Ecological Exposure Research
Exposure is the contact of people and other organisms with an environmental stressor for a specific duration of time. Environmental stressors can include chemical pollutants; microbes or pathogens; or physical agents, like radiation; or even processes such as alteration of wildlife habitat.
In order to protect the environment and safeguard human health, EPA must understand the risks posed by pollutants and other stressors.
Exposure assessment is one critical input used by EPA and others to assess those risks. Chemicals that are quite toxic may pose little actual risk if exposures are low. Conversely, relatively nontoxic stressors may pose substantial risks if people or wildlife are highly exposed.
Understanding exposure is essential in assessing the risks that may arise from current or new technologies, policies and regulations, increased population growth, changes in energy use