‘Weak evidence’ for pesticide link to hypospadias

A study of several hundred chemicals used in commercial pesticides has found only weak evidence that any of them are associated with hypospadias, the authors reported.

In the study, which was published online in Pediatrics (Oct. 28, 2013), researchers analyzed thousands of birth records and commercial pesticide application records for eight counties in California’s heavily agricultural Central Valley. The authors aimed to determine whether children were at increased risk of hypospadias if their mothers had lived in relatively close proximity to where pesticides were used while pregnant.

In the most detailed study of the largest data sets done to date, 292 individual chemicals and 57 groups of structurally similar chemicals were analyzed. Of those, the study identified 15 that had possible associations with hypospadias. But the authors say further studies need to be done.

“We didn’t see many chemicals that suggested an increased risk, and of those that did, most of them were infrequently used. It is good news that such exposures are rare, but at the same time, when exposures are rare, it makes studies harder to do,” said lead author Suzan Carmichael, PhD, of Stanford University School of Medicine, Stanford, CA.

Most previous studies of pesticides and hypospadias focused on risks associated with occupations that involve the use of pesticides. Some studies have suggested slightly increased risks for infants whose mothers or fathers work around pesticides, but many studies suggest no association.

The study population included all male infants born from 1991 to 2004 to mothers residing in any of the eight counties at the time of birth. The study sample comprised 690 cases of hypospadias, as well as 2,195 controls randomly selected for comparison.

The authors considered pesticides used within 500 meters of the mother’s residence during weeks 1 to 14 of each pregnancy.

In addition to exposures to individual chemicals and compounds, the authors looked at exposure to multiple chemicals, but found no evidence to suggest that mothers’ exposures to multiple pesticides put their babies at an increased risk of hypospadias.

“These results extend what we know, but at the end of the day they need to be replicated before we can really be sure whether there is, or is not, a real risk associated with these chemicals,” said co-author Gary Shaw, DrPH.

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