by Marion Nestle
Apr 25 2011

Do farm pesticides reduce kids’ IQs?

The Environmental Working Group announces the publication of three studies finding a correlation between diminished IQ and blood levels of pesticides.

The studies were done separately by groups of researchers from the Mt Sinai School of Medicine, University of California Berkeley’s School of Public Health, and Columbia University’s Mailman School of Public Health.  All were published in Environmental Health Perspectives and are available at that site (although sometimes with a delay and you have to look hard for the pdf of the whole article).

All three studies examined levels of organopesticides in the blood of pregnant women.  All looked at one or more measures of IQ taken when the children were 1 to 9 years old.

The Berkeley study, Prenatal Exposure to Organophosphate Pesticides and IQ in 7-Year Old Children, examined Latino farmworkers and their children.  Researchers found a difference of 7 IQ points between children with the highest and lowest levels of organopesticides.

The Mt. Sinai study, Prenatal Exposure to Organophosphates, Paraoxonase 1, and Cognitive Development in Childhood, was done with a prenatal population in New York City.

The Columbia study, 7-Year Neurodevelopmental Scores and Prenatal Exposure to Chlorpyrifos, a Common Agricultural Pesticide, also was done on an inner-city population.

It has been difficult to demonstrate demonstrable harm from agricultural pesticide use except among farmworkers exposed to very high doses.  These studies mean that lower doses experienced by people who merely eat agricultural products also can cause harm.

The study will undoubtedly be criticized for not adequately controlling for socioeconomic variables that influence IQ—they were all done with low-income populations—and, more importantly, for not explaining precisely how pesticides might influence childhood learning and achievement.  And some will surely argue that a 7-point IQ difference is well within experimental error.

But at the very least, pesticides are a marker for poorer cognitive outcome.  The fact that three independent groups of investigators arrived at similar conclusions means that the results need to be seriously considered.

Organic vegetables anyone?

And just for the record, here’s the Environmental Working Group’s list of the foods with highest and lowest levels of pesticides:

Highest Levels Lowest Levels
Bell Peppers
Kale/Collard Greens
Grapes (imported)
Sweet Corn
Sweet Peas
  • Brandon

    You said “Organic vegetables anyone?”

    But don’t pesticides also accumulate in the fat of animals such as chicken, cows, and pigs? Time for some organic milk and beef too…

    Another issue, on top of ther others, is not only “is 7 points experimental error” but also “is 7 points significant”?

  • Doc Mudd

    Let’s not overlook exposure to urban chemicals. EPA has estimated some 70 million pounds of active pesticide ingredients are applied annually to urban lawns alone.

    Not to mention household use of chemical controls for insect infestations, annoying flying insects, etc.

    You would do well to look close to home before reflexively bashing anonymous farmers at a distance. If you can bring yourselves to attempt more factchecking and less spurious bashing, that is.

  • Benboom

    Look over there! Shiny object! Glad to see the resident troll is still on the job.

  • Lee Poe

    Ah, agribusiness. All that leftover nerve gas after World War Ii and suddenly no market for it and all its chemical constituents. Good thing they figured out something useful to do with all those costly products, like flooding agriculture with chemicals that don’t kill people immediately but wait a few years. As long as it happens slowly, they figure they won’t get caught and will get rich along the way.

    And of course look indoors. Anyone remember those Raid commercials where the happy mom was wetting down with floral-scent insecticide all the drapes and furniture in the family room, while the kids happily played in the mist? That couldn’t have been very good for their development.

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