To reach their conclusions, researchers measured the AGDs of 126 men born in or after 1988, a small but statistically significant sample, Swan said.

The study did not address what might cause certain men to have short AGD measurements.

But previous studies, published in 2005 and 2008, looked at the possible link between mothers who were exposed to chemicals called phthalates during pregnancy and the AGD of their infant and toddler sons.

Phthalates are a group of chemicals widely used in industrial and personal care products, including fragrances, shampoos, soaps, plastics, paints and some pesticides.

In these earlier studies, the scientists tested for the presence of phthalates in the pregnant women’s urine. They found that women who had high levels of phthalates in their urine during pregnancy gave birth to sons who were 10 times more likely to have shorter than expected AGDs.

Swan, who also co-authored the earlier papers, said they showed the correlation between prenatal phthalate exposure and shorter AGD.

The latest study does not address prenatal phthalate exposure directly, “but it does answer the question of why we should care about AGD,” Swan said. “And it does suggest that whatever is altering AGD is also altering sperm count.”

SOURCE: Environmental Health Perspectives, online March 4, 2011.