Weak electromagnetic fields and cancer in the context of risk assessment

We review the issue of possible health effects from low-level nonionizing electromagnetic fields from the perspective of risk assessment, in particular cancer risk assessment. We define risk and describe briefly the weight-of-evidence criteria used by agencies (in particular the Environmental Protection Agency and the International Agency for Research on Cancer) in their classification of carcinogens. Last, we review three issues related to electromagnetic fields and cancer: residential exposure to power-frequency magnetic fields and childhood leukemia, occupational exposure to power-frequency magnetic fields and breast cancer, and exposure to low-level radio-frequency fields from communications antennas and cancer. These case histories were chosen to illustrate the problematic nature of the scientific evidence, not to present a comprehensive survey of the entire field. In all of these cases, the evidence in support of links between the fields and cancer is weak and inconsistent. However, in view of the difficulties that are inherent in cancer risk assessment and in proving the negative in general, it is not possible to prove that no such links exist. Moreover, there have been numerous reports of links between nonionizing electromagnetic fields and diverse other health endpoints, so controversy about such links is likely to continue indefinitely. This conundrum may require a more sophisticated understanding of risk and risk communication by people and organizations that are professionally involved with electrotechnology.