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
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
model, but will require old levels of proof that may delay protection for decades.
UPdate, Fall 2008, Environmental Health Association of Nova Scotia