Children's vulnerability to pesticides' exposure may extend much longer into childhood than expected, according to a new study by researchers at the University of California, Berkeley.

Scientists found that adult levels of PON1 - an enzyme critical to the detoxification of organophosphate pesticides - are not reached by age 2, as was thought, but the enzyme level remained low in some individuals through age 7.

Based upon the findings, published in the journal Environmental Health Perspectives, the study authors recommend that the U.S. Environmental Protection Agency (EPA) re-evaluate the current standards for acceptable levels of pesticide exposure.

"Current EPA standards of exposure for some pesticides assume children are 3 to 5 times more susceptible than adults, and for other pesticides the standards assume no difference," said Nina Holland, UC Berkeley adjunct professor of environmental health sciences and senior author of the paper. "Our study is the first to show quantitatively that young children may be more susceptible to certain organophosphate pesticides up to age 7. Our results suggest that the EPA standards need to be re-examined to determine if they are adequately protecting the most vulnerable members of the population."

In 2001, the EPA began restricting organophosphate pesticides in products sold for use in homes, mainly because of risks to children. However, organophosphate pesticides, such as chlorpyrifos and diazinon, are still used in agriculture in the United States and elsewhere.

The study, conducted by UC Berkeley's Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS), involves 458 children from an agricultural region who were followed from birth through age 7.

"What's important about this study is that it shows that young children are potentially susceptible to certain organophosphates for a longer period of time than previously thought," said Brenda Eskenazi, UC Berkeley professor of epidemiology and director of CHAMACOS and the Center for Children's Environmental Health Research. "Policymakers need to consider these vulnerable populations when establishing acceptable levels of exposure to different pesticides."

Source: www.berkeley.edu