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Can the decline in rational thinking that we seem to be experiencing these days be due to pesticide exposure while we were in the womb? That may not be as harebrained as it sounds. 

A number of recent studies have explored this possibility by measuring levels of organophosphate pesticides either in the urine of pregnant women or in umbilical cord blood and administering various intelligence test to their offspring. Organophosphates are a common family of pesticides and function by inhibiting the action of an enzyme that breaks down the neurotransmitter acetylcholine. So essentially they kill by overstimulating nerve activity in insects. Since human nerves also use acetylcholine as a neurotransmitter, organophosphates can be expected to interfere with the workings of our nervous system as well. And brain activity of course depends on how nerve cells communicate with each other.

In one study urine from pregnant women in a farming community was collected and analyzed for organophosphate content. The same was done for their children at 6 months of age, as well as at 1, 2, 3.5 and 5 years. When the children turned seven, intelligence tests were administered. The higher the pesticide level in the mother’s urine, the worse the offspring performed in terms of working memory, processing speed, verbal comprehension, perceptual reasoning and IQ. The differences were not great, but statistically significant. Remarkably, there was no correlation with pesticides in the childrens’ urine, suggesting that the pesticide effect occurs during pregnancy. Another study examined the effects of chlorpyrifos, an organophosphate, on inner-city children whose mothers were exposed. Levels of the chemical were measured in umbilical cord and again intelligence tests were performed at seven years of age. Again there were small declines in IQ and working memory with an increase in chlorpyrifos in umbilical blood.

Yet a third study examined prenatal maternal blood for organophosphates as well as for the presence of paraoxonase, a key enzyme in the metabolism of organophosphates. In this case too, cognitive development was affected in parallel to increased blood levels of organophosphates and furthermore there was a genetic involvement. Children of mothers who carried a gene that imparts slow activity to the enzyme that helps break down organophosphate were more affected. These studies are very interesting, but there are a few items to note. Organophosphate use is declining and has been virtually eliminated from all but agricultural use. It is not used in insecticides designed for home use, the scenario where pregnant women would most likely be exposed. Also such studies can show an association but cannot prove cause and effect. What other factors were involved? Alcohol? Smoking? Nutritional differences? Mercury exposure? Still, the fact that measures of intelligence were linked to levels of pesticides in maternal urine or umbilical blood in a proportional fashion is very suggestive of pesticides being the culprits.

The take-home message here is that we have to be careful with the use of these chemicals. Frivolous indoor spraying has to be curbed, although the prospect of rodents and cockroaches scooting about, possibly spreading disease, is not an attractive one. But when it comes to agriculture, we cannot get away from pesticides. We can, however, do a better job at applying them in a safer fashion. Perhaps the most important point that these studies make is that much of our future may be governed by what happens in the womb. Start kicking from the inside if you feel mom is driving a tractor spraying pesticides.