With diagnoses of autism on the rise, people are pointing fingers. The fingers have been pointed at parents, who in turn have pointed at poisons in the environment to deflect the blame from their defective parenting or genes. We discussed previously that there have been no winners from almost 5,000 lawsuits claiming that the preservative thimerisol, used in childhood vaccines, contained autism-inducing mercury. In that article, we suggested that because there were no studies linking autism to environment, the most reasonable explanation for the “autism epidemic” is that doctors are more aware of the disorder and thus more likely to diagnose it. However, a new study of pesticides in California may shift some focus back onto the environment in this ongoing debate.
The California Department of Public Health (CDPH) has spent over a decade compiling a map of pesticide use and health problems, and their diligent work may have finally born fruit. Hundreds of pesticides are used near populated areas in California, but only two showed a correlation with autism. Both are organochlorines, a type of chemical with a toxicity first brought to public attention by Rachel Carson in her 1962 exposé Silent Spring. While many organochlorines, most famously DDT, have been discontinued, others remain in use.
The CDPH focused its investigation on women in the Central Valley who lived within 500 meters of sprayed fields during the first trimester of their pregnancy. A staggering 28% of their children developed autism. Dr. Mark Horton, director of the CDPH, told the L.A. Times that these results should interpreted cautiously:
"We have found very preliminary data that there may be an association. We are in no way concluding that there is a causal relationship between pesticide exposure of pregnant women and autism.
Caution is certainly necessary given the history of rash accusations against chemicals suspected of causing autism. While 28% is a many-fold increase over the normal prevalence of less than 1% in the general U.S. population, we must keep in mind that the number of women who fit the criteria for this study (29) is too small to assure that randomness is not the culprit. Nevertheless, further study of organochlorines is certainly prudent because there is an additional piece of damning spatial evidence-- risk for women increased the closer they lived to the fields. This is much more specific than a general observation that women living in the vicinity of organochlorine-sprayed fields have a higher risk, and it requires an explanation not based on factors common to a whole community.
The use of organochlorines was already declining before this new discovery, but the implications of this study go beyond the evaluation of individual pesticides. The causes of autism remain a mystery, and any chemical shown to increase its prevalence will surely help scientists better understand why some children develop cognitive abnormalities. If certain chemicals directly cause the disorder by altering fetal development, then specific actions could be taken to alleviate those factors. Even if these chemicals only encourage an already existing problem, their behavior can help scientists home in on the root problem. If more states take action to create comprehensive maps of toxins and disorders, we may soon have more answers.
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