WASHINGTON (Reuters) – Children whose mothers were exposed to certain types of pesticides while pregnant were more likely to have attention problems as they grew up, US researchers reported recently.

The study, published in Environmental Health Perspectives, adds to evidence that organophosphate pesticides can affect the human brain.

Researchers at the University of California Berkeley tested pregnant women for evidence that organophosphate pesticides had actually been absorbed by their bodies, and then followed their children as they grew.

Women with more chemical traces of the pesticides in their urine while pregnant had children more likely to have symptoms of attention deficit hyperactivity disorder, or ADHD, at age five, the researchers found. "While results of this study are not conclusive, our findings suggest that prenatal exposure to organophosphate pesticides may affect young children's attention," Amy Marks and colleagues wrote in the study. To test for ADHD, the researchers questioned the mothers and also gave the children standardised tests.

Organophosphates are designed to attack the nervous systems of bugs by affecting message-carrying chemicals called neurotransmitters including acetylcholine, which is important to human brain development.