Prenatal exposure to phthalates—a group of chemicals commonly used in personal care products—strongly correlated with abnormalities in male genital development, a study published last week in the online version of Environmental Health Perspectives found.
The study team, led by Shanna Swan at the University of Rochester Department of Obstetrics and Gynecology, looked at 85 mother-son pairs. The researchers tested the mothers? prenatal urine samples for the presence of nine phthalate metabolites, and examined the 85 infant boys for genital characteristics. Researchers found that high levels of four of the compounds correlated with a smaller penis and scrotum and an increased likelihood of undescended testicles. They used an anogenital index—a measurement of the distance between the anus and the base of the penis—to quantify their results. The AGI strongly correlates with penile volume, they said. ?A boy with short AGI has, on average, an AGI that is 19 percent shorter than expected based on his age and weight." Of the 11 boys whose phthalate scores were low, only one had a short AGI.
Phthalates, a group of plasticizing chemicals, prevent nail polish from chipping and help stabilize the scent in shampoos and lotions. They are also widely used in soft vinyl toys and medical tubing and fluid bags. In 1999-2000, the Centers for Disease Control and Prevention found that a majority of the U.S. population had measurable exposures to multiple phthalates. The U.S. Food and Drug Administration does not require premarket testing of ingredients in personal care products. However, a rarely enforced regulation does require products to carry a warning label if one or more of its ingredients has not been proven safe.
Swan said the team plans to write a separate report detailing the correlation between the women?s phthalate levels and their use of personal care products.
Apart from social consequences, the results raise other issues. ?The health concerns relate to the altered levels of testosterone that have a number of consequences,? Swan said, noting that in animals ?there is an entire syndrome associated with prenatal phthalate exposure.? Previous studies have shown that phthalates impaired fertility and semen quality in rats, she said. In summarizing the current study, Swan and her peers wrote, ?These changes in humans ? suggest that these widely used phthalates may undervirilize humans as well as rodents.?
?It?s a really important study,? said Lauren Sucher, a spokeswoman for Environmental Working Group, a consumer watchdog organization that has lobbied for safer personal care products. ?Our policy in this country that allows companies to pollute first and answer questions later should be reversed,? she said.
In the past, the FDA has quieted concerns about phthalates, saying it ?does not have compelling evidence that phthalates, as used in cosmetics, pose a safety risk.? On its Web site, the FDA cites a review by the National Institutes of Health, which concluded that "exposures to phthalates from cosmetics are low compared to levels that would cause adverse effects in animals.?
This is the first phthalate study to assess the effect of phthalates on genital development in humans. Swan and her colleagues noted that the phthalate levels in the mothers whose boys had impaired development were not exceptionally high. ?The median concentrations ? are below those found in one-quarter of the female population of the United States,? they wrote. ?These data support the hypothesis that prenatal phthalate exposure at environmental levels can adversely affect male reproductive development in humans.?
FDA did not immediately return calls seeking new comment on phthalates. Swan said it?s possible the FDA may change its position. ?There is a lot of discussion now about phthalates in the European Union, California and, I hear, in New York—so maybe. At this point, I would be happy just to see better product labeling.?
The American Chemistry Council?s Phthalate Esters Panel—which comprises the major manufacturers of phthalates—predictably disputes the findings, citing an analysis by ?an independent group associated with George Mason University.?
The Statistical Assessment Service—a group based at Mason that ?monitors the media to expose the abuse of science and statistics,? according to its Web site—questioned the statistical and research methods Swann?s group used. ?The authors of the study have attempted to make their case stronger than it is,? STATS reported.
?All choices of models, indexes and cut-points were made prior to examining phthalate metabolite concentrations. We consulted with toxicologists working in this area and were informed that [anogenital distance] was the most analogous measure to that used in rodents. It is also the measurement that is most reliable,? Swann responded in a statement.