Precautionary approach to methylmercury needed

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 damage.

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 develop.

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.

The 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.

"Until 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

Related studies

Philippe Grandjean, David Bellinger, Ake Bergman, Sylvaine Cordier, George Davey-Smith, Brenda Eskenazi, David Gee, Kimberly Gray, Mark Hanson, Peter van den Hazel, Jerrold J Heindel, Birger Heinzow, Irva Hertz-Picciotto, Howard Hu, Terry T-K Huang, Tina Kold Jensen, Philip J Landrigan, I Caroline McMillen, Katsuyuki Murata, Beate Ritz, Greet Schoeters, Niels Erik Skakkebaek, Staffan Skerfving, Pal Weihe, The Faroes Statement: Human Health Effects of Developmental Exposure to Chemicals in Our Environment, Basic Clin. Pharmacol. Toxicol., 102/2 (2008) 73-5. DOI: 10.1111/j.1742-7843.2007.00114.x

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

Frodi Debes, Esben Budtz-Jørgensen, Pal Weihe, Roberta F. White, Philippe Grandjean, Impact of Prenatal Methylmercury Exposure on Neurobehavioural Function at Age 14 years, Neurotoxicol. Teratol., 28 (2006) 363-375. DOI: 10.1016/j.ntt.2006.02.004

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

 Related information

Youtube: September 28, 2007: How Mercury Kills the Brain (set of videos)

Related EVISA Resources

Link Database: Toxicity of organic mercury compounds
Link Database: Environmental mercury pollution
Link Database: Biogeochemical cycling of mercury
Link Database: Possible hazards and rules and legislation related to organo-mercury compounds
Link Database: Analysis for organo-mercury compounds

Related EVISA News (newest first)

February 11, 2005: New findings about Thimerosal Neutotoxicity
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last time modified: May 22, 2024