How much risk is there? How much evidence?
Public concern about AC magnetic fields reached a maximum in the
late eighties and early nineties, when the media were giving
coverage to scientific findings of elevated
cancer risk among children living in houses with high
In the years since then, our information about risk has
not altered substantially. We do not now have a clear
indication that magnetic fields are safer than we previously
believed they were -- as some have incorrectly stated. Nor do we
have indication that they are more dangerous.
Instead what we have is a little better evidence about the
range of possibilities. We have more evidence than we had
before that these fields are neither very risky nor
completely innocuous. We know better where we stand,
although much still remains uncertain.
At its highest, public concern
was due in part to media coverage implying that a large risk
was possible. Their coverage of the scientific findings did
not always make it clear that the highest disease incidences then
actually being seen with elevated fields (and the highest
that are now being seen) still left childhood cancer as a
very rare disease, compared to the more common adult types
(lung cancer or breast cancer, say).
One source of confusion is that epidemiologists have
usually described a disease effect in terms of a ratio of
the disease risk (with and without exposure to some possible
carcinogen) rather than in terms of an increase of
the disease risk. But with a rare disease having a basic
lifetime risk of, say, one in a thousand (childhood cancer
has roughly that) a doubling of risk will increase that risk
only to two in a thousand.
Of course an increase by one in a thousand is not a
totally negligible risk increase. But we can compare it
with what we would have if some environmental exposure
caused a doubling in the risk of a more common type of
cancer -- say breast cancer, which has a lifetime risk of
around one in ten. If such an exposure added another one in
ten risk for women experiencing the exposure, that would
represent a very large increase in the number of women
involved, compared with a much smaller increase in the
number of childhood cancer patients -- even though both
represent a doubling of the "unexposed risk." Obviously, an
exposure that doubles the risk of a common disease (if it is
a widespread exposure) affects far more people than does
something that doubles the risk of a very rare disease.
Why have we been concerned?
Even when the rarity of childhood cancer was clarified,
however, public concern has been great partly because a
child with cancer has a special poignancy or terror for us.
And that concern has existed in spite of advances in
treatment that have turned the most common type of childhood
leukemia into an essentially non-fatal disease. Of course
such treatment (using fairly intensive chemotherapy) is
still not a pleasant process -- not a part of growing up
that anyone would wish on any child, or on any child's
Moreover, at least a portion of the public's initial
reaction was valid because of the possibility that the
fairly small cancer risk increases that had been seen could
prove to be an underestimate. With cancer, we rarely know
exactly what has caused a particular person to have the
disease. For each sort of exposure, we can only count how
many get the disease among those who are exposed -- compared
with how many get it among people who are not exposed.
(This is why we so frequently talk in terms of risk ratios,
since those ratios are what we directly study.)
Thus especially at the beginning, it was possible that
when further studies identified the most relevant or potent
sorts of field exposures, those exposures could turn out to
give far greater risk ratios than had been seen earlier. We
might have finally found the "exposed group" to look at, to
count cancer cases in, that would show the greatest effect.
In other words, it seemed possible -- as had been seen
with asbestos, for instance -- that substantial risks of
high AC magnetic field exposure could simply have gone
unnoticed during the gradual growth of electric power use
and its associated magnetic fields. That this could have
happened without our realizing is specially plausible since
over the most recent several decades -- during which our
cancer diagnosis and record keeping has been at its best --
magnetic fields have generally gone down, or held constant,
due to modern wiring (and plumbing) methods, even though power use
has continued to increase.
Because of the uncertainty and concern, there was
public pressure to do further studies to try to resolve the
issue. Congress became involved. Even Hollywood waded in.
And power companies found themselves with a need to confirm
the safety of their "product" -- to do, belatedly, something
like the environmental impact studies that might have been
required if electric power were only now being introduced.
In order to home in on the valid answers, a group of
further studies were commissioned, including several large
and expensive ones, done in the US, Canada, and Great
Britain. Those studies are now completed, and we are at a
kind of breathing place in the process -- with more
information than we previously had, but not as much clarity
or certainty as we had hoped we would get. Our knowledge is
still incomplete -- although those who have made an effort
to reach a balanced evaluation by combining the evidence
from various studies have said that, overall, there is
consistent evidence that unusually high residential field
levels can affect the risk of childhood leukemia. (See the
references given below, at Recent Epidemiologic Studies.)
Note that magnetic fields have been studied more
intensively with respect to childhood cancer, especially childhood
leukemia, than with respect to other cancer types. Those
childhood cancer studies have been taken by some as a proxy
for whether there may or may not be other health effects.
But that will remain essentially a leap of faith - until we
understand much better than we now do, the mechanisms that
may be involved.
Different players - Different criteria
In this milieu of further study and residual
uncertainty, various groups have participated, with various
agendas of their own. In order for the rest of us to sort
through the scientific work, and what is being said about
it, it may be useful if we can understand where these
various participants are coming from.
First there were the scientists (with whom I have
worked) who observed cancer risk increments. For the most
part, "retrospective" epidemiologic observations were used.
This means that in order to study very rare disease events,
one does not need to begin by identifying highly exposed
homes in advance, and then waiting to see if the children
living there will be more likely to develop cancer. (That
would be called a "prospective" study; and, while desirable, would
require too many homes to be evaluated, and too much waiting -- in
other words, a very costly study.) Instead, one focuses on
already-diagnosed cancer "case" children -- though even
finding as many as several hundred such cases in a large
city requires drawing from several years' accumulation of
these rare childhood cancer cases. One then compares the AC
magnetic field levels estimated retrospectively at the "case
houses" with those similarly estimated at houses occupied by
typical children selected as "healthy controls."
