The Effects of Pesticides on IQ
As reported in Science News in May of 2011, the effects of
pesticides are not as benign as once thought. While there is
still little evidence that pesticide residues on fruits and vegetables
are harming us as consumers, the research now shows that those
exposed to higher levels as children are impacted negatively.
Specifically, studies found that kids exposed to high levels
of neurotoxic pesticides have lower IQs by the time they enter
school, compared to those who have not had such exposure.
Three similar studies found similar effects. In a University
of California study woman who worked harvesting fruits and vegetables
were tested for exposure to clorpyrifos, diazinon, malathion
and other organophosphate compounds used in insect killers. These
compounds can cross the human placenta. On average, the children
of the 20% of woman with the highest exposure to these pesticides
scored 7 points lower on IQ tests when entering school.
A study done at Columbia University followed low-income black
and Hispanic mothers, testing them for levels of clorpyrifos.
For each additional 4.6 picograms of the substance per gram of
blood during pregnancy, there was a drop of 1.4% in the IQ of
the child, and a 2.8% drop in a measure of working memory.
A third study at Mount Sinai School of Medicine found similar
effects, but also found that the largest cognitive impacts were
in the children of mothers who had a particular gene variant
- one which about a third of people have. The bottom line is
that pesticide exposure during pregnancy may have lifelong cognitive
effects on children.
There has not yet - and may not be in the future - evidence
of any significant effects on the brains of adults exposed to
these pesticides. One obvious recommendation here is that any
woman who is pregnant or plans to get pregnant or might get pregnant,
stop working in the fields until after she has children. Probably
young children should also be kept away from agricultural settings
as well, since their brains are still developing.
The good news is that most of us do not have to worry about
pesticides damaging our brains or those of our children. The
levels of residue on fruits and vegetables is probably not enough
to hurt us - and washing well can eliminate most of that. Also,
the use of most of these chemicals for residential gardening
and yard care has been banned for years.