Children whose mothers were exposed to certain pesticides while pregnant have an increased chance of attention problems, according to a new study by researchers at the University of California at Berkeley.

Researchers tested the urine of pregnant mothers to determine if their bodies had absorbed organophosphate pesticides, and later tracked the development of the women’s children as they grew up, Reuters reports.

To determine if the children had symptoms of attention deficit hyperactivity disorder, researchers gave the kids standardized tests and interviewed the mothers. according to the findings, women with more traces of the pesticides in their urine were more likely to have kids with symptoms of ADHD by age 5.

The children of mothers who had a tenfold increase in traces of the pesticides in their urine were six times as likely to have symptoms of ADHD by age 5. The apparent link was even stronger in male children.

“While results of this study are not conclusive, our findings suggest that prenatal exposure to organophosphate pesticides may affect young children’s attention,” researcher Amy Marks wrote.

Organophosphate pesticides attack the nervous system of bugs by affecting neurotransmitters, which carry messages through the nervous system. One of these neurotransmitters, acetylcholine, is also important to human brain development.

Other studies have linked exposure to the pesticides to Parkinson’s disease, a degenerative disorder of the nervous system.

The report was published online in the journal Environmental Health Perspectives.