Amiga Plus 1995 #2/Amiga Plus CD - 1995 - No. 2.iso/internet/faq/englisch/staticemfields&cancer

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FAQs on Static Electromagnetic Fields and Cancer - Introduction

* Purpose

The purpose of this FAQ sheet is to examine the laboratory and
epidemiological evidence relevant to the issue of whether static (direct
current, DC) magnetic or electric fields cause or contribute to cancer in
humans.

* Table of Contents
* Part 2
1) Does anyone think that static magnetic fields cause cancer?
2) When evaluating whether there might be a connection between EM fields
and cancer, can all EM fields be considered the same?
3) When evaluating whether there might be a connection between static EM
fields and cancer, do we have to consider EM radiation as well as EM
fields?
4) When evaluating whether there might be a connection between static EM
fields and cancer, do we have to consider the electric as well as the
magnetic component of the field?
5) What units are used to measure static magnetic fields?
6) What sort of static magnetic fields are common in residences?
7) What sort of static magnetic fields are common in workplaces?
8) What is known about the relationship between occupational exposure to
static magnetic fields and cancer?
9) How do scientists determine whether an environmental agent, such as a
static EM field causes or contributes to the development of cancer?
10) How does the epidemiological evidence relevant to a connection between
static fields and cancer stand up to the Hill criteria?
11) How could laboratory studies be used to help evaluate the possible
relationship between static magnetic fields and cancer?
12) Are static magnetic fields genotoxic?
13) Do static magnetic fields enhance the effects of other genotoxic agents?
14) Do laboratory studies indicate that static magnetic fields have any
biological effects that might be relevant to cancer?
15) Do static magnetic fields show any reproducible biological effects in
laboratory studies?
16) Do static magnetic fields of the intensity encountered in occupational
settings show reproducible biological effects?
17) Are there known mechanisms that would explain how static magnetic
fields of the intensity encountered in occupational settings could cause
biological effects?
18) How does the sum of the laboratory and epidemiological evidence
relevant to a connection between static magnetic fields and cancer stand
up to the Hill criteria?
19) Have any independent bodies reviewed the research on static electric
and magnetic fields and possible human health effects?
20) Do exposure standards for static electric and magnetic fields exist?
21) What is the basis for the safety standards set by Lawrence Livermore,
WHO, ACGIH, NRPB, and ICNIRP?

* part 3:  Annotated bibliography

Revision Notes:
v1.0 (27-Dec-94):  Draft circulated for comments on sci.med.physics,
sci.physics.electromag, and sci.med.diseases.cancer
v1.1 (12-Jan-95):  Minor modification made based on newsgroup comments,
formatted for news.answers, and submitted for approval.
v1.3 (21-Feb-95):  Approved by news.answers, pointer (part0) section added.

** 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: static-fields-cancer-FAQ/part1
Archive-name: static-fields-cancer-FAQ/part2
Last-modified: 1995/2/21
Version: 1.3
Maintainer: [e-mail]

FAQs on Static Electromagnetic Fields and Cancer


1) Does anyone think that static magnetic fields cause cancer?

While most public concern about electromagnetic (EM) fields and cancer has
concentrated on power-frequency, microwave (MW) and radiofrequency (RF)
fields, claims have been made that static magnetic fields cause or
contribute to cancer.


2) When evaluating whether there might be a connection between EM fields
and cancer, can all EM fields be considered the same?

No.  The nature of the interaction of an EM source with biological
material depends on the frequency of the source, so that different types
of EM sources must be evaluated separately.

X-rays, ultraviolet (UV) light, visible light, MW/RF, magnetic fields from
electrical power systems (power-frequency fields), and static magnetic
fields are all sources of EM energy.  These different EM sources are
characterized by their frequency or wavelength.

The frequency of an EM source is the rate at which the electromagnetic
field changes direction and/or amplitude and is usually given in Hertz
(Hz) where 1 Hz is one change (cycle) per second.  The frequency and
wavelength are related, and as the frequency rises the wavelength gets
shorter.  Power-frequency fields are 50 or 60 Hz and have a wavelength of
about 5000 km.  By contrast, microwave ovens have a frequency of 2.54
billion Hz and a wavelength of about 10 cm, and X-rays have frequencies of
10^15 Hz and, and wavelengths of much less than 100 nm.  Static fields, or
direct current (DC) fields do not vary regularly with time, and can be
said to have a frequency of 0 Hz and an infinitely long wavelength.

Although we usually discuss EM sources as though they produce waves of
energy, sometimes EM energy acts like particles (photons), particularly at
the higher frequencies.  At the very high frequencies characteristic of
X-rays, photons have sufficient energy to break chemical bonds
(ionization), and this part of the electromagnetic spectrum is termed
ionizing.  The well-known human health hazards from exposure to ionizing
radiation are the result of the breaking of chemical bonds in the genetic
material (DNA).

For frequencies below that of UV light, DNA damage does not occur because
the photons do not have enough energy per photon to break chemical bonds,
and this part of the electromagnetic spectrum is termed non-ionizing.  A
principal mechanism by which non-ionizing EM sources such as RF, MW and
visible light cause biological effects is by inducing electrical currents
that cause heating.  This heating can kill cells, and if enough cells are
killed, long-term and possibly permanent tissue damage can occur.  The
efficiency with which a non-ionizing EM source causes heating depends on
the frequency of the source.  At frequencies below those used for AM radio
(500,000 Hz), EM sources are very inefficient at heating.

Static EM fields cannot break bonds because the energy per photon is too
low.  The static field intensities to which people are exposed in the vast
majority of residential and occupational settings cannot cause heating
because the induced electrical currents are too low. Thus the known
mechanisms through which ionizing radiation, visible light, RF, and MW
affect biological material have no relevance for static fields.


3) When evaluating whether there might be a connection between static EM
fields and cancer, do we have to consider EM radiation as well as EM
fields?

No.  Static EM sources do not produce radiation.

In general, EM sources produce both radiant energy (radiation) and
non-radiant energy (fields).  Radiated energy exists apart from its
source, travels away from the source, and continues to exist even if the
source is turned off.  Fields are not projected away into space, and cease
to exist when the energy source is turned off.  For static EM fields there
is no radiative component.


