The overwhelming body of scientific evidence supports the safety of myriad chemicals in use today.
A fusillade of recent items by the New York Times, US News, CNN, and others purports to show how certain common pesticides lead to reduced IQs among children of women exposed to these chemicals while pregnant.Dismayed, I carefully went over the paper that lies at the ground zero of the media frenzy. It is a study of the organophosphate (OP) class of pesticides by a group of researchers based at the University of California at Berkeley and led by Brenda Eskenazi.
OP insecticides were in widespread use from the mid-1960s until about ten years ago, when they were replaced in many applications by more effective chemicals. They are known for their brief persistence in the environment. The Environmental Protection Agency (EPA) continues to monitor these compounds for toxicity, and the permissible levels used have demonstrated no adverse effects at thousands of times their approved concentrations in laboratory animal testing. They work by inhibiting an enzyme needed for nerve conduction—but the levels effective against insect nerve function are orders of magnitude lower than any conceivable effect in humans. (A large 2008 U.S. study specifically seeking evidence of human health effects from the most commonly used OP pesticide, chlorpyrifos, found no such evidence.)
The Berkeley study is riddled with errors of commission and omission. It glibly assumes conclusions based on no science at all.The Berkeley study is riddled with errors of commission and omission. It glibly assumes conclusions based on no science at all. For instance, despite the weak effect detected and the lack of any biologically plausible hypothesis of sufficient scientific merit to link pesticide exposure and IQ, the authors assert such a link; there is, simply, clearly no basis for implying a cause-and-effect relationship between the pesticide and change in IQ. Merely calling a chemical a “neurotoxin” does not justify such a leap.
Further, allegedly toxic byproducts of a pesticide are acknowledged to be of indefinite source: the authors admit that the breakdown products of the pesticide they analyzed—supposedly valid proxies for the levels of the pesticide itself—could not be definitively traced back to any individual pesticide, nor even to any group of pesticides, but may have arrived pre-formed in the mothers’ diets. Adding to the confusion—the uncertainties given short shrift by the authors and the breathless media coverage—the study ignores potential confounders (factors known to influence IQ that are unrelated to pesticides) as significant as parental smoking and alcohol intake—indeed, any paternal characteristics at all.
