New Government Report On Possible Links of EMF to Adverse Health Effects May Stir Controversy

On May 4, 1999, the National Institute of Environmental Health Sciences (NIEHS) issued a report evaluating the evidence of a risk of cancer and other human disease from exposure to the electromagnetic fields (EMF) around power lines. This report is based on a literature review and six years and $60 million of accelerated, Congressionally-mandated research. The report applies to the extremely low frequency electric and magnetic fields surrounding the big power lines that distribute power and the smaller but closer electric lines in homes and appliances. Microwaves emitted from consumer products (such as cell phones and microwave ovens) were not included in the NIEHS study and raise different scientific issues. There are some significant (and perhaps unintended) regulatory and toxic tort consequences to this report.


A 1998 National Academy of Sciences report (NAS) and a long list of other expert reports over the years found insufficient evidence of any adverse health effects from exposure to magnetic fields. The 1999 NIEHS report muddies this prior consensus.

The report concludes that "[w]hile the support from individual studies is weak, these 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." Significantly, the NIEHS report also recommends recognizing magnetic fields as a "possible" cancer hazard, although the report emphasized the weakness of the data and the low risk that may be involved.

The report also states, however, that "[v]irtually all of the laboratory evidence in animals and humans and most of the mechanistic studies in cells fail to support a causal [i.e., cause and effect] relationship." The report clarifies that "the probability that EMF exposure is truly a health hazard is currently small. The weak epidemiological associations and lack of any laboratory support for these associations provide only marginal scientific support that exposure to this agent is causing any degree of harm." The weakness of this conclusion is further highlighted by the language used by a panel of scientists who reviewed the data in open, public hearings: A "role in cancer could not be ruled out." The report states that EMF exposure "cannot be recognized as entirely safe." These statements are hardly scientific claims of causation. Rather, it seems as if NIEHS assumes that the equivocal and weak association shown in some epidemiological studies should prevail unless NIEHS can prove the negative -- that magnetic fields are "safe."

The NIEHS report sends conflicting signals and its conclusions seem to be based more on policy preferences and assumptions than a strong scientific interpretation of the scientific studies. For example, the NIEHS report and cover letter to Congress encourages regulatory efforts to reduce exposure to magnetic fields. However, the report also states that the evidence is "insufficient to warrant aggressive regulatory concern." What is aggressive or too much regulatory concern is left undefined. It is doubtful whether this caution will be remembered if the public becomes concerned about exposures to a "possible" carcinogen.


The NIEHS report and the cover letter communicating the report to Congress contain confusing discussions of the cancer classification of magnetic fields. In part, the confusion stems from the differing carcinogen classification schemes used by the International Agency for Research (IARC), the National Toxicology Program (NTP), and the Environmental Protection Agency (EPA).

The report states that one of the group of experts who reviewed the data at the request of NIEHS concluded that magnetic fields are a group 2B carcinogen using the IARC classification system (i.e., magnetic fields are a "possible" carcinogen rather than a "known" or "probable" carcinogen). It is very unlikely that these experts understood the legal implications of classifying magnetic fields as a "possible" carcinogen. For example, EPA has included IARC 2B carcinogens in their list of hazardous air pollutants subject to the new National Air Toxic Program Integrated Urban Strategy. In fact, EPA specifically rejected comments on the EPA Integrated Urban Strategy that urged EPA not to include "possible" carcinogens because of the weaker scientific support for that classification (see also the next section, below).

The NIEHS report itself evaluated the data on magnetic fields in light of the cancer classification scheme of the NTP (i.e., a substance may be a "known" or "reasonably anticipated" to be a carcinogen) and found that magnetic fields were "not reasonably anticipated" to be a carcinogen. EPA's proposed new cancer classification scheme includes four categories -- "known," "likely," "cannot be determined," and "not likely." Recent statements by some EPA personnel suggest that EPA will treat IARC 2B carcinogens as "likely" carcinogens pursuant to its new scheme, as a preventive approach. Thus, EPA will continue to regulate "possible" carcinogens essentially the same as "known" carcinogens.

According to NIEHS' cover letter to Congress, the next NTP annual report to Congress will not list magnetic fields as "reasonably anticipated" to be a carcinogen. However, absent efforts by industry, the NTP Annual Report will probably reflect the finding of magnetic fields as a "possible" carcinogen, as defined by IARC. Depending upon the exact language used, the debate over magnetic fields may change in tone, at least incrementally.


Once something classified is a carcinogen, there are regulatory impacts, which are discussed below. This discussion only briefly highlights some initial questions. The substantive issues raised by the NIEHS report should probably be examined more thoroughly before any definitive conclusion can be reached.

