One Chance to Develop a Brain: Neurotoxic chemicals and children’s health
UPdate Fall 2008

A “silent pandemic” is affecting the brain development of children. Scientists have identified 201 common industrial chemicals as likely culprits contributing to autism, attention deficit disorder, mental retardation, cerebral palsy and lowered IQs. The majority of the 201 compounds are present in the environment, in food, or in consumer goods. The report from scientists at Harvard School of Public Health pinpoints “great gaps” in chemical testing and regulation as a major problem.

" The bottom line is you only get one chance to develop a brain," said Philippe Grandjean, M.D., lead author of the study in an interview with WebMD. "We have to protect children against chemical pollution because damage to a developing brain is irreversible."

One in six children now has a developmental disability, most of which are linked to the nervous system. A team from the Harvard School of Public Health has identified 201 known neurotoxic chemicals in common use which have not been regulated to protect the developing brains of children. The chemicals include lead, methylmercury, solvents including toluene and benzene, and dozens of pesticides. Over half of the 201 chemicals are classified as high volume chemicals, meaning that over one million pounds a year a produced annually.

The authors point out that the 201 chemicals have been identified not because they are necessarily the most dangerous, but because they have been studied the most. "The few substances proven to be toxic to human neurodevelopment should be viewed as the tip of a very large iceberg," they wrote.

“Of the thousands of chemicals used in commerce, fewer than half have been subjected to even token laboratory testing for toxicity… and 80% have no information about developmental or paediatric toxicity,” the report states. “Even with so little testing, 201 chemicals are knows to be toxic to human brain development. The number of chemicals that have been shown to cause neurotoxicity in laboratory studies probably exceeds 1000.”

In the nine month period when the fetal brain develops, growth occurs within ''a tightly controlled time frame, in which each developmental stage has to be reached on schedule and in the correct sequence.'' This creates ''windows of unique susceptibility to toxic interference'' that can have permanent consequences, say Grandjean and co-author Philip J. Landrigan, a professor at Mount Sinai School of Medicine.

"Even if substantial documentation on their toxicity is available, most chemicals are not regulated to protect the developing brain," says Grandjean. Only a few substances, such as lead and mercury, are controlled with the purpose of protecting children. ''The 200 other chemicals that are known to be toxic to the human brain are not regulated to prevent adverse effects on the fetus or a small child."

Pesticides figure prominently in the report. Over 90 of the substances listed are pesticides, including 2,-4D, an ingredient found in weed and feed products and many other herbicides.
The report also points to three emerging neurotoxins – manganese, fluoride, and perchlorate. These are chemicals for which evidence of neurotoxic effects are becoming strong. Manganese is prominent in Canada as a component of no-knock fuel. Perchlorate has become a widespread water contaminant in some areas of the US. It comes from ammonium perchlorate, which is used as a solid-fuel propellant for rockets and missiles.

“The idea is to take a precautionary approach and introduce strong regulation, which could later be relaxed if the hazard turned out to be less than anticipated,” says Grandjean.

The Canadian government continues to promise that its chemical management plan will provide effective protection, but to date little has been done. Canadian non-profit organizations focusing on environment, social policy and health are concerned that the federal government will not base its actions on the European precautionary model, but will require old levels of proof that may delay protection for decades.

UPdate, Fall 2008, Environmental Health Association of Nova Scotia