4) When evaluating whether there might be a connection between static EM
fields and cancer, do we have to consider the electric as well as the
magnetic component of the field?

No.  Only the magnetic field component is relevant to possible health effects.

The magnetic fields associated with static EM sources exists only when
current is flowing.  These magnetic fields are difficult to shield, and
easily penetrate buildings and people.  The electrical fields associated
static EM sources exist whenever voltage is present, and regardless of
whether current is flowing.  In contrast to magnetic fields, these
electrical fields have very little ability to penetrate skin or
buildings.  Thus any biological effects from routine exposure static
fields must be due to the magnetic component of the field.


5) What units are used to measure static magnetic fields?

Static magnetic fields are generally measured in Tesla (T), milliTesla
(mT), and microTesla (microT) where 1000 mT = 1 T, and 1000 microT = 1
mT.  In the US, fields are sometimes still measured in Gauss (G) and
milliGauss (mG), where 10,000 G equals 1 T (1 G = 100 microT; 1 microT =
10 mG).

Magnetic fields can be specified in either magnetic flux density or
magnetic field strength.  In the US and Western Europe field strengths are
usually specified in units of magnetic flux density (Tesla or Gauss).  In
some of the Eastern European literature, however, magnetic fields are
specified in Oersteds (Oe), which are units of magnetic field strength.
When dealing with exposure of non-ferromagnetic material, such as animals
or cells, magnetic flux density and magnetic field strength can be assumed
to be equal, so 1 Oersted = 1 Gauss = 100 microT.

Direct effects on ferromagnetic objects and electronic equipment are the
only things that most people would notice below about 4000 mT.  There is
really no threshold for effects on ferromagnetic objects; a good compass
will twitch at fields as low as 10 microT, but it takes a much larger
field (above 1 mT) to makes metal objects dangerous.  Electronics can also
sense quite low fields; a high resolution color monitor, for example, will
show color distortions at fields as low as 0.2 mT.


6) What sort of static magnetic fields are common in residences?

Residential and environmental exposure to static magnetic fields is
dominated by the Earth's natural field, which ranges from 0.03 to 0.07 mT,
depending on location.  Static magnetic fields under direct current (DC)
transmission lines are about 0.02 mT.  Small artificial sources of static
fields (permanent magnets) are common, ranging from the specialized (audio
speakers components, battery-operated motors, microwave ovens) to trivial
(refrigerator magnets).  These small magnets can produce fields of 1-10 mT
within a cm or so of their magnetic poles [1].  The highest static
magnetic field exposures to the general public are from magnetic resonance
imaging (MRI), where the fields range from 150-2000 mT.


7) What sort of static magnetic fields are common in workplaces?

Persons with occupational exposures to static fields include operators of
magnetic resonance imaging (MRI) units, personnel in specialized physics
and biomedical facilities (for example, those working with particle
accelerators), and workers involved in electrolytic processes such as
aluminum production.  Some aluminum manufacturing workers are reported to
be exposed to fields of 10-15 mT for long periods of time, with maximum
exposures up to 60 mT [2,3]; but another study reports average fields of
only 2-4 mT [4].  Workers in plants using electrolytic cells are reported
to be exposed to fields of 4-10 mT for long periods of time, with maximum
exposures up to 30 mT [5,6].  Individuals working with particle
accelerators are exposed to fields above 0.5 mT for long periods of time,
with exposures above 300 mT for many hours, and maximum exposures of up to
2,000 mT [7].


8) What is known about the relationship between occupational exposure to
static magnetic fields and cancer?

There have been relatively few studies of cancer incidence in workers
exposed to static magnetic fields.  Budinger et al [7] found no excess
cancer in workers exposed to 300 mT fields from particle accelerators, and
Barregard et al [6] found no excess cancer in workers exposed to 10 mT
fields in a chlorine production plant.

There are also studies of aluminum reduction plant workers [8,9,10].  The
studies were not designed to analyzed the effects of static fields, but
these workers are exposed to static fields of 2-15 mT [2,3,4].  In the
aluminum reduction plant studies, the only significant excess cancer
reported was for lymphoreticular tumors, and this was seen in one study
[8].


9) How do scientists determine whether an environmental agent, such as a
static EM field causes or contributes to the development of cancer?

There are certain widely accepted criteria, often called the "Hill
criteria" [11], that are weighed when assessing  epidemiological and
laboratory studies of agents that may cause human cancer.  Under the Hill
criteria one examines the strength, consistency, and specificity of the
association between exposure and the incidence of cancer, the evidence for
a dose-response relationship, the laboratory evidence, the biological
plausibility of the association, and the coherence of the proposed
association with what is known about the agent and about cancer.

- The first Hill criterion is whether there a clear increase in cancer
incidence associated with exposure.  The excess cancer found in
epidemiological 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 static fields, the comparison is actually "high
exposure" versus "low exposure".  A RR of 1.0 means no effect, a RR of
less than 1.0 means a decreased risk in exposed groups, and a RR of
greater than 1.0 means an increased risk in exposed groups.  A strong
association is one with a relative risk (RR) of 5 or more.  Tobacco
smoking, for example, shows a RR for lung cancer 10-30 times that of
non-smokers.

- The second Hill criterion is whether most studies show about the same
increased incidence of the same type of cancer.  Using the smoking
example, essentially all studies of smoking and cancer have shown an
increased incidence of lung and head-and-neck cancers.

- The third Hill criterion is whether cancer incidence increase when the
exposure increases?  Again, the more a person smokes, the higher the
increased risk of lung cancer.

- The fourth Hill criterion is whether there is laboratory evidence
suggesting that the cancer is associated with exposure.  Epidemiological
associations are greatly strengthened when there is laboratory evidence to
support such an association.

- The fifth Hill criterion is whether there are plausible biological
mechanisms that suggest that there should be an association between the
agent and cancer.  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 General's report, the association was highly
plausible because there were known cancer-causing agents in tobacco smoke.

- The sixth Hill criterion is whether the association between exposure to
an agent and cancer is coherent (consistent) with other things that we
know about the biophysics of the agent and the biology of cancer.

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 acceptable 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.


