Environmental estrogens: roles in male reproductive tract problems and in breast cancer.

It has been hypothesized that endocrine disruptors and particularly synthetic estrogenic environmental contaminants (xenoestrogens) are etiologic factors in the global decrease of sperm counts and other problems of the male reproductive tract, including cryptorchidism, hypospadias, and testicular cancer. Xenoestrogens might also be linked to an increased incidence of breast cancer in women. These hypotheses have stimulated research addressing the current incidence rates and time-dependent changes in these human health problems, and the results do not support the hypotheses. With the exception of testicular cancer, the evidence does not indicate that sperm counts and other male reproductive tract problems are increasing, and correlations with xenoestrogen exposure have not been made. Moreover, initial observations that the level of certain organochlorine pollutants is higher in breast cancer patients vs. controls have not been duplicated in more recent studies. The results do not preclude an environmental eitology to some of these health problems or to susceptible subpopulations, and these areas require further research and critical scrutiny.