
and there are technical reasons to question the validity of this
assumption.


24) What studies are needed to resolve the cancer-EMF issue?

In the epidemiologic area, more of the same types of studies are unlikely
to resolve anything.  Studies showing a dose-response relationship between
measured fields and cancer incidence rates would clearly affect thinking,
as would studies identifying confounders in the residential and
occupational studies.

In the laboratory, more genotoxicity and promotion studies may not be very
useful.  Exceptions may be in the area of cell transformation, and
promotion of chemically-induced breast cancer. Long-term rodent exposure
studies (the standard test for carcinogenicity) would have a major impact
if they were positive, but if they were negative it would not change many
minds.  Further studies of some of the known bioeffects would be useful,
but only if they identified mechanisms or established the conditions under
which the effects occur (e.g., thresholds, dose-response relationships,
frequency-dependence, optimal wave-forms).


25) Is there any evidence that power-frequency fields cause any human
health hazards, such as miscarriages, birth defects or Alzheimer's
disease?

While this FAQ sheet, and most public concern, has centered around cancer,
there have also been suggestions that there might be a connection between
non-ionizing EM exposure and birth defects.  This concern has focused as
much on video display terminals (VDTs) as on power lines.  Little
epidemiologic [J1,J5,J6,J9,J10] or laboratory [J3,J4,J8] support for a
connection between non-ionizing EM exposure and birth defects has been
found.  Cox et al [J3], Chernoff et al [J2] and Brent et al [J7] have
recently reviewed this field.

There is a report of excess Alzheimer's disease in occupations with
"probably medium to high exposure" to power-frequency fields [E16].  This
study reports that dressmakers, seamstresses and tailors have excess rates
of Alzheimer's disease; and these groups are exposed to power-frequency
fields from sewing machines.  Interestingly, no excess Alzheimer's disease
were found in any other "electrical occupations".


26) What are some good overview articles?

There are really no up-to-date reviews of power-frequency fields and human
health.  The reviews by Davis et al [A1], Doll et al [B4] and the two
French review [A3,A4] are good, but were published before many of the
important epidemiologic, genotoxicity, and promotion studies were
available.

There are up-to-date reviews of specific areas:  Heath [B9] has recently
reviewed the residential cancer epidemiology; Loscher & Mevissen [K6] have
reviewed the animal carcinogenesis studies; and Moulder & Foster [A8] have
reviewed the biological evidence for carcinogenesis.  The latter review
[A8] was derived directly from this FAQ document.


27) Are there exposure guidelines for power-frequency fields?

Yes, a number of governmental and professional organizations have
developed exposure guidelines.  These guidelines are based on keeping the
body currents induced by power-frequency EM fields to a level below the
naturally-occurring fields (Q8).  The most generally relevant are:

- National Radiation Protection Board (UK) [M4]:
  50 Hz: 1,600 microT (16 G) and 12 kV/m
  60 Hz: 1,330 microT (13.3 G) and 10 kV/m
  This document also contains guidelines for other frequencies.

- American Conference of Governmental Industrial Hygienists [M5]:
  At 60 Hz: 1,000 microT (10 G); 100 microT (1 G) for pacemaker wearers
  This document also contains guidelines for other frequencies.

- International Commission on Non-Ionizing Radiation Protection [M6]
  24 hr general public: 100 microT (1 G) and 5 kV/m
  Short-term general public: 1,000 microT (10 G) and 10 kV/m
  Continuous occupational: 500 microT (5 G) and 10 kV/m
  Short-term occupational: 5,000 microT (50 G) and 30 kV/m


27A) What about the report that a US government agency (the NCRP) is about
to recommend strict limits on occupational and residential exposure to
power-frequency fields.

The July/August issue of Microwave News contained extensive quotes from a
draft report of a US NCRP (National Commission on Radiation  Protection)
committee.  According to the Microwave News article, the NCRP report
recommends strict standards for occupational and residential exposure to
power-frequency (and other ELF) electric and magnetic fields.  The
Microwave News article was subsequently picked up by Science and the New
Scientist and then by the mass media.

According to an official statement by the NCRP (August 22, 1995), this
draft report "has absolutely no standing at this time".  The NCRP
statement goes on to say that "the draft in question is still undergoing
revisions to prepare it for entry into the initial review phase, it exists
only as a working draft that should not have been released outside [the
Committee].  Thus it should not be copied, quoted, or referenced outside
of the NCRP."

A later (October 11, 1995) official statement says that contrary to many
erroneous sources of information, the NCRP has not made recommendations on
ELF EMF and notes that "considering the extensive nature of the review
process, it is impossible to predict when the NCRP may have a report on
the subject of ELF and it is not possible to know the extent or
recommendations that might be made".  The full text of the October 11
statement can be found at: ftp://ftp.mcw.edu/pub/emf-and-cancer

In view of the NCRP's request that "interested parties will ignore the
improperly disseminated draft report material and allow the NCRP process
to proceed", and the fact that there are more than one version of the
draft in circulation, the FAQ sheet will not quote or further discuss
this issue until the NCRP issues an official report.


28) What effect do power lines have on property values?

There is very little hard data on this issue.  There have been "comparable
property" studies, but any studies done prior to about 1991 (when London
et al [C12] was published) might be irrelevant.  One comparable value
study has been published recently [L5], and another has been presented at
a meeting [L8].  Neither study shows evidence for an impact of power lines
on property values.  However, both studies indicate that many owners think
that there will be an impact, particularly if concerns about health
effects become widespread.

It appears that the presence of obvious transmission lines or substations
can adversely affect property values if there has been recent local
publicity about health or property value concerns.  It appears less likely
that the presence of "high current configuration" distribution lines of
the type correlated with childhood cancer in the US studies [C1,C6,C12]
would affect property values, since few people would recognize their
existence. If buyers start requesting magnetic field measurements, no
telling what will happen, since while measurements are relatively easy to
do (Q29 & Q30), they are essentially impossible to interpret (Q14).


29) What equipment do you need to measure power-frequency magnetic fields?

Power-frequency fields are measured with a calibrated gauss meter.  The
meters used by environmental health professionals are too expensive for
"home" use.  A unit suitable for home use should meet the following
criteria.
- a reasonable degree of accuracy and precision (plus/minus 20% seems
reasonable for home use);
- true rms detection, otherwise readings might be exaggerated if the
waveform is non-sinusoidal;
- a tailored frequency response, because if the unit is too broad-band,
higher frequency fields from VDTs, TVs, etc. may confound the
measurements;
- the correct response to overload; if the unit is subjected to a very
strong field, it should peg, not just give random readings;
- a strong electric field should not affect the magnetic field measurement.

Meters meeting these requirements are expensive.  A 1993 issue of
Consumer's Report found that the inexpensive (under $200) meters available
in the USA were unreliable.  A recent review of meters by Iowa State
[F15], found a $450 meter they rated a suitable for use by a lay-person.
For the expert or non-expert who has a good multimeter, and knows how to
use a spread sheet, a suitable unit can be gotten for as little as $115
[F15].

The suggestions that one wind a coil and use headphones or a high
impedance multimeter are misguided.  A clever physicist or engineer can
anticipate and correct for nonlinearity and interference, but for the
average person, even one technically trained, this is unreasonable.


30) How are power-frequency magnetic fields measured?

Measurements must be done with a calibrated gauss meter (Q29) in multiple
locations over a substantial period of time, because there are large
variations in fields over space and time.  Fortunately, the magnetic field
is far easier to measure than the electric field. This is because the
presence of conductive objects (including the measurer's body) distorts
the electric field and makes meaningful measurements difficult. Not so for
the magnetic field.

It is important for the person who is making the evaluation to understand
the difference between an emission and exposure. This may seem obvious,
but many people, including some very smart physical scientists, stick an
instrument right up to the source and compare that number with an exposure
standard.  Also, if the instrument is not isotropic, measurement technique
must compensate for this.

In the case of power distribution line and transformer fields, the
magnetic fields will probably vary considerably over time, as they are
proportional to the current in the system.  A reasonable survey needs to
be done over time, with anticipated and actual electricity usage factored
in. It may seem to be as simple as walking in and reading the meter, but
it's not.  Several formal protocols for making residential measurements
have been developed and published, including one from the IEEE [F9].


31) Do the issues discussed in this FAQ sheet apply to EM fields other
than power-frequency fields?

This FAQ sheet concerns itself primarily with sinusoidal fields at
frequencies of 50 or 60 Hz.  However, certain general issues are relevant
to some other types of EM sources.


31A) Do the issues discussed in this FAQ sheet apply to sub-RF fields
other than sinusoidal power-frequency fields?

The basic principles and data discussed in the FAQ sheet are generally
applicable to EM sources with frequencies between 1 Hz and 30,000 Hz (30
kHz).  The major issue encountered when dealing with low-frequency sources
other than power-frequency is that the currents induced by time-varying
magnetic fields depend on frequency and wave-form, as well as field
intensity.  As the frequency increases, so do the induced currents.  Thus
safety guidelines change with frequency [M4,M5].  For example, the NRPB
magnetic field exposure guideline [M4] which is 1,330 microT at 60 Hz,
rises to 80,000 microT at 1 Hz and falls to 80 microT at 3 kHz.

Estimating the currents induced by non-sinusoidal ELF wave forms is more
complex, because the magnitude of the induced current depends on the rate
at which the magnetic field changes.  Thus a square wave of the same
frequency and amplitude of a sinusoidal wave will induced a much greater
current.


31B)  Do the issues discussed in this FAQ sheet apply to static electric
and magnetic fields?

Static electric and magnetic fields, and ELF fields with frequencies below
1 Hz are covered in a companion FAQ sheet called "FAQs on Static
Electromagnetic Fields and Cancer".  The static field FAQ sheet is posted
regularly to sci.med.physics, sci.answers, and news.answers.  It is
available from the same sources as the power-frequency FAQ sheet, under
the archive name: "static-fields-cancer-FAQ".  For standards and
regulations concerning occupational and environmental exposure to static
fields see the ICNIRP guidelines [M7].


31C)  Do the issues discussed in this FAQ sheet apply to radiofrequency
and microwave frequencies?

Above 30 kHz, one moves into the radiofrequency (RF) and microwave (MW)
range, and biophysical and biological issues arise [M1,M3] that are not
within the scope of this FAQ sheet.  First, as the wavelength gets
shorter, there is non-ionizing radiation as well as electric and magnetic
fields to consider.  Second, as the frequency rises into the MHz range,
heating due to induced electric currents may no longer be negligible.  To
our knowledge, there are no on-line resources on RF/MW bioeffects and
human health issues.  Some of the general issues involved with RF and MW
exposure are covered in Q2, Q3 and Q7.  For standards and regulations
concerning occupational and environmental exposure to RF and MW sources
see the ICNIRP guidelines [M3].


32) What about the new study claiming that radon exposure is increased by
the presence of electromagnetic fields.

British TV has reported on a paper in an upcoming issue of Int J Radiat
Biol [H22].  The paper reports that the radioactive decay products of
radon are attracted to power-frequency electric field sources.  The
authors claim that this provides a mechanism for the alleged connection
between powerlines and childhood leukemia.

The basic observation of increased deposition of radon daughter containing
aerosols on strong electric (not magnetic) field sources is quite
plausible.  However, if the radon daughter containing aerosols plate out
on the source of the electrical field, it would seem that they would then
not be available for inhalation (which is how carcinogenic human exposure
to radon occurs).

The jump to a generalized power-frequency field cancer connection is
implausible.  There are particular problems with the suggestion that this
could explain the alleged connection between powerlines and childhood
leukemia.
 - Residences along powerlines do not have elevated electrical fields
[C11,C12], and it is electrical fields that the Henshaw theory requires
[H22].
 - The residential epidemiological studies that have looked at both
electrical and magnetic fields have found that the association (where
there is any) is for the magnetic, not the electrical field [C11,C12].
 - Elevated radon exposure is linked with adult lung cancer (not reported
in excess), not childhood leukemia [L18].
 - Outdoors, powerline electrical fields might be strong enough to attract
and concentrate radon daughter aerosols, but the outdoor concentrations of
radon is generally very low.  Since the half-life of the critical
alpha-emitting radon daughters is very short, they are not going to "pile
up".