10) How does the epidemiological evidence relevant to a connection between
static fields and cancer stand up to the Hill criteria?

Application of the Hill criteria shows that the current epidemiological
evidence for a connection between static magnetic fields and cancer is
weak to non-existent.

- First, the association between static magnetic fields and cancer is
weak, since there is only one study that shows an excess risk [8], and
that excess risk is not large.

- Second, the association between static magnetic fields and cancer is
inconsistent since studies of workers exposed to static magnetic fields in
industries other than aluminum reduction plants show no association
between exposure to static fields and cancer.

- Third, since only one study reports a statistically significant
association between exposure to static fields and cancer, the issue of
specificity is moot.

- Fourth, the only study reporting an association between exposure to
static fields and cancer shows no evidence of a dose-response
relationship.

Thus the epidemiological evidence for an association between static
magnetic fields and cancer is weak and inconsistent, and fails to show a
dose-response relationship.


11) How could laboratory studies be used to help evaluate the possible
relationship between static magnetic fields and cancer?

When epidemiological evidence for a causal relationship is weak to
non-existent, as in the case of static magnetic fields and cancer,
laboratory studies would have to provide very strong evidence for
carcinogenicity in order to tip the balance.

Laboratory evidence that static magnetic fields might be carcinogenic
would be evidence that these fields directly damage the genetic material
of cells (genotoxicity) or evidence that they increase the chance that a
genotoxin would cause cancer (epigenetic activity).


12) Are static magnetic fields genotoxic?

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

Whole organism genotoxicity studies with static magnetic fields have been
somewhat limited.  Beniashvili et al [12] found no increase in mammary
cancer in mice exposed to a 0.02 mT field.  Mahlum et al [13] found that
exposure of mice to a 1000 mT field did not cause mutations, and other
investigators found a similar lack of mutagenesis in fruit flies exposed
to 1000-3700 mT [14,15,16,17] fields.

Cellular genotoxicity studies have been more extensive.  Published
laboratory studies have reported that static magnetic fields do not cause
any of the effects that indicate genotoxicity.  Static magnetic fields do
not cause chromosome aberrations [18,19,20,21,22,23], sister chromatid
exchanges [18,20,22,24], cell transformation [19,25] or mutations
[26,27,28].

Some studies of static electrical fields have also been conducted.  These
have been reviewed by McCann et al [29], who concluded that while there
were some reports of genotoxicity for static electrical fields, "all
reports of positive results have utilized exposure conditions likely to
have been accompanied by auxiliary phenomena such as corona, spark
discharge, and transient electrical shocks, whereas negative reports have
not."


13) Do static magnetic fields enhance the effects of other genotoxic agents?

In general, static magnetic fields do not appear to have this type of
epigenetic activity.  There are a few studies that suggest that static
magnetic fields might enhance the effects of other genotoxic agents, but
none of these studies has been replicated.

Three studies [14,30,31] have found that 140-3700 mT static fields do not
enhance the mutagenic effects of  ionizing radiation; but one study [32]
reported that 1100-1400 mT static fields caused a slight increase in the
number of chromosome aberrations produced by exposure to high doses of
ionizing radiation, and another study reported that a 4000 mT field
slightly increased radiation-induced cell killing [33].  Repair of
radiation-damage was reported not be affected by a 140 mT field [31], but
to be inhibited at 4000 mT [33].  Kale & Baum [34] reported that 1300-3700
mT static fields did not enhance the mutagenic effects of a known chemical
genotoxin.

Two studies [35,36] found that 150-800 mT static fields did not enhance
the development of chemically-induced mammary tumors, but a third study
[12] reported that a 0.02 mT static field did enhance the development of
chemically-induced mammary tumors.


14) Do laboratory studies indicate that static magnetic fields have any
biological effects that might be relevant to cancer?

No.  Laboratory studies of the effects of static magnetic fields show that
these fields do not have the type of effects on tumor growth, cell growth,
immune system function or hormonal balance that have been associated with
carcinogenesis.

- Tumor growth:  In general, static magnetic fields of 13-1150 mT appear
to have no effect on the growth of either chemically-induced [36] or
transplanted [37,38,39] tumors.  There is one report that suggests that a
15 mT static field increases the growth rate of chemically-induced tumors
[35].

- Cell growth:  Static magnetic fields of 45-2000 mT appear to have no
effect on the growth of human [20,39,33] or animal [25,39,31,42] cells;
but there is one report of inhibition of growth of human lymphocytes at
4000-6300 mT [33].

- Immune system effects:  In most studies, static magnetic fields of
13-2000 mT appear to have no effect on the immune system of animals
[38,40,41,42], although one study reports that the implantation of small
magnets into the brains of rats enhanced their immune response [43].  Two
studies of humans [5,44] have reported that workers in aluminum reduction
plants, where exposure to static magnetic fields is common, have minor
alterations in the numbers of some types of immune cells.  These minor
alterations in cell number are of no known clinical significance, and may
not even be related to magnetic field exposure.

- Hormonal effects:  There are some reports that static magnetic fields of
the order of the natural earth field (about 0.05 mT) can affect melatonin
production in rats [45,46,47].  It is not clear that this observation has
any significance for human health.  While it has been suggested that
melatonin might have "cancer-preventive" activity [48,49], there is no
evidence that static magnetic fields affect melatonin levels in humans, or
that melatonin has anti-cancer activity in humans.


15) Do static magnetic fields show any reproducible biological effects in
laboratory studies?

Yes.  While the laboratory evidence does not suggest a link between static
magnetic fields and cancer, studies have reported that static magnetic
fields do have "bioeffects", particularly at field strengths above 2000 mT
[1,50,51,52,53,54,55].  These "bioeffects" have no obvious connection to
cancer.


16) Do static magnetic fields of the intensity encountered in occupational
settings show reproducible biological effects?

Yes.  A few biological effects have been reported in laboratory systems
for fields as low as 60 mT, and some organisms appear to be able to detect
changes in the strength and/or orientation of the Earth's static magnetic
field (0.03-0.05 mT) [54].  In addition, the rates of some chemical
reactions can be affected by magnetic fields as low as 10 mT [56,57].


17) Are there known mechanisms that would explain how static magnetic
fields of the intensity encountered in occupational settings could cause
biological effects?

