Recent studies hint that exposure to toxic chemicals, such as methylmercury can cause harm at levels previously considered safe.
A new analysis of the epidemiological evidence in the International Journal of Environment and Health,
suggests that we should take a precautionary approach to this and
similar compounds to protect unborn children from irreversible brain
Philippe Grandjean of the Department of Environmental
Health at Harvard School of Public Health, in Boston, and the
University of Southern Denmark in Odense, explains that the causes of
suboptimal and abnormal mental development are mostly unknown. However,
severe exposure to pollutants during the development of the growing
fetus can cause problems that become apparent as brain functions
develop - and ultimately decline - in later life. Critically, much
smaller doses of chemicals, such as the neurotoxic compound
methylmercury, can harm the developing brain to a much greater extent
than the adult brain.
Methylmercury is a chemical compound
formed in the environment from released mercury. Unfortunately, the
methylmercury can be transported quickly around the body and may enter
the brain. Serious problems will ensue if important developmental
processes are blocked as there will be only one chance for the brain to
The researchers point out that until recently
research into the effects of pollutants on the brain has been clouded
by the lack of information on actual exposure. Moreover, finding a
direct link between specific problems with the brain and exposure
relies on statistical, or epidemiological, analysis rather than
case-by-case understanding. The researchers say that neurodevelopmental
disorders of possible environmental origin affect between 5% and 10% of
babies born worldwide, leading to dyslexia, mental retardation,
attention deficit/hyperactivity disorder, cerebral palsy, and autism.
toxicity of methylmercury is well known, but the researchers believe
that the medical world has underestimated the risk of brain damage
associated with exposure to this compound as well as numerous others.
Professor Grandjean emphasizes that little research has been carried
out into the effects of other neurotoxic chemicals.
there is enough evidence to rule out effects of certain chemicals on
the developing nervous system, a cautious approach would involve strict
regulation of suspected developmental neurotoxicants and prudent
counseling of expectant mothers regarding exposures to untested
substances," the researchers conclude.
The cited study
Philippe Grandjean, Marian Perez, Development neurotoxicity: implications of methylmercury research, Int. J. Environ. Health, 2/3-4 (2008) 417-428. DOI: 10.1504/IJENVH.2008.020933
Philippe Grandjean, Marian Perez, Potentials for exposure to industrial chemicals suspected of causing developmental neurotoxicity, brief report
Anna L. Choi, Philippe Grandjean, Methylmercury exposure and health effects in humans, Environ. Chem. , 5/2 (2008) 112-120. DOI: 10.1071/EN08014
D. Mozaffarian, E.B. Rimm, Fish intake, contaminants, and human health: evaluating the risks and the benefits, J. Am. Med. Assoc., 296/15 (2007) 1885-99.
P. Grandjean, P.J. Landrigan, Developmental neurotoxicity of industrial chemicals, Lancet, 368 (2006) 2167-2178. DOI: 10.1016/S0140-6736(06)69665-7
F. Debes, Impact of Prenatal Methylmercury Exposure on Neurobehavioural Function at Age 14 years, Neurotoxicol. Teratol., 28 (2006) 363-375.
Leonardo Trasande, Philip J. Landrigan, Clyde Schechter, Public Health and Economic Consequences of Methylmercury Toxicity to the Developing Brain, Environ. Health Perspect., 113/5 (2005) 590-596. doi:10.1289/ehp.7743
Mark F. Blaxill, Lyn Redwood, Sallie Bernard, Thimerosal and autism? A plausible hypothesis that should not be dismissed, Med. Hypotheses, 62 (2004) 788-794. doi:10.1016/j.mehy.2003.11.033
E.M. Yokoo, J.G. Valente, L. Grattan, S.L. Schmidt, I. Platt, E.K. Silbergeld, Low level methylmercury exposure affects neuropsychological function in adults, Environ. Health, 2 (2003) 8. doi:10.1186/1476-069X-2-8
The Faroes Statement: Human Health Effects of Developmental Exposure to Chemicals in Our Environment
Prisonplanet.com, September 28, 2007: How Mercury Kills the Brain (set of videos)
Related EVISA Resources
EVISA Link Database: Toxicity of organic mercury compounds
EVISA Link Database: Environmental mercury pollution
EVISA Link Database: Biogeochemical cycling of mercury
EVISA Link Database: Possible hazards and rules and legislation related to organo-mercury compounds
EVISA Link Database: Analysis for organo-mercury compounds
EVISA News, July 10, 2008: Methyl mercury metabolism in man influenced by genetic factors
EVISA News, October 9, 2007: New CDC study on the effect of thimerosal exposure on neuropsychological characteristics of children is fueling the debate about the origin of autism
EVISA News, March 11, 2007: Methylmercury contamination of fish warrants worldwide public warning
EVISA News, May 3, 2006: Texas Study Relates Autism to Environmental Mercury
EVISA News, February 9, 2006, Study show high levels of mercury in women related to fish consumption
EVISA News, April 27, 2004: New kind of mercury found in fish
News, April 27, 2004: FDA/EPA recommends pregnant women to restrict
their fish consumption because of methylmercury content
last time modified: October 30, 2008