Pseudoscience and the Paranormal

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MICROWAVES AND ELECTROMAGNETIC FIELDS

The alleged health risks of microwave radiation formed the prelude to the next major incident of (in this case) international mass hysteria. The fear here was that the electromagnetic fields (EMFs) from power lines caused, among other things, cancer, especially in children who grew up near power lines. The fear about the dangers of microwaves first surfaced in the mid-1970s with the publication of two articles in the popular New Yorker magazine that were later published in book form (Brodeur 1977). According to Brodeur, exposure to microwaves produced numerous unpleasant health effects, up to and including cancer. During the mid- to late 1970s, microwave ovens were introduced and becoming popular, so there was fertile soil for the seeds of fear to fall on.

The most serious claim was, of course, that microwaves caused cancer. But, as Park (2000) has noted, there is no mechanism by which microwaves could cause cancer. When cancer is caused by some external agent (as opposed to cancer caused by genetic problems within the individual’s genome), the mechanism is the breaking of chemical bonds in the DNA. Microwave radiation simply doesn’t have enough energy to break these bonds. Park (2000) uses an excellent analogy to clarify this point: Imagine trying to throw stones across a river to break a target on the other side. If you’re not strong enough to get the stones across the river, it doesn’t matter how many you throw, the target will remain undamaged.

Throwing more stones in this analogy is equivalent to increasing the intensity of the microwaves. This does have a result—heat. That is why microwave ovens work. But by the time this increased heat had broken any DNA bonds, the target tissue would have been cooked and cancer would be the least of its worries. For a more technical discussion of this point, the reader should see Adir (1991). The anxiety over the would-be dangers of microwaves faded out over the next several years, probably, as Park cogently points out, because of the realization that microwave ovens were extremely handy things to have around the kitchen.

But if the microwave portion of the electromagnetic spectrum had ceased to inspire fear and dread, another portion was just becoming a target for even more panic. And once again, Paul Brodeur was in the lead. It was Brodeur who sounded the alarm, again in a series of articles in the New Yorker which were later published as a book (Brodeur 1989). The subtitle of Brodeur’s book indicates that he had climbed on the conspiracy theory bandwagon: “Power Lines, Computer Terminals, and the Attempts to Cover Up Their Threat to Your Health.” In a later book, subtitled “How the Utilities and the Government Are Trying to Hide the Cancer Hazard Posed by Electromagnetic Fields,” Brodeur (1993) continued the conspiracy theme. Brodeur’s writings brought to the attention of a wide public audience the claims and rumors that power lines caused cancer, which had been circulating for about ten years. Some of the claims were based on published epidemiological studies (i.e., Wertheimer and Leeper 1979), and others were based on what can best be called amateur epidemiology. In this case, individuals or groups with little or no training in data collection and analysis sought out evidence for a power line/cancer relationship. Evidence generated in this way was both the least reliable and the most emotionally compelling—a dangerous combination. Amateur epidemiology often starts when tragedy strikes a family, usually in the form of childhood cancer. The most common type of cancer in childhood is acute lymphoblastic leukemia (ALL). The cause of this type of cancer is unknown, which is obviously extremely frustrating to the parents of diagnosed children and in some cases starts a search for the cause of the cancer. As rumors about power lines began to spread, these lines became a handy and common target. After all, it was almost always easy to find a group of power lines somewhere near the affected child’s home, school, or playground. Equally, it was often possible to find groups of affected patients, a so-called cancer cluster, scattered over the landscape in space and time. And, of course, sometimes the cancer cluster seemed to coincide with areas with high concentrations of power lines. To the amateur epidemiologist, such coincidences of cancer clusters and power lines were all that was needed to prove that the power lines were causing the cancer. In fact, some individuals believed that the mere existence of cancer clusters by themselves proved that some environmental factor was responsible for cancer.

