(HealthDay)—Only a weak link exists between pesticide exposure and a common birth defect in baby boys, according to a new study.
Researchers examined the association between hundreds of chemicals used in commercial pesticides and a birth defect called hypospadias, in which the urethral opening on the penis is on the underside rather than on the tip.
This birth defect occurs in about five of every 1,000 male infants, and the cause is usually unknown. Some studies have suggested a slightly increased risk for infants whose parents work around pesticides, but many have found no such link.
"We didn't see many chemicals that suggested an increased risk, and of those that did, most of them were infrequently used," study lead author Suzan Carmichael, an associate professor of pediatrics at Stanford University, said in a university news release.
"It is good news that such exposures are rare, but at the same time, when exposures are rare, it makes studies harder to do," she said.
In the study, researchers compared data from 690 male infants born with hypospadias and nearly 2,200 male infants who did not have the birth defect. The infants were born in California's Central Valley, which has one of the highest rates of pesticide use in the nation, according to the study. The mothers of the children lived fairly close to where pesticides were used.
The researchers found that 15 chemicals used in pesticides had possible associations with hypospadias, but they said further research is needed, according to the study, which was published online Oct. 28 in the journal Pediatrics.
Study co-author Gary Shaw, a professor of pediatrics at Stanford, said the jury is still out on the possible association between pesticides and 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," Shaw said in the news release.
Explore further: Hypospadias not related to organic diet during pregnancy
The U.S. National Institute of Environmental Health Sciences has more about pesticides.