Tap water chemicals not linked to penis defect
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Though some research has linked chemicals in chlorinated tap water to the risk of birth defects, a new study finds no strong evidence that the chemicals contribute to a common birth defect of the penis.
The defect, known as hypospadias, occurs when the urinary outlet develops on the underside of the penis rather than at the tip. Genetics are thought to play a large role in hypospadias risk, but the other potential causes are not fully understood.
Some past studies have suggested that certain chemicals in tap water—byproducts of the chlorination process used to kill disease-causing pathogens—may contribute to the risk of birth defects and miscarriage. Other studies, though, have found no such links.
For the current study, researchers led by Tom J. Luben of the U.S. Environmental Protection Agency used birth records from 934 boys born in Arkansas between 1998 and 2002. Of these children, 320 were born with hypospadias.
Luben’s team analyzed monitoring data from local water utilities to estimate the mothers’ exposure to two major classes of water-disinfection byproducts during pregnancy.
Overall, the researchers found, women with the greatest exposure to these chemicals were no more likely to give birth to a boy with hypospadias than women with the least exposure.
They report the findings in the journal Occupational and Environmental Medicine.
“Our results do not support the hypothesis that continuous or intermittent exposure to tap water disinfection byproduct concentrations within regulatory limits during gestation is associated with giving birth to a son with hypospadias,” Luben and colleagues write.
However, the findings are not the final word, either.
The researchers did find that when they accounted for mothers’ total exposure to certain chemicals—through drinking, bathing and showering—there was some evidence of a link to hypospadias.
There was, however, no clear pattern of hypospadias risk climbing as mothers’ exposure to tap water chemicals increased. Such patterns, known as a “dose-response” relationship, are considered to be evidence of cause-and-effect.
The results, according to Luben’s team, “could be due to chance.”
They call for further studies, with more-precise information on individual women’s exposure to tap water chemicals, to help settle the question.
SOURCE: Occupational and Environmental Medicine, June 2008.
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