DDT-Like Pesticides Linked to Autism, Study Suggests

By Anastacia Mott Austin

Scientists hoping to discover the root causes of autism may have found a new link to the disorder. A study published online this week in the journal Environmental Health Perspectives shows a possible connection between two kinds of pesticides and the proximity of pregnant women living near fields where they were sprayed.

The study was performed by the California Department of Public Health, and involved sampling "drift" concentrations of pesticides from agricultural fields to nearby residential areas in parts of the California Central Valley.

The researchers examined the records in 19 different California counties of over 270,000 children who were born between 1996 and 1998. Of the children studied, 465 had autism or autism-spectrum disorders (also called ASD). The records of where the children’s mothers lived during pregnancy were then compared to how close they lived to agricultural fields where many various pesticides were used.

"There seemed to be an association the closer [they] were to the fields," said Mark Horton, a state health director at the California Department of Public Health, to reporters.

The researchers found a particularly high incidence of autism among the children of 29 women who had lived quite near (about 500 yards) from fields where two specific pesticides had been used. The class of pesticides called organochlorines, the most well-known of which is DDT, have mostly been banned in the U.S. for many years. However, two organochlorines are still in use in this country: dicofol an endosulfan. It was these two pesticides that seemed to be most strongly linked to the autism cases. Of the 29 women, eight had babies who later developed autism – a sixfold increase over the general population.

The incidence of autism was the greatest for women living nearest the fields, and decreased in relationship to the distance away from them.

And while the conclusion cannot be made definitively at this time, primarily because the group of women who had the strongest apparent pesticide-autism link was so small, many experts viewing the report feel that further study is essential.

Susan Kegley, a spokesperson from the Pesticide Action Network North America, feels that this study confirms growing evidence that dicofol and endosulfan are harmful to humans. "This is one of the first papers that link use of pesticide to incidence of a disease, and autism in particular," Kegley told reporters at The Los Angeles Times. "The findings are very strong. This is a sixfold risk factor in comparison to someone who is not exposed. There aren’t too many studies that come out like that."

"We’re going to be working very closely with the state department of public health," said Glenn Brank, a representative of the California Department of Pesticide Regulation, to reporters. "The implications of this study certainly are of great concern to us although you can note from the report itself there is a lot more research that needs to be done before any firm conclusions can be drawn."

Brank added that though the study’s conclusions were alarming, the state of California has been using progressively lower amounts of dicofol and endosulfan. Newer pesticides more frequently focus on reproductive disruption rather than neurotoxic agents, lessening the harmful effects on humans.

In addition, the Department of Pesticide Regulation released a recent report stating that endosulfan seems to travel further by air than previously thought, potentially exposing larger numbers of the population to it, and the agency is expected to classify it as a "toxic air contaminant," which should further reduce its use.

For members of the community affected by autism, the study is seen as a potential addition to the array of possible causes of the disorder.

Some firmly believe that autism is caused by mercury or some other toxin contained in the MMR (Mumps Measles Rubella) vaccination; others believe environmental toxins are to blame. Some experts think that autism is caused by a genetic weakness or mutation, or a combination of genetic and environmental causes.

The study’s authors seem to concur with the latter. "The [alterations in brain function] might result from genetic factors, environmental insults, or a combination of the two," reads the report in part.

Regardless of one’s opinion on the cause of autism, most experts agree that the preliminary study is significant and needs to be researched further.

While the link between the 29 women in the study and the pesticides is compelling, one might wonder if such a potentially toxic load might cause any number of neurological disorders in addition to autism.

There was no information available at press time as to whether the researchers studied any other ill effects suffered by people living within 500 yards of an agricultural field sprayed with hundreds of different pesticides.

Pablo Rodriguez, director of the Dolores Huerta Community Organizing Institute, told The Bakersfield Californian, "It’s important for the people of the Central Valley to advocate for continued study, more information and access to that information so we can make the best decision to sustain agriculture. We need more information to make the best possible decisions for our communities."