THURSDAY, March 2, 2017 (HealthDay News) -- Children exposed to a widely used group of insecticides may be at increased risk for behavioral problems, according to a new study.
The insecticides are called pyrethroids. They're used on crops but can also be found in some mosquito repellents and in products used to treat head lice, scabies and fleas, the French research team explained.
Like many types of insecticides, pyrethroids work by damaging nerves, and concerns have recently been raised about their possible effects on children who have been exposed.
The study can't prove cause-and-effect. However, according to one child psychiatrist, it does raise troubling questions.
"The pesticide class studied are considered 'safe' pesticides and this study is cause for concern as to how safe it really is," said Dr. Matthew Lorber, who reviewed the new findings. He directs child and adolescent psychiatry at Lenox Hill Hospital in New York City.
The new study was led by Jean-Francois Viel of the University Hospital in Rennes, France. His team measured hundreds of pregnant women's exposure to pyrethroids, as well as their children's exposure, by assessing levels of pyrethroid metabolites in their urine.
At age 6, the children underwent behavioral assessments.
Viel's team found a link between pyrethroids and behavioral problems in the children.
Specifically, higher levels of a certain pyrethroid-linked chemical in the urine of pregnant women was associated with an increased risk of internalizing behaviors -- for example, an inability to share problems and ask for help -- in their children.
The presence of one such chemical in children's urine was also associated with an increased risk of externalizing disorders -- defiant and disruptive behaviors. And another pyrethroid-linked chemical was associated with a lower risk of externalizing disorders, the researchers said.
Overall, children with the highest levels of pyrethroid metabolites in their urine were about three times more likely to have abnormal behavior, the French study found.
Pyrethroids may trigger behavioral problems by affecting neurochemical signaling in the brain, the study authors suggested.
"The current study suggests that exposure to certain pyrethroids at the low environmental doses encountered by the general public may be associated with behavioral disorders in children," Viel's group wrote.
For his part, Lorber called the findings "concerning, because the amounts determined to be 'low exposure' are consistent with what children are typically exposed to in the environment."
Dr. Andrew Adesman is chief of developmental and behavioral pediatrics at Cohen Children's Medical Center in New Hyde Park, N.Y. He agreed with Lorber that the findings suggest that pyrethroids "may not be as safe as we would like when it comes to young children."
According to Adesman, "Common sense suggests that pregnant women should minimize their exposure to insecticides and other toxins, as well as other industrial chemicals. Further study is warranted to determine if the insecticides that are now widely used are indeed as safe as people believe."
The study was published online March 1 in the journal Occupational & Environmental Medicine.
The U.S. Environmental Protection Agency has more on pesticides.