There are known biological mechanisms through which strong (greater than
2000 mT) static magnetic fields could cause biological effects [1,50], but
these mechanisms could not account for biological effects of static fields
with intensities of less than about 200 mT [1,50].  It is conceivable that
biological effects could be mediated through effects on chemical reactions
at field strengths as low as 1 mT [56,57], but there is no evidence that
this actually occurs.


18) How does the sum of the laboratory and epidemiological evidence
relevant to a connection between static magnetic fields and cancer stand
up to the Hill criteria?

Application of the Hill criteria [Q9] shows that the evidence for a causal
association between exposure to static fields and the incidence of cancer
is weak to nonexistent.

- A review of the epidemiological evidence shows that the association
between exposure to static magnetic fields and cancer is weak to
nonexistent [Q9].

- The laboratory studies of static fields show no evidence of the type of
effects on cells, tissues or animals that point towards static fields
causing, or contributing to, cancer [Q12,Q13,Q14].

- From what is known about the biophysics of static magnetic fields and
the effects of static magnetic fields on biological systems, there is no
reason to even suspect that they would cause or contribute to cancer
[Q17].


19) Have any independent bodies reviewed the research on static electric
and magnetic fields and possible human health effects?

Yes.  There have recently been a number of such reviews of the
epidemiological and laboratory literature.  None of these reviews have
concluded that static magnetic or electrical fields of the intensity
encountered in residential and occupational settings are human health
risks.

A 1993 review by the United Kingdom (British) National Radiological
Protection Board [58] concluded that for static electric fields "there is
no biological evidence from which basic restrictions on human exposure to
static electric fields can be derived... " and that "for most people, the
annoying perception of surface electric charge... will not occur during
exposure to static electric fields of less than about 25 kV/m".

For static magnetic fields the NRPB [58] concluded that: "there is no
direct experimental evidence of any acute, adverse effect on human health
due to short-term exposure to static magnetic fields up to about 2 T [2000
mT]... Effects on behavior or cardiac function from exposure to much
higher magnetic flux densities than 2 T [1000 mT] cannot be ruled out...
There is little experimental information on the effects of chronic
exposure.  So far, no long term effects have become apparent... There is
no convincing evidence that static magnetic fields are mutagenic... Tumor
progression and, by implication, tumor promotion seems to be unaffected by
exposure to static fields of at least 1 T [1000 mT]"

In 1993, the American Conference of Governmental Industrial Hygienists
(ACGIH) [59] concluded in their review of the literature of static
magnetic fields that: "no specific target organs for deleterious magnetic
field effects can be identified at the present time... Although some
effects [of static magnetic fields] have been observed in both humans and
animals, there have not been any clearly deleterious effects conclusively
demonstrated at magnetic field levels up to 2 T [2000 mT]."

In 1994, the International Commission on Non-Ionizing Radiation Protection
(ICNIRP) [50] concluded that: "current scientific knowledge does not
suggest any detrimental effect on major developmental, behavioral and
physiological parameters in higher organisms for transient exposure to
static field densities up to 2 T [2000 mT].  From analysis of the
established interactions, long-term exposure to magnetic flux densities of
200 mT should not have adverse consequences."


20) Do exposure standards for static electric and magnetic fields exist?

Yes.  A number of governmental and professional organizations have
developed exposure standards, or have modified or reaffirmed their
previous standards.

In 1987, the US Lawrence Livermore National Laboratory developed and
published guidelines for personnel exposure to static magnetic fields
[54].  Under their guideline, people with pacemakers and prosthetic
devices are limited to a peak field of 1 mT, training and medical
surveillance is required for persons exposed to fields above 50 mT, and
time-weighted average fields are limited to 60 mT to the whole-body and
600 mT to the arms and legs.  Peak exposures are limited to 2000 mT.

In 1987, the World Health Organization (WHO) published health criteria for
workers exposed to static magnetic fields [60].  Their report concluded
that: "from the available data it can be concluded that short-term
exposure to static magnetic fields of less than 2 T [2000 mT] does not
present a health hazard."

In late 1993, the British National Radiation Protection Board (NRPB)
issued exposure guidelines for static fields [58].  For static magnetic
fields, the limits recommended are 200 mT averaged over 24 hours, 2000 mT
as a maximum whole-body field, and 5000 mT as a maximum to arms and legs.
For static electrical fields the limit recommended is 25 kV/m.  This
standard applies to both residential and occupational exposure.

Also in 1994, the American Conference of Governmental Industrial
Hygienists (ACGIH) reaffirmed a standard for exposure to static magnetic
fields [59].  The static magnetic field limit is 1 mT for pacemaker users
and 600 mT for everyone else.  This is a "should not exceed" rather than a
time-weighted standard.  Because of the nature of ACGIH this standard is
applied only to occupational settings.

In 1994, the International Commission on Non-Ionizing Radiation Protection
(ICNIRP) published guidelines for exposure to static magnetic fields
[50].  For the general public the magnetic field exposure standard is 40
mT for continuous exposure, except for persons with cardiac pacemakers and
other implanted electronic devices, where the standard is lower (about 1
mT).  For occupational exposure, the standard is 200 mT for continuous
exposure, 2000 mT for short-term whole-body exposure, and 5000 mT for
exposure to arms and legs.


21) What is the basis for the safety standards set by Lawrence Livermore,
WHO, ACGIH, NRPB, and ICNIRP?

The standards are based on several considerations.  One objective is to
keep the electrical currents induced by movement through the static
magnetic field to a level less than those that occur naturally in the
body.  A second objective is to keep the electrical currents induced in
large blood vessels by blood flow to a level that will not produce
hemodynamic or cardiovascular effects.  The pacemaker restriction is
designed to prevent interference with pacemaker operation, although these
units are designed to minimize such effects.  The restriction on
prosthetic devices is to avoid the attraction or torque exerted on these
objects if they are ferromagnetic.

