|July 17, 2012||
Children’s Cognitive Health: The Influence of Environmental Chemical Exposures
David C. Bellinger, PhD, MSc
Over the past forty years, concern has grown that some of the 80,000 chemicals used commercially could be exerting adverse effects on children’s health. Many of these chemicals were synthesized for the first time within recent decades, suggesting that the body’s detoxification mechanisms, the results of thousands of years of evolution, might not be effective in limiting their impact. The potential for exposure is substantial, as the US Environmental Protection Agency (US EPA) estimates that 2.5 billion pounds of chemicals are emitted yearly by large industrial facilities. At the same time, it is remarkable how limited are the data on the toxicities associated with most of these chemicals. The US EPA maintains the Integrated Risk Information System (IRIS), which serves as the repository of the consensus scientific opinions on chemical toxicity. Yet IRIS lists only 550 chemicals (www.epa.gov/iriswebp/iris/stand-al.htm), indicating significant lacunae in the knowledge needed to estimate and manage the risks associated with current exposures.
For many chemicals, most of the available data pertains to occupational exposures. The amount of data available regarding the potential effects of chemicals on children’s brain development is much more limited. It was not until the 1990s that the US EPA published guidelines for registrants with regard to testing in animal models of the developmental neurotoxicity of certain chemicals, primarily organophosphate pesticides, for application in human risk assessments (US EPA OPPTS Health Effects Test Guideline 870.6300; www.epa.gov/EPA-TOX/1998/May/Day-14/t12303.htm). At present, for many of the chemical exposures of current
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