The findings, reported in a study published in the online edition of Environmental Health Perspectives, are the first to"support the hypothesis that prenatal phthalate exposure at environmental levels can adversely affect male reproductive development in humans", the authors state.
Previous studies on male animals, mainly rodents, have shown that high levels of phthalates can make them more feminine and lead to poor sperm quality and infertility. The new study indicates that exposure to normal levels of phthalates may have a similar effect on humans. In the study researchers from a number of universities analysed human exposure to phthalates, which are commonly used in consumer products assolvents and to soften plastics for bags.
Phtalates can also be found in soft vinyl plastic toys, medical tubing and fluid bags, and a variety of cosmetics such as perfume, lotion, shampoo, make-up, nail polish, and hairspray.
A national study in the US found that the majority of the general population had measurable exposure to multiple phthalates, the scientists stated. Researchers collected data from 85 mother andson pairs. Prenatal urine samples were analysed for the presence and quantity of nine phthalate metabolites. The 85 male children were then examined for genital characteristics that serve as markers of normal sexual development.
"The findings suggest that some phthalates have antiandrogenic effects, meaning they may suppress the hormones involved in male sexual development," the scientists state. "Higher levels of four phthalate metabolites (mono-ethyl phthalate [MEP], mono-n-butylphthalate [MBP], mono-benzyl phthalate [MBzP] and mono-isobutyl phthalate [MiBP]) were found to correlate with a higher-than-expected number of abnormalities in genital development including smaller anogenital distance, scrotum, andpenis and an increased likelihood of undescended testicles."
The findings were consistent with those from previous rodent studies on phthalate exposure, they stated.
"These changes in humans associated with prenatal exposure to some of the same phthalate metabolites that cause such alterations in male rodents suggest that these widely used phthalates may undervirilize humans as well as rodents," the authorswrote.
The lead author of the study was Shanna Swan of the University of Rochester's department of Obstetrics and Gynecology. Environmental Health Perspectives is published by a section of the US health andhuman services department.