Copyright (C) by John Moulder and the Medical College of Wisconsin
end: static-fields-cancer-FAQ/part2
Archive-name: static-fields-cancer-FAQ/part3
Last-modified: 1995/2/21
Version: 1.3
Maintainer: [e-mail]

FAQs on Static Electromagnetic Fields and Cancer -- Bibliography

1)  CI Kowalczuk, ZJ Sienkiewicz & RD Saunders:  Biological Effects of
Exposure to Non-ionizing Electromagnetic Fields and Radiation  I.  Static
Electric and Magnetic Fields (NRPB-R238), National Radiation Protection
Board, Chilton, (1991).
  "There are insufficient data on which to base restrictions on human
exposure to static electric fields.  For static magnetic fields, the data
suggest that occupational exposures should not exceed about [2000 mT]...
Prolonged exposure to static magnetic fields of up to [2000 mT] does not
produce any detrimental effects of many developmental, behavioral and
physiological parameters in animals... There is no evidence of mutagenesis
or carcinogenesis... In view of the relative lack of information regarding
the possible long-term effects, it is reasonable on present evidence to
restrict the exposure of workers so that the average exposure over one day
does not exceed 200 mT and to restrict exposure of members of the public
to less than 200 mT."

2)  MA Stuchly:  Human exposure to static and time-varying magnetic
fields, Health Phys. 51:215-225 (1986).
  Review of human exposures to static and ELF magnetic fields, and
regulations covering exposure.

3)  NIOSH Health Hazard Evaluation Report:  Alumax of South Carolina,
Centers for Disease Control and Prevention, National Institute for
Occupational Safety and Health, (1994).
  In an aluminum reduction plant, static fields were as high as 70 mT with
time-weighted averages of 15-16 mT.

4)  R VonKaenelet al:  The determination of the exposure to
electromagnetic fields in aluminum electrolysis, In: "Light Metals 1994",
U Mannweiler., ed., The Minerals, Metals & Materials Society, pp. 253-260
(1994)..
  Static fields were 4-20 mT at various locations around the pots.
Personnel monitoring showed average fields of 2-4 mT, with very large
variations and peaks as high at 25 mT.

5)  JL Marsh et al:  Health effect of occupational exposure to steady
magnetic fields, Amer. Indust. Hygiene Assoc. J. 43:387-394 (1982).
  Case-control study of electrolysis workers exposed to a static fields of
up to 20 mT.  No significant effects were found. Some effects on white
cell counts were found, but they were not statistically significant.

6)  L Barregard et al:  Cancer among workers exposed to strong static
magnetic fields (letter), Lancet October 19, 1985:892 (1985).
  Cohort study of Swedish workers in a chloralkali plant.  Measured fields
ranged from 4 to 29 mT.  SMRs for total cancer were 0.1 (.3-1.6) for
workers exposed for greater than 1 year, and 0.8 (0.3-1.9) for workers
exposed for more than 5 years.

7)  TF Budinger et al:  Biological effects of static magnetic fields, In:
"Proceedings of the 3rd Annual Meeting of the Society for Magnetic
Resonance in Medicine", Society for Magnetic Resonance in Medicine,
Berkeley, pp. 113-114 (1984).
  Case-control study of worker who were exposed to static magnetic fields
from accelerators.  Exposures ranged from 0.5 mT for long periods of time
to 300 mT for short periods.  No significant increase in malignant or
benign neoplasms was found.

8)  S Milham:  Mortality in aluminum reduction plant workers, J. Occup.
Med. 21:475-480 (1979).
  Cohort study with an emphasis on air quality, the exposure to static
fields was coincidental.  Elevated mortality from lymphatic and
hematopoietic cancer (1.8) and fatal benign brain tumors (3.9).  Leukemia
and brain cancer mortality was not elevated.

9)  HE Rockette & VC Arena:  Mortality studies of aluminum reduction plant
workers:  Potroom and carbon department, J. Occup. Med. 25:549-557 (1983).
  Cohort study of aluminum reduction plant workers designed to investigate
a hypothesized excess of lung cancer, the exposure to static fields was
coincidental.  No statistically significant excess cancer rates were found
for any site, although non-significant excesses were observed for
pancreatic cancer, kidney cancer, lymphatic and hematopoietic cancer.

10)  JM Mur et al:  Mortality of aluminium reduction plant workers in
France, Int. J. Epidemiol. 18:257-264 (1987).
  Standardized mortality ratio study of workers in aluminum reduction
plants, designed to look for excess lung cancer.  The SMR for overall
cancer was 1.09 (0.97-1.22), and no individual types of tumors were found
to be in significant excess.

11)  AB Hill:  The environment and disease:  Association or causation?
Proc. Royal Soc. Med. 58:295-300 (1965).
  Formal enunciation of the principles used to determine causation for
occupational and environmental exposures (the Hill criteria).

12)  DS Beniashvili et al:  Low-frequency electromagnetic radiation
enhances the induction of rat mammary tumors by nitrosomethyl urea, Cancer
Letters 61:75-79 (1991).
  Study of the effects of a 0.2 mT static fields (0.5 or 3 hrs/day for 2
years) on the induction of mouse mammary tumors by nitrosomethyl urea.
Authors report no effects are reported for static fields alone, but
promotion was reported for 3 hr exposures.  Exposure, and particularly
sham-exposure conditions are poorly described.

13)  DD Mahlum et al:  Dominant lethal studies in mice exposed to
direct-current magnetic fields, In: "Biological effects of extremely low
frequency electromagnetic fields", RD Phillips MF Gillis WT Kaune et al.,
eds., Technical Information Center, Springfield, pp. 474-484 (1979).
  Male mice were exposed under three conditions: 1000 mT static field for
28 days; 2.5 T/m (100-1000 mT) gradient field for 28 days; an on-off
ramped 2.5 T/m (100-1000 mT) gradient field for 42 hours.  No increase in
dominant lethal mutations was observed.

14)  S Mittler:  Failure of magnetism to influence production of X-ray
induced sex-linked recessive lethals, Mutat. Res. 13:287-288 (1971).
  Fruit flies were exposed to a 1100 mT static field and/or 3300 R of
X-rays.  The magnetic field alone did not increase the number of
mutations, and the field did not increase the incidence of x-ray induced
mutations.

15)  JR Diebolt:  The influence of electrostatic and magnetic fields on
mutation in Drosophila melanogaster spermatozoa, Mutat. Res. 57:169-174
(1978).
  No sex-linked recessive mutation in fruit flies exposed to static (0.3
kV/cm) electric and magnetic (927 mT) fields.