Using this as an explanation of the alleged cancer increase in some
electrical occupations also has problems.
 - No one appears to have reported an association of cancer with
occupational exposure to electrical fields; and you can't assume that
electrical field exposure is equivalent to magnetic field exposure, since
the correlation between occupational electric and magnetic field exposure
is not very strong [F16].
 - Increased exposure to radon would be expected to increase lung, skin
and oral/throat cancer [L18], none of which have generally been found in
excess in "electrical occupations".
 - The construction and ventilation of most work places is such that high
concentrations of radon would not be very common.

The British National Radiation Protection Board has made the following
comments (14-Feb-96) on the paper.

"The authors indicate that electric fields increase plateout of radon
daughters present in the air in a room... The consequence of increased
plateout is that fewer radon daughters will remain in the air to be
breathed... The authors of the paper go on to speculate that there may be
some mechanism by which electric fields cause radiation doses from the
inhalation of radon daughters to be increased, but offer no credible
explanation why this should occur.  The theory is implausible: the weight
of evidence would suggest that the presence of electric fields will, if
any thing, slightly reduce human exposure to radon daughters"

The NRPB goes on:

"There is a well established causal link between exposure to radon
daughters and lung cancer...  It has not been established that radon
daughters cause any other cancers.  This reflects differences in doses
between the lung and other internal body tissues"

and

"The position of the Board... is that there is no convincing evidence that
the electric and magnetic fields generated by overhead powerlines or
electrical apparatus are harmful to health...  The paper, which is purely
speculative in the issue of radon and EMFs, does not change the Board's
view"


33) Should I buy a house next to a power line?

This is not a question for which FAQ sheet can provide a direct answer.
Rather, the goal of the FAQ sheet is to suggest approaches to answering
the question, and to provide a referenced and up-to-date summary of what
is known and what is not known about the science.

Clearly there is a broad consensus in the scientific community that no
causal association has been established between residential exposure to
power-frequency fields, and human health hazards.  Similarly, there is a
broad consensus that exposure to these fields has not been, and cannot be,
proven to be _absolutely_ safe.  There is also a growing consensus that if
there is a human health hazard, it is either very small or restricted to
small subgroups; that is, that the possibility of a large and general
hazard has been ruled out.  The scientific controversy is over whether
power-frequency fields might be shown to be hazardous by future studies,
and the related issues of what additional studies should be done, and what
priority those studies should be given.

Regardless of the science, the public controversy remains.  This is seen
in the continuing litigation over cancers that are alleged to have been
caused by exposure to power-frequency fields, and by the public opposition
that meets almost all attempts to site or upgrade power lines.  The public
concern is sustained by uneven reporting on this issue by the mass media,
by the inability of scientists to guarantee that no risk exists, and by
statements from scientists and government officials that more research is
needed.  This public concern is further encouraged by lay-oriented books
that allege that there has been a conspiracy to conceal the health risks
of power-frequency fields [L3].

Public controversy about electricity and health will continue either until
future research shows that the fields are hazardous, or until the public
learns that science cannot guarantee absolutely safety.


Copyright (C) by John Moulder
end: powerlines-cancer-FAQ/part5

      -----------------------------------------------------------


                    Powerlines & Cancer FAQs 6/8: Biblio 1
                                       

Archive-name: powerlines-cancer-FAQ/part6
Last-modified: 1996/2/20
Version: 3.4.1
Maintainer: jmoulder@its.mcw.edu
Keywords: powerlines, magnetic fields, cancer, EMF, non-ionizing
  radiation, EMR, ELF, FAQ


Annotated Bibliography on Powerlines and Cancer (Part 1 of 3)


A) Recent Reviews of the Biological and Health Effects of Power-Frequency Field
s

A1) JG Davis et al: Health Effects of Low-Frequency Electric and Magnetic
Fields. Oak Ridge Associated Universities, 1992.
  "...there is no convincing evidence in the published literature to
support the contention that exposure to extremely low-frequency electric
and magnetic fields generated by sources such as household appliances,
video display terminals, and local power lines are demonstrable health
hazards."

A2) JA Dennis et al: Human Health and Exposure to Electromagnetic
Radiation (NRPB-R241), National Rad Protect Board, Chilton, 1993.
  "the bulk of the evidence points to there being no effects at levels to
which people are normally exposed".

A3) P Guenel & J Lellouch: [Synthesis of the literature on health effects
from very low frequency electric and magnetic fields], Nat Inst Health
Medical Res (INSERM), Paris, 1993.
  "laboratory studies have never shown any carcinogenic effect [but] the
epidemiological results presently available do not permit exclusion of a
role for magnetic fields in the incidence of leukemia, particularly in
children... The effect of magnetic fields on human health remains a
research problem.  It will only become a public health problem if definite
effects are confirmed."

A4) J Roucayrol: [Report on extremely low-frequency electromagnetic fields
and health]. Bull Acad Nat Med 177:1031-1040, 1993.
  "There is no conclusive evidence linking EMF to reproductive and
teratogenic effects, and/or that EMF has a role in the initiation,
promotion or progression of certain cancers, even though some data cannot
exclude this possibility... reported associations between EMF and certain
pathologies like leukemia and other childhood and adult cancers cannot be
supported by current epidemiological data."

A5) JE Moulder & KR Foster:  Biological effects of power-frequency fields
as they relate to carcinogenesis.  Proc Soc Exp Med Biol 209:309-324,
1995.
  This is a peer-reviewed article based on the FAQ sheet.  The review
discusses the biophysics of power-frequency electromagnetic fields as it
relates to biological effects, summarizes the current state of the cancer
epidemiology, and then concentrates on the laboratory studies which are
relevant to addressing the possibility that power-frequency fields are
carcinogenic.


B) Reviews of the Epidemiology of Exposure to Power-Frequency Fields

B1) M Coleman & V Beral: A review of epidemiological studies of the health
effects of living near or working with electrical generation and
transmission equipment. Int J Epidem 17:1-13, 1988.
  Review of both occupational and residential studies, including
meta-analysis showing a small excess incidence of leukemia in electrical
occupations.

B3) GB Hutchison: Cancer and exposure to electric power. Health Environ
Digest 6:1-4, 1992.
  Meta-analysis of residential exposure studies shows an excess incidence
of childhood brain cancer, but not of childhood leukemia or lymphoma.
Analysis also shows an excess of leukemia and brain cancer in electrical
occupations, but no significant excess of lymphoma or overall cancer.

B4) R Doll et al, Electromagnetic Fields and the Risk of Cancer, NRPB,
Chilton, 1992.
  A review of both ELF and RF frequencies that includes a meta-analysis of
the childhood cancer data.  For leukemia, the analysis shows an elevated
incidence for wirecodes, but not for proximity or measured fields.  For
brain cancer, the analysis shows an elevated incidence for wirecodes and
proximity, but not for measured fields.  For all childhood cancer the
analysis shows an elevated incidence for wirecodes and measured fields,
but not for proximity.

B5) A Ahlbom et al: Electromagnetic fields and childhood cancer. Lancet
343:1295-1296, 1993.
  Pooled analysis of the Scandinavian childhood cancer studies indicates
that if calculated historic power-line fields are used as a measure of
exposure, a small increase is seen in the incidence of leukemia, but no
statistically significant increase is seen in the incidence of CNS cancer,
lymphoma, or overall cancer.

B6) DA Savitz et al: Update on methodological issues in the epidemiology
of electromagnetic fields and cancer.  Epidem Rev 15:558-566, 1993.
  Review of the occupational and residential exposure studies, and a
consideration of methodological issues, particularly control selection and
exposure assessment issues.  Discussion of some flaws in the argument that
historical increases in electrical consumption should have caused increase
in the overall incidence of cancer if there were a true causal connection.

B7) EP Washburn et al: Residential proximity to electrical transmission
and distribution equipment and the risk of childhood leukemia, childhood
lymphoma, and childhood nervous system tumors: Systematic review,
evaluation, and meta-analysis. Cancer Causes Control 5:229-309, 1994.
  Meta-analysis of the childhood cancer - power line studies that reports
an elevation in leukemia (RR=1.6) and brain cancer (RR=1.9), but not
lymphoma.  Only proximity is used as the index of exposure.

B8) LI Kheifets et al: Occupational electric and magnetic field exposure
and brain cancer:  A meta-analysis. J Occup Environ Med 37:1327-1341,
1995.
  This meta-analysis finds a relative risk for brain cancer in electrical
occupations of 1.2.  RRs are elevated for studies done in the US, but not
for those done in the Nordic counties.  Electrical engineers have one of
the highest RRs, despite being a group that generally shows low
exposures.  The authors state that "because of the lack of exposure
information and a clear dose response pattern, it is not possible to
conclude that EMF is causally associated with the observed excess of brain
cancer"

B9) CW Heath: Electromagnetic field exposure and cancer:  A review of the
epidemiologic evidence. CA-A Cancer Journal for Clinicians 46:29-44, 1996.

  "The weakness and inconsistent nature of the epidemiologic data,
combined with the continuing dearth of coherent and reproducible findings
from experimental laboratory research, leave one uncertain and rather
doubtful that any real biologic link exists between EMF exposure and
carcinogenicity"


C) Epidemiology of Residential Exposure to Power-Frequency Fields

C1) N Wertheimer & E Leeper: Electrical wiring configurations and
childhood cancer. Am J Epidem 109:273-284, 1979.
  Case-control study of childhood leukemia and brain cancer using type of
power lines (wirecodes) as an index of exposure.  An excess incidence of
leukemia and brain cancer were reported.

C2) N Wertheimer & E Leeper: Adult cancer related to electrical wires near
the home. Int J Epidem 11:345-355, 1982.
  Case-control study of adult cancer.  An excess incidence was reported
for total cancer and brain cancer, but not for leukemia.

C3) JP Fulton et al: Electrical wiring configurations and childhood
leukemia in Rhode Island. Am J Epidem 111:292-296, 1980.
  Case-control study using wire-dose as an index of exposure.  No excess
of child leukemia was found.

C4) ME McDowall: Mortality of persons resident in the vicinity of
electrical transmission facilities. Br J Cancer 53:271-279, 1986.
  Standardized mortality ratio study of persons in the UK living within 50
m of a substation or 30 m of a transmission line.  No increase in overall
cancer, leukemia, or female breast cancer.  No dose-response relationship
between proximity to wires and cancer incidence.

C5) L Tomenius: 50-Hz electromagnetic environment and the incidence of
childhood tumors in Stockholm County. BEM 7:191-207, 1986.
  Case-control study of childhood cancer using proximity to electrical
equipment as indices of exposure.  Proximity to 200 kV lines was
associated with an excess of total cancer, but proximity to other types of
electrical equipment carried no excess risk.  No excess incidence of
leukemia or brain cancer was reported for any index of exposure.

C6) DA Savitz et al: Case-control study of childhood cancer and exposure
to 60-Hz magnetic fields. Am J Epidem 128:21-38, 1988.
  Case-control study of childhood leukemia and brain cancer, using
measurements and wirecodes as indices of exposure.  An excess incidence of
leukemia was found for high-current-configuration wirecodes, but not for
measured fields.  An excess incidence of brain cancer was found for
high-current-configuration wirecodes, but not for measured fields.

C7) RK Severson et al: Acute nonlymphocytic leukemia and residential
exposure to power-frequency magnetic fields. Am J Epidem 128:10-20, 1988.
  Case-control study of childhood leukemia in Washington state, using
measurements and wirecodes as indices of exposure.  No excess leukemia for
wirecodes or measured fields.

C8) S Preston-Martin et al: Myelogenous leukemia and electric blanket use.
Bioelectromag 9:207-213, 1988.
  Electric blanket use increases electric field exposure by 35 (20-100)%
and magnetic field exposure by 80 (40-300)%.  A case-control study showed
no excess of either acute or chronic myeloid leukemia.

C9) MP Coleman et al: Leukemia and residence near electricity transmission
equipment: a case-control study. Br J Cancer 60:793-798, 1989.
  Case-control study of childhood and adult leukemia, using proximity to
power lines and transformers as an exposure index.  No excess of leukemia
was found.

C10) A Myers et al: Childhood cancer and overhead powerlines: a
case-control study. Br J Cancer 62:1008-1014, 1990.
  Case-control study of childhood and adult leukemia, using proximity to
power lines as an exposure index.  No excess of leukemia, solid tumors or
all cancer was found.

