Pesticides' Influence on IQ
Air Date: Week of August 5, 2011
Three recently published papers in Environmental Health Perspectives document the effects of low-level organophosphate pesticide exposure on children's IQ.
GELLERMAN: From the Jennifer and Ted Stanley Studios in Somerville, Massachusetts, we recycle some classic stories from Living on Earth. I'm Bruce Gellerman. Pesticides are designed to kill pests, not hurt people. But now, three independent studies find two organophosphate pesticides, widely used on foods in the field, can have devastating effects on a child’s IQ if their moms are exposed during pregnancy. The studies appeared in the journal Environmental Health Perspectives. Researchers from Columbia University and Mount Sinai Medical Center studied pregnant women and their children in New York City. Epidemiologist Brenda Eskenazi and her team from UC Berkeley focused on the children of agricultural workers in Salinas, California. Dr. Eskenazi, welcome to Living on Earth!
ESKENAZI: Pleasure to be here!
GELLERMAN: So how great was the drop in IQ for the children who had been exposed to these organophosphates?
ESKENAZI: We measured organophosphates by something called dialkyl phosphate metabolites in the mother’s urine during the pregnancy. For every tenfold increase in the mother’s levels of these metabolites during her pregnancy, we saw a 5.5 point decrease in the child’s IQ. That translates to meaning that the children in the very highest 20 percent group of exposure, versus the very lowest - we see about a seven point difference in IQ.
GELLERMAN: So you looked at these mothers’ exposures and then you measured the children as they developed.
ESKENAZI: Yes, that’s right. We enrolled women during their pregnancies and have been following their children up until age seven at the point of the study.
GELLERMAN: How important is this type of IQ reduction, this kind of level - what effect does that have on a child’s chances of success in school?
ESKENAZI: Well, we are looking at a population level result, not an individual result. And so the way to think about this is that if you see a five or seven point shift in the IQ in the general population, you will see more children that are going to need special services and more children that would be driven into the area of IQ that we would be concerned about them.
GELLERMAN: Should we be surprised by these findings? I mean, these organophosphate chemicals - they’re sometimes called nerve agents. I mean, they’re designed to affect the brain.
ESKENAZI: There is no doubt that at high doses, these chemicals are neurotoxicants. Children and farm workers have been poisoned for years at high doses. The question that we were faced with is what happens with low-level - maybe chronic exposure - but low-level exposure to these chemicals, and how does it affect a child during a critical window of development.
GELLERMAN: These chemicals - how widespread is their use now? Will I find it in my house?
ESKENAZI: Organophosphates were voluntarily removed for home use in the early 2000s. However, they have been widely used in agriculture since that time.
GELLERMAN: So if I buy organic, do I lessen my exposure to these?
ESKENAZI: Yes, you probably would have lower levels of exposure, if any.
GELLERMAN: For individual parents and children, these findings could be quite tragic. On a societal level, the educational level, it could be quite costly. Do you have any idea of the economic impact of this kind of decrease in IQ is having in our school systems?
ESKENAZI: No, it’d be very hard to estimate that. And also, it would be very important to make sure that parents know that eating a good diet may also affect neurodevelopment. And so we don’t want to restrict people from eating fruits and vegetables because of their concern about organophosphates - that would be an anti-public health message.
GELLERMAN: So what are people to make out of this study?
ESKENAZI: What I would say is eat lots of fruits and vegetables, make sure you wash those fruits and vegetables really well - even if it has a skin, and if you can and afford it - eat organic. And if you’re going to use pesticides in your home - even though we don’t use organophosphates in the home any longer, we are still using other pesticides that we know even less about - and the best thing would be to use integrative pest management, where we don’t use sprays, but we use baits and traps and other herbal remedies to rid ourselves of ants and roaches and other critters.
GELLERMAN: Now your study is one of three that just came out. There were studies at Mt. Sinai and Columbia University, and researchers there have just found similar declines in IQ of children exposed to these very same chemicals. Were you surprised by those findings?
ESKENAZI: I was surprised that we saw the same types of associations in three parallel studies, and the fact that we saw similar findings is noteworthy.
GELLERMAN: So I can imagine a mom feeling guilty, getting these results and knowing that something that they ate prenatally is affecting their kids now.
ESKENAZI: I would hope not. I would hope that the mother would feel that she did the best, knowing what she knew, and she ate well, and she tried to protect her child as much as possible. And that’s really the best we all can do is base our behavior on what we know now.
GELLERMAN: Dr. Eskenazi, thanks a lot, really appreciate it.
ESKENAZI: Thank you for having me.
GELLERMAN: Brenda Eskenazi is a professor of epidemiology and maternal and child health at UC Berkeley.
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