Researchers have identified a link between exposure in the womb to widely used chemicals known as phthalates and adverse effects on genital development in male babies, according to a new report. Previous toxilogical studies had suggested that fetal exposure to the chemicals can affect reproductive development in rodents, but the new results indicate that developing humans could be vulnerable as well.

Phthalates are common components of items ranging from plastics to paints to personal care products such as nail polish and shampoo. In the first study of prenatal exposure to phthalates in humans, Shanna H. Swan of the University of Rochester and her colleagues studied 85 mother-son pairs. Prior to giving birth, the mothers supplied urine samples, which were analyzed for the presence and quantity of nine phthalate metabolites. The doctors also examined the children, who were between the ages of two and 30 months, for genital characteristics used as markers of normal sexual development.

When the researchers correlated the results with the mothers' level of exposure, they found that higher levels of four metabolites in their urine were correlated with a higher-than-expected number of changes to genital development in the baby boys. These changes include smaller scrotum and penis size and a smaller measurement known as the anogenital distance (AGD). None of the children were grossly abnormal, however, and the scientists detected no complete malformations or definite markers of disease. The results are consistent with the findings of animal studies, the authors note, but they caution that the use of AGD as a marker of sexual development in people is relatively new. Nevertheless, they conclude that the findings "support the hypothesis that prenatal phthalate exposure at environmental levels can adversely affect male reproductive development in humans." A report detailing the study will be published in an upcoming issue of the journal Environmental Health Perspectives.