C11)  DA Savitz et al: Magnetic field exposure from electric appliances
and childhood cancer. Amer J Epidemiol 131:763-773, 1990.
  A case-control study of cancer and appliance (particularly electric
blanket) use.  For prenatal use of electric blankets, an excess incidence
of brain cancer was found; but no significant increase in leukemia or
overall cancer was seen.  No increased cancer incidence was found for
postnatal use of electric blankets or for exposure to other electric
appliances.

C12) SJ London et al: Exposure to residential electric and magnetic fields
and risk of childhood leukemia. Am J Epidem 134:923-937, 1991.
  Case-control study of childhood leukemia in Los Angeles, using
measurements and wirecodes as indices of exposure.  An excess incidence of
leukemia was found for high current configuration wirecodes, but no excess
risk was found for measured fields.

C13) JHAM Youngson et al: A case/control study of adult haematological
malignancies in relation to overhead powerlines. Br J Cancer 63:977-985,
1991.
  Case-control study of adult leukemia and lymphoma using proximity to
power lines and estimated fields as measures of exposure.  No excess
incidence of cancer found.

C15) JM Peters et al: Exposure to residential electric and magnetic fields
and risk of childhood leukemia. Rad Res 133:131-132, 1993.
  Discussion of the implications of finding a correlation of cancer with
wire-codes, but not with measured fields.  There could be a true
association masked by a methodological bias in the measurement technique.
There could be a true association, but average and/or spot fields might
not be the correct exposure metric.  There might be selection bias in the
control group or a confounder.

C16) PJ Verkasalo et al: Risk of cancer in Finnish children living close
to power lines. BMJ 307:895-899, 1993.
  A cohort study of cancer in children living within 500 m of high-voltage
lines, with calculated retrospective fields were used to define exposure.
Calculated fields are based on 110+ kV lines, and ignore other sources.
Both average fields and cumulative fields were used as exposure metrics.
The incidence of childhood cancer was not elevated for average exposure
above 0.20 microT, or cumulative exposure above 0.50 microT-yrs.  An
excess of brain cancer was found in boys, due to one exposed boy who
developed three independent brain tumors.  No excess incidence was found
for brain tumors in girls or for leukemia, lymphomas or other cancers in
either sex.

C17) JH Olsen et al: Residence near high voltage facilities and risk of
cancer in children. BMJ 307:891-895, 1993.
  A case-control study of childhood leukemia, brain tumors and lymphomas.
Exposure was assessed on the basis of calculated fields over the period
from conception to diagnosis.  No overall increase in cancer was found
when 0.25 microT was used as the cut-off point to define exposure (as
specified in the study design).  After the data were analyzed, it was
found that the overall incidence of childhood cancer was elevated if 0.40
microT was used as the cut-off point.  No significant increase was found
for leukemia or brain cancer incidence.  An increase in lymphoma was found
for the 0.10 microT cut-off point but not for higher cut-offs.

C18) GH Schreiber et al: Cancer mortality and residence near electricity
transmission equipment: A retrospective cohort study. Int J Epidem
22:9-15, 1993.
  A cohort study of people in an urban area in the Netherlands.  People
were considered exposed if they lived within 100 meters of transmission
equipment (150 kV lines plus a substation).  Fields in the exposed group
were 0.1-1.1 microT, fields in the unexposed group were 0.02-0.15 microT.
The total cancer incidence in the exposed group was less than that in the
general Dutch population.  No cases of leukemia or brain cancer were seen
in the exposed group.

C19) M Feychting & A Ahlbom: Magnetic fields and cancer in children
residing near Swedish high-voltage Power Lines. Am J Epidem 7:467-481,
1993.
  Case-control study of children who lived within 300 m of high-voltage
power lines.  Exposure assessed by measurements, calculated retrospective
assessments, and distance from lines.  No overall increase in cancer was
found for any measure of exposure.  An increase in leukemia (but not brain
or other cancers) was found in children in one-family homes for fields
calculated to have been 0.2 microT or above at the time of cancer
diagnosis, and for residence within 50 m of the power line.  No increase
in cancer was found for measured fields.

C20) TL Jones et al: Selection bias from differential residential mobility
as an explanation for associations of wirecodes with childhood cancer. J
Clin Epidem 46:545-548, 1993.
  The type of "high current configuration" distribution lines associated
with cancer in the Wertheimer [C1], Savitz [C6] and London [C12] studies
were more common in residential areas that were older, poorer, and which
contained more rental properties.  This could lead to a false association
of high current configurations with disease.

C21) M Feychting & A Ahlbom: Magnetic fields, leukemia, and central
nervous system tumors in Swedish adults residing near high-voltage power
lines, Epidemiology 5:501-509, (1994).
  Case-control study of adults who lived within 300 m of high-voltage
power lines.  No increased leukemia or brain cancer was found for adults
when exposure was based on measured fields, distance from power lines or
retrospective field calculations.

C22) RH Lovely et al: Adult leukemia risk and personal appliance use: a
preliminary study. Amer J Epidemiol 140:510-517, 1994.
  A case-control study of adult acute nonlymphocytic leukemia and use of
electric razors, hair dryers, and  massage units.  Use of one or more of
these appliances was not associated with increased leukemia. There was an
excess of leukemia in users of massage units, and a decrease in leukemia
in users of hair dryers.

C23) JE Vena et al: Risk of premenopausal breast cancer and use of
electric blankets. Amer J Epidemiol 140:974-979, 1994.
  Case-control study of breast cancer in premenopausal women who used
electric blankets.  No increased incidence of breast cancer was seen in
electric blanket users.

C24) JD Sahl: Viral contacts confound studies of childhood leukemia and
high-voltage transmission lines. Cancer Causes Control 5:279-283, 1994.
  "This paper elaborates on  the hypothesis that residential proximity to
electric utility transmission systems is a surrogate for viral contacts...
The assumption made here is that a significant component of childhood
leukemia has an infectious etiology.  Increased viral contacts can result
from residential mobility..."

C25) JG Gurney et al: Childhood cancer occurrence in relation to power
line configurations: A study of potential selection bias in case-control
studies. Epidemiology 6:31-35, 1995.
  The type of electrical wiring ("wirecode") was found to be correlated
with income, with high current configurations being more common in
families with lower incomes.  As low income families are generally less
likely to agree to participate as controls, this would introduce a bias in
relative risk estimates from case-control of up to 1.2

C26) M Feychting & A Ahlbom: Re "Magnetic fields and cancer in children
residing near Swedish high-voltage power lines:"  Authors' reply (letter).
Amer J Epidemiol 141:378-379, 1995.
  In response to a letter questioning the statistical significance of
their results [C19,C21]: "we have not referred to statistical significance
anywhere in our paper, so this [the issue of statistical significance]
would only be a problem for those readers who try to interpret the
location of our confidence boundaries in terms of presence or absence of
statistical significance... It can be questioned whether the usual
probability models are applicable to observational epidemiologic data
under any circumstances..."

C27) JD Bowman, DC Thomas, et al: Hypothesis: The risk of childhood
leukemia is related to combinations of power-frequency and static magnetic
fields. Bioelectromag 16:48-59, 1995.
  The authors hypothesize that the risk of childhood leukemia is related
to specific combinations of static (geomagnetic) and ELF fields.
Childhood leukemia data from the Los Angeles childhood were analyzed on
the basis of these combinations.  No correlation between measured static
or AC fields were found, and point estimates for the selected combinations
did not show significant associations.  The authors do claim a positive
trend for the combined AC/static data.  A significant association is
reported for wire codes.

C28) JG Gurney et al: Childhood brain tumor occurrence in relation to
residential power line configurations, electric heating sources, and
electric appliance use. Amer J Epidemiol 143:120-128, 1996.
  A case-control of childhood brain cancer which finds no association of
brain cancer with residence near powerlines power lines (based on
wirecodes).  The study also found no association of brain cancer incidence
with childhood or fetal exposure to fields from electric blankets,
electric water beds, electric space heating or any other electrical
appliances.

C29) S Preston-Martin et al: Los Angeles study of residential magnetic
fields and childhood brain tumors. Amer J Epidemiol 143:105-119, 1996.
  Case-control study of childhood brain cancer and residential exposure to
power-line fields.  No association was found between brain cancer risk and
measured fields, wire codes or appliance use.



D) Epidemiology of Occupational Exposure to Power-Frequency Fields

D1) S Milham: Mortality from leukemia in workers exposed to electrical and
magnetic fields (letter). NEJM 307:249, 1982.
  Proportional mortality study of electrical occupations showing an excess
incidence of leukemia.

D2) WE Wright et al: Leukaemia in workers exposed to electrical and
magnetic fields (letter). Lancet 8308 (Vol II):1160-1161, 1982.
  Proportional incidence study of electrical occupations showing an excess
of acute, but not chronic leukemia.

D3) S Bastuji-Garin et al: Acute leukaemia in workers exposed to
electromagnetic fields.  Eur J Cancer 26:1119-1120, 1990.
   Case-control study of leukemia in electrical occupations.  Non-welding
jobs showed an increase in acute leukemia, but welding (a high exposure
occupation) showed no significant increase.  Increases in acute leukemia
incidence were also shown for benzene and herbicide exposure.

D4) T Tynes & A Anderson: Electromagnetic fields and male breast cancer.
Lancet 336:1596, 1990.
  Norwegian electrical workers were compared to census data, and an
elevated incidence of male breast cancer was found.

D5) PA Demers et al: Occupational exposure to electromagnetic fields and
breast cancer in men.  Amer J Epidemiol 134:340-347, 1991.
  Case-control study of occupations with self-reported exposure to
power-frequency fields.  An excess incidence of male breast cancer was
found.  The elevated incidence was highest among electricians, telephone
linemen and electric power workers, those exposed young, and those exposed
many years prior to diagnosis.

D6) GM Matanoski et al: Electromagnetic field exposure and male breast
cancer (letter).  Lancet 337:737, 1991.
  Retrospective cohort study of male telephone company workers in New
York, showing a nonsignificant excess incidence of breast cancer.

D7) DP Loomis: Cancer of breast among mean in electrical occupations
(letter).  Lancet 339:1482-1483, 1992.
  Proportional mortality study found a nonsignificant excess incidence of
breast cancer.  The greatest excess was for telephone company workers.

D11) GM Matanoski et al: Leukemia in telephone linemen. Am J Epidem
137:609-619, 1993.
  Case-control study of telephone company workers, with exposure defined
by job titles plus some retrospective measurements.  The incidence of
leukemia was not significantly increased in workers with higher exposures
to magnetic fields.  The authors interpret their data as showing higher
risk with increasing exposure, but the trend is not statistically
significant.

D12) B Floderus et al: Occupational exposure to electromagnetic fields in
relation to leukemia and brain tumors: A case-control study in Sweden.
Cancer Causes Control 4:463-476, 1993.
  A case-control study of leukemia and brain tumors in
occupationally-exposed men.  Exposure calculations were based on the job
held longest during the 10-year period prior to diagnosis.  Measurements
were taken using a person whose job was most similar to that of the person
in the study. An elevation in incidence was found for leukemia, but not
for brain cancer.

D13) JD Sahl et al: Cohort and nested case-control studies of
hematopoietic cancers and brain cancer among electric utility workers.
Epidemiology 4:104-114, 1993.
  Cohort plus nested case-control of electrical utility workers in
California.  Dosimetry was done on selected workers.  Electricians had the
highest exposures, with a time-weighted mean of 3 microT.  Neither cohort
nor case-control analysis showed a significant excess of total cancer,
leukemia, brain cancer or lymphoma.  No significant dose-response trend
was found for any cancers.

D14) P Guenel et al: Incidence of cancer in persons with occupational
exposure to electromagnetic fields in Denmark. Br J Indust Med 50:758-764,
1993.
  A case-control study based on all cancer.  Each occupation-industry
combination was coded on the basis of estimated 50-Hz magnetic field
exposure.  No significant increases were seen for breast cancer, malignant
lymphomas or brain tumors.  Leukemia incidence was elevated among men in
the highest exposure category; women in similar exposure categories showed
no increase in leukemia.

