In a new study published in The Lancet, researchers from Harvard School of Public Health (HSPH) and Icahn School of Medicine at Mount Sinai have implicated six new chemicals they believe contribute to the development of mental disorders in children, such as ADHD (attention deficit hyperactivity disorder) and autism.

Coming off the heels of a study conducted by the authors in 2006, where the team identified five “developmental neurotoxicants,” the study now includes manganese, fluoride, chlorpyrifos and DDT (pesticides), tetrachloroethylene (a solvent), and the polybrominated diphenyl ethers (flame retardants). These industrial chemicals not only pose threats to mothers and their unborn children, the team argues; they’re capable of leaving serious neurological damage in the form of devastating brain disorders.

The problem, as co-author and adjunct professor of environmental health at HSPH Philippe Grandjean sees it, is twofold: helping people avoid risky environments and encouraging corporations to perform regulatory checks of their products.

“Organic foods are of course useful, and seafood should favor shrimp, salmon, and other species low in the food chain,” Grandjean told Medical Daily. “But many substances appear where the consumer has no way of knowing or detecting them. So this requires a systematic approach and initiatives on a national and international level.”

Grandjean and his co-author, Mount Sinai’s Dean for Global Health, Dr. Philip Landrigan, found certain chemicals linked directly to specific mental disorders. Manganese, while required for many enzymatic reactions in the body, may also appear in overabundance in certain dusty environments and lead to diminished intellectual function and impaired motor skills. Upholding the findings of one 2003 study, solvents were found to have significant ties to aggressive behavior and hyperactivity in children. And certain kinds of pesticides showed links to cognitive delays.

While light on the specific mechanisms of transmission, the authors make explicit the chemical nature of these disorders. Autism, and ADHD in particular, are often thought of as overdiagnoses, especially as more kids with behavioral challenges seem to “grow out of” their diagnosis. For Grandjean, the social component of mental disorders has at least one surefire corollary.

“Social factors have been blamed for causing problems for kids, but research on lead exposure shows the opposite,” he explained. “Some of the behavioral abnormalities and school problems are more likely due to lead, including part of those that have been attributed to social factors.”

Lead poisoning is especially hazardous for pregnant women, as her unborn child is also at risk. When a mother inhales small quantities of lead, the chemical gathers in the bloodstream and eventually makes its way to the placenta, where it accumulates in the growing fetus’ bones and brain. Grandjean and Landrigan believe this is just one chemical of many, many more that exist in the world and are carelessly exposed to consumers on a regular basis. Together, the chemicals contribute to what the team calls, “a silent pandemic.”

"The problem is international in scope, and the solution must therefore also be international," said Grandjean in a news release. "We have the methods in place to test industrial chemicals for harmful effects on children's brain development — now is the time to make that testing mandatory."

 

Source: Grandjean P, Landrigan P. Neurobehavioural effects of developmental toxicity. The Lancet. 2014.