One out of every six children suffers from some form of neurodevelopmental abnormality, mostly of unknown causes. Some diagnoses, such as autism spectrum disorder and ADHD have apparently become more common, but we do not know why. Due to the recent surge in the occurrence of these diagnoses, the problems are not likely to be of genetic origin, and some environmental factors clearly play a role.
Several environmental chemicals, such as lead, mercury, arsenic, and certain pesticides and solvents, are known to cause damage to the brain, especially during the vulnerable early stages of development. Some of the discoveries were made decades ago, but detailed documentation did not emerge until fairly recently. After decades of research, we are finally realizing that these chemicals can damage the brain functions of the next generation. Chemical brain drain is a fact.
The understanding of brain drain was hampered by misconceptions and misunderstandings (see Errors of the past). The main problem was that scientific documentation of serious health risks was demanded before any usage restrictions could be accepted. Evidence was not considered “convincing” for 50 years in regard to lead additives in gasoline, and brain drain due to mercury in food was not recignized internationally until 50 years after the first cases of children with mercury poisoning. In the meantime, whole generations of children have been exposed to toxic amounts of chemical brain drainers.
There are thousands of chemicals in the environment and in consumer products that have not even been tested for possible damage to brain development. Yet, we ignore this problem in risk assessment, where lack of evidence is assumed to mean no risk.
Yet, some of the brain drain risks we have to deal with today originate from sins of the past. Hundreds of sites, perhaps thousands, worldwide are so contaminated with lead from mining, smelting and other production, that hazardous lead exposure is affecting the millions of pregnant women and children who live there. Lead paint alone in the US is a serious hazard in about 1 million homes, and several million houses contain water pipes made of lead that may leach to the drinking water.
See Philippe Grandjean’s video on lead (3 minutes):