D15) G Theriault et al: Cancer risks associated with occupational exposure
to magnetic fields among utility workers in Ontario and Quebec, Canada and
France: 1970-1989. Amer J Epidem 139:550-572, 1994.
  Case-control study with exposure to magnetic fields estimated from
measurements of current exposure of workers performing similar tasks.  No
association with magnetic fields was observed for overall cancer or for
any of the other 29 cancer types studied, including melanoma, overall
leukemia, brain cancer or male breast cancer.  Workers with cumulative
exposure above 3.1 microT-yrs had an excess incidence of acute
non-lymphocytic and acute myeloid leukemia, but there were no clear
dose-response trends.

D16) T Tynes et al: Leukemia and brain tumors in Norwegian railway
workers, a nested case-control study.  Amer J Epidemiol 139:645-653, 1994.
  Case-control study of workers on electric and non-electric railroads.
Analysis showed no significant excess of leukemia or brain cancer, and no
significant trend for either magnetic or electric fields.  On the
electrified railroads fields averaged 20 microT, and 0.8 kV/m.

D17)  PF Rosenbaum et al: Occupational exposures associated with male
breast cancer.  Amer J Epidemiol 139:30-36, 1994.
  Case-control study of male breast cancer from the New York tumor
registry.  Elevated breast cancer incidence was associated with
occupational exposure to heat, but not with exposure to power-frequency
fields.

D18)  DP Loomis et al: Breast cancer mortality among female electrical
workers in the United States.  J Natl Cancer Inst 86:921-925, 1994.
  Death certificate based study of female electrical workers.  An elevated
incidence of breast cancer was found in occupations with presumed exposure
to power-frequency fields (largely "male-dominated" occupations), but not
in occupations with "potential exposure" (largely "female-dominated"
occupations).  The authors note that the excess breast cancer may only
indicate that women working in male-dominated jobs have a reproductive
history which increases their risk of breast cancer.

D20) B Armstrong et al: Association between exposure to pulsed
electromagnetic fields and cancer in electric utility workers in Quebec,
Canada, and France. Amer J Epidemiol 140:805-820, 1994.
  Using the database used by Theriault et al [D15], the authors found that
workers exposed to short-duration pulsed EM fields (PEMFs) had significant
increases in lung cancer.  The association of lung cancer with PEMF is
reported to be strong, and to have a significant dose-response
relationship.  No relationship was found between PEMF exposure and other
types of cancer.  The dosimetry for this study is based on a dosimeter
that may not actually measure "PEMF" [D21].

D21)  JL Guttman et al: Frequency response characterization of the
positron electromagnetic dosimeter pulsed electromagnetic
field/high-frequency transient channel; PS Maruvada & P Jutras: Study of
the response of the HFT channel of the positron dosimeter.  Ann Rev Res
Biol Effects Elec Magn Fields, Albuquerque, 1994.
  The HFT channel of the Positron dosimeter used by Armstrong et al [D20]
to assess "PEMF" exposure was designed to respond to signals having an
electric field component greater than 200 V/m at 2-20 MHz.  However, in
the utility environment the HFT channel responds poorly to switching
transients, but is exquisitely sensitive to radio transmissions near 150
MHz, a band that is now (but only recently) heavily used for portable
radio communication in the utility industry.

D22) T Tynes et al: Incidence of cancer among workers in Norwegian
hydroelectric power companies.  Scand J Work Environ Health 20:339-344,
1994.
  A cohort study of leukemia, brain cancer, lymphoma, other cancer and
overall cancer.  Exposure was estimated from individual work histories
plus data from recent workplace measurements.  Exposures ranged from 1-8
microT, with maximums of 100-200 microT.  The incidence of leukemia,
lymphoma, brain cancer and overall cancer were not elevated.   No type of
cancer was significantly elevated or decreased.  If only workers with
cumulative exposures of greater than 35 microT-yrs are assessed, then the
incidence of malignant melanoma is increased.  Confounders studied include
spark discharges, PCB contamination, asbestos.

D23) SJ London et al: Exposure to magnetic fields among electrical workers
in relationship to leukemia risk in Los Angeles County. Amer J Indust Med
26:47-60, 1994.
  Case-control study of electrical workers.  All individual electrical
occupations had higher exposures than non-electrical occupations, except
for electrical engineers, whose exposures were lower.  For all leukemia in
all occupations, there was an increase in leukemia incidence.  For
individual occupations only electrical engineers (who do not have elevated
exposures) and telephone line workers and cable splices have an elevated
incidence of leukemia.  There was a weakly-positive trend linking exposure
with leukemia incidence.

D24) B Floderus et al: Incidence of selected cancers in Swedish railway
workers, 1961-1979. Cancer Causes Control 5:189-194, 1994.
  Reanalysis of cancer incidence data for electrical railroad workers
found a non-significant increase in chronic lymphocytic leukemia, acute
myeloid leukemia and lymphoma in the first decade of data, but not in
later data.  Some evidence for an increased incidence breast and pituitary
cancer was seen in the first decade of data.

D25) DA Savitz & DP Loomis: Magnetic field exposure in relation to
leukemia and brain cancer mortality among utility workers. Amer J
Epidemiol 141:123-134, 1995.
  A case-control study of leukemia, brain cancer and overall cancer in
electric utility workers.  Exposure was estimated from individual work
histories plus data from recent workplace measurements.  Total mortality
and overall cancer mortality rose slightly with estimated exposure,
reaching RRs of 1.2 in the group with the highest estimated exposure.
Leukemia mortality was not linked with estimated exposure.  Brain cancer
mortality was elevated only in the group with the highest exposure.

D26) KP Cantor et al: Breast cancer mortality among female electrical
workers in the United States. J Natl Cancer Inst 87:227-118, 1995.
  Using the mortality records used by Loomis et al [D18] the authors found
no association of breast cancer with occupational exposure to either
radiation frequency or power-frequency fields.

Copyright (C) by John Moulder
end: powerlines-cancer-FAQ/part6

        -------------------------------------------------------


                    Powerlines & Cancer FAQs 7/8: Biblio 2
                                       

Archive-name: powerlines-cancer-FAQ/part7
Last-modified: 1996/2/20
Version: 3.4.1
Maintainer: jmoulder@its.mcw.edu


Annotated Bibliography on Powerlines and Cancer (Part 2 of 3)


E) Human Studies Related to Power-Frequency Exposure and Cancer

E1) AB Hill: The environment and disease: Association or causation? Proc
Royal Soc Med 58:295-300, 1965.
  Concise statement of the methods use to assess causation in
epidemiologic studies.

E2) M Bauchinger et al: Analysis of structural chromosome changes and SCE
after occupational long-term exposure to electric and magnetic fields from
380 kV-systems. Rad Env Biophys 19:235-238, 1981.
  Lymphocytes from occupationally exposed 50 Hz switchyard workers showed
no increase in the frequencies of chromosome aberrations.

E3) I Nordenson et al: Clastogenic effects in human lymphocytes of power
frequency electric fields:  In vivo and in vitro studies. Radiat Environ
Biophys 23:191-201, 1984.
  Authors report increased chromosome and chromatid breaks in both smoking
and non-smoking switchyard workers.  All cases except one had acute
exposure to high electrical fields and spark discharges immediately prior
to donation.  In a separate study, excess chromosome breaks were found
human lymphocytes were exposed to spark discharges in cell culture.

E4)  W Den Otter: Tumor cells do not arise frequently.  Cancer Immunol
Immunother 19:159-162, 1985.
  A hypothesis which greatly influenced thinking in tumor immunology in
the 70's was that tumor cells frequently and that the majority of these
potential tumors were killed by immune surveillance mechanisms.  Newer
studies lead to the conclusion that an efficient natural immunity that
could kill many tumor cells is lacking, that few tumors arise when normal
immune surveillance and/or natural resistance are absent.

E5) I Nordenson et al: Chromosomal effects in lymphocytes of 400
kV-substation workers.  Rad Env Biophys 27:39-47, 1988.
  Lymphocytes from switchyard workers showed an increase in the frequency
of chromosome aberrations.  Spark discharges were closely associated with
the increased frequency of chromosome aberrations.

E6) DA Savitz & L Feingold: Association of childhood leukemia with
residential traffic density. Scan J Work Environ Health 15:360-363, 1989.
  Analysis of the authors power line study [C6] using traffic density as
the exposure.  Significant excess risk of leukemia and total cancer
associated with high traffic density.

E7) I Penn: Why do immunosuppressed patients develop cancer? Crit Rev
Oncogen 1:27-52, 1989.
  Review of the relationship between cancer development and immune suppression

E8) GR Krueger: Abnormal variation of the immune system as related to
cancer. Cancer Growth Prog 4:139-161, 1989.
  Review of the relationship between cancer development and immune suppression.

E9) JD Jackson: Are the stray 60-Hz electromagnetic fields associated with
the distribution and use of electric power a significant cause of cancer?
Proc Nat Acad Sci USA 89:3508-3510, 1992.
  Argument that lack of correlation between electric power use and
leukemia rates over time argues against a causal relationship.

E10) T Sinks et al: Mortality among workers exposed to polychlorinated
biphenyls.  Amer J Epidemiol 136:389-398, 1992.
   A study of workers exposed to PCBs found no increase in overall cancer,
brain cancer, leukemia or lymphoma, but significant increases for skin
cancer and heart disease. "On the basis of evidence from animal studies,
polychlorinated biphenyls (PCBs) are considered potentially carcinogenic
to humans.  However, the results of studies in human populations exposed
to PCBs has been inconsistent".

E11) J Valjus et al: Analysis of chromosomal aberrations, SCEs and
micronuclei among power linesmen with long-term exposure to 50-Hz
electromagnetic fields. Radiat Environ Biophys 32:325-336, 1993.
  Chromosomal aberrations, SCEs and micronuclei were assessed among 27
power linesmen (nonsmokers) with long-term exposure to 50-Hz fields; the
control group were matched telephone linesmen.  No exposure related
differences in SCEs, replication indices or micronuclei were observed, but
an exposure-related increase in chromatid breaks was found among previous
smokers.

E12) K Skyberg, I L Hansteen, et al: Chromosome aberrations in lymphocytes
of high-voltage laboratory cable splicers exposed to electromagnetic
fields. Scand J Work Environ Health 19:29-34, 1993.
  The authors report increased rate of chromosome breaks in exposed
workers (high voltage laboratory cable splicers) who were also smokers (no
increase in non smokers) but no increase in SCE or ploidy.   The authors
state that they are "unable to exclude spark discharges as a causal
factor".  This "positive" finding may be a multiple testing artifact.

E13) G Ciccone, D Miarbelli, et al: Myeloid leukemia and myelodisplastic
syndromes:  Chemical exposure, histologic subtype and cytogenetics in a
case-control study. Cancer Genet Cytogenet 68:135-139, 1993
  Case-control study showed excess incidence of myeloid leukemias among
welders, electricians, drivers, farmers and textile workers.  An increase
in chromosome aberrations were not associated with chemical exposure, but
a nonsignificant association was noted for power-frequency fields

E14) AM Khalil et al: Cytogenetic changes in human lymphocytes from
workers occupationally exposed to high-voltage electromagnetic fields.
Electro Magnetobio 12:17-26, 1993.
  Chromosome aberrations and SCEs were studies in 15 substation workers.
The author claims that number of aberrant cells was increased and the
mitotic index decreased in the exposed group, with no effect on SCE rate,
and no effect of smoking.  No correlation was found between effects and
the duration of exposure.

E15) C Graham et al: Nocturnal melatonin levels in men exposed to magnetic
fields: A replication study. Ann Rev Res Biol Effects Elect Magnet Fields,
Albuquerque, pp. 51-52 (1994).
  In a previous study men were exposed at night to 1 or 20 microT
intermittent 60-Hz fields.  No overall effects on melatonin were observed,
but subgroup analysis indicated that men with low pre-existing melatonin
levels did show field related suppression.  In a replicate study at 20
microT, no effects were observed overall or in any subgroup.

E16) E Sobel et al:  Occupations with exposure to electromagnetic fields:
a possible risk factor in Alzheimer's disease.  Amer J Epidem 142:515-524,
1995.
  A case-control study reporting excess Alzheimer's disease in
dressmakers, seamstresses and tailors.  These groups are exposed to
power-frequency fields from sewing machines.  No excess Alzheimer's
disease was reported in other "electrical occupations".