In reality, a causal association between an environmental factor such as power lines and a disease such as ALL requires a much higher standard of proof than just noting the presence of occasional coincidences. Clearly something is causing cancer in affected individuals. But even if causation was totally random over time and space, there would still be cancer clusters, due simply to the laws of chance. As an analogy, imagine a room twenty feet square divided into four hundred individual one-foot-square sections. Into this room we throw 1,600 marbles that come to rest at random throughout the room. Obviously, not every single one of the four thousand one-foot squares will end up with exactly four marbles in it. There will be some squares with lots of marbles and some with none. And yet there is no special “marble attractor” (i.e., depressions in the floor in some squares or some such) that causes more marbles to come to rest in certain squares. The laws of chance simply dictate that will be “marble clusters,” even in the absence of any nonchance factors.

Let us repeat the marble demonstration—but this time the floor has patterns of lines drawn on it that represent power lines. Again, 1,600 marbles are thrown into the room and scatter at random. Will it be possible to find squares in which there is a concentration of both “power lines” and marbles? Certainly. And, again, the coincidence will be due purely to chance factors, not to any ability of the drawn lines to attract marbles to them. To determine if the relationship between power lines (or any other variable) and disease is real, it is necessary to show that the association occurs more frequently than would be predicted by chance alone.

By 1997, after eighteen years of research on the issue, it was clear that there was no association between power lines and cancer. Studies claiming to show such an association suffered from various serious flaws in methodology and statistical procedures (see National Research Council 1997; Linet et al. 1997; Lacy-Hulbert, Metcalf, and Hesketh 1998, for highly detailed reviews). One study (Feychting and Ahlbom 1993), done in Sweden, at first, looked like truly strong evidence that power line exposure was casual in childhood leukemia. The results looked so powerful, in fact, that the Swedish government was planning to switch children from schools near power lines to schools farther from such lines. In the published study, sixty-six risk ratios are reported. A risk ratio (RR) is a number giving the relative risk of some outcome (i.e., disease, accident, etc.) in a group exposed to some condition relative to a control group that is not exposed. If the RR is 1, there is no difference between the risk of the outcome in the exposed and nonexposed groups. RRs of less than 1 indicate that the exposed group is less likely to suffer the outcome. (Lest this seem implausible, note that the RR for dying in a traffic accident is less than 1 for a group “exposed” to wearing seat belts). RRs of greater than 1 indicate that the risk of the outcome is greater in the exposed group. Note, by the way, that RRs can’t be negative, so that there is much more “room” to find RRs of greater than 1 than those of less than 1. Generally, RRs of 2 and above, if found consistently, are considered good evidence that exposure to whatever is being studied does have a real effect on the probability of suffering the outcome. For example, the RR for contracting lung cancer in smokers is 20 compared to nonsmokers; that is, smokers are about twenty times more likely to get lung cancer than nonsmokers.

With that background in mind, the Swedish study (Feychting and Ahlbom 1993) seemed rather impressive. One of the RRs it reported was 3.8 for leukemia in children. In other words, children exposed to power line radiation were almost four times more likely than nonexposed children to develop leukemia. But even in the context of the published paper, that single result loses some of its terror-inducing properties when one notes that the paper reported sixty-five other RRs for different types of cancer and different measures of exposure to EMFs. Of the total of sixty-six RRs, twenty-three were 1 or less. Still, it was the 3.8 RR that was the focus of attention. It turned out, however, that the published paper didn’t tell the whole story. When the results of all the comparisons that the investigators made were released in the mid 1990s, that single RR of 3.8 turned out to be much less significant. The investigators had in fact calculated a total of nearly eight hundred different RRs (Frontline 1995). Of this huge number, the RR of 3.8 for leukemia was simply the one that happened to be the largest. If one calculated eight hundred RRs for such things as picking your nose, using pens with red ink, or listening to National Public Radio, it would be extremely surprising if, just by chance, you didn’t turn up one or two RRs of 3.5 to 4! When the real nature of the results of this study became clear, the Swedish government abandoned its plans to bus children to new schools.

It has also been claimed that studies of animals and of individual cells in culture have shown harmful effects of exposure to EMFs. As is so often the case, a few initial and preliminary studies seemed to show positive results.