A new study is linking the pesticides chlorpyrifos and DDT and other chemicals to a rise in cases of neurodevelopmental disabilities. (Shutterstock)

Toxic chemicals may be responsible for a growing number of children with autism and other neurodevelopmental disabilities, researchers say.

In a report published online Saturday in the journal Lancet Neurology, researchers from the Harvard School of Public Health and the Icahn School of Medicine at Mount Sinai are warning of what they call a “silent pandemic” resulting from limited regulation of chemicals.

Exposure to toxic substances could be triggering an increasing number of cases of autism, attention-deficit hyperactivity disorder, dyslexia and other conditions, they say.

“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 Philippe Grandjean of the Harvard School of Public Health.

The review is an update to one the researchers first published in 2006 which singled out five chemicals — lead, methylmercury, arsenic, polychlorinated biphenyls and toluene — as ones that can cause brain deficits.

The current report, which is based on a review of previously published studies, adds six other chemicals to the list: manganese, fluoride, the pesticides chlorpyrifos and DDT, a solvent often used in dry cleaning called tetrachloroethylene and the flame retardants polybrominated diphenyl ethers.

Specifically, the researchers said that manganese is linked to diminished intellectual functioning and impaired motor skills while solvents like tetrachloroethylene can bring about hyperactivity and aggression and pesticides contribute to cognitive delays.

The developing brain is especially vulnerable to such chemicals during pregnancy, the researchers said.

“The problem is international in scope, and the solution must therefore also be international,” Grandjean said. “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.”

The chemical industry, however, refuted the findings from Grandjean and his colleague, Philip Landrigan of Mount Sinai. In a statement, the American Chemistry Council called the pair’s conclusions “flawed.”

“What is most concerning is that the authors focus largely on chemicals and heavy metals that are well understood to be inappropriate for children’s exposure, are highly regulated and/or are restricted or being phased out. They then extrapolate that similar conclusions should be applied to chemicals that are more widely used in consumer products without evidence to support their claims. Such assertions do nothing to advance true scientific understanding and only create confusion and alarm,” the council said.

Read more stories like this one. Sign up for Disability Scoop's free email newsletter to get the latest developmental disability news sent straight to your inbox.