“We have only one chance to develop a brain”

Philippe Grandjean, Adjunct Professor of Environmental Health at Harvard University, delivered a lecture in Barcelona invited by Jordi Sunyer, from the CREAL, a ‘model institution’ according to Grandjean. Sunyer introduced the talk about what the Danish-born scientist calls a ‘silent pandemic’: the effect of chemical pollutants on neurodevelopment.

To what extent do in utero conditions affect adult health? 
There are several studies that show that exposing pregnant women to mercury can affect the development of their children, even if they are not affected themselves. Minamata disease, a neurological syndrome caused in children whose mothers suffer severe mercury exposure, was discovered in Japan in the 1950s, and was a shock to the world. Since then many other studies have demonstrated the effect of mercury exposure on foetal development. However, it wasn’t until 2009 that an international agreement was reached to control mercury emissions into the environment!

How many pollutants can be neurotoxic during early development? 
There are about 100,000 chemicals in the world. About 200 have been documented as being neurotoxic to adult humans, and only five to foetuses: lead, mercury, PCBs (polychlorinated biphenyls), arsenic and toluene. However, the foetal brain is much more sensitive than the adult one! So I think we are only seeing the tip of the iceberg. For example, many pesticides can be neurotoxic to humans, as the nervous system of the insects that the pesticides attack is very similar to ours. For example, we did a study in Ecuador on pregnant women working in flower plantations, who were exposed to pesticides. Their children at school age presented a delay of up to two years in their brain development.

Are these effects irreversible? 
The brain has great plasticity, so one might think that with enough effort we could get kids with lower cognitive abilities to catch up with the rest. But the problem is for this plasticity to occur your neurones must be in the right place. You cannot develop your full potential if you don’t have the correct anatomical foundation and if your nerve cells and connections are abnormal.

And does mercury exposure cause anatomical problems in the brain? 
Normally we have no way of checking, but with Minamata disease, quite a few of the children died, and when they were examined at autopsy it was seen that their brain cells appeared in a disrupted pattern, as if their migration during brain development had been affected. So yes, we think so.

If they are so dangerous, why are these pollutants not banned? 
The problem is that chemicals are not banned unless it’s proven that they are dangerous. But then it’s too late! I think we need to move towards the opposite strategy: a chemical should be banned unless it is proven not to be dangerous to brain development. Prevention should come before science. After all, we have only once chance to develop a brain.


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