To the scientists who work with such epidemiology, the
primary motivation may be an intellectual curiosity about
the causes of disease; so it doesn't matter if the disease
is one that affects very few individuals (except that
finding enough subjects tends to make the study of rare
diseases harder to do).
Second, there are other doctors and scientists whose
interest (and their statutory mandate, even) is to save
lives by whatever means are effective. If a cure can be
found that works on almost all diagnosed cases, this can be
a more potent way to deal with a rare disease than making
environmental changes (by reducing everyone's exposure to
fields, for instance).
As with the epidemiologic study of rare diseases, if
the goal is to save lives, time and expense are saved by
focusing on those few children who actually have the
disease. Although environmental changes might be less
expensive, per person, than treating a cancer case when it
occurs; those environmental changes can still work out to be
more expensive in total, if they would have to be done at a
thousand homes to avoid just one or two extra cancer cases.
And with better treatment, we help both those cases that may
be caused by fields and those that would have happened
regardless of any field level reductions. It is hard to
argue with that viewpoint.
Thus It is important for us to understand that the
"medical establishment" voices that have sometimes been
quick to downplay the value of magnetic-field-and-cancer
research or its findings are not somehow less concerned and
compassionate about the toll that childhood cancer takes --
but rather may be more focused on devoting limited resources
in ways they see as doing the most good. These doctors and
scientists may or may not question the validity of the
magnetic field findings to date -- but do question the
usefulness of those findings for society as a whole,
compared with focusing on treatment.
Unfortunately that valid perspective is at times a hard
concept for them to explain to us. It is perhaps simpler
for them just to say, "These supposed dangers of magnetic
fields are unproven (or wrong)" -- and to maintain that stated opinion in
the face of evidence to the contrary -- when what they may
really mean is that the magnetic field dangers, if they are
real, are so diffuse that it is not effective to fight them
directly, compared with curing the disease when it appears.
In other spheres, disease-prevention measures can be
effective in saving lives, and can be more economical for
society than improved treatment. But preventive measures will be
most effective where they can alter the likelihood of a
disease that is relatively common -- one that a greater
number of people will get if they don't take precautions --
a disease such as heart attack or diabetes or lung cancer.
Third, there were the journalists. Some of them
remembered the unfortunate situation with asbestos, where
early indication of risk had gone unnoticed, or had even
been knowingly ignored by manufacturers (perhaps for reasons
of profit, or perhaps because asbestos was saving lives in
other ways, such as fire prevention). To those journalists,
AC magnetic fields looked like history repeating itself.
Moreover, journalists do like a good story -- one that is
dramatic and attention-getting, and preferably one that is
new, rather than one that essentially repeats what was
written last year or last month. Some have said, "Old news
is no news;" and even the New York Times is not above such
Thus an earlier "media event" exaggerated the risks that
were observed. Now a rebound "media event" says there is no risk.
The actual evidence lies between those extremes, and has not
Fourth were the power companies. The owners and
employees of those companies naturally did not want to
believe themselves to be purveyors of cancer risk. But
there was an important difference between power companies
and asbestos companies. Power companies have traditionally
operated in a regulated, non-competitive structure, where a
certain return on investment is guaranteed to them. This
means that if hazards are proven, then any extraordinary
expenses incurred in reducing those hazards are reimbursed
by approved rate increases for their customers.
Thus power companies have been somewhat more willing
than asbestos companies to consider the possible risks of
magnetic fields and to take proactive steps. That system
doesn't work perfectly, however; and the idea of a hazard is
still resisted by power companies -- and perhaps should be,
to avoid incurring unwarranted costs for all of us by
mitigating risks that are still in the not-yet-proven
category. A certain amount of resisting expenditures has to
be a part of their job description. In a way, it is
appropriate to leave to state regulatory agencies (public utilities
commissions) what is essentially their job: to decide
whether the power companies should go ahead and spend part of
their customers' money on reducing fields.
A fifth group of players are the government and the
military. Like the power companies, they are themselves
producers of various kinds of "non-ionizing radiation"
(including radio, radar, and AC magnetic fields). And, like
the power companies, they can theoretically pass any cost of
reducing such fields through to all of us by increasing
taxes (or decreased government services in other spheres).
But they would rather not. They get flak if they increase
the cost of government, and (as with the doctors who are
committed to saving lives) spending substantial public money
for one thing may cramp their style In pursuing some other
projects that they see a need for (and that will help
For whatever reasons, government agencies and the
military have at times been a source of vigorous opposition
to various scientific findings -- and
that opposition has been effective partly because we expect
them to be impartial. We don't readily understand the
government's vested Interest, but we need to. Science
is political, whether we like it or not. By comparison, the
power industry has been a pussycat, and has sponsored some
of the most thorough and impartial research in this area --
because we are constantly looking over their shoulders, just
waiting for them to do something fishy.
Sixth: Homeowners may legitimately have a still
different set of priorities from any of the above groups --
one of wanting to reduce the chance of serious outcomes for
their own family in particular. For that goal, very few
families have the wealth to contribute large enough funds to
make a real difference to the national or international
cancer research effort. But many of us do have the time
and resources to alter the AC magnetic fields in just our
own home. If that can make even a small difference in the
risk for our own family, that may be our vested interest -
perhaps especially if the fields are particularly high at
our own house, but can be reduced.