- Report Published -
|Final Report: Monitoring of Ongoing Research on the Health Effects of High Voltage Transmission Lines|
|Department of Health|
|SB 379 (Regular Session, 1998 )|
|Pursuant to Senate Bill No. 379 of the 1998 session of the General Assembly, VDH submits this final report on monitoring of ongoing research on the human health effects of high voltage transmission lines to the members of the 2001 Virginia General Assembly. This report summarizes the results of the five-year Electric and Magnetic Fields Research and Public Information Dissemination (EMF·RAPID) Program mandated by the U.S. Congress under the 1992 Energy Policy Act. The Congress instructed the National Institute of Environmental Health Sciences (NIEHS) and the U.S. Department of Energy (DOE) to direct and manage a program of research and analysis aimed at providing scientific evidence to clarify the potential for health risks from exposure to extremely low electric and magnetic fields (EMF) surrounding both the high voltage power or transmission lines and the smaller but closer electric lines in homes and appliances.|
The EMF-RAPID program was funded jointly by federal and matching private funds. Authorized funding for this program was approximately $46 million. In addition, the NIEHS contributed $14.5 million for support of extramural grants and contracts and intramural research, as well as long-term toxicity studies conducted by the National Toxicology Program. The EMF-RAPID program ended December 31, 1998, and the results of the research were presented in three major reports: the NIEHS working group report "Assessment of Health Effects from Exposure to Power-line Frequency Electric and Magnetic Fields", dated August 1998; the follow up report by the NIEHS Director entitled "Health Effects from Exposure to Power-line Frequency Electric and Magnetic Fields" submitted to the U.S. Congress in May 1999; and the National Research Council (NRC) report reviewing and evaluating the EMF-RAPID program's scientific and technical content of research projects entitled "Research on Power Frequency Fields Completed Under the Energy Policy Act 1992" published in 1999.
The possible adverse health effects of EMF were first reported in literature from the former Union of Soviet Socialist Republics (USSR) in the mid-1960s. Several subjective complaints, involving the cardiovascular, digestive, and central nervous systems, were reported by electric switchyard workers. Subsequent studies of electric utility linemen in the United States failed to observe the same adverse health effects reported by their counterparts in the former USSR. In 1979, an epidemiological study conducted in the Denver, Colorado area implicated a possible association between childhood cancer mortality and proximity of homes to power distribution lines. Since that time, public concern as well as scientific uncertainty regarding potential health effects from exposure to power frequency EMF emanating from nearby high voltage electrical transmission lines have generated considerable controversy among scientists, courts, regulatory bodies and public policy makers. Public concern was the major driving force for the enactment of the 1992 Energy Policy Act under which the EMF-RAPID program was established.
The NIEHS report (1998) concluded that the scientific evidence suggesting that extremely low frequency EMF exposures pose any health risk is weak. The strongest evidence for health effects comes from associations observed in human populations with two forms of cancer: childhood leukemia and chronic lymphocytic leukemia in occupationally exposed adults. While the support from individual studies is weak, the epidemiological studies demonstrate, for some methods of measuring exposure, a fairly consistent pattern of a small, increased risk with increasing exposure that is somewhat weaker for chronic lymphocytic leukemia than for childhood leukemia. In contrast, the mechanistic studies and the animal toxicology literature fail to demonstrate any consistent pattern across studies although sporadic findings of biological effects have been reported. No increase of leukemias in experimental animals has been observed. Epidemiologic studies have serious limitations in their ability to demonstrate a cause and effect relationship whereas laboratory studies, by design, can dearly show that cause and effect are possible. Virtually all of the laboratory evidence in animals and humans and most of the mechanistic work done in cells fail to support a causal relationship between exposure to EMF at environmental levels and changes in biological function or disease status. The lack of consistent, positive findings in animal or mechanistic studies weakens the belief that this association is actually due to EMF, but it cannot completely discount the epidemiologic findings.
