Exposure to chemicals, offspring sex ratios, and their relevance to teratology

Rationale for the study of the human sex ratio in population studies of polluted environments

The human secondary sex ratio remains a subject of substantial interest. The possibility has been raised that environmental chemical exposures have played a role in the changes associated with the sex ratio in a number of countries. The possibility that such an effect may be present is supported at least theoretically by the observation that clomiphene citrate, a drug used in the treatment of infertility with powerful estrogenic and anti-estrogenic properties, has profound effects on the sex ratio resulting in significantly fewer males at birth. Using a model of causality based on the clinical identification of adverse drug effect methodology one may improve the objectivity of the assessment of significant environmental exposures on this human reproductive outcome.