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Environmental exposure from hundreds of industrial chemicals could be damaging the developing brains of children worldwide, but few of the potentially toxic compounds are regulated because too little is known about their effects, researchers say.

In a paper published on-line Wednesday in The Lancet, two specialists in environmental medicine (each of whom have spent decades studying the effects of lead and mercury exposure on the fetus and children) compiled a list of 201 industrial chemicals they say have the capacity to cause irreparable damage to the developing human brain.

Lead author Dr. Philippe Grandjean, chair of environmental medicine at the University of Southern Denmark, said he and co-author Dr. Philip Landrigan of New York's Mount Sinai School of Medicine both had similar experiences while studying the neurotoxicity of lead and mercury.

“First, things were seen in adults and later on, the disease was seen in children born to pregnant women or children exposed in early childhood at much lower doses,” Dr. Grandjean said Tuesday from Copenhagen. “Later on, it was found that these effects were more serious and they were permanent (in children).”

“And then we wondered: Is this only happening with mercury and lead?”

The two researchers then undertook an extensive review of published data on chemical toxicity to create a list of those agents most likely to harm the developing brain. Their tally of 201 compounds includes everything from arsenic to benzene and phenol. About half of the chemicals are ubiquitous in industrial processes and products — and could make their way into the environment through air, water and food.

But because there is a dearth of research on the effects of these chemicals specifically on children, their use has not been regulated in the same way as mercury, lead and PCBs.

Dr. Grandjean and Dr. Landrigan argue that the lack of international regulation is putting children around the globe at potential risk, and they worry whether exposure to such chemicals could be behind such conditions as autism and attention deficit hyperactivity disorder. (The cause of these conditions remain unknown.) Calling the potential for harm a “silent pandemic,” the researchers are urging governments worldwide to begin strictly controlling these chemicals, instead of waiting for years of testing to provide definitive scientific proof that they are either harmful or benign.

“What we are saying is we cannot afford to wait decades because that way we will expose another generation of children to toxic chemicals that will affect their brains permanently,” Dr. Grandjean said. “We cannot afford to do that.”

“In the knowledge society of today — and certainly in the future — we need all the brain power we have . . . It's a crucial resource that we need to protect and we're behaving as if it's not important at all.”

But Warren Foster, director of the Centre of Reproductive Care at Ontario's McMaster University, said there is no data to support the idea that chemical exposure is harming children or that diseases such as autism are caused by such pollution.

While Mr. Foster has high regard for the two researchers and calls the goal of their review “lofty,” he said their suggestion that industrial chemicals are causing neurotoxic effects in fetuses and young children is “a hypothesis that requires testing.”

“The kids actually have to be exposed,” Mr. Foster said from Hamilton. “Simply because things are in the environment does not necessarily mean that children are exposed or are exposed to the concentrations necessary to create the neurotoxicity.”

“I don't think it helps them to create fear when we don't have evidence of a problem.”

Still, Mr. Foster concedes that until there is definitive evidence of their effects, people should be cautious in limiting exposure to industrial chemicals, for instance, by not heating food in margarine tubs that can produce harmful compounds.

However, he's more concerned that governments could start banning chemicals based on insufficient data, only to replace them with compounds about which nothing is known.

“We still need coolants, we still need plasticizers, we still need flame retardants, we still need solvents,” he said. “So if we ban these, they're going to be replaced with something else. And just because something else comes along that we know nothing about doesn't mean it's safer.”

“So I would rather live with and regulate something that we know might have problems and minimize release into the environment and minimize human exposure by modulating our behaviour.”