16)  PG Kale & JW Baum:  Genetic effects of strong magnetic fields in
Drosophila melanogaster, I.  Homogeneous fields ranging from 13,000 to
37,000 Gauss, Mutat. Res. 1:371-374 (1979).
  No induction of mutations in fruit flies exposed to 1300-3700 mT static
fields.

17)  JR Diebolt:  The influence of electrostatic and magnetic fields on
mutation in Drosophila melanogaster spermatozoa, Mutat. Res. 57:169-174
(1978).
  No sex-linked recessive mutation in fruit flies exposed to static (0.3
kV/cm) electric and magnetic (927 mT) fields.

18)  P Cooke & PG Morris:  The effects of NMR exposure on living
organisms.  II.  A genetic study of human lymphocytes, Br. J. Radiol.
54:622-625 (1981).
  Lymphocytes were exposed to 500 and 1000 mT static fields or to MRI
imaging procedures.  No effects of chromosomal abnormalities or sister
chromatid exchanges were observed.

19)  CR Geard et al:  Magnetic resonance and ionizing radiation:  A
comparative evaluation in vitro of oncogenic and genotoxic potential,
Radiology 152:199-202 (1984).
  Mouse cells were exposed to static fields of up to 2700 mT for periods
of up to 17 hours, together with the gradient field, and the RF fields
that would be used in MRI.  Ionizing radiation was used as a positive
control.  No effect on transformation and chromosome abnormality rates
were found.

20)  FJ Peteiro-Cartelle & J Cabezas-Cerrato:  Absence of kinetic and
cytogenetic effects on human lymphocytes exposed to static magnetic
fields, J. Bioelec. 8:11-19 (1989).
  PHA-stimulated human lymphocytes were exposed for 72-96 hours in culture
to a static field at 45 and 125 mT.  No effects on chromosome aberrations
or cell growth were observed.

21)  VV Shevchenko et al:  [On the problem of induction of chromosome
aberrations in plants by a constant magnetic field], Genetika 14:1101-1103
(1978).
  Plant seeds were germinated in a static magnetic field at 900 mT and
1200 mT for 2 days, or dry seeds were exposed for 2 months to a  900 mT
static magnetic field.  No increase in chromosome aberrations was
observed.

22)  S Wolff et al:  Magnetic resonance imaging:  Absence of in vitro
cytogenetic damage, Radiology 155:163-165 (1985).
  Human (stimulated and unstimulated) lymphocytes and CHO cells were
exposed for 12.5 hrs to a MRI unit with a static field of 2400 mT plus
100-MHz RF.  No increases in chromosome aberrations or sister chromatid
exchanges were observed.

23)  S Wolff et al:  Tests for DNA and chromosomal damage induced by
nuclear magnetic resonance imaging, Radiology 136:707-710 (1980).
  CHO cells were exposed for 14 hrs to a 350 mT static field together with
a gradient field (up to 0.2 mT/cm), and the RF fields (15 MHz at 5 mW/cm2)
that would be used in MRI.  Experiments were also run with higher RF
power.  No chromosomal aberrations were observed.

24)  E Yamazaki et al:  Effect of Gd-DTPA and/or magnetic field and
radiofrequency exposure on sister chromatid exchange in human peripheral
lymphocytes, Acta Radiol. 34:607-611 (1993).
  PHA-stimulated lymphocytes were exposed to a 1500 mT static field plus
RF at 64 MHz (SAR of 0.4 W/kg) and Gd-DTPA.  The addition of the Gd-DTPA
caused an increase in chromosome aberrations, but no effects on chromosome
aberrations were observed for the fields alone.

25)  ME Frazier et al:  In vitro evaluations of static magnetic fields,
In: "Biological effects of extremely low frequency electromagnetic
fields", RD Phillips MF Gillis WT Kaune et al., eds., Technical
Information Center, US Department of Energy, Springfield, pp. 417-435
(1979).
  Mammalian cells were exposed to 500 or 1000 mT static fields for 2, 4 or
24 hours, or to 100 or 300 mT fields for up to 67 days.  No effects on
cell growth rates, cell viability or cell transformation were observed.

26)  RL Moore:  Biological effects of magnetic fields:  studies with
microorganisms, Can. J. Microbiol. 25:1145-1151 (1979).
  Ames test with exposures at 0 to 0.3 Hz to fields of 15 and 30 mT.  No
increase in mutations were observed.

27)  JL Schwartz & LE Crooks:  NMR imaging produces no observable
mutations or cytotoxicity in mammalian cells, Amer. J. Roent. 139:583-585
(1982).
  Mammalian cells were exposed for 24 hrs to a static field at 300 mT,
together with a gradient field (up to 0.2 mT/cm), and the RF fields (15
MHz at 3 mW/sq.-cm) that would be used in MRI. No cytotoxicity or
mutagenicity (6-TG system) were observed.

28)  A Thomas & PG Morris:  The effects of NMR exposure on living
organisms.  I.  A microbial assay, Br. J. Radiol. 54:615-621 (1981).
  Bacteria were exposed to a 1000 mT static field and to the conditions
used in an MRI (900 mT static field plus RF and gradient field).  Not
mutagenic or cytotoxic effects were observed.

29)  J McCann, F Dietrich, C Rafferty, et al:  A critical review of the
genotoxic potential of electric and magnetic fields, Mutat. 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."

30)  PG Kale & JW Baum:  Genetic effects of strong magnetic fields in
Drosophila melanogaster, II.  Lack of interaction between homogeneous
fields and fission neutron-plus-gamma radiation, Environ. Mutagen.
2:179-186 (1980).
  No enhancement of radiation-induced mutations in fruit flies exposed to
a 3700 mT static field.

31)  S Rockwell:  Influence of a 1400-gauss magnetic fields on the
radiosensitivity and recovery of EMT6 cells in vitro, Int. J. Radiat.
Biol. 31:153-160 (1977).
  Mouse mammary tumor cells were exposed to a 140 mT field alone, during
or after x-ray treatment.  Fields alone has no effect on cell growth.
Fields had no effect on radiation-induced cell killing or on the repair of
radiation damage.

