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Environmental Levels of Phthalates Adversely Affect Male
Reproductive Development in Humans
Report in Environmental Health Perspectives suggests that exposure to a common
class of chemicals poses serious health concerns
[RESEARCH TRIANGLE PARK, NC] For the first time, researchers have identified an
association between pregnant women's exposure to a nearly ubiquitous class of
chemicals known as phthalates and adverse effects on genital development in
their male children. The findings, reported in a study published today in the
online edition of the peer-reviewed journal 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 write.
Most previous studies focusing on phthalate prenatal exposure were in rodents.
The current study analyzed human exposure to phthalates, which are commonly used
in consumer products as solvents and to soften plastics. Phthalates are also
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. Often, the presence of these chemicals is not noted on labels. A
1999-2000 national study found that the majority of the general population of
the United States had measurable exposure to multiple phthalates.
Researchers collected data from 85 eligible mother-son pairs. All mothers had
previously participated in a multicenter pregnancy cohort study. Prenatal urine
samples were analyzed for the presence and quantity of nine phthalate
metabolites at the Division of Laboratory Sciences, National Center for
Environmental Health, Centers for Disease Control and Prevention. The 85 male
children were examined for genital characteristics that serve as markers of
normal sexual development. These measurements were then correlated with the
mothers' prenatal urinary phthalate levels. The findings suggest that some
phthalates have antiandrogenic effects, meaning they may suppress the hormones
involved in male sexual development.
Higher levels of four phthalate metabolites (mono-ethyl phthalate [MEP],
mono-n-butyl phthalate [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, and penis, and an increased likelihood of undescended testicles.
These findings were consistent with those from previous rodent studies on
phthalate exposure. "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 authors write.
The study also noted that the median concentration of phthalate metabolites
associated with adverse male genital development was below the levels found in
one in four women in the United States, based on a nationwide sample.
The lead author of the study was Shanna H. Swan of the University of
Rochester, Department of Obstetrics and Gynecology. Other authors included
Katharina M. Main, Fan Liu, Sara L. Stewart, Robin L. Kruse, Antonia M. Calafat,
Catherine S. Mao, J. Bruce Redmon, Christine L. Ternand, Shannon Sullivan, and
J. Lynn Teague.