Two prominent medical researchers are calling for global restrictions on industrial chemicals so as to protect children from “a global, silent pandemic” of brain disorders, among them ADHD and autism.

“Our very great concern is that children worldwide are being exposed to unrecognized toxic chemicals that are silently eroding intelligence, disrupting behaviours, truncating future achievements and damaging societies,” the scientists warn in a review published Friday in The Lancet Neurology.

Developing brains in the womb and throughout childhood are much more susceptible to harmful toxins than are those of adults, said co-author Dr. Philippe Grandjean in an interview from Copenhagen. (He is a professor at the University of Southern Denmark.)

Current regulations are “woefully inadequate” to protect children from daily exposure to contaminants in clothes, toys and furniture and in the air they breathe, said Grandjean, who also teaches at the Harvard School of Public Health.

He and co-author Dr. Philip Landrigan call for the creation of an international clearing house that would co-ordinate testing of all existing and new compounds.

It’s time, they say, to put the onus on manufacturers to prove chemicals are low-risk before they are used rather than rely on the “dangerous presumption” that new chemicals are safe until proven otherwise.

Their paper coincides with steady increases in worldwide rates of neurodevelopmental conditions such as autism and ADHD (attention deficit hyperactivity disorder). One in 88 children is currently diagnosed with autism, up 600 per cent in the past 20 years. In the U.S., the diagnosis rate for ADHD has skyrocketed by more than 50 per cent in the past decade.

While new diagnostic criteria and greater awareness play a role in the alarming increases, scientists are also exploring other explanations.

Autism researchers, who once focused on the disorder’s genetic roots, are now exploring how the complex interaction of genes and environment may trigger the disorder in some children.

There is currently little scientific evidence linking industrial chemicals to specific disorders like autism, says Evdokia Anagnostou, clinician scientist at Holland Bloorview Kids Rehabilitation Centre in Toronto.

However, to safeguard developing brains, more stringent rules and testing are long overdue, she said.

“This is not about avoiding a specific disorder. This is about promoting brain health,” said Anagnostou, who is also a principal investigator with the Province of Ontario Neurodevelopmental Disorders Network.

Both Grandjean and Landrigan have spent more than 30 years studying the impact of chemicals on children’s health. Landrigan is a professor at Mount Sinai School of Medicine in New York and director of the hospital’s Children’s Environmental Health Center.

In a 2006 review, Grandjean and Landrigan documented five chemicals harmful to brain development, including lead and methyl mercury. Since then, the number of known “neurotoxicants” has doubled and the two scientists believe many more — still unrecognized — are doing damage.

If action is not taken now, “we are endangering the brains of the future,” said Grandjean.

Environmentalist Rick Smith, executive director of the Broadbent Institute and co-author of two books on the subject, called this latest paper important, saying it reflects the “indisputable” science and the mounting worry about the impact of chemicals we absorb daily.

The study will likely draw attention from patients as well as those in the field, said Dr. Rosanna Weksberg, a specialist in epigenetics at the Hospital for Sick Children’s research institute in Toronto.

Despite the lack of research on the role of chemical exposure in developmental disorders like autism, Weksberg said that “there is enough scientific evidence that there may be a link and that it deserves appropriate in-depth investigation.”

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