F) Biophysics and Dosimetry of Power-Frequency Fields

F1) J Sandweiss: On the cyclotron resonance model of ion transport. BEM
11:203-205, 1990.
  Cyclotron resonance theory inconsistent with basic physical principles
because radius of ion rotation would be about 50 m, and because collisions
would occur much too often for resonance to be achieved.

F2) JC Weaver & RD Astumian: The response of living cells to very weak
electric fields: The thermal noise limit. Science 247:459-462, 1990.
  A model suggesting how fields could be detected well beyond the thermal
noise limit.  "...smaller fields (microV/cm) can be detected if there is a
response in only a narrow band of frequencies or if signal averaging
occurs through field-induced variation in the catalytic activity of
membrane-associated enzymes...".

F3) RK Adair: Constraints on biological effects of weak
extremely-low-frequency electromagnetic fields, Phys Rev A 43:1039-1048,
1991.
  "Because of the high electrical conductivity of tissues, the coupling of
external electric fields in air to tissues of the body is such that the
effects of the internal fields on cells is smaller than thermal noise..."
To get an effect you need a resonance mechanism, and "such resonances are
shown to be incompatible with cell characteristics... hence, any
biological effects of weak ELF fields [less than 50 microT] on the
cellular level must be found outside of the scope of conventional
physics".

F4) JL Kirschvink et al: Magnetite in human tissues: A mechanism for the
biological effects of weak ELF magnetic fields.  Bioelectromag Suppl
1:101-113, 1992.
  A calculation that magnetite-containing bodies in cells could response
to ELF fields, and could cause changes in ion channels if the channels
were mechanically controlled by these "magnetosomes".  The model requires
power-frequency field fields on the order of 60 microT to achieve
detectable effects.

F5) RK Adair: Criticism of Lednev's mechanism for the influence of weak
magnetic fields on biological systems. Bioelectromag 13:231-235, 1992.
  A review of the multiple biological and biophysical problem with
Lednev's cyclotron resonance model.  "I show that for four independent
reasons, no such mechanism can operate".

F6) T Dovan et al: Repeatability of measurements of residential magnetic
fields and wirecodes. BEM 14:145-159, 1993.
  Repeat measurement of homes that had been included in Savitz study [C6]
found that neither measured fields nor wirecodes had changed significantly
over a five-year period.

F7) WT Kaune: Assessing human exposure to power-frequency electric and
magnetic fields.  Environ Res 101 (Suppl 4):121-133, 1993.
  Good review of electric and magnetic field levels in occupational and
residential settings, and of current issues in dosimetry.

F8) S Galt et al: Theoretical study of the resonant behavior of an ion
confined to a potential well in a combination of AC and DC magnetic
fields. Bioelectromag 14:299-314, 1993.
  Theoretical considerations indicates that "cyclotron resonance" will not
occur except at very high (greater than 100 milliT) fields strengths.

F9) M Misakian et al: A protocol for spot measurements of residential
power frequency magnetic fields. IEEE Trans Power Delivery 8:1386-1393,
1993.
  A simple protocol for measuring power frequency magnetic fields in
residences, with a discussion of the terminology and measurement examples

F10) WT Kaune et al: Development of a protocol for assessing
time-weighted-average exposures of young children to power-frequency
magnetic fields.  Bioelectromag 15:33-51, 1994.
  Mean residential exposures were 0.105 microT, with a range from 0.02 -
0.7 microT.  Wire codes were correlated with 24-hr personal exposure, but
the wire-codes accounted for only 18% of the variability in the measured
fields.  No characteristics of the magnetic fields were found to be
strongly correlated with wire-codes.

F11) JD Sahl et al: Exposure to 60 Hz magnetic fields in the electric
utility work environment.  Bioelectromag 15:21-32, 1994.
  Average exposures ranged from less than 0.20 microT in clerical staff to
greater than 1.5 microT in electricians and substation operators.  Typical
maximum daily exposures were 4-7 microT, but exposures above 15 microT
were recorded on rare occasions.

F12) RK Adair: Constraints of thermal noise on the effects of weak 60-Hz
magnetic fields acting on biological magnetite.  Proc Nat Acad Sci USA
91:2925-2929, 1994.
  "Previous calculations of limits imposed by thermal noise on the effects
of weak 60-Hz magnetic fields on biological magnetite are generalized and
extended... The results indicate that the energies transmitted to the
magnetite elements by fields less than 5 microT... will be much less than
thermal noise energies... However, the arguments presented here do not
preclude effects from larger 60-Hz fields"

F13) C Polk: Effects of extremely-low-frequency magnetic fields on
biological magnetite. Bioelectromag 15:261-270, 1994.
  The author disputes Adair's analysis [F12] of the biophysics of the
interaction of ELF fields with biological magnetite.  Polk claims that
Adair's conclusions are strongly dependent on assumptions about
cytoplasmic viscosity.  The author argues that the model would allow
interactions down to fields of about 2 microT.

F14) JC Scaiano et al: Application of the radical pair mechanism to free
radicals in organized systems: Can the effects of 60 Hz be predicted from
studies under static fields? Bioelectromag 15:549-554, 1994.
  "The influence of 60-Hz magnetic fields on free radical reactions can be
quantitatively predicted from... the effect of static fields...  A
corollary of our observations is the fact that no [magnetic field] effect
of free radical origin would be anticipated for oscillating fields of
strength significantly below that of the Earth".

F15) Testing and evaluation of magnetic field meters.  Electrical Power
Research Center, Ames, Iowa, 1994.
  Tests and evaluations of 12 magnetic field meters that are
representative of what is currently available plus basic information on 20
additional model.  In addition to the usual performance tests, each meter
is rated for its use by the expect, the non-expert and the lay-person.

F16) DA Savitz et al: Correlations among indices of electric and magnetic
field exposure in electric utility workers. Bioelectromag 15:193-204,
1994.
  Detailed dosimetry was conducted on exposures of electrical workers.
Magnetic and electrical field exposures were only weakly correlated.
Average measurements were 55 V/m and 0.9 microT; geometric mean
measurements were 7 V/m and 0.3 microT; the 90th percentiles were 144 V/m
and 1.9 microT.


G) Laboratory Studies of Power-Frequency Fields and Cancer

G1) MM Cohen et al: Effect of low-level, 60-Hz electromagnetic fields on
human lymphoid cells: I. Mitotic rate and chromosome breakage in human
peripheral lymphocytes. BEM 7:415-423, 1986.
  100 & 200 microT fields had no effect on chromosome abnormalities or
mitotic index of human lymphocytes.  Also no effect for electric field or
combined electric and magnetic fields.

G2) MM Cohen et al: The effect of low-level 60-Hz electromagnetic fields
on human lymphoid cells. II: Sister-chromatid exchanges in peripheral
lymphocytes and lymphoblastoid cell lines. Mut Res 172:177-184, 1986.
  100 & 200 microT fields had no effect on rates of SCEs in human
lymphocytes.  Also no effect for electric field or combined electric and
magnetic fields.

G3) J Juutilainen & A Liimatainen: Mutation frequency in Salmonella
exposed to weak 100-Hz magnetic fields. Hereditas 104:145-147, 1986.
  0.125-125 microT 100 Hz fields were not mutagenic in the Ames test, and
did not increase the mutagenicity of known mutagens in the Ames test.

G4) RD Benz et al, Mutagenicity and toxicity of 60 Hz magnetic and
electric fields, New York State Powerlines Project, New York, 1987.
  Mice were exposed over multiple generations to a 60 Hz fields of 1,000
microT plus 50 kV/m or 300 microT plus 15 kV/m.  No effect were seen on
dominant lethal mutations, fertility or SCE rates.

G5) K Takahashi et al: Influence of pulsing electromagnetic field on the
frequency of sister-chromatid exchanges in cultured mammalian cells.
Experientia 43:331-332, 1987.
  Mammalian cells were exposed to 100 Hz pulsed, fields at 180-2,500
microT for 24 hours.  No effect the rate of SCEs was observed.

G6) JA Reese et al: Exposure of mammalian cells to 60-Hz magnetic or
electric fields: Analysis for DNA single-strand breaks. BEM 9:237-247,
1988.
  100 & 200 microT 60-Hz fields had no effect on single-strand breaks.
Also no effect with electric field or combined electric and magnetic
fields.

G7) RAE Thomson et al: Influence of 60-Hertz magnetic fields on leukemia.
BEM 9:149-158, 1988.
  1.4, 200, 500 microT 60-Hz fields had no effect on leukemia progression
in mice.

G8) M Rosenthal & G Obe: Effects of 50-Hertz EM fields on proliferation
and on chromosomal aberrations in human peripheral lymphocytes untreated
and pretreated with chemical mutagens. Mutat Res 210:329-335, 1989.
  A 5,000 microT 50-Hz field had no effects on chromosome or chromatid
breaks or exchanges, and no effects on SCE rate.  Some increase in SCE
rates were seen for cells pretreated with other mutagens. Enhanced
progression though the cell cycle was seen.

G9) A Cossarizza et al: DNA repair after gamma-irradiation in lymphocytes
exposed to low-frequency pulsed electromagnetic fields. Radiat Res
118:161-168, 1989.
  A 2,500 microT pulsed field (50 Hz) had no effect on repair of
radiation-induced DNA damage in human lymphocytes.

G10) ME Frazier et al: Exposure of mammalian cells to 60-Hz magnetic or
electric fields: analysis of DNA repair of induced, single-strand breaks.
BEM 11:229-234, 1990.
  A 1,000 microT 60-Hz fields had no effect on repair of radiation-induced
DNA damage in human lymphocytes.  Also no effect for electric field or
combined electric and magnetic fields.

G11) JRN McLean et al: Cancer promotion in a mouse-skin model by a 60-Hz
magnetic field: II. Tumor development and immune response. BEM 12:273-287,
1991.
  A 20,000 microT 60-Hz fields did not promote or co-promote (with TPA)
cancers in DMBA-induced skin tumor model.  Also no effect on progression
of skin tumors, and no effect on NK cells or spleen size.

G12) GK Livingston et al: Reproductive integrity of mammalian cells
exposed to power-frequency EM fields. Environ Molec Mutat 17:49-58, 1991.
  A 220 microT 60-Hz field had no effect on SCEs, growth rates, cell cycle
kinetics, or micronucleus formation rates in human lymphocytes or CHO
cells.  No effects were seen for electric fields.

G13) AM Khalil & W Qassem: Cytogenetic effects of pulsing electromagnetic
field on human lymphocytes in vitro: chromosome aberrations,
sister-chromatid exchanges and cell kinetics. Mut Res 247:141-146, 1991.
  A 1,050 microT field pulsed at 50 Hz caused chromosome abnormalities,
and a decrease in the mitotic index in human lymphocytes.

G14) A Bellossi: Effect of pulsed magnetic fields on leukemia-prone AKR
mice. No effect on mortality through five generations. Leuk Res
15:899-902, 1991.
  Leukemia-prone mice were exposed to a 6,000 microT pulsed field at 12
and 460 Hz pulsed fields over five generations, with no effect on leukemia
rates.

G15) E Saalman et al: Lack of c-mitotic effects in V79 Chinese hamster
cells exposed to 50 Hz magnetic fields. Bioelectrochem Bioenerg
26:335-338, 1991.
  Mammalian cells were exposed to a 50-Hz field at 30 microT for 1-85
min.  No increase in the number of abnormal mitoses were observed.

G16) DS Beniashvili et al: Low-frequency electromagnetic radiation
enhances the induction of rat mammary tumors by nitrosomethyl urea.
Cancer Let 61:75-79, 1991.
  A preliminary report of a study of the effects of 20 microT 50-Hz or
static fields (0.5 or 3 hrs/day for 2 years) on chemically-induced mouse
mammary tumors.   An increase in number of tumors was reported for 3 hr
exposures to a 50 Hz field alone (genotoxicity) and for 60-Hz plus NMU
(promotion), but not for 0.5 hr exposures.  No genotoxic effects were
reported for DC fields alone, but promotion was reported for 3 hr
exposures to the DC field.  The study has incomplete information about
exposure conditions and experimental design, and the control animals
appear to have been treated differently than the exposed animals.

