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Toxins and the Brain

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There are no second chances

By Josie Glausiusz


 

I spend a great deal of time thinking about ways to protect my small children from everyday dangers—idiotic drivers who text at the wheel, for example. I hope I would do everything in my power to defend them against less commonplace perils; a marauding bear, say. But some dangers are unseen, subtle, omnipresent. And so I was deeply concerned to read a new report in the journal The Lancet/Neurology about common chemicals that have toxic and irreversible effects on the developing brain.

The review, by medical epidemiologist Philippe Grandjean of Harvard School of Public Health and Philip J. Landrigan of Icahn School of Medicine at Mount Sinai in New York City, identifies six chemicals that epidemiological studies have shown to be “developmental neurotoxicants.” They are (1) manganese, (2) fluoride, (3) the insecticides chlorpyrifos and (4) the infamous DDT, (5) the dry cleaning fluid tetrachloroethylene, and (6) polybrominated diphenyl ethers (PBDEs), which are widely used flame retardants. (Six additional brain-damaging chemicals, including lead and methylmercury, were described by the same researchers in a review published in 2006.)

As Grandjean and Landrigan note, such disorders and disabilities as autism, attention-deficit hyperactivity disorder (ADHD), dyslexia, and other “cognitive impairments” are diagnosed in millions of children worldwide, and cases of autism and ADHD appear to be escalating. A number of epidemiological studies have shown that exposure to specific chemicals in the womb or during infancy can have detrimental effects into childhood and beyond.

For example, a French study of 3,000 children linked maternal exposure to solvents during pregnancy—in nurses, chemists, cleaners, or hairdressers—with increased risks of hyperactivity and aggressive behavior in their children. Other studies have shown correlations between a pregnant woman’s exposure to chlorpyrifos with a small head circumference in the infant at birth, which indicates slowed brain growth in the womb. Evidence from studies conducted in Europe and the United States shows that increased prenatal exposures to PBDEs—used in manufacturing furniture, textiles, plastics, and cars—are correlated with “neurodevelopmental deficits” in children.

“You only get one chance to develop a brain,” Grandjean points out, and that development is so complex that “just a little bit going wrong can have severe and permanent effects.” Environmental contaminants can cross the placenta to the developing fetus, and some 200 alien chemicals have been detected in umbilical cord blood. Contaminants can be transmitted to the infant in breast milk. Impaired brain function can not only lead to disruptions in behavior but also to decreased intelligence, which in turn can have profound economic effects across societies.

What to do? The two call for an “international clearinghouse on neurotoxicity” or, as Grandjean wrote to me in an email, “a facility to coordinate, inspire, and evaluate research and documentation on chemical brain drainers.” Such an agency would screen existing industrial chemicals for their neurotoxic effects, with legally required testing of new chemicals before they hit the market. “Exposures are global, and the safety of brain development everywhere would be to our joint benefit,” Grandjean explains. From my perspective, a world that’s safe for my children’s creative brains is a world I am willing to fight for.

Josie Glausiusz has written about every topic known to science, from physics to furry animals, for magazines that include Nature, National Geographic, Scientific American Mind, Discover, New Scientist, and Wired. She is the co-author of Buzz: The Intimate Bond Between Humans and Insects.

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