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April 23, 2011

Imagine that, every day, you make yourself a cocktail to have with dinner. Not the usual kind, but a “mystery cocktail”. You mix together a variety of chemicals from unmarked bottles…a little of this, a little of that, more or less at random, until you have a glass full of perhaps a dozen different compounds. Now imagine that you get sick. Could it be the cocktail? Possibly…but which chemical is it? Your neighbor drinks the same thing each night and has no problems at all…is it something about your metabolism? One of the ingredients? The way a few of them interact with each other?

A study is just out in the journal Environmental Health Perspectives titled “Prenatal Exposure to Organophosphate Pesticides and IQ in Seven Year Old Children” (by Maryese Bouchard and colleagues). It makes a convincing case that children exposed to pesticides prior to birth are prone to later developmental problems and that they test significantly lower on IQ testing by the time they enter school. The more pesticide exposure, the worse the effect. How much of an effect is it? It’s a complicated question that will be different for each child, but one way of looking at it is that, for an average child, the effect could knock their level of intellectual functioning down from the 50th percentile (better than half of their peers) to around the 30th percentile (better than less than one-third of their peers).

This is not the first time that pesticide exposure has been linked with developmental problems, but the design and length of this study are particularly impressive. It comes at a time when we’re increasingly reminded of the chemical cocktail that we are raising our children in. Recent publicity has focused on the FDA’s consideration of the possible role of food dye in the development of ADHD. In a close vote the board decided not to place warning labels on foods with those dyes. This may or may not be a good decision, but it comes at a time when a new study, published in the British medical journal The Lancet, provides the most compelling evidence yet that food intake substantially influences ADHD symptoms, at least for some children. In the study (“Effects of a Restricted Elimination Diet on the Behavior of Children with Attention Deficit Hyperactivity Disorder – a Randomized Controlled Trial”; Lidy Pelsser and colleagues), many children with ADHD showed a positive response to a restricted elimination diet. Subsequently, these responders were challenged with foods for which prior testing had suggested that they had an atypical immune response. Most experienced a symptom relapse.

The relationship between chemicals in the environment and problems in child development is likely to be very complicated and to involve many different factors. Another recent study in Environmental Health Perspectives (“Prenatal Exposure to Organophosphates, Paraoxanase 1, and Cognitive Development in Childhood” by Stephanie Engel and colleagues) also showed that prenatal pesticide exposure harms future cognitive development, but also showed that this impact was literally “filtered” by the mother’s genetics. Specifically, moms with a gene that predisposed them to slower metabolism of the pesticide had kids who were more severely impacted by the early exposure. Their bodies seemed to let the pesticides float around longer, allowing more time for the fetus to be damaged.

Sometimes I think of our children’s developing brains as the “canary in the mine”, warning us of the impact of an increasingly poisonous environment. Yet it’s incredibly difficult to tease out which chemicals are the culprits, and how they are doing their damage. In this context, it’s worth taking a moment to recognize the profoundly harmful impact of scientists who offer up misleading theories about environmental contaminants. The New York Times ran an article this week reviewing the case of Dr. Andrew Wakefield, the physician who originally made a connection between the MMR vaccine and autism (“The Crash and Burn of an Autism Guru” by Susan Dominus: Setting aside the illnesses and deaths associated with vaccine refusal, and also setting aside the needless guilt endured by parents of autistic children who blame themselves for letting their kids get vaccinated, the relentless propounding of this sort of (completely) discredited theory saps the legitimacy of valid research into environmental causes of developmental disorders and clouds our ability to see the connections that we need to understand.

So, returning to the cocktail, let’s change the story a little bit. Imagine now that it’s not you, but your child who has to drink the cocktail and who gets sick. And imagine that the cocktail isn’t optional; it’s literally part of the air they breath, the food they eat, the water they drink. How urgent would you feel it was to isolate the offending ingredients and to get rid of them?

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