Worrying about Toxins

Nicholas Kristof wonders if some chemical poison causes autism:

Over recent decades, autism and other development disorders also appear to have proliferated, along with certain cancers in children and adults. Why? No one knows for certain [but] suspicions are growing that one culprit may be chemicals in the environment. An article in a forthcoming issue of a peer-reviewed medical journal, Current Opinion in Pediatrics, just posted online, makes this explicit.

The article cites “historically important, proof-of-concept studies that specifically link autism to environmental exposures experienced prenatally.” It adds that the “likelihood is high” that many chemicals “have potential to cause injury to the developing brain and to produce neurodevelopmental disorders.”

The chief author is Dr. Philip J. Landrigan, a prominent pediatrician. He told Kristof that while the science is still iffy, he is personally certain that most autism is caused by toxins.

“The crux of this is brain development,” he said. “If babies are exposed in the womb or shortly after birth to chemicals that interfere with brain development, the consequences last a lifetime.”

Some small studies have indicated increased risk of autism and other developmental abnormalities from a variety of drugs and other chemicals:

Suspicions of toxins arise partly because studies have found that disproportionate shares of children develop autism after they are exposed in the womb to medications such as thalidomide (a sedative), misoprostol (ulcer medicine) and valproic acid (anticonvulsant). Of children born to women who took valproic acid early in pregnancy, 11 percent were autistic. In each case, fetuses seem most vulnerable to these drugs in the first trimester of pregnancy, sometimes just a few weeks after conception.

None of these studies have been replicated on a large scale, so none of this can be considered very certain. All such studies suffer from the problem that we are exposed to so many bio-active chemicals, natural and man-made -- before you get outraged over the dangers of modern life you should remember that soot from wood fires is full of dangerous poisons -- that we may never be able to figure out which chemicals or combinations of chemicals cause which problems. It is a dangerous world we inhabit.