A new study published in a U.S. government journal argues, for the first time, that exposure to phthalates in the womb can affect sexual development in male infants.
The study said evidence suggests that phthalates, which are widely used in cosmetics, paints and as softening agents for vinyl products, can suppress male sexual hormones in babies, mirroring effects seen in laboratory animals.
The research, published in the journal Environmental Health Perspectives and funded in part by the Environmental Protection Agency, said adverse effects were seen at phthalate levels below that found in 25 percent of women in the United States.
But the phthalates industry strongly criticized the study, saying that it has a small sample - 85 mother and child pairs - and questioning whether it would stand up to additional scientific analysis.
The Phthalate Esters Panel, a unit of the American Chemistry Council, in Arlington, Va., said ``initial analyses indicate that the study has many weaknesses,'' and noted that the study's authors say that none of the boys in the study had any obvious genital defects or malformations.
What it did find was a relationship between higher levels of the phthalates and changes in genital development, including increased likelihood of smaller scrotums, penises and undescended testes.
The phthalates panel said it's not clear what the changes mean, and said that the authors of the study concede that one of their key measurements, called anogenital index, may not be clinically relevant. The phthalates panel said the link between phthalate exposure and a small anatomical change is of ``unknown significance.''
The study's lead author, University of Rochester professor of obstetrics and gynecology Shanna Swan, said the results could indicate ``profound'' changes in testicular functions, if they are validated in future work.
``If the change holds up in future studies, it is of tremendous significance,'' she said. ``It has profound effects for the development of the entire organism. To say it is a change of unknown significance is not quite correct.''
The study said the findings ``support the hypothesis that prenatal phthalate exposure at environmental levels can adversely affect male reproductive development in humans,'' the study said.
The study, which also was funded by the National Institute of Environmental Health Sciences and the State of Iowa, is not the first to suggest that phthalates affect human sexual development, but it is the first to look at prenatal exposure.
A 2000 study, for example, found premature breast development in young girls with high phthalate levels, but subsequent research said that might have reflected contamination from lab equipment, the Rochester study said.
A few other studies of humans have suggested that some phthalates are linked to reproductive toxicity, the study said.
The phthalates panel said a detailed review of the study raises questions because it disagrees with conclusions of other studies.
The level of phthalates found in the mothers was thousands of times lower than levels that caused similar changes in rodents, according to ACC. And the industry group said none of the studies showing human health effects have been validated.