Human brain development is among the most complex processes in nature – and exquisitely sensitive to the environment. Long before birth, brain cells, or neurons, actively form the connections that determine lifetime intelligence. Thanks to sound government regulation, pregnant women know to avoid cigarette smoke and alcohol during this critical time in their baby’s development. But hidden in our environment are neurotoxicants such as lead, polychlorinated biphenyls (PCBs) and certain pesticides, which pose a high risk of permanent and irreversible dysfunction.

The consequences of these exposures can include loss of intelligence (IQ), disruption of behavior, increased risk of attention deficit disorder and heightened risk of autism. Methyl mercury is among the most potent neurotoxicants. When a pregnant woman eats mercury-contaminated fish, the methylmercury from the fish enters the mother’s blood stream. From the mother’s bloodstream, the methylmercury can move directly across the placenta to enter her child’s body. The placenta poses no barrier to the passage of methylmercury.

Once in the child, themethylmercury accumulates in and *irreversibly* damages the developing brain. In 2000, the National Academy of Sciences reviewed three large-scale, prospective epidemiologicstudies – one in the Seychelles Islands in the Indian Ocean, another in New Zealand and a third in the Faroe Islands of Denmark – and found strong evidence for the toxicity of methyl mercury to children’s developing brains, even at *low* levels of exposure.