The most compelling evidence of the risks of carcinogenic effects of environmental pollutants comes from animal data, such as the reproductive failure and anomalous development witnessed in birds and fish exposed to DDT. Line But can human health effects of a compound be judged without a consensus of (5) independent epidemiological studies and experimental findings on humans subjects? One would argue not, even though increases in breast cancer have recently been correlated to exposure to environmental pollutants. Scientists reviewing worldwide morbidities of certain hormonally responsive organs have found that while the incidence of breast cancer has been increasing, that of (10) cancer of the uterus, another hormonally responsive organ, has been decreasing. There is thus no evident increase in uterine cancer that would support the claim that a pollutant is causally responsible for the recent increase in breast cancer. It has been suggested that the increase may be the result of increased diagnosis, and geographical differences in cancer susceptibility are so (15) large that the currently available statistics do not permit a definite conclusion. The primary purpose of the passage is to treat the potential correlation between environmental pollutants and carcinogenic effects in which of the following ways?