Leading chemical experts are calling for a radical overhaul of chemical regulation to protect children from everyday toxins that may be causing a global ''silent epidemic'' of brain development disorders such as autism, dyslexia and attention-deficit hyperactivity disorder.
A review published in The Lancet Neurology on Saturday said current regulations were inadequate to safeguard foetuses and children from potentially hazardous chemicals found in the environment and everyday items such as clothing, furniture and toys.
Philippe Grandjean from Harvard School of Public Health in Boston and Philip Landrigan from Mount Sinai School of Medicine in New York said that, in the past seven years, the number of recognised chemical causes of neurodevelopmental disorders doubled from six to 12.
These include lead, arsenic, pesticides such as DDT, solvents, methylmercury that is found in some fish, flame retardants that are often added to plastics and textiles, and manganese - a commonly mined metal that can get into drinking water.
The list also controversially includes fluoride, a mineral found in water, plants and toothpaste.
Many health authorities including the World Health Organisation and Australian governments say low levels of fluoride in drinking water is safe and protects teeth against decay, but Dr Grandjean and Dr Landrigan said a meta-analysis of 27 studies, mainly from China, had found children in areas with high levels of fluoride in water had significantly lower IQ scores than those living in low-level fluoride areas.
Dr Grandjean and Dr Landrigan said that, since 2006, the number of chemicals known to damage the human brain more generally, but that are not regulated to protect children's health, had increased from 202 to 214.
Of the newly identified toxins, pesticides constitute the largest group. The pair said this could be the tip of the iceberg because the vast majority of the more than 80,000 industrial chemicals widely used in the United States have never been tested for their toxic effects on the developing foetus or child.
They said one of the barriers was the logistics of studying the impact of such chemicals on children's brains to meet the "huge amount of proof required" before regulation such as banning a chemical was enacted.
"The only way to reduce toxic contamination is to ensure mandatory developmental neurotoxicity testing of existing and new chemicals before they come into the marketplace," Dr Landrigan said.
They proposed a new international prevention strategy that would put the onus on chemical producers to demonstrate that their products are low risk using a similar testing process to pharmaceuticals. They also proposed a new international regulatory agency to co-ordinate these measures.
Professor Ian Rae, who advises the United Nations Environment Program, said authorities in Australia, Canada and Japan were already working on better data for chemicals introduced without the kind of testing required now.
''Our National Industrial Chemical (Notification and Assessment) authority is prioritising the 38,000 chemicals on the Australian list and generating assessments for those of greatest concern,'' he said.
Oliver Jones, a lecturer in analytical chemistry at RMIT University, said many of the chemicals listed in the review were already strictly controlled or banned in Australia and that, where they are used, it was not "for fun or with malice but to save lives".
"DDT helps stop the spread of malaria, flame retardants reduce deaths from fires in the home and manganese is a required trace element for all living organisms," Dr Jones said.
"In addition, testing every single chemical in use for every possible affect is impossible. That said, we should never be complacent and more reasoned debate and research into best practice of the management of chemicals is very welcome."