32)  T Takatsujiet al:  Effect of static magnetic fields on the induction
of chromosome aberrations by 4.9 MeV protons and 23 MeV alpha particles,
J. Radiat. Res. 30:238-246 (1989).
  Human lymphocytes were irradiated with and without a 1000-1400 mT static
magnetic field.  The authors report an increase in the incidence of
radiation-induced dicentrics in cells exposed to the static fields.  The
increase, while statistically significant is very small.

33)  T Norimuraet al:  Effects of strong magnetic fields on cell growth
and radiation response of human T-lymphocytes in culture, Sangyo Ika
Diagaku Zasshi 15:103-112 (1993).
  Human lymphocytes were exposed to static magnetic fields.  An inhibition
of cell growth was observed at 4000 - 6300 mT, but not at 2000 mT or
below.  Exposure to a 4000 mT field increased radiosensitivity and
decreased repair of radiation-induced damage.

34)  PG Kale & JW Baum:  Genetic effects of strong magnetic fields in
Drosophila melanogaster   III.  Combined treatment with homogeneous fields
and gaseous DBCP, Mutat. Res. 105:79-83 (1982).
  A 1300 mT static magnetic field had no effects on the mutagenic effects
of a chemical.

35)  M Mevissen et al:  Effects of magnetic fields on mammary tumor
development induced by 7,12-dimethylbenz(a)anthracene in rats,
Bioelectromag. 14:131-143 (1993).
  Animals were exposed to a 15 mT static field in the DMBA-induced breast
tumor system.  Exposure was for 24 hrs/day for 91 days.  No overall
promotion effects was observed.  An increase in tumor weights was
reported.

36)  A Bellossi:  The effect of a static uniform magnetic field on mice a
study of methylcholanthrene carcinogenesis, Radiat. Environ. Biophys.
23:107-109 (1984).
  Mice previously treated with methylcholanthrene (an initiator) were
exposed to static magnetic fields from the day of methylcholanthrene
injection until death, with fields of 300-800 mT, for 5-60 minutes per day
and 1-5 days per week.  No significant effect on survival or body weight
was detected.

37)  A Bellossi:  The effect of a static non-uniform magnetic field on
mice a study of Lewis tumour graft, Radiat. Environ. Biophys. 25:231-234
(1986).
  Mice inoculated with tumor cells were exposed to a static field for 5
days/week, beginning the day of transplant and continuing until death.
Exposure was for 0.5-2 hrs/day at fields of 170-900 mT.  No effects on
life span, spleen weight, or metastatic potential were found.

38)  A Bellossi & L Toujas:  The effect of a static uniform magnetic field
on mice:  A study of a Lewis tumor graft, Radiat. Environ. Biophys.
20:153-157 (1982).
  Mice with tumor implants were exposed to static field of 13-915 mT.
Exposure continued 5 days/week for 0.5-8 hours per day.  No effect on
animals survival was found in any group.  The failure-to-take rate (the
tumor is immunogenic) was also unchanged..  There also appears to have
been no effect on the rate of lung metastasis, but the manuscript is a bit
unclear.

39)  S Chandra & S Stefani:  Effect of constant and alternating magnetic
fields on tumor cells in vivo and in vitro, In: "Biological Effects of
Extremely Low Frequency Electromagnetic Fields, Proceedings of the 18th
Hanford Life Symposium ", RD Phillips MF Gillis WT Kaune et al., eds.,
Technical Information Center, U. S. DoE, Springfield, pp. 436-446 (1979).
   Exposure was to a 60-Hz field at 100-1000 mT or to a 11,500 mT static
field.  Exposure was for 0.5 to 3 hours/day, 1-3 days.   Two human tumor
cell lines exposed in vitro, and no effect on cell growth was observed.
Mouse mammary tumor cells were exposed in culture, then implanted; no
effect on tumor growth was observed.  The mouse mammary tumor cells were
also implanted and exposed in vivo; again, no effect on tumor growth was
observed.

40)  JH Battocletti et al:  Exposure of rhesus monkeys to 20,000 G steady
magnetic field:  Effect on blood parameters, Med. Phys. 8:115-118 (1981).
  Monkeys were exposed to a uniform 2000 mT static field or to a gradient
static field (700-2000 mT at 34 mT/cm) for 63-67 hours.  Changes in white
cells counts were found in both exposed animals; subsequent sham-exposures
caused similar changes.  No significant differences were observed between
exposed and sham-exposed animals.

41)  M Osbakken, J Griffith & P Taczanowsky:  A gross morphologic,
histologic, hematologic, and blood chemistry study of adult and neonatal
mice chronically exposed to high magnetic fields, Magnet. Reson. Med.
3:502-517 (1986).
  Mice were raised for varying periods of time in a 1890 mT static
magnetic field.  No differences were found in gross and microscopic
morphology, blood counts or blood chemistry.

42)  TS Tenforde & M Shifrine:  Assessment of the immune responsiveness of
mice exposed to a 1.5-Tesla stationary magnetic field, Bioelectromag.
5:443-446 (1984).
  Mice were exposed for 6 days to a 1500 mT static field.  No effects on
immune response or on mitogen-stimulated lymphocyte proliferation were
observed.

43)  BD Jankovic et al:  Potentiation of immune responsiveness in aging by
static magnetic fields applied to the brain.  Role of the pineal gland,
Ann. NY Acad. Sci. 719:410-418 (1994).
  Micromagnets (60 mT) were implanted into the brains of rats; controls
were sham-implanted with iron beads.  The authors report an enhancement of
animals immune response.

44)  RL Davis & S Milham:  Altered immune status in aluminum reduction
plant workers, Amer. J. Indust. Med. 18:79-85 (1990).
  Authors report that a previous study had found excess lymphoma in
employees of an aluminum reduction plant.  Volunteers in similar jobs has
elevated levels of certain classes of immune cells.  The authors state
that the cause and significance of the altered immunological parameters
are unknown.

