There's evidence - but not proof - of a link between a commonly used household pesticide and attention deficit hyperactivity disorder (ADHD) in children and young teens, according to a new study.
Specifically, researchers found an association between exposure to pyrethroid pesticides and adhd, as well as ADHD symptoms such as hyperactivity and impulsivity.
The link between the pesticides and ADHD was stronger in boys than in girls, according to the findings published online in the journal Environmental Health.
However, researchers only found an association between pesticides and ADHD. The study did not prove a cause-and-effect relationship.
Pyrethroid pesticides considered safer
Pyrethroid pesticides - considered safer than organophosphate pesticides - are the most widely used pesticides for home and public health pest control, and their use in agriculture is increasing, according to the researchers.
"Given the growing use of pyrethroid pesticides and the perception that they may represent a safe alternative, our findings may be of considerable public health importance," study corresponding author Dr. Tanya Froehlich, a developmental paediatrician at Cincinnati Children's Hospital Medical Center, said in a hospital news release.
She and her colleagues analysed data from nearly 700 children between the ages of 8 and 15. The children had taken part in the 2000-2001 National Health and Nutrition Examination Survey. The researchers looked at levels of 3-PBA - a chemical indicator of exposure to pyrethroids - in the children's urine.
Boys with detectable levels of 3-PBA in their urine were three times more likely to have ADHD than those without detectable 3-PBA. For every 10-fold increase in 3-PBA levels in boys, there was a 50 percent increased risk for hyperactivity and impulsivity - both symptoms of ADHD.
In girls, levels of 3-PBA were not associated with increased risk of ADHD or symptoms of the disorder.
"Our study assessed pyrethroid exposure using 3-PBA concentrations in a single urine sample," Froehlich said. But because these chemicals don't stay in the body for long, she suggested that future studies need to take multiple measurements over time. Such studies would need to be done before "we can say definitively whether our results have public health ramifications," she said.
Previous studies have found that pyrethroid exposure increases hyperactivity, impulsivity and abnormalities in the dopamine system in male mice, according to the researchers. Dopamine is a brain chemical believed to play a role in many activities, including those that govern ADHD, the researchers said.
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