Science is necessary to generate important documentation, but it provides an incomplete basis for protection of the brain against chemical toxicity. The main problem is that science has covered only a handful of chemicals, and we know the dose-response relationships only for substances, such as lead, mercury, arsenic, and polychlorinated biphenyls (PCBs).
However, we know from clinical poisonings that more than 200 chemicals can cause neurological symptoms in adults. Thus, these chemicals can obviously gain access to the brain and exert toxic effects on brain cells. The same must be true for the fetus or newborn child. So if a chemical can cause toxicity to the adult brain, these chemicals very likely can also damage the developing brain, with much more serious and permanent consequences likely to occur, even at doses much lower than those that can harm mature brains.
As a second limitation of scientific evidence, research on chemical brain drain takes time and involves many uncertainties. The best studies must measure the chemical exposures of the mother during pregnancy and the child postnatally, perhaps with analyses of cord blood. Then the researchers must examine the child’s brain development. However, the detailed brain functions are difficult to test in small children, and researchers often have to wait until the child has reached school age. Thus, such studies take many, many years to complete.
As a supplement, animal experiments are helpful, but the human brain is very different from the nervous system that usual laboratory animals must be content with. Also, standard toxicology protocols just require that the weight of the brain is measured, and only a decrease of more than 5% for a newborn rodent pup is considered an adverse effect.Such loss of brain weight would of course lead to overwhelming brain damage in humans and in no way reflects the brain drain that we would like to prevent. There are also possibilities to use cell cultures, but again such results may not fully reveal the damage that may occur in a human brain.
Because of the uncertainties, the conclusions from existing scientific documentation must be cautious. A third problem is therefore that scientists usually express themselves in ‘soft’ language, using ‘hedged’ expressions with maybe, perhaps and other terms like that, while caveats are highlighted. This tradition in academic science has served to negotiate guarded conclusions, while balancing between skepticism and gullibility. However, vested interests have taken advantage of this tradition and raised doubt about the conclusions that can be drawn from the evidence. This has led to a belief that chemical safety is not needed unless proven by science, that is, ‘sound’ science. So a chemical is considered safe, unless otherwise proven.
The combination of these three problems – a triple whammy – puts the developing brain at extreme risk. While waiting for science to provide the desired documentation, we are exposing the next generation to risks of chemical brain drain.