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.
This article appeared on page B - 6 of the San Francisco Chronicle
