IQ and Pesticides: Another Important Study

By: Dr. Chuck Benbrook

The April 2012 issue of Environmental Health Perspectives (EHP) has an extraordinary paper by David Bellinger of the Children's Hospital, Harvard Medical School, entitled "A Strategy for Comparing the Contributions of Environmental Chemicals and Other Risk Factors to Neurodevelopment of Children."  In this paper, Bellinger calculates the impact on Full-Scale IQ (FS-IQ), the most reliable measure of intelligence, of several risk factors including premature birth, autism, ADHD, diabetes, congenital heart disease, and three environmental contaminants for which there are adequate data to make an estimate of population-wide impacts on IQ — mercury, lead, and organophosphate (OP) insecticides.

Bellinger calculates and reports the total FS-IQ points lost across the nation’s 25.5 million children as a result of 15+ health risk factors and the three chemical contaminants, ranked from largest impact to smallest.  The top five risk factors driving down FS-IQ --

  • Preterm birth — 34,031,025
  • Lead — 22,947,450
  • OP Insecticides — 16,899,488
  • ADHD – 16,799,400
  • Iron deficiency – 9,409,500

It is worth emphasizing, as well, that several studies have implicated pre-natal exposures to OP insecticides as risk factors in contributing to pre-term birth, ADHD, and autism!  The lifetime economic impact triggered by loss of IQ is measured in the billions of dollars and the share of loss attributed to pre-natal OP exposures in the hundreds of millions.

For years, we have been told there are no credible data or studies documenting any adverse impact of pesticide on human health.  And even when supporters of pesticides acknowledge there might have been a few, isolated impacts, they argue the overall benefits exceed the risks.  Now, there is clear and compelling data documenting adverse impacts that translate into enormous economic costs that dwarf even the most generous estimates of OP pesticide benefits.

-Dr. Chuck