Using criteria developed by the International Agency for Research on Cancer (IARC), the NIEHS working group did not consider the scientific evidence strong enough to label extremely low frequency EMF as a "known human carcinogen" or "probable human carcinogen." However, a majority of the working group concluded that exposure to extremely low frequency EMF is a "possible human carcinogen" based largely on "limited evidence of an increased risk for childhood leukemias with residential exposure and increased occurrence of chronic lymphocytic leukemias associated with occupational exposure." For other cancers and for non-cancer health endpoints, the working group categorized the experimental data as providing much weaker evidence or no support for effects from exposure to EMF. The NlEHS emphasized that the probability that EMF exposure is truly a health hazard is currently small. The weak epidemiologic associations and lack of any laboratory support for these associations provide only marginal, scientific support that exposure to EMF is causing any degree of harm.
At the request of the DOE, following the directive of the 1992 Energy Policy Act, the NRC reviewed and evaluated the scientific and technical contents of the projects completed under the EMF-RAPID program. The NRC established a committee of scientists and engineers to review the activities conducted under the EMF-RAPID program. The NRC committee disagreed with the conclusion drawn by the NIEHS with respect to classification of EMF as a "possible human carcinogen." In its report, the NRC committee noted, "The NIEHS working group produced an extensive, updated review of the entire literature related to all aspects of research on the effects, if any, of magnetic fields - a useful accomplishment that unfortunately was overshadowed by the use of the IARC method to review the status of magnetic fields as a potential human carcinogen. Labeling power-frequency EMF as a possible human carcinogen conveys to the public a conclusion that our committee believes is not supported by the underlying research." The NRC committee concluded that the results of the EMF-RAPID program do not support the contention that the use of electricity poses a major unrecognized public health danger.
Weak associations between exposure to EMF and cancer observed in some epidemiologic studies provide the strongest evidence for adverse health effects of EMF. Epidemiology can be a powerful tool for identifying potential risks when there is a strong correlation between increased risk of disease and specific environmental conditions. Epidemiology is most successful in cases where there are large differences in exposure, where· the adverse effects are not rare, and when large samples can be studied prospectively. However, when the association is weak, interpretations are more difficult, and conclusions concerning risk less convincing. Epidemiologic studies are at a serious disadvantage if they are used in an effort to prove that weak associations exist or do not exist.
Epidemiologic studies examining the possible association between EMF and cancer have some inherent strengths and weaknesses. In order to detect an association between a given risk factor and disease, an epidemiologic study must control for other potential risk factors that may be confounding this association. Even when all potential risk factors are known and controlled to the maximum extent possible, it is frequently impossible to rule out confounding when the strength of an association observed between the risk factor of interest and disease is weak. In reality, it is seldom possible to control for all other potential risk factors, because for many diseases, like various forms of cancer, those other risk factors are unknown. Some epidemiologic studies have found that exposure to EMF may confer a two- to three-fold increased risk of certain cancers. This is a fairly small increase when compared to the association between cigarette smoking and cancer, where the risk is increased by ten-fold or greater.
Furthermore, exposure to EMF is universal and unavoidable. Thus, it is not possible to find a control group of individuals who would be unexposed; only populations with relatively greater or lesser exposure can be compared. Also, past exposure can only be estimated based on electrical wiring configurations found in the homes of study participants. There is no biological test to assess past exposure and current environmental measurements may be misleading. The assumption that the exposed group would have had a higher exposure to EMF than the rest of the population may not be true and, therefore, may skew the interpretation of the results of studies.
Although epidemiologic studies may fail to find an association between a given risk factor and disease, it is practically impossible for any epidemiologic study to rule out the possibility of a weak association. This is because the power of a study to confirm a negative association hinges on the prevalence of the disease of interest and the size of the study population. Because of the rarity of most tumors, any competent epidemiologic study that attempts to rule out very small associations between EMF and one type of cancer would have to include an exceedingly large population. Such a study would almost certainly be cost-prohibitive.
Scientific proof of a cause and effect relationship cannot be readily inferred from epidemiologic studies alone. Causality is established using multiple criteria, only one of which is epidemiologic association. Other important factors in confirming a cause and effect relationship include strength of association, consistency and specificity of observations, appropriate temporal relationship, dose-response relationship, biological plausibility, and experimental verification. None of these factors by itself is sufficient to prove or disprove that an observed association represents a true cause and effect relationship. In the case of EMF, these tests for causality have not been satisfied for the implicit deleterious health effects.