Signs of a link between exposure to insect repellents and a common congenital anomaly were reported today by a team of epidemiologists in Occupational and Environmental Medicine.

 

“No previous study has linked hypospadias with insect repellents,” write Julien Dugas and colleagues, from research institutions in the UK and Spain.

 

They looked into the use of insect repellents or biocides in the first trimester of pregnancy, but say the study should be followed up with a more detailed investigation of the exposure.

“The use of insect repellent warrants further investigation, specifically in relation to type, content and frequency of use since this information was missing from the current study.”

 

Insect repellents come in various formulations that may contain DEET, picaridin, permethrin, or other active ingredients. The US Environmental Protection Agency (EPA) estimates that each year about a third of the country’s population use any one of 140 repellents, which are made up of 4–100% DEET. Although the chemical is considered safe with proper use of these products, concerns still linger over potential toxicity.

“High doses of DEET are toxic and it can cross the placental barrier, but its consequences are not well understood,” say the authors.

 

One of the unknowns is how use of the pest-control products could influence the risk of hypospadias, a congenital disorder of the urethra and penis. The disorder has been associated with exposure to pesticides among other factors, and last year a study co-authored by members of the research team reported a link between hypospadias and exposure to phthalates among hairdressers.

 

For this investigation the team recruited 471 mothers of babies who were referred to surgeons for the birth defect in South-East England between 1997 and 1998, and 490 mothers of healthy babies born in the same period and geographic area. In telephone interviews the authors asked them to recall any use of insect repellents and biocides in the first three months of pregnancy, and collected information on other factors that could influence the results.

 

Compared to mothers of healthy children, those who gave birth to children with the defect were more likely to have used insect repellents early on in their pregnancy. “We found a significant association for risk of hypospardias with the use of insect repellents and total biocide score, but not with the use of individual biocides or indicators for its use,” note Dugas and colleagues.

 

The total biocide score indicates a combined high exposure to biocides in various forms including garden pesticides, ant powders, and rat poison. But the authors caution that this measure could also stand for other exposures that have a bearing on the risk of hypospadias. They add that before conclusions can be drawn, more studies will be needed to confirm the findings and analyse more specific information about exposure to the repellents.