Research Programs: Safe Communities
Children's Health
NHEERL Research Programs
Sensitive Subpopulations and Children's Health
Problem: There are over 20,000 pesticide products containing 620 active ingredients on the market. Each year, 1 billion pounds of active ingredients in conventional pesticides are applied in the United States. There are over 80,000 existing chemicals on the TSCA inventory and each year an additional 2,000 chemicals are added. Release of these chemicals into the environment through agricultural and nonagricultural application and other means poses serious risks to both human health and ecosystems (e.g., plant and wildlife). In order to accurately characterize risk from and appropriately regulate the manufacture and use of pesticides and other chemicals, EPA must conduct a cost benefit analysis for each product. Data needed for such analyses are provided, for the most part, by the manufacturer. It is, however, the responsibility of the Agency to provide detailed data collection protocols. This is accomplished through the publication of test guidelines. The guidelines, including those that specifically address increased sensitivities to pesticides and other chemicals experienced by certain subpopulations, must be developed and periodically reviewed.
Scientific Questions:
- What are the characteristic(s) that define subpopulations?
- Are observed differences in sensitivity qualitative or quantitative in nature?
- What is the magnitude of differences between the general population and the subpopulations?
Approach: This research is expected to result in more accurate risk management decisions for compounds that are anticipated to effect sensitive subpopulations, including children. NHEERL research to address the first question listed above is directed at identifying factors such as developmental stage, age, sex, genetics and health status that may impact sensitivity to pesticides and other chemicals. We are conducting studies in both laboratory animals and humans. Clinical and epidemiological data are used to produce guidance to health care providers as well as individuals. They also can provide insight into the development of appropriate animal models to study specific effects. We are characterizing quantitative differences in sensitivity through studies that directly compare groups of subjects that differ in regard to one of the factors listed above on the same endpoint or endpoints. Characterization of qualitative differences is most commonly approached by comparing groups that differ on terms of developmental status or sex. We are determining the magnitude of response differences between sensitive subpopulations and the general population in order to evaluate the adequacy of protection provided by standard risk assessment practices. A major focus within this research area is on studies that evaluate the potential increased sensitivity in developing organisms; this includes research to develop methods and models to detect, characterize and predict effects stemming from prenatal and early postnatal exposures.
Recent Highlights:
- We found differences in both the dose-response and time-course of behavioral and biochemical effects of pesticides in rats. Rat pups approximating the infant/toddler stage were about five times more sensitive than adults to chlorpyrifos, while pups approximating pre-adolescents were about twice as sensitive. The mechanism for this marked sensitivity in the immature animal is believed to be due to the fact that the young rat is less able to detoxify this pesticide than the adult because they are deficient in enzymes that detoxify the pesticide. This has regulatory ramifications: young humans may also be deficient in these same detoxification enzymes.
- In collaboration with the National Institute of Environmental Health Sciences on the long-term effects of perinatal exposure to pesticides, we have shown that adults display reproductive effects following early exposures to methoxychor, an endocrine disrupting pesticide.