G17) AM Khalil & W Qassem: Cytogenetic effects of pulsing electromagnetic
field on human lymphocytes in vitro:  chromosome aberrations,
sister-chromatid exchanges and cell kinetics. Mutat Res 247:141-146, 1991.
  Human  lymphocytes were exposed  to 10 msec 1050 microT pulses at 50 Hz
for 45-72 hours.  Author reports an increase in chromosome abnormalities
at all intervals, and an increase in SCE rate after 72 hours only; the
increases are said to be significant, but the data is not convincing.  The
mitotic index was reported to be decreased by exposure to the magnetic
field.

G18) MA Stuchly et al: Modification of tumor promotion in the mouse skin
by exposure to an alternating magnetic field. Cancer Letters 65:1-7, 1992.
  A 2,000 microT 60-Hz field (exposure time of 23 weeks) did not
significantly increase the number of chemically-induced skin tumors in
mice, although the tumors appeared earlier.

G19) DD Ager & J A Radul: Effect of 60-Hz magnetic fields on ultraviolet
light-induced mutation and mitotic recombination in Saccharomyces
cerevisiae. Mut Res 283:279-286, 1992.
  A 1,000 microT 60-Hz fields do not cause mutations or chromosome damage
in yeast, and do not affect UV-induced DNA damage.

G20) M Fiorani et al: Electric and/or magnetic field effects on DNA
structure and function in cultured human cells. Mut Res 282:25-29, 1992.
  0.2-200 microT 50-Hz fields did not cause DNA damage in human cells, and
did not affect the growth of human cells in culture.  Also showed no
effect for electric fields.

G21) J. Nafziger et al: DNA mutations and 50 Hz EM fields. Bioelec
Bioenerg 30:133-141, 1993.
  1 & 10 microT 50-Hz fields did not cause mutations in bacteria or
mammalian cells, and did not increase the amount of DNA damage in
virus-transformed cells.

G22) Y Otaka et al: Sex-linked recessive lethal test of Drosophila
melanogaster after exposure to 50-Hz magnetic fields. BEM 13:67-74, 1992.
  500 & 5,000 microT 50-Hz fields do not cause mutations in fruit flies.

G23) A. Rannug et al: A study on skin tumor formation in mice with 50 Hz
magnetic field exposure. Carcinogenesis 14:573-578, 1993.
  500 & 5,000 microT 50-Hz fields do not increase the incidence of skin
tumors or leukemia in mice, and did not increase the frequency of
DMBA-induced skin tumors.

G24) R. Zwingelberg et al: Exposure of rats of a 50-Hz, 30-mT magnetic
field influences neither the frequencies of sister-chromatid exchanges nor
proliferation characteristics of cultured peripheral lymphocytes. Mutat
Res 302:39-44, 1993.
  A 30,000 microT 50-Hz field did not cause chromosome damage in human
cells, and did not affect the growth of human lymphocytes in culture.

G25) A Rannug et al: Rat liver foci study on coexposure with 50 Hz
magnetic fields and known carcinogens. BEM 14:17-27, 1993.
  0.5 & 500 microT 50-Hz fields did not increase the frequency of
chemically-induced liver tumors.

G26) W Loscher et al: Tumor promotion in a breast cancer model by exposure
to a weak alternating magnetic field. Cancer Letters 71:75-81, 1993.
  A 100 microT 50-Hz field increased the frequency of chemically-induced
mammary tumors.

G27) M Mevissen et al: Effects of magnetic fields on mammary tumor
development induced by 7,12-dimethylbenz(a)anthracene in rats. BEM
14:131-143, 1993.
  A 30,000 microT 50-Hz fields did not increase the frequency of
DMBA-induced mammary tumors.

G28) A Rannug et al: A rat liver foci promotion study with 50-Hz magnetic
fields. Environ Res 62:223-229, 1993.
  0.5-500 microT 50-Hz fields did not increase the frequency of
chemically-induced liver tumors.

G29) C Cain et al: 60-Hz magnetic field acts as co-promoter in focus
formation of C3H/10T1/2 cells. Carcinogenesis 14:955-960, 1993.
  A 60-Hz, 100 microT field plus TPA caused an increase in cell
transformation.  The author has subsequently reported at meetings that the
study cannot be replicated.

G30) MA Stuchly: Tumor co-promotion studies by exposure to alternating
magnetic fields. Radiat Res 133:118-119, 1993.
  Mice were exposed to 60-Hz  fields at 2000 microT for 23 weeks.   Prior
to exposure mice were treated with DMBA (a skin tumor initiator) and
during exposure animals were treated with TPA (a skin tumor promoter).
Tumors appeared earlier and in more animals in exposed group, but the
effect was not significant at the end of the study.

G31) A Rannug et al: Intermittent 50-Hz magnetic field and skin tumour
promotion in Sencar mice. Carcinogenesis 15:153-157, 1994.
  Skin tumor promotion study using DMBA as an initiator and TPA as a
positive control.  Exposure was to 50 & 500 microT fields, continuous or
15s on/off, 20 hrs/day for 105 weeks.  No significant promotion of skin
tumors was found.

G32) W Loscher et al: Effects of weak alternating magnetic fields on
nocturnal melatonin production and mammary carcinogenesis in rats.
Oncology 51:288-295, 1994.
  Rats exposed to 50-Hz 0.3-1.0 microT field for 91 days after induction
of mammary tumors with DMBA.  A small but statistically significant
decrease in nocturnal melatonin was observed, but there was no increase in
the incidence of induced mammary tumors.

G34) I Nordenson et al: Chromosomal aberrations in human amniotic cells
after intermittent exposure to fifty hertz magnetic fields. Bioelectromag
15:293-301, 1994.
  Amniotic cells were exposed for 72 hours to a 50 Hz field at 30 microT
in a 115 sec on, 15 sec off cycle.  Exposure resulted in an increase in
the frequency of chromosome aberrations.  Continuous exposure did not
affect the aberration frequency.

G35) RW West et al: Enhancement of anchorage-independent growth in JB6
cells exposed to 60 hertz magnetic fields. Bioelectrochem Bioenerg
34:39-43, 1994.
  A promotion-sensitive mouse epidermal cell line was exposed to a 60 Hz
field at 1100 microT.  Exposure resulted in an increase in colony-forming
efficiency, suggesting an effect on growth.

G36) DL McCormick et al: Exposure to 60 Hz magnetic fields and lymphoma
development in PIM transgenic mice, In: "The Annual Review of Research on
Biological Effects of Electric and Magnetic Fields from the Generation
Delivery and Use of Electricity", Albuquerque, pp. 44-45 (1994).
  Lymphoma-prone mice treated with a genotoxic nitrosamide were also
exposed to continuous 60-Hz fields at 2, 200 and 1,000 microT or to a
60-Hz on-off field at 1,000 microT.  Exposure to the fields had no effect
on the incidence of lymphoma.

G37) DW Fairbairn & KL O'Neill: The effect of electromagnetic field
exposure on the formation of DNA single strand breaks in human cells. Cell
Molec Biol 4:561-567, 1994.
  Cultured human cells were exposed for 1 or 24 hours to a 50-Hz pulsed
field at 5000 microT.  No increase in single-strand breaks was found using
the comet assay.  Hydrogen peroxide was used as a positive control.

G38) MR Scarfi et al: Lack of chromosomal aberration and micronucleus
induction in human lymphocytes exposed to pulsed magnetic fields. Mutat
Res 306:129-133, 1994.
  Human lymphocytes were exposed for 72 hrs to 50-Hz pulsed fields at 2500
microT.  No effects were observed on micronucleus formation, chromosomal
or chromatid breaks, but an increase in the mitotic index was observed.

G39) A Baum et al: A histopathological study of alterations in
DMBA-induced mammary carcinogenesis in rats with 50 Hz, 100 microT
magnetic field exposure. Carcinogenesis 16:119-125, 1995.
  Rats were treated with DMBA (a breast cancer carcinogen) and 50-Hz
fields at 100 microT for 91 days.  In the animals treated with DMBA and
fields, there were more, and larger, tumors than observed in animals
treated with DMBA alone.   Histopathological examination showed no
difference in the number of neoplastic lesions "indicating that magnetic
field exposure had not altered the incidence of mammary lesions, but had
only accelerated tumor growth."  The author refer to this as
"co-promotion", a non-standard use of that term.

G40) W Paile et al: Effects of 50 Hz sinusoidal magnetic fields and spark
discharges on human lymphocytes in vitro. Bioelectrochem Bioenerg
36:15-22, 1995.
  Human lymphocytes were exposed to a 50-Hz field at 30 microT, 300 microT
and 1 mT.  No effects on chromosome aberrations, micronuclei or
proliferation were seen.  A weak effect of SCE's was seen in one
experiment, but not in a replicate.  Exposure of cells to a spark
discharge did not produce chromosome aberrations, but did kill large
numbers of cells

G41) S Galt et al: Study of effects of 50 Hz magnetic fields on chromosome
aberrations and the growth-related enzyme ODC in human amniotic cells.
Bioelectrochem Bioenerg 36:1, 1995.
  Human amniotic cells were exposed to a 50-Hz field at 30 microT. No
increase in chromosome breaks was observed, and there was a trend towards
decreased breaks.

G42) A Antonopoulos et al: Cytological effects of 50 Hz electromagnetic
fields on human lymphocytes in vitro. Mut Res Let 346:151-157, 1995.
  Exposure of human lymphocytes to a 50 Hz field at 5,000 microT lead to
changes in the cell cycle, but had no effects of SCE rates.

G43) CI Kowalczuk et al:  Dominant lethal studies in male mice after
exposure to a 50 Hz magnetic field. Mutat Res 328:229-237, 1995.
  Male mice were exposed for eight weeks at a 10,000 microT sinusoidal
field at 50 Hz.  These male were mated to unexposed females at various
intervals after exposure.  No statistically significant effect was seen on
pregnancy rates or fetal survival.  Since only the males were exposed,
this is a test for mutagenic effects, not fetal effects.

G44) J McLean et al:  A 60-Hz magnetic field increases the incidence of
squamous cell carcinomas in mice. Cancer Letters 92:121-125, 1995.
  Mice were exposed for 52 weeks at a 2,000 microT sinusoidal field at 60
Hz plus DMBA, a known skin tumor carcinogen. Significantly more skin
tumors were found in the field-exposed group.   The protocol is identical
to that used in Stuchly et al [G18], except that the exposure period was
52 rather than 23 weeks.

G45) S Tofani et al: Evidence for genotoxic effect of resonant ELF
magnetic fields. Bioelectrochem Bioenerg 36:9-13, 1995.
  Human lymphocytes exposed to a 50 Hz field at 140 microT or to a 32-Hz
field at 75 or 150 microT with the geomagnetic field nulled showed no
increase in micronuclei formation.  Exposure to the field also did not
affect the drug-induced genotoxicity.  When the geomagnetic field was not
nulled (42 microT parallel to the AC field) the authors report a
significant increase in micronuclei.

G46) S Kwee & P Raskmark: Changes in cell proliferation due to
environmental non-ionizing radiation .1. ELF electromagnetic fields.
Bioelectrochem Bioenerg 36:109-114, 1995.
  Two human cell lines were exposed to a 50 Hz field at 80 microT  for
15-90 minutes.  Increased proliferation was seen in one cell line at
80-130 microT, but not at lower (25 or 40 microT) or higher (150 or 180
microT) field intensities.  At 80 microT, increased proliferation was seen
for 30 min exposures, but not for 16 or 60 min, and only for nonconfluent
cells.  The positive effects may be a multiple comparison artifact.

Copyright (C) by John Moulder
end: powerlines-cancer-FAQ/part7

       ---------------------------------------------------------


                    Powerlines & Cancer FAQs 8/8: Biblio 3
                                       

Archive-name: powerlines-cancer-FAQ/part8
Last-modified: 1996/2/20
Version: 3.4.1
Maintainer: jmoulder@its.mcw.edu


Annotated Bibliography on Powerlines and Cancer (Part 3 of 3)


H) Laboratory Studies Indirectly Related to Power-Frequency Fields and Cancer

H1) AR Liboff et al: Time-varying magnetic fields: Effects on DNA
synthesis. Science 223:818-820, 1984.
  15-4,000 Hz, 1.6-400 microT fields appeared to increase tritiated
thymidine uptake in human fibroblasts.  The effect is reported to be
independent of frequency and field strength.  Neither proliferation nor
DNA synthesis were directly measured in the study.

