of in vitro effects does not necessarily imply potential adverse human-health risk. Animals see because a neural effect occurs; light enters the eye, strikes the retina, and the brain forms messages on the basis of information it receives. Yet, the effect of vision is not a deleterious human-health effect, even though an effect, indeed, has been demonstrated. For example, although tests have shown that many animals can detect electric fields at 1 to 5 kV/m, there has been no evidence that these effects imply a health hazard.

Exposure to electric and magnetic fields is not genotoxic at any level of exposure. After considering the effects of exposure to electric and magnetic fields on laboratory animals, the committee concludes that the effects of such fields have no consistent pattern as a direct carcinogen. Evidence, not yet replicated, does show that exposure to electric and magnetic fields combined with exposure to high concentrations of known carcinogens increases the number of rat tumors and accelerates their appearance. Such evidence does not identify electric and magnetic fields as a probable carcinogen.

Finally, after analyzing the epidemiologic data, the committee concludes that the evidence of an association between exposure to electric and magnetic fields and cancer is not convincing, although residential wire codes have been associated with cancer. In addition to these data, no plausible biophysical mechanism has been identified that would suggest that the action of electric and magnetic fields is carcinogenic.

The data at different biologic complexities, taken in total, do not provide convincing evidence that electric and magnetic fields experienced in residential environments are carcinogenic. No tests or studies can prove that an agent is not carcinogenic at some dose level, in combination with some other biologic agent, or for some sensitive populations of humans. All that can be stated is that, under the exact experimental conditions of an extremely large number of studies, exposure to power-frequency electric and magnetic fields at environmental strengths does not produce patterns of data similar to those found for other agents that have been shown to be carcinogens. Possibly, such fields can be hypothesized to act as a nongenotoxic cocarcinogen or to act through hormonal pathways to suppress protective molecules, such as melatonin. Although such hypotheses must be tested carefully when scientific justification exists to do so, the overall conclusion that must be drawn from all the data in the studies of cells, lower animals, and humans is that the data are negative or inconclusive. Electric and magnetic fields are neither genotoxic in cells, nor a direct carcinogen in animals, nor associated conclusively with cancer in exposed humans.

The association between residential proximity to high-wire-code configurations and increased rates of childhood leukemia remains unexplained, as do the associations between occupational exposures and leukemia and brain cancer. Positive human epidemiologic data are the strongest evidence in evaluating any human-health risk. The associations for childhood leukemia have been shown to be statistically reliable and robust findings that must be considered carefully in