Rather, we must ensure that successive generations can reproduce. When an animal is exposed at the same time to many chemicals that individually are at nontoxic levels, additivity, antagonism, potentiation, and synergy can result in unpredictable consequences. Concomitant exposure to multiple chemicals can cause massive or subtle, but potentially tragic, effects. When chemically induced syndromes have been identified in the past, it has been difficult to establish cause and effect relationships, and to do so has frequently taken decades. The basic tenets of epidemiology have proved valuable in organizing information to infer causal relationships.
Wildlife are reliable sentinels of effects of chemicals on human populations.
Lesions at every level of biological organization provide parallels and excellent models for assessing the response of humans exposed to the same chemicals. Effects seen at the cellular levels to the population levels among wildlife populations should be an integral part of assessments of risk or injury to human health. The implications of cumulative exposure to the vast number of chemicals released in the environment are difficult to determine. Although data may become available on the mechanisms of action of certain chemicals, there is no way to account for the interaction of the large number of chemicals to which an animal is exposed. Regional differences in land-use practices, industrial activity, and geophysical characteristics must be factored into a cumulative, multimedia exposure model.