Due to a lower amount of protective natural enzymes, children are more susceptible to the effects of pesticides than scientists previously thought, according to a new study by UC Berkeley researchers.

The study, published this month in Environmental Health Perspectives, found that long-term pesticide exposure for children inhibits their levels of paraoxonase, a human enzyme that protects the body from chemicals found in pesticides.

"This is the first time we're able to put quantitative information together," said Nina Holland, a co-author of the study and an adjunct associate professor of genetics and toxicology at UC Berkeley. "We were able to add numbers and more sufficient data to this concept of children being susceptible to pesticides."

The enzyme level would normally increase as the child grows up, according to the study, but continued

exposure to pesticides could stunt the production of the enzymes.

The limitation on the enzyme production could leave children open to serious health problems, as pesticides can contain chemicals typically used as agents in chemical warfare, Holland said.

"It could cause many problems-deadly," she said.

The study, conducted by UC Berkeley's Center for the Health Assessment of Mothers and Children, tested the enzyme levels of 458 Mexican-American children from Salinas, Calif.

The testing started more than 10 years ago when the mothers of the children were pregnant. The children are now nine years old.

The children were tested five times from infancy until they were seven years of age, according to the study.

The research team noticed a trend in the blood samples and saw that the amount of the enzyme in the subjects-which is supposed to reach adult levels by the time a person is two years old-had not reached those levels by the time they were seven, according to the study.

The study concluded that the abnormally low levels were a sign that production of the enzyme had stopped.

"In the past it was assumed that while newborns have very low (paraoxonase) levels, they gradually increased and reached a plateau at the age of two," said Karen Huen, a graduate student in environmental health science and co-author of the study, in an e-mail. "Now we know that the window of increased susceptibility is much longer in kids."

The study recommends that the U.S. Environmental Protection Agency extend its standard window of pesticide susceptibility in children from ages 3 to 5 to at least 3 to 7 years.

"This means that the EPA 3 to 5 fold susceptibility standards may not be adequate for protecting young children," Huen said. "It will be important to consider this new data to determine whether the current standards are stringent enough to protect children."

Tags: ENVIRONMENTAL PROTECTION AGENCY