  • OSHA Hazard Communication Implications

OSHA might decide to apply hazard communication requirements to magnetic fields. OSHA Hazard Communication guidance requires worker notification of hazards based on the IARC cancer classification scheme. Certain OSHA hazard communication requirements are imposed if the cancer hazard is an IARC group 2A carcinogen (i.e., a "possible" carcinogen), although no labeling requirements apply to an IARC group 2B carcinogen (i.e., "probable" carcinogen).

  • California Proposition 65 Implications

California Proposition 65 (a consumer labeling and warning statute) also might be triggered. California Proposition 65 requires labeling on any product sold in the state which contains a substance found by an authoritative body to be a carcinogen. NIEHS and its report to Congress is an authoritative body. As of 1995, approximately 93 percent of the IARC group 2B carcinogens (i.e., "possible" carcinogens) had been listed as carcinogens on the California Proposition 65 list of substances known to the State of California to cause cancer. As a result of lawsuits, the State of California generally adds any substance or chemical which is listed as a carcinogen by NIEHS to the Proposition 65 list of chemical substances known to the state to cause cancer.

This article does not definitively assess whether Proposition 65 would apply to magnetic fields. For example, it is unclear whether or not magnetic fields fall within the jurisdiction of the statute. The answer may depend on whether magnetic fields, which are energy waves, not substances or chemicals, are covered by the statute. There are arguments against such a draconian interpretation. However, the Proposition 65 court decisions and settlements to date have been draconian. Everything from china plates and the caps used to cover the corks on wine bottles to parking garages have been alleged to require warnings. Significant interpretation issues still need to be addressed.

If California were to list magnetic fields as a carcinogen or even a "possible" carcinogen, electric consumer products and power lines in California might be required to have warning labels. Once something is placed on the California Proposition 65 list, in effect, the burden shifts to the defendant to disprove that a reasonable exposure would result in a significant risk.

  • Triggering Regulatory Action Generally

Listing of magnetic fields as a "possible" carcinogen by NIEHS may result in a number of governmental agencies deciding to assess the risks from magnetic fields and concluding that regulatory action is warranted. As noted above, in many programs EPA uses IARC and other cancer classification schemes as a method of prioritizing substances to be considered for regulation. In fact, in some situations, federal or state agencies might be forced to develop mandatory magnetic field standards because regulatory action is required for "possible" carcinogens.

Classifying magnetic fields as a "possible" carcinogen is particularly worrisome because "possible" carcinogens are generally regulated almost as stringently as known carcinogens. For example, 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin) is an IARC group 2B carcinogen. This fact has not stopped EPA from regulating dioxin vigorously.


The tone of the NIEHS report is alarmist, given the actual facts reported. The NIEHS does not attempt to explain the reason for the difference in emphasis between this report and last year's NAS report. There is no dramatic new positive evidence of harm caused by magnetic fields.

Most of the new data in the NIEHS report does not support the NIEHS characterization of the risk. For example, one of the studies sponsored by NIEHS was a classical rat/mouse exposure study. In these studies, at least two species of test animals were exposed to magnetic fields of varying strengths over their lifetime. The studies found no increase in tumors due to the magnetic fields. The experimental findings are consistent with other studies evaluated which do not even suggest a biological theory that could explain the adverse impacts. Ironically, the one animal mechanism study that had argued that it supported a biological mechanism (even though the study seemed to be incapable of independent repetition) has been withdrawn by the author because of allegations of scientific misconduct or fraud. Normally, a finding of no adverse effects in animal studies and the lack of plausible biological theory would lead researchers to conclude that the substance or radiation tested is not a carcinogen.

The report repeatedly states that there is a small increased risk using some methods of "measuring magnetic fields." The methods of measuring exposure to magnetic fields which is weakly associated with a small increase in risk, however, refers to "wiring configuration codes," rather than measured magnetic field exposure. In fact, the association is weakened or disappears when actual magnetic field measurements are used.

In this context, the finding of the report that magnetic fields are a "possible" carcinogen is an overreaction and clearly based on the impossible burden of being required to prove safety.


Alas, it seems inevitable that there may never be a "definitive" study on this topic. It has always been difficult, if not impossible, to prove a negative. NIEHS seems to have concluded that the data must demonstrate magnetic fields are "safe" to a high degree of certainty before they will conclude that magnetic fields are not a carcinogen. Also, it is perhaps merely coincidental that it is in the financial interest of NIEHS and the research community generally to recommend further research. Thus, some funding for further EMF research is likely. In fact, given the budget surpluses, it would be surprising if all research funding ended.