Keywords: methylmercury, chemical exposure, developmental toxicity, neurotoxicity, prenatal exposure, delayed effects, neurodevelopmental disorders, foetal development, mercury toxicity, postnatal exposure
Development neurotoxicity: implications of methylmercury research
The causes of neurodevelopmental disorders are mostly unknown. Exposure to certain chemicals during early foetal development can cause permanent brain injury at doses much lower than those that affect the adult brain. Recent epidemiological evidence on methylmercury has shown adverse effects at exposure levels previously thought to be safe. Major obstacles in this research field include non-specific neurobehavioural outcomes and imprecise exposure assessments that result in a bias towards the null. Epidemiological studies may therefore easily underestimate the risk, but they are nonetheless often considered with scepticism. Neurodevelopmental toxicity potentials of numerous other chemicals have not yet been documented to the same extent as mercury, and exposures are therefore not regulated to protect the developing brain. The experience on mercury toxicity suggests that a precautionary approach to potential developmental neurotoxicants is warranted.