EPA suspects ELF fields can cause cancer.
In its two-year analysis of studies exploring a possible connection between cancer and extremely low frequency (ELF) electromagnetic fields, the EPA concludes that a growing body of data now shows "a consistent pattern of response which suggests, but does not prove, a causal link." The draft report, unveiled in summary form last week, comes on the heels of several new epidemiologic studies linking cancers with exposures to ELF fields.
Electric and magnetic fields abound in nature. They also emanate from the flow of electricity through everything from transmission lines to household appliances. In the 11 years since Nancy Wertheimer and Edward Leeper reported their groundbreaking study suggesting a link between electric power lines and childhood leukemia (SN: 4/21/79, p.263), more than three dozen epidemiologic investigations have focused on the connection between electromagnetic fields and human cancer. Biological studies, however, have yet to prove a cause-and-effect relationship.
The eight strongest epidemiologic studies, all involving children, "consistently found modestly elevated risks (some statistically significant) of leukemia, cancer of the nervous system and, to a lesser extent, lymphomas," the EPA report states. Those results do not seem attributable to confounding factors or biases generated by study design, according to the report.
Occupational studies, though weaker, point to excesses of the same cancers and "tend to support" these childhood studies, the report's authors note. Moreover, they say, tissue and cellular studies suggest it's "biologically plausible" that such fields might cause cancer.
In an earlier draft, the EPA authors concluded that ELF fields appear to represent a "probable human carcinogen," MICROWAVE NEWS reported last week in its May/June issue. However, according to the newsletter, that phrase was stricken sometime after March 12 and replaced with a more equivocal conclusion. MICROWAVE NEWS quotes William Farland, director of EPA's health and environmental assessment office, as saying he made the change because he would have "concerns classifying [ELF fields] as a probable human carcinogen if I really did not understand how it was working."
In an April 25 letter to EPA Administrator William Reilly, Rep. Peter H. Kostmayer (D-Pa.) argued that EPA's technical reasons "for not formally classifying power-line electromagnetic fields as a potential carcinogen may have merit, but for the purpose of protecting American citizens the distinction is moot. . . . Electromagnetic fields have passed the 'duck test'; if it acts like a potential carcinogen, it must be addressed as a potential carcinogen."
But this potential carcinogen is like no other, according to a May 1989 background paper on its biological effects by the congressional Office of Technology Assessment (OTA). "ELF fields appear to be an agent to which there is no known analog," the OTA authors stated, noting that ELF effects on human tissue are subtle, complex and poorly understood, and that researchers don't even know what dose-related characteristics are important. "It may not be safe to assume that if ELF field exposure leads to health risks, exposure to stronger fields or exposure for longer periods is worse than exposure to weaker fields or for brief periods," they wrote.
Even as EPA was completing its review, the AMERICAN JOURNAL OF EPIDEMIOLOGY published four more reports on ELF fields and cancer. One, in the May issue, showed no statistical link between a parent's work exposure to ELF fields and a child's chance of developing neuroblastoma, one of the most common childhood cancers. A similar study in the June issue found that men in certain industries face double the normal risk of fathering a child with neuroblastoma.
Two reports in the May issue focused on electric blankets. A study of white men turned up no link between the blankets and testicular cancer, while a study of women and children revealed a quadrupling in the risk of brain tumors among children whose mothers slept under electric blankets during the first trimester of pregnancy. The latter study, conducted by David Savitz and his co-workers at the University of North Carolina in Chapel Hill, also hinted that a child's use of electric blankets might increase his or her risk of childhood cancer by 50 percent, although the researchers say the subset of individuals involved was too small to be statistically significant.
Yale University researchers have begun documenting ELF exposures among 4,000 pregnant women. Because the average ELF exposures associated with electric blankets are so large, "we should be able to see the effects of those exposures if there are any," says epidemiologist Leeka Kheifets of the Electric Power Research Institute in Palo Alto, Calif., which is sponsoring the study.
EPA is now distributing a draft of its full report to two outside panels of scientific reviewers. Meanwhile, Congress stands poised to consider a pair of bills that could boost federal funds for research into the biological effects of electromagnetic fields, including ELF fields from residential power lines.
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|Title Annotation:||extremely low frequency electromagnetic fields; U.S. Environmental Protection Agency|
|Date:||Jun 30, 1990|
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