Rachel Shaffer is a research assistant.
Seven years ago, leading children’s environmental health experts Philippe Grandjean and Philip Landrigan published a groundbreaking review that identified five chemicals prevalent in the environment—lead, methylmercury, polychlorinated biphenyls (PCBs), arsenic, and toluene—as developmental neurotoxicants. In their follow-up review released last week, they have added six more chemicals—manganese, fluoride, polybrominated diphenyl ethers (PBDEs), chlorpyrifos, DDT, and tetrachloroethylene (PERC)—to this list. The implications of early-life exposures to these common compounds, say the authors? A “global silent pandemic of neurodevelopmental toxicity.”
The developing fetus and newborn are uniquely susceptible to chemical exposures, and disruptions to critical developmental “programming” during this sensitive period can have life-long consequences. In the environmental health field, this concept is known as the “Developmental Origins of Health and Disease” and suggests that even low-level exposures that would have little or no effect on adults could forever alter the development and life-course of a newborn or young child.
The individual and societal consequences of early-life exposures to developmental neurotoxicants can be devastating. Damage to the brain can lead to permanent decreases in IQ or developmental disabilities, which in turn have implications for academic potential, earning capacity, and, at a population level, effects on national gross domestic product (GDP). Research also suggests that these developmental neurotoxicants can lead to antisocial or criminal behavior; evidence is particularly strong for the case of lead. Yet, in contrast to high-dose poisoning events, effects of these exposures can be subtle and often do not manifest until years later, making it difficult to identify and characterize the linkages to chemical exposures.
Based on mounting data from recent epidemiological studies, Grandjean and Landrigan have now classified the following compounds as known human developmental neurotoxicants:
- Metals and inorganic compounds: arsenic/arsenic compounds, lead, methylmercury, fluoride, manganese
- Organic solvents: toluene, tetrachloroethylene
- Pesticides: chlorpyrifos, DDT/DDE
- Other halogenated organic compounds: polychlorinated biphenyls, polybrominated diphenyl ethers
Their updated report should serve as yet another wake-up call that we are jeopardizing the health and full potential of future generations because of early-life exposures to these common toxic chemicals.
To tackle this growing problem, we need further research and improved chemical testing techniques to identify additional developmental neurotoxicants, and stronger regulatory policies to reduce exposures to them. Fortunately, progress is being made in all three of these areas.
Because of the growing recognition of the severe consequences of exposure to developmental neurotoxicants, researchers across the country are working to identify these compounds and better understand how they act in the body. In fact, earlier this week, the EPA awarded over $3 million in grants to several research institutions to support these investigations. Sustained funding for such critical public health research is essential.
In conjunction with an improved understanding of these toxicants, we need to advance our capacity to screen and test chemicals for their neurodevelopmental effects. New toxicity testing techniques may hold promise towards this end, and engagement with the scientific community studying such chemicals and adverse effects is necessary to ensure that challenges and limitations associated with applying these new tools can be resolved.
And finally, we need a new framework for our national chemicals policy– one that will give the EPA the authority to get and use this information to effectively protect public health. A bipartisan proposal in the Senate opens a path to securing the necessary improvements, and many stakeholders and members of both houses of Congress are working hard on the measure to ensure it delivers the needed reforms.
While challenging, progress in all of these areas is essential to the well-being of our society. As study co-author Grandjean has said, “the brains of our children are our most precious economic resource… You only have one chance to develop a brain.”