Toxic chemicals including some pesticides and solvents may be behind the increasing number of cases of neurodevelopmental disabilities—including autism and attention-deficit hyperactivity disorder—among children, researchers warn.
The findings are presented in a study by Philippe Grandjean, adjunct professor of environmental health at Harvard School of Public Health (HSPH) and Philip Landrigan, Dean for Global Health at Mount Sinai published online Saturday in Lancet Neurology.
"The greatest concern is the large numbers of children who are affected by toxic damage to brain development in the absence of a formal diagnosis. They suffer reduced attention span, delayed development and poor school performance. Industrial chemicals are now emerging as likely causes," said Grandjean.
The new study follows similar research by the authors published in 2006 in which they reviewed clinical and epidemiological studies and identified five industrial chemicals as developmental neurotoxicants: lead, methylmercury, polychlorinated biphenyls, arsenic and toluene.
Grandjean and Landrigan's current review updates that list and adds six newly recognized developmental neurotoxicants: manganese, fluoride, chlorpyrifos and DDT (pesticides), tetrachloroethylene (a solvent), and the polybrominated diphenyl ethers (often used as flame retardants).
Manganese has been linked to diminished intellectual function and impaired motor skills, and solvents have been linked to hyperactivity and aggressive behavior, the authors write.
The effects of neurotoxicity can be society-wide, the authors note, as loss of IQ points may bring down earnings thereby affecting GDP. They can be costly as well; for example, the annual cost of lead poisoning in the U.S. is $50 billion, while behavioral problems associated with neurotoxicant exposure could also require special educational services and may even lead to incarceration, the authors write.
"The presumption that new chemicals and technologies are safe until proven otherwise is a fundamental problem," the authors write, adding, "Voluntary controls seem to be of little value."
To confront this "global, silent pandemic," the authors urge an international strategy that takes a precautionary approach to fully evaluate new chemicals before they hit the markets. Testing on industrial chemicals and pesticides already on the market should also take place, they say.
"The problem is international in scope, and the solution must therefore also be international," Grandjean stated. "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."