Three studies published in Environmental Health Perspectives, suggest that prenatal pesticide exposure may result in lower average IQs and decreased working memory in kids. These pesticides are widely used in commercial agriculture, with some also still registered for use in home gardens. The pesticides looked at in these studies included chlorpyrifos and diazinon. Chlorpyrifos is one of the most widely used pesticides, used in farming on crops such as corn, soybeans, broccoli, and apples, and for non-agricultural uses, such as on golf courses. While diazinon is no longer available for residential use, it is still used on crops such as rice, sugarcane, corn, and potatoes. It is also used in pet products to protect against fleas and ticks.

The first study examined the associations between prenatal and postnatal exposure to organophosphate (OP) pesticides and cognitive abilities in school-age children. Most studies demonstrating the adverse health effects of these pesticides have been done in occupational settings at high exposure levels. In comparison, researchers of this study wanted to look at the effect these pesticides may have on kids who experience chronic, low-level exposure from due to use at home, living near an agricultural field, and residues in food. In theory, kids should be at higher risk for pesticide toxicity than adults due to their developing brain, the dose of pesticides per body weight is likely to be higher in children, and kids have lower activity and levels of enzymes that detoxify activated forms of certain OP pesticides. Researchers assessed exposure to OP pesticides by measuring dialkyl phosphate (DAP) metabolites in urine collected during pregnancy and from kids at age 6 months and 1, 2, 3-1/2 and 5 years. Testing showed that  children in the highest quintile of maternal DAP concentrations had an average deficit of 7.0 IQ-points compared with those in the lowest quintile.

A Mount Sinai Children’s Environmental Health Study looked at the relationship between biomarkers of organophosphate exposure, PON1 and cognitive development at ages 12 and 24 months and 6 to 9 years. The pesticides examined in this study included chlorpyrifos and diazinon, which haven’t been approved for residential use since 2004. Researchers found that a couple years later, 78% of randomly selected US homes still had measurable levels of chlorpyrifos and 35% had measurable levels of diazinon. This indicates that individuals are still getting ongoing exposure from past residential use, plus via the consumption of conventionally grown produce. The findings of this study suggest that prenatal exposure to organophosphates negatively impacts cognitive development, particularly perceptual reasoning, with children of mothers who carried the PON1 Q192R QQ genotype appearing to be particularly susceptible.

The goal of the last study was to estimate the relationship between prenatal exposure to chlorpyrifos (CPF) and neurodevelopment among children at 7 years of age. The EPA banned CPF for indoor residential use at the end of 2001, which did result in a substantial decrease in both indoor air and plasma blood levels, there remains continued low-use exposure due to the consumption of conventionally grown produce. Researchers reported evidence of deficits in Working Memory Index and Full-Scale IQ as a function of prenatal CPF exposure. It’s important to note that while socioeconomic and cultural differences can impact full-scale IQ, those are less likely to affect working memory.

These studies demonstrate the importance of choosing organic produce whenever possible – at the very least, sticking with the Clean 15 & Dirty Dozen list from the Environmental Working Group. If you can’t grow your own veggies, you should always try to get to know your local farmers to get a better understanding of what farming practices they use, so that you can make more educated decisions and support those who are producing the healthiest food for you and your family.