45)  A Lerchl et al:  Marked rapid alterations in nocturnal pineal
seratonin metabolism in mice and rats exposed to weak intermittent
magnetic fields, Biochem. Biophys. Res. Commun. 169:102-108 (1990).
  Mice were exposed to fields that were designed to reverse the earth's
static field (0.4 mT).  The coils were activated 6 times per hour for 5
minutes, so this is a pulsed field experiment.  The exposure is reported
to affect seratonin metabolism (but not very much) but not melatonin
levels.

46)  K Yaga, RJ Reiter, LC Manchester, et al:  Pineal sensitivity to
pulsed static magnetic fields changes during the photoperiod, Brain
Research Bulletin 30:153-156 (1993).
  Melatonin production in rats was studied after exposure to a pulsed
static magnetic field (1 min pulses for 45 minutes).  The static field
appears to have resulted in reversal of the Earth field.  Slight decreases
in melatonin production were reported, but only for exposures at certain
times of day.

47)  J Olcese et al:  Evidence for the involvement of the visual system in
mediating magnetic field effects on pineal melatonin synthesis in the rat,
Brain Res. 333:382-384 (1985).
  Normal and blinded rats exposed to 0.05 and 0.1 mT  static fields that
produced a rotation of the horizontal component of the Earth field.   The
field is reported to cause a decrease in melatonin in intact, but not in
blinded animals.  Whether this suggests that the retina is the site of
action of the magnetic field, or that there are visual clues is unclear.

48)  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.  The review notes that pulsed fields are the more effective
than static or sinusoidal fields.

49)  RJ Reiter:  Electromagnetic fields and melatonin production, Biomed.
Pharmacother. 47:439-444 (1993).
  "the current data are not sufficient compelling to conclude that any
cancer which may appear to occur in individuals exposed to magnetic fields
has any association with a change in melatonin synthesis"

50)  MH Repacholi et al:  Guidelines on limits of exposure to static
magnetic fields, Health Phys. 66:100-106 (1994).
  The ICNIRP occupational guideline is that continuous occupational
exposure should be limited to a time-weighted value that does not exceed
200 mT.  Continuous exposure of the general public should not exceed 40
mT.  These values may not be suitable for people with cardiac pacemakers,
ferromagnetic implants and implanted electronic devices; for these people,
exposures should be kept below 0.5 mT.

51)  E Kanal, FG Shellock & L Talagala:  Safety considerations in MR
imaging, Radiology 176:593-606 (1990).
  Eight area of potential concern in MRI safety are reviewed.  "It may be
safely concluded that although no deleterious biological effects from the
static magnetic fields used in MRI have been definitively associated with
this modality, all the facts are by no means in yet, and further research
is continuing..."

52)  International Non-Ionizing Radiation Committee of the International
Radiation Protection Association:  Protection of the patient undergoing a
magnetic resonance examination, Health Phys. 61:923-928 (1991).
  For the static magnetic-field the IRPA guideline is to monitor
cardiovascular status above 2000 mT, and not exceed 10,000 mT. "The
scientific literature does not indicate adverse effects from exposure of
the whole-body to 2 T and of the extremities to 5 T".

53)  JF Schenck:  Health and physiological effects of human exposure to
whole-body four-Tesla magnetic fields during MRI, Ann. NY Acad. Sci.
649:285-301 (1992).
  "Although no health abnormalities were noted [in preclinical trials of
4000 mT MRI units], there were several instances of mild sensory
effects... A strong argument can be made that the potential hazards of
these effects up to field strengths of 4 T [4000 mT] are well below
thresholds set the stability of human tissue..."

54)  G Miller:  Exposure guidelines for magnetic fields, Amer. Indust.
Hygiene Assoc. J. 48:957-968 (1987).
  The Lawrence Livermore static magnetic field exposure guidelines, with a
detailed review of the bioeffects data and of the basis for the standard.
Guidelines: at 1 mT, exclude pacemakers and warn those with prosthetics;
at 50 mT, training and medical surveillance are required, and those with
sickle cell anemia are excluded; 2000 mT is the peak exposure allowed.

55)  FS Prato et al:  Blood-brain barrier permeability in rats is altered
by exposure to magnetic fields associated with magnetic resonance imaging
at 1.5 T, Micro. Res. Tech. 27:528-534 (1994).
  Exposure of rats to MRI conditions or to a 1500 mT static field
increased blood-brain barrier permeability.  "The effect of MRI on
blood-brain barrier permeability is poorly understood... additional
experiments are needed to understand the importance of static field, RF
field and gradient field".

56)  K Schulten:  Magnetic field effects in chemistry and biology, Adv.
Solid State Phys. 22:61-83 (1982).
  "Chemical and biological photoprocesses which involve bimolecular
reactions between non-zero spin intermediates... can be influenced by
magnetic fields".  The examples discussed all involve field strengths of
at least 1 mT, and generally over 10 mT.

57)  JC Scaiano et al:  Model for the rationalization of magnetic field
effects in vivo.  Application of the radical-pair mechanism to biological
systems, Photochem. Photobiol. 59:585-589 (1994).
  A model is proposed for magnetic field effects in biological systems.
The model involved effects on the chemistry of radical pairs.  The result
of the magnetic field is to increase the life-time and hence the
concentration of free radicals.

58)  National Radiation Protection Board:  Restrictions on human exposure
to static and time varying electromagnetic fields and radiation, Document
of the NRPB 4 (5):1-69 (1993).
  The basic restrictions for static magnetic fields are 5000 mT maximum to
limbs, 2000 mT maximum to whole body and 200 mT averaged over 24 hours.
For static electric fields the maximum is 25 kV/m.

59)  Documentation of Threshold Limit Values, American Conference of
Government Industrial Hygienists, Cincinnati, OH, (1994).
  The static field standard is that "routine occupational exposures should
not exceed 60 mT (600 G) whole body or 600 mT (6000 G) to the extremities
on a daily, time-weighted basis... A flux density of 2 T [2000 mT] is
recommended as a ceiling value.

60)  Environmental Health Criteria 69, Magnetic Fields, World Health
Organization, Geneva, Switzerland, (1987).
  "from the available data it can be concluded that short-term exposure to
static magnetic fields of less than 2000 mT does not present a health
hazard."

Copyright (C) by John Moulder and the Medical College of Wisconsin
end: static-fields-cancer-FAQ/part3