Back in May, researchers found that children with high levels of pesticides in their urine were almost twice as likely to develop ADHD as those with undetectable levels.  A new study, published in Environmental Health Perspectives, takes this study one step further, finding a link between prenatal pesticide exposure and the development of ADHD, or attention deficit hyperactivity disorder, in children.

For the study, researchers at the University of California Berkeley tested pregnant women for evidence of exposure to organophosphate pesticides.  Pregnant women with more chemical traces of the pesticides in their urine had children who were more likely to have symptoms of ADHD by age five.

The researchers tested Mexican-American women living in the Salinas Valley of California, an area of intensive agriculture, with a high level of pesticide exposure.  They tested both the pregnant mothers and then their children after they were born and as they grew for breakdown products or metabolites from pesticides in urine samples.

There weren't many symptoms for children up until the age of three, but by age five, researchers noted a tenfold increase in pesticide metabolites in the mother's urine correlated to a 500 percent increase in the chances of ADHD.  And the trend was stronger in boys.