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.
Migratory species pose additional difficulties when determining sources of exposure.
No systematic, coordinated effort has been undertaken to determine the geographic extent to which contaminants contribute to the degradation of wildlife populations. While there is evidence in areas where researchers have suspected and looked for wildlife damage, there are many more areas of the continent that have not yet been surveyed. Consequently, the magnitude of the damage is incompletely understood for major wildlife taxa. U.S. and Canadian governmental agencies no longer appear willing to commit sufficient long-term, fiscal resources for documenting the effects of chemical exposure in wildlife. Until responsible parties are designated and given adequate appropriations to address wildlife health problems, biodiversity will continue to decline.