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 fields.

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 family.

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.

Action taken

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 considerations.

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 substantially changed.

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 reelect them).

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.

(Note that the book Silencing the Fields does not address questions of whether AC magnetic fields create health risks. Instead, it deals with how such fields can be reduced if that is desired.)

Recent Epidemiologic Studies

A short review of recent studies of childhood cancer and AC magnetic field exposure.

Ed Leeper
6112 Fourmile Canyon
Boulder, CO 80302

303-442-3773