H2) WC Parkinson & CT Hanks: Experiments on the interaction of
electromagnetic fields with mammalian systems. Biol Bull 176(S):170-178,
1989.
  A 3,000 microT 60-Hz field had no effects of mammalian cell growth.  No
effects on Calcium ion transport were seen under cyclotron resonance
conditions, or under any conditions tested.

H3) S Baumann et al: Lack of effects from 2000-Hz magnetic fields on
mammary adenocarcinoma and reproductive hormones in rats. BEM 10:329-333,
1989.
 100, 1000 & 2000 microT 2,000-Hz fields had no effect on the growth of
transplanted mammary tumors.

H4) R Goodman & A Shirley-Henderson: Transcription and translation in
cells exposed to extremely low frequency EM fields. Bioelec Bioenerg
25:335-355, 1991.
  Pulsed and sinusoidal fields of different types and intensities caused
alterations in transcription of genes, with evidence for frequency,
intensity and duration windows.

H5) AV Prasad et al: Failure to reproduce increased calcium uptake in
human lymphocytes at purported cyclotron resonance exposure conditions.
Radiat Environ Biophys 30:305-320, 1991.
  Study was unable to replicate the 1987 report of Liboff that calcium ion
uptake was increased under cyclotron "resonance conditions".

H6) JL Phillips et al: Magnetic field-induced changes in specific gene
transcriptions. Biochim Biophys Acta 1132:140-144, 1992.
 60-Hz field at 100 microT and above produced changes in gene transcription.

H7) RJ Reiter & BA Richardson: Magnetic field effects on pineal
indoleamine metabolism and possible biological consequences. FASEB J
6:2283-2287, 1992.
  Review of the hypothesis linking EMF effects with effects on melatonin
production.  Notes that pulsed fields are the most effective.

H8) RP Liburdy et al: ELF magnetic fields, breast cancer, and melatonin:
60-Hz fields block melatonin's oncostatic action on ER+ breast cancer cell
proliferation. J Pineal Res 14:89-97, 1993.
  0.2 & 1 microT 60-Hz fields did not affect the growth of human breast
cancer cells in culture.  Melatonin caused inhibition of growth that was
blocked by a 1.2 microT field.

H9) S Paradisi et al: A 50-Hz magnetic field induces structural and
biophysical changes in membranes. BEM 14:247-255, 1993.
  A 3,500 microT 50-Hz field did not affect the growth of mammalian cells
in culture.

H10) M Kato et al: Effects of exposure to a circularly polarized 50-Hz
magnetic field on plasma and pineal melatonin levels in rats. BEM
14:97-106, 1993.
  50-Hz fields at 1-250 microT caused a small decrease in melatonin that
was unrelated to field strength, fields of 1 microT and below had no
effect.

H11) JM Lee et al: Melatonin secretion and puberty in female lambs exposed
to environmental electric and magnetic fields. Biol Reproduc 49:857-864,
1993.
  Exposure to a 500 kV transmission line field (4 microT, 6 kV/m) had no
effect on melatonin levels.

H12) AV Prasad et al: A test of the influence of cyclotron resonance
exposures on diatom motility.  Health Phys 66:305-312, 1994.
  The study was unable to replicate reports (McLeod et al, 1987; Smith et
al, 1987) that certain combinations of ELF and static magnetic fields
could influence diatom motility via an "cyclotron resonance" effect on
calcium ions.

H13) M Kato et al: Horizontal or vertical 50-Hz, 1 microT magnetic fields
have no effect on pineal gland or plasma melatonin concentration of albino
rats.  Neurosci Letters 168:205-208, 1994.
  Horizontal or vertical 50-Hz, 1 microT magnetic fields have no effect on
pineal gland or plasma melatonin concentration of albino rats. This is in
contrast with the authors earlier report [H10] that circularly-polarized
fields did affect melatonin levels.

H14) JP Blanchard & CF Blackman: Clarification and application of an ion
parametric resonance model for magnetic field interactions with biological
systems. Bioelectromag 15:217-238, 1994.
  Nerve growth factor stimulation of neurite outgrowth was used to test a
resonance model proposed in the companion article.  Exposures were at 25
and 45 Hz with AC and DC fields that fit predicted resonances.  Effects
are reported for AC fields as low as about 10 microT, and are said to
support the resonance model.

H15) TA Litovitz et al: Temporally incoherent magnetic fields mitigate the
response of biological systems to temporally coherent magnetic fields.
Bioelectromag 15:399-409, 1994.
  The authors hypothesize that a power-frequency signal needs to be
spatially and temporally coherent for at least 10 seconds to effect
biological activity.  The authors report that a coherent 10 microT field
caused a 2-fold enhancement of enzyme activity, and that an incoherent
(noise) field blocked the effect.

H16) SM Yellon: Acute 60-Hz magnetic field exposure effects on the
melatonin rhythm in the pineal gland and circulation of the adult
Djungarian hamster. J Pineal Res 16:136-144, 1994.
  Adult hamsters were exposed at a 100 microT, 60-Hz field, for 15
minutes.  In the first experiment this exposure reduced the duration and
magnitude of the normal night-time rise in melatonin.  In a replication 6
months later, the effects was much less dramatic, and in a third
replication, no effect was found. If the data for the three experiments
are pooled, all evidence for an effect disappears.

H17) A Lacy-Hulbert et al: No effect of 60 Hz electromagnetic fields on
MYC or beta-actin expression in human leukemic cells. Rad Res 144:9-17,
1995.
  An attempt at replication of the Goodman and Henderson gene expression
studies (e.g., H4) failed to find any effect of 0.57-100 microT 60 Hz
fields on MYC and b-actin expression

H18) JD Saffer & SJ Thurston: Short exposures to 60 Hz magnetic fields do
not alter MYC expression in HL60 or Daudi cells. Rad Res 144:18-25, 1995.
  An attempt at replication of the Goodman and Henderson gene expression
studies (e.g., H4) failed to find any effect of 5.7 microT 60 Hz fields on
MYC and b-actin expression.

H19) JM Lee et al: Melatonin and puberty in female lambs exposed to EMF: a
replicate study. Bioelectromag 16:119-123, 1995.
  A replicate of an earlier study [H11] that has found no effect on
melatonin levels in sheep penned under a 500 kV line.  In the replicate 15
lambs were exposed to a field that averaged 6.3 kV/m and 3.77 microT for
10 months.  No effects on night-time melatonin were found.  The
sensitivity of the study was such that a 1 hr change in the duration of
the night time elevation or a 10% change in the mean melatonin level
during the night would have been detectable.

H20) P Hojevik et al: Ca^2+ Ion transport through patch-clamped cells
exposed to magnetic fields . Bioelectromag 16:33-40, 1995.
   Calcium ion transport through patch-clamped cell membranes was measured
during exposure to combinations of AC (21 microT at 10-23 Hz) and DC
magnetic fields (21 microT) under "cyclotron resonance" conditions.  No
effects on ion transport were observed.

H21) M Mevissen et al:  In vivo exposure of rats to a weak alternating
magnetic field increases ornithine decarboxylase activity in the mammary
gland by a similar extent as the carcinogen DMBA. Cancer Letters
90:207-214, 1995.
  Rats were exposed for 6 weeks to a 50-Hz sinusoidal field at 50 microT
or to DMBA, a known carcinogen.  Both the magnetic field exposure and the
DMBA exposure caused a similar increase in the activity of ornithine
decarboxylase (ODC) in mouse mammary tissue, an enzyme which frequency
rises after exposure of animals to tumor promoters.

H22) DL Henshaw, AN Ross, et al: Enhanced deposition of radon daughter
nuclei in the vicinity of power frequency electromagnetic fields. Int J
Radiat Biol 69:25-38, 1996.
  The authors report that radon daughters (the source of radiation
exposure from radon) in normal room air are attracted to power frequency
electric (not magnetic) field sources.  They go on to speculate that this
could provide a mechanism for an increase in childhood leukemia in
residence near powerlines, but provide no credible explanation of how this
could occur.


J) Studies of Power-Frequency Fields and Reproductive Toxicity

J1) LJ Dlugosz et al: Congenital defects and electric bed heating in New
York State: A register-based case-control study. Am J Epidem
135:1000-1011, 1992.
  A case-control study that found no statistically significant
relationship between the use of electric bed heating and any type of
congenital defects.

J2) N Chernoff et al: A review of the literature on potential reproductive
and developmental toxicity of electric and magnetic fields. Toxicol
74:91-126, 1992.
  "From our review we conclude that laboratory experimental and
epidemiological results to date have not yielded conclusive data to
support the contention that such fields induce adverse reproductive
effects under the test or environmental conditions studied."

J3) CF Cox et al: A test for teratological effects of power-frequency
magnetic fields on chick embryos. IEEE Trans Micro Theory Tech 40:605-610,
1993.
  50-Hz 10 microT fields had no effects on the incidence of developmental
abnormalities in chick embryos.  The paper reviews other published studies
and concludes that there is little statistical basis to hypothesize that
magnetic fields cause malformations in chick embryos.

J4) H Huuskonen et al: Effects of low-frequency magnetic fields on fetal
development in rats. BEM 14:205-213, 1993.
  36 microT 50-Hz field has no significant effect on fetal development in rats.

J5) J Juutilainen et al: Early pregnancy loss and exposure to 50-Hz
magnetic fields. BEM 14:229-236, 1993.
  Case-control study of early pregnancy loss and residential exposure to
50 Hz fields (fields measured at the front door) which found an increase
in the rate of early pregnancy loss in exposed cases.

J6) E Robert: Birth defects and high voltage power lines - An exploratory
study based on registry data. Reproduc Toxicol 7:283-287, 1993.
  Case-control study of the association between maternal residential
proximity to power line magnetic fields and congenital anomalies which
found no excess malformations, and a lower rate of skeletal and cardiac
malformations in the exposed group.

J7) RL Brent et al: Reproductive and teratologic effects of
electromagnetic fields. Reproduc Toxicol 7:535-580, 1993.
  "The more consistent finds indicate that [power-frequency] EMF, even at
higher exposure, do not generate a measurable increase in reproductive
failure in the human population... The increasing generation of electric
power during this century is not associated with a concomitant rise in the
incidence of birth defects... The chick embryo studies were of little
assistance... [Studies] do not indicate that EMH have the potential for
deleteriously affecting proliferating and differentiating embryonic cells
at the exposures to which populations are usually exposed... There does
not appear to be a measurable risk of reproductive failure and birth
defects from EMF exposure in humans..."

J8) M Mevissen et al: Effects of static and time-varying (50-Hz) magnetic
fields and reproduction and fetal development in rats. Teratology
50:229-237, 1994.
  Mated rats were exposed to a 30 mT static or 50-Hz field from day 1 to
day 20 of pregnancy.  No adverse effects were seen in dams.  "The
increased fetal loss during static magnetic field exposure suggests that
static magnetic fields of such high flux density may induce embryotoxic
effects, while 50-Hz magnetic field exposure does not seem to be
associated with any severe reproductive risks".

J9) MB Bracken et al: Exposure to electromagnetic fields during pregnancy
with emphasis on electrically-heated beds: Association with birth weight
and intrauterine growth retardation. Epidemiology 6:263-270, 1995.
  Case-control study of fetal defects and electrically-heated beds.
Exposure to power-frequency fields was found to have no important
relationship to low birth weight or fetal growth retardation.  Also
unrelated to fetal defects were VDT use, exposure to fields of greater
than 0.20 microT, and wirecode.

J10) DK Li et al: Electric blanket use during pregnancy in relation to the
risk of congenital urinary tract anomalies among women with a history of
subfertility. Epidemiology 6:485-489, 1995.
  Case-control study of infants with known chromosomal abnormalities. No
overall association with VDT, electric blanket or electrically heated
water beds were found.  Subgroup analysis identified a possible
association in women with a history of subfertility whose exposure was
first trimester.

