Although it is known that infants are more susceptible than adults to the toxic effects of pesticides, this increased vulnerability may extend much longer into childhood than expected, according to a new study by researchers at the University of California, Berkeley. Among newborns, levels of paraoxonase 1 (PON1), an enzyme critical to the detoxification of organophosphate pesticides, average one-third or less than those of the babies’ mothers. It was thought that PON1 enzyme activity in children approached adult levels by age two, but instead, the UC Berkeley researchers found that the enzyme level remained low in some individuals through age seven. Based upon the findings, reported in the journalEnvironmental 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 three to five times more susceptible than adults, and for other pesticides the standards assume no difference,” said Nina Holland, Ph.D., 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 seven. 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.”