Electromagnetic fields Dear Editors: ”Health Effects on Low-Frequency Electric and Magnetic Fields” plus the report of the U.S. Government Committee ( E S b T , Jan. 1993, pp. 42-58) miss an important point discussed in the literature. Namely, it is the “spiking” or rapid fluctuations in magnetic fields that may be causing health problems rather than the steady or strong fields that may be present. Presumably this is the cause of reported cataracts and birth defects with video display operators. This is illustrated by the comments in the article that “observed no cases of male breast cancer among the company’s line workers, but an excess was found among the central office workers.” Presumably the lines have a steady field but the workers are exposed to “switching” or fluctuating fields. This has been more critical with power company employees. Another point made was that magnetic resonance imaging diagnostic units show no exposure effects. It is critically important that such devices have a very consistent and nonfluctuating magnetic field to eliminate background and irreproducibility. Such devices as nuclear magnetic resonance spectrometers have their magnetic pole fields varied by changing radio frequency electric fields, while their magnetic fields are kept as consistent as possible. I developed cataracts at an early age for no apparent reason after sleeping with my head on a fluctuating electric heating pad while simultaneously beginning computer operations. I do not use such magnetic or UV lab equipment. Paul B. Bertan Chemistry Professor Onondaga Community College Syracuse, NY 13215
Dear Editors: David Savitz puts forward some serious ideas against the CIRRPC panel’s conclusions about EMF effects ( E S b T , Jan. 1 9 9 3 , p. 5 2 ) . As interesting as his ideas seem, I’m bothered by his initial question, “Is there theoretical or empirical evidence that exposure to electric and magnetic fields at com580 Environ. Sci. Technol., Vol. 27, No. 4, 1993
monly encountered levels poses a threat to health?”. Virtually everyone who receives a technical education learns early on what empirical evidence is, but the meaning of “theoretical evidence” escapes me. Are we to take it that this is represented by his statement at the end of the same paragraph of a “hypothesized pathway linking such exposures to cancer?” Would Savitz like us to believe that taking some research result and conceptually extending it by a plausible (yet hypothetical) path to an endpoint one is interested in can in any sense be considered evidence, even with the adjective “theoretical” placed in front of it? There may indeed be theories that EMFs pose a threat to health, but the existence of theories carries little weight. There is indeed some evidence, but its meaning is precisely the subject of this controversy. In dealing with topics as difficult as the effects of EMFs, authors need to state their positions in clear terms. When the potent potential consequences are as serious and the evidence as tenuous as in this arena, readers trying to reasonably weigh the contended points certainly need no more impediments. David E. Nadziejka 6009 Osage Avenue Downers Grove, IL 60516
The author responds: Mr. Nadziejka makes a valid point regarding the distinction between empirical evidence and what I should have perhaps called “theoretical pathways.” I agree that the latter is limited only by our imagination and that many agents for which a theory can be developed through which they might harm health do not actually do so. However, in regard to EMF, an entire body of empirical evidence from epidemiology and from the laboratory has been dismissed based on theoretical objections of Dr. Robert Adair and others, including to some extent by the CIRRPC panel. In that case, physical theory is argued to prohibit the reported empirical observations. As noted in my commentary in ESbT, if the empirical observations
are incorrect, then improved research is the only method that can reveal those errors, but the data are not necessarily in error and thus dismissible merely because they “must be” according to a particular theory. The conflict between the data and the theory serves primarily as an impetus to scrutinize the evidence more thoroughly. In response to those who argue that theory supersedes the existing evidence, I may have overstated the value of credible pathways through which such agents might adversely affect health. David A. Savitz Professor The University of North Carolina at Chapel Hill
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