K) Reviews of Laboratory Studies of Power-Frequency Fields

K1) TS Tenforde: Biological interactions and potential health effects of
extremely-low-frequency magnetic fields from power lines and other common
sources. Ann Rev Publ Health 13:173-196, 1992.
  Review of ELF magnetic field effects from a biologist's perspective

K2) J Walleczek: Electromagnetic field effects on cells of the immune
system: the role of calcium signaling. FASEB J 6:3177-3185, 1992.
  Review of ELF effects on the immune system and the possible role of
calcium.  Suggests that the threshold for proliferation effects for 50/60
Hz fields is between 200 & 5,000 microT.

K3) J McCann et al: A critical review of the genotoxic potential of
electric and magnetic fields. Mut Res 297:61-95, 1993.
  "The preponderance of evidence suggests that neither ELF nor static
electric and magnetic fields have a clearly demonstrated potential to
cause genotoxic effects.  However, there may be genotoxic activity from
exposure under conditions where phenomena auxiliary to an electric field,
such as spark discharges, electric shocks or corona can occur."

K4) JC Murphy et al: Power-frequency electric and magnetic fields: A
review of genetic toxicology. Mut Res 296:221-240, 1993.
  "Considering the total body of available information, there is little
evidence that exposure to [power-frequency electric or magnetic fields]
directly causes genetic changes in biological systems."


K6) W Loscher & M Mevissen: Animal studies on the role of 50/60-Hz
magnetic fields in carcinogenesis.  Life Sci 54:1531-1543, 1994.
  Review of published and unpublished animals studies.  "If 50/60-Hz
magnetic fields are truly associated with an increased risk of cancer,
then these fields must act as a promoter or co-promoter of cancer... the
available animal data... seem to indicate that intermediate exposure
exerts co-promoting effects in different tumor models... the existing
experimental evidence is still insufficient for discerning a cause-effect
relationship for exposure and human disease or injury"


L) Miscellaneous Items

L1) SJ Popock et al: Statistical problems in the reporting of clinical
trials. New Eng J Med 317:426-432, 1987.
  A discussion and analysis of statistical issues in clinical trials,
including multiple endpoint issues, subgroup analysis and selection of
results for the summary.

L2) EM Silberhorn et al: Carcinogenicity of polyhalogenated biphenyls:
PCBs and PBBs.  Crit Rev Toxicol 20:440-496, 1990.
  Most experimental evidence supports the view that PCB formulations are
not genotoxic or mutagenic, and are not initiating agents.  PCB mixtures
are tumor promoters in both rats and mice.  Epidemiological studies are
few and small, but suggest that PCBs may increase the risk of liver
cancer.

L3)  MG Morgan: Expose treatment confounds understanding of a serious
public-health issue. Sci Amer 262:118-123, April 1990.
  Review of "Currents of Death" by P Brodeur . "Brodeur tends to impute
bad faith and an effort to cover up to any individual or institution that
disagrees with his point of view.  Reporting on very complex science, he
cites findings selectively... Currents of Death deliberately
oversimplifies and misrepresents the complexity of the scientific process
and the evidence it has produced.  The book cites portions of this
evidence in a highly selective manner..."

L4) RG Stevens et al: Electric power, pineal function, and the risk of
breast cancer. FASEB J 6:853-860, 1992.
  Presentation of the EMF-melatonin-breast cancer hypothesis.

L5) H Kung & CF Seagle: Impact of power transmission lines on property
values: A case study. Appraisal J 60:413-418, 1992.
  Survey of homeowners who lived along transmission lines. None "had any
knowledge of possible evidence connecting power transmission lines to
health risks"; but 87% said that if they had known of potential health
risks, it would have adversely affected the price they were willing to
pay.  The values of comparable houses adjacent to, and not adjacent to,
the power lines were found to be similar.

L6) K Victorin: Review of the genotoxicity of ozone.  Mutat Res
277:221-238, 1992.
  Ozone is genotoxic to mammalian cells in culture.  Ozone produces
chromosome aberrations in lymphocytes from hamsters but from mice, and
does not cause SCEs.  Evidence for whole animal carcinogenicity is limited
to lung adenomas in one strain of mice.

L7) HI Morrison et al: Herbicides and cancer.  J Natl Cancer Inst
84:1866-1874, 1992.
  Review of the literature shows some weak evidence that exposure to
phenoxy herbicides increases the incidence of non-Hodgkin's lymphoma, and
possibly soft-tissue sarcomas.  Evidence supporting an association between
herbicides and leukemia is weak, and is limited to a single study [D3].
The available evidence does not support any association of herbicide
exposure with brain cancer.

L8) DE Martin: A highlight summary of the impact of electrical
transmission lines on improved real estate values. EEI EMF Taskforce
Meeting, Seattle, April, 1993.
  A utility study in Kansas City found no sale price or rental fee
evidence for impacts of transmission lines on commercial property,
apartment complexes, or single-family developments.  However, a
substantial fraction of the residential owners thought that future prices
would be impacted.

L9) High-voltage overhead lines and the potential risk of cancer in
children.  Press Release, 27-August-1993, Danish Ministry of Health.
  "Neither the latest nor previous scientific research documents that, for
dwellings near the high-voltage plants of the power supply, a magnetic
field of 50-Hz would be carcinogenic in children... There are no
scientific grounds for fixing the limits of magnetic field exposure...
there are no current grounds for considering a minimum distance between
existing high-voltage overhead lines and dwellings"

L10) Magnetic fields and potential health risks based on what we know in
May 1994, National Electricity Safety Board, Stockholm, (1994).
  "Our current knowledge about how magnetic fields affect humans is not
sufficient.  We therefore do not have sufficient grounds to determine
limit values.  But the suspicions of a connection between magnetic fields
and cancer are such that we recommend a certain caution.  Therefore... if
such can be done within reasonable costs, strive to design and/or place
new power lines and electrical facilities so that magnetic fields are
limited... In our society we must constantly evaluate how much money we
shall invest in health and the environment... As far as we know today,
magnetic fields from power lines could cause two cases of childhood
leukemia per year [in Sweden].  The costs to eliminate those eventual
cases are very large.   In such a situation, it can be of greater urgency
to reduce the number of cases of cancer caused by radon... or to reduce
the number of traffic accidents..."

L11) D G Altman et al: Dangers of using "optimal" cutpoints in the
evaluation of prognostic factors. J Natl Cancer Inst 86:829-835, 1994.
  The search for a cutpoint that will maximize differences may lead to
major increases in false positives.  "We recommend that authors... use
prespecified cutpoints... If possible the choice of cutpoints should be
guided by biological reasoning... We think that the so-called 'optimal'
cutpoint approach should not be used.  If it is used, the P value must be
corrected"

L12) HP Beck-Bornholdt & HH Dubben: Potential pitfalls in the use of
p-values and in interpretation of significance levels. Radiother Oncol
33:171-176, 1994.
  "In multi-parameter analysis of clinical data the likelihood of
obtaining significant results, just by chance, increases considerably with
the overall number of testes performed.  This can be compensated by
adjusting p-values".

L13) S Greenland: A critical look at some popular meta-analytic methods.
Amer J Epidemiol 140:290-296, 1994.
  Review of modern meta-analysis techniques, with a discussion of the
potential problems and biases.  "Meta-analysis is essential for obtaining
reproducible summaries of study results and valuable for discovering
patterns... A good meta-analysis will highlight and delineate the
subjective components of these processes and vigorously search for
heterogeneity.  Unfortunately, these objectives are not always met..."

L14) LJ Kinlen: Epidemiological evidence for an infective basis in
childhood leukaemia. Br J Cancer 71:1-5, 1995.
  Brief review of the evidence for an infective basis of childhood leukemia.

L15) DA Savitz & AF Olsham: Multiple comparisons and related issues on the
interpretations of epidemiologic data. Amer J Epidemiol 142:904-908, 1995.
  The argument is made that the existence of multiple comparisons and
post-hoc hypothesis does not necessarily affect the statistical
significance of epidemiologic studies.  The authors argue that "a concern
about multiple comparisons in unwarranted...'" and that "How and when the
idea for collecting and analyzing data occurred is irrelevant to assessing
the validity of the product...".  However, the authors also note that:
"Statistical considerations aside, asking a study to yield any
associations ('Is something going on in the data?') is a poor research
strategy".

L16) E Farber: Cell proliferation as a major risk factor for cancer:  A
concept of doubtful validity. Cancer Res 55:3759-3762, 1995.
  It is now being proposed that the presence of cell proliferation by
itself or the stimulation of cell proliferation in a quiescent tissue...
should in and of themselves major concerns for cancer development...
However, whether cell proliferation, per se, is a risk factor for the long
process of cancer development has not been demonstrated... 

L17) The Criteria Group for Physical Risk Factors:  Magnetic fields and
Cancer - a criteria document, Sweden, 1995.
  "This document summarizes certain issues concerning whether scientific
support exists for developing limits on exposure for occupational exposure
to low frequency magnetic fields... There is lack of knowledge concerning
the relevant exposure measure... An overall evaluation of both animal and
experimental studies is that occupational exposure could possibly be a
human carcinogen.  There is, however, a lack of data to determine whether
a dose-response relationship exists... The scientific database is
insufficient to develop limits of exposures"

L18) Axelson O: Cancer risks from exposure to radon in homes. Environ
Health Perspec 103 (Suppl 2):37-43, 1995.
  "Exposure to radon and its decay products in mines is a well recognized
risk of lung cancer in miners... Indoor radon  became a concern in the
1970s... [but] exposure assessment remains a difficult and uncertain issue
in these studies, most of which indicate a lung cancer risk from indoor
radon... More recently there are also some studies... suggesting other
cancers also to be related to indoor radon, especially leukemia, kidney
cancer, and malignant melanoma, and some other cancers as well. The data
are less consistent and much more uncertain than for indoor radon and lung
cancer, however; and there is no clear support from studies of miners in
this respect."


M) Regulations and Standards for Ionizing and Non-ionizing EM Sources.

M1) RC Petersen: Radiofrequency/microwave protection guides. Health Phys
61:59-67, 1991.
  A summary of RF/MW protection guidelines.

M2) International Commission on Radiation Protection: Recommendations.
Report 60, New York, Pergamon Press, 1991.
  Current recommendations for occupational and public protection standards
for ionizing radiation

M3) AS Duchene et al: IRPA guidelines on protection against non-ionizing
radiation. Pergamon Press, New York, 1991.
  Current recommendations for occupational and public protection standards
for non-ionizing EM sources.

M4) Restriction on human exposures to static and time varying EM fields
and radiation. Documents of the NRPB 4(5): 1-69, 1993.
  Exposure limits for power-frequency fields, as well as static fields and
MW/RF frequencies; the standards apply to both residential and
occupational exposure.  For 60-Hz the limits recommended are 10 kV/m for
the electric field and 1,330 microT for the magnetic field.

M5) Sub-radiofrequency (30 kHz and below) magnetic fields, In:
Documentation of the threshold limit values, ACGIH, pp. 55-64, 1994.
  For 60-Hz fields the standard is 100 microT for pacemaker users and
1,000 microT for everyone else, this standard is applied only to
occupational settings.  Similar documentation is available for other
frequencies.

M6) HP Jammet et al: Interim guidelines on limits of exposure to 50/60 Hz
electric and magnetic fields. Health Physics 58:113-122, 1990 [this is the
1990 ICNIRP interim guidelines that were approved in 1993].
  For the general public the 50/60 Hz exposure standard is 100 microT for
continuous exposure and 1,000 microT for short-term exposure.  For
occupational exposure the standard in 500 microT for continuous exposure
and 5,000 microT for short-term exposure.  In 1993, the International
Commission on Non-Ionizing Radiation Protection (ICNIRP) confirmed these
guidelines (ICNIPR Press Release dated 12 May 1993).

M7) MH Repacholi et al: Guidelines on limits of exposure to static
magnetic fields.  Health Phys 66:100-106, 1994.
  ICNIRP guidelines are based on keeping induced currents below 100
mA/m2.  Occupational guideline is that continuous occupational exposure
should be limited to a time weighted value that does not exceed 200
milliT.  Continuous exposure of the general public should not exceed 40
milliT.  For people with cardiac pacemakers, ferromagnetic implants and
implanted electronic devices exposures should be kept below 500 microT.

Copyright (C) by John Moulder
end: powerlines-cancer-FAQ/part8

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