Topic 3.16 Environmental estrogens and sperm counts*

The term “environmental estrogen” refers to chemical substances that exhibit some degree of estrogen-like activity. The primary emphasis for potential adverse effects resulting from exposure to environmental estrogens is on in utero exposure because such exposure can occur during critical periods of organogenesis. Assessment of biological plausibility can be based, in part, on the extensive data on the effects of diethylstilbestrol (DES). The available evidence is too limited to judge with any confidence whether sperm counts have declined during the past 50 years. Based on both animal and human data with DES, it is biologically plausible that in utero exposures to exogenous estrogenic compounds are capable of reducing sperm production in adult men. However, the apparent existence of a maternal dose threshold for DES-induced effects on sperm counts undermines the likelihood that environmental estrogens, which are substantially less potent, are capable of causing similar effects.