Possible Health Effects of Exposure to Residential Electric and Magnetic Fields (1997) / Chapter Skim
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6 Risk Assessment
6 Risk Assessment
Pages 191-199
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From page 191... ...
The task of risk assessment is made more accurate and compelling if the epidemiologic and laboratory data are consistent in positively identifying the suspected agent of disease as the causal factor; a good estimate of the exposure is possible; a dose-response relationship is evident in the data (that is, if one smokes more cigarettes, one is more likely to get lung cancer) ; and a biologically plausible explanation exists for the relationship between the action of the presumed causal agent and the observed effect.
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From page 192... ...
Together with information about costs, benefits, and sociopolitical concerns, risk assessments are used to formulate policies to reduce risks, a process called risk management. The basic tenet of risk assessment is that data on health effects detected in small populations exposed to high concentrations of suspected hazardous agents, usually chemicals, can be extrapolated to predict health effects in large populations exposed to lower concentrations of the same agent.
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From page 193... ...
In this final stage, a quantitative risk assessment is made; that is, a numerical estimate of the magnitude of human risk. The assessments from all these stages are combined with other insights, such as the presence or absence of a biologic explanation for the relationship between exposure and effect, to reach a judgment about the overall concern warranted by exposure to an agent.
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From page 194... ...
Some members of the committee considered the data so inconclusive as to preclude any attempt at risk assessment. Others believe that, even though a quantitative prediction of risk is technically possible, the interpretation of the resulting risk number would be problematic and likely lead to misinterpretations.
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From page 195... ...
Evidence from epidemiologic studies is the most important class of data when performing a risk assessment. The studies involve humans, and the results of the studies can be applied directly.
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From page 196... ...
It is critical to the understanding of our risk assessment to recognize that the epidemiologic studies showing an association between wire codes and childhood leukemia do not establish an association between directly measured electric and magnetic fields and disease, because wire codes have not been validated as an appropriate indirect measure of the fields.
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From page 197... ...
A copromoter might not have the ability to initiate the cancer process, but the risk of cancer can increase when the test biologic system is subjected to a copromoter after the system has been exposed to an initiator. Overall Conclusions for Risk Assessment The body of evidence, in the committee's judgment, has not demonstrated that exposure to power-frequency electric and magnetic fields is a human-health hazard.
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From page 198... ...
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.
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From page 199... ...
Other Possible Human-Health Effects The committee was asked to examine not only data for cancer but also data from studies investigating a possible association between exposure to electric and magnetic fields and health effects related to reproduction and development and necrologic effects expressed as learning or behavioral disorders. Although fewer studies of these effects have been conducted, the committee concludes that no studies to date have shown an association between exposure to residential electric and magnetic fields and an adverse human-health effect.
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