Pesticide threat to babies linked to enzyme levels
Researchers find them much more at risk than adults
06.03.2006 |Sascha Gabizon
Source: San Fransisco Chronicle
Jane Kay, Chronicle Environment Writer
Friday, March 3, 2006
The regulation of pesticides might not be strict enough to protect newborns and infants, a study published Thursday by UC Berkeley researchers suggests.
The study of 130 mothers and their children in California's Central Valley revealed that a natural enzyme in the human body that breaks down toxicants, including commonly used pesticides, varies to such a degree that some of the population's youngest members may be virtually defenseless against some chemicals.
For the first time, researchers believe they can predict people's vulnerability to certain pesticides based on their enzyme levels, their age and their genetics.
"People have this remarkable difference in enzymes that defend their health from pesticide exposure,'' said Nina Holland, a UC Berkeley adjunct professor and molecular epidemiologist in children's environmental health.
"In developing regulatory standards for safe levels of exposure, we need to protect the most sensitive in a population, particularly because children and unborn fetuses are involved,'' said Holland, an author of the study published in the journal Pharmacogenetics.
The human body contains dozens to hundreds of important enzymes that control metabolism. Other studies already have shown that this particular enzyme, PON-1, is linked to protection against neurodegenerative or cardiovascular diseases.
The study was designed to examine the protective levels of the enzyme against a class of chemicals called organophosphates, which were developed in the 1940s as warfare agents. In pesticides, they attack the nervous systems of insects.
Two common organophosphate pesticides, diazinon and chlorpyrifos, were widely used before they were restricted for most household uses by the state and the U.S. Environmental Protection Agency by 2002. Chlorpyrifos was a key ingredient in the popular Raid spray pesticide before the restriction took effect.
By analyzing the enzyme in newborns, the researchers found that some newborns may be 26 times more susceptible to diazinon exposure than newborns with the highest level of the enzyme, and 65 times more susceptible than adults with the highest enzyme levels.
With chlorpyrifos, some of the newborns may be 50 times more susceptible than newborns with high enzyme levels and 130 to 164 times more susceptible than some of the adults. The enzyme typically reaches adult levels by the time children reach 2 years old.
The two pesticides are still used on cropland, where the brand names for chlorpyrifos are Dursban and Lorsban.
"Chlorpyrifos was banned in households largely because of its hazards to children,'' said Margaret Reeves, senior scientist at Pesticide Action Network of North America in San Francisco. "But it's still widely in farm applications, putting at risk the health and well-being of farmworkers, farm families and rural-urban interface areas.''
The EPA reported that about 20 percent of all foods for sale in 2001 had residues of one or more organophosphate pesticides, according to the group.
An author of the new study, Brenda Eskenazi, UC Berkeley professor of epidemiology and director of the school's Center for Children's Environmental Health Research, coordinated the research through the school's Salinas-based Center for the Health Assessment of Mothers and
Children.
In addition to the study, the researchers have collected samples from 470 other mothers and their children, which they will continue to follow along with the original 130.
