How is the toxicity of PCBs determined?
To evaluate the potential toxicity of chemicals and the levels associated with the toxicity, EPA uses data from human epidemiological studies, laboratory animal toxicity studies and supporting information that may include structure activity analysis or tests on cells. Epidemiology is the study of the causes of disease. One type of human epidemiological study looks at people who have been exposed to the chemical over a long period of time. These studies evaluate the occurrence of disease in the exposed population with the occurrence of disease in a non-exposed population. PCB epidemiology includes studies of workers exposed in factories that manufactured capacitors and people exposed by eating contaminated fish. The advantage of human epidemiological studies in determining human health risk assessment is obvious since we are concerned with risk to humans. The disadvantages include the difficulties in determining exposures that may have occurred over 30 years ago (based on known cancer l
