SALINAS CALIFORNIAN

July 6, 2006

DDT found in kids of farm-worker moms
Some exposed to chemical in Mexico

 

By ZACHARY STAHL
The Salinas Californian

Babies born to Mexican farm-worker women exposed to the insecticide DDT in their homeland have developmental delays that include mental and physical impairment, according to a study published Wednesday.

Conducted through the University of California, Berkeley, Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS), the study measured blood levels of DDT in 360 pregnant women who recently emigrated from Mexico to the Salinas Valley.

For every tenfold rise in DDT exposure, the children's scores on mental tests dropped two to three points at 12 and 24 months.

The Bayley test is designed so that the average score is 100 and scores below 85 indicated a possible developmental delay.

In the most severe cases, the highest DDT doses were associated with a 7- to 10-point drop in the mental scores of 2-year-old children compared with those who were not exposed.

"The level of effects we saw are definitely quite significant and for the most highly exposed kids could affect how they learn and how they acquire language," said Asa Bradman, co-author of the study and associate director of CHAMACOS.

The study is part of the federally-funded U.C. Berkeley project that, since 1999, has investigated the exposure of pregnant women and children to pesticides and allergens.

Developed in the beginning of World War II, DDT was initially used to combat malaria and other insect-borne human diseases among both military and civilian populations by killing area insects.

Used in Mexico until 2000

Because DDT has been banned in the United States since 1972, Bradman said the women likely were exposed to the insecticide through sprayed applications in Mexico or from consuming food with residue from the chemical.

Ninety percent of the women in the study were born in Mexico, where DDT was widely used to keep insects off crops during the 1970s. It was then gradually phased out. By 1995, DDT applications were banned anywhere in Mexico other than to abate the spread of malaria by killing mosquitoes. In 2000, a complete ban went into effect.

DDT is transmitted to a fetus from its mother via the placenta.

Researchers used development assessments known as the Bayley Scales of Infant Development to observe the effects of the insecticide.

In the motor skills evaluations, there were 2-point decreases in children's scores at 6 and 12 months for each tenfold increase in DDT levels in the mothers.

The children, who just turned 5 years old, will be reevaluated at age 7, once they have had a full year of school, Bradman said.

"It will be important to see how (DDT) exposure is related to functions in school," he said.

Global relevance to study

Considering that Monterey County has a large immigrant population, primarily coming from Mexico.

Bradman said DDT levels were higher for women born in the coastal regions of Mexico than the interior. Use of DDT decreased faster in the central areas of the country, where more crops were exported to the United States, which had banned the chemical.

"People who are from certain regions of Mexico whose parents grew up in certain times may carry these exposures," Bradman said.

César Lara, executive director of the Central Coast Citizenship Project, said more research is needed on the subject. If the findings are corroborated, children and mothers should receive testing for DDT and treatment, Lara said.

The study is the first to examine the effects of maternal levels of DDT, rather than its breakdown products, on the development of mental and physical skills in children.

The study's findings have particular relevance to the current debate on the use of DDT in Africa to combat malaria.

Despite the fact that DDT is also transmitted through breast milk, the study found that the longer the children nursed, the better they scored on developmental tests.

"Breastfeeding is really the best way to give your kids a head start in terms of their health and development," Bradman said.

Current pesticides studied

In the fall, CHAMACOS will publish several papers on the effects of pesticides used today, he said.

Mike Meuter, director of litigation, advocacy and training for California Rural Legal Assistance in Salinas, said the DDT study shows more data is needed on the long-term health effects of pesticides being sprayed on crops in Monterey County.

"It reinforces the need for more research like this on these alarmingly high quantities of pesticides that are still in use here in California," said Meuter, who is also a member CHAMACOS' community advisory board.

Meanwhile, the Monterey County District Attorney's Office is in settlement negotiations with potential defendants in a pesticide leak incident that occurred in October, said Deputy District Attorney Matt Bogoshian.

About 60 northeast Salinas residents experienced eye and throat irritation from a chloropicrin leak in a nearby strawberry field Oct. 5. The soil fumigant was applied through a drip-irrigation system - a relatively new means of application - and spread to the neighborhood.

Bogoshian said no criminal complaint has been filed, but a resolution could come within the next few months.