15 June 2016. Today, two years after the original deadline, the European Commission published its conclusions that certain industrial chemicals should be classified as endocrine disruptors according to the definition proposed several years ago by the World Health Organization. This classification must rely on the weight of the scientific evidence. As could be expected, opinions differed substantially. Thus, industry organizations objected against consideration of this new type of risk, while consumer organizations and environmental NGOs expressed concern that the Commission did not go far enough.
So what does this mean in regard to the protection of developing brains against chemicals that may interfere with hormonal substances that are crucial for the maturing brains? Not much, sadly.
Probably the most important hormone for brain development is the thyroid hormone. It would make sense then to screen industrial chemicals for interference with the thyroid gland. However, the science in this field is still under development, and screening protocols are not quite ready. The OECD has developed standard protocols for studying toxicity in rodents, but they are time-consuming and expensive.
Estrogen is another crucial hormone for brain development, including sex-dimorphic functions. But testing for estrogen effects are not that simple. Recent studies at the U.S. National Center for Toxicology Research showed that bisphenol A, an estrogenic chemical, could cause adverse effects in the neonatal rat brain at concentrations that were 120,000-fold below those that cause effects in the uterus that would have been expected to be the main target organ.
Last year, an international group of researchers evaluated the costs to the EU from exposures to endocrine disruptors. The greatest costs (over €100 billion per year) were due to adverse effects on brain development from organophosphate pesticides. These chemicals are considered endocrine disruptors, as they can affect the thyroid gland, and they were therefore included in the cost calculations. But do we know that hormonal interference is the reason that they are toxic to human brain development? No, we don’t.
The way the European Commission phrases the need for scientific evaluation, the adverse effects on brain development will probably not qualify for intervention. Thus, the strict criteria for recognizing industrial chemicals as endocrine disruptors will not help in the battle to protect the next generation’s brains.
Why not make it a priority to prevent exposure to chemical brain drainers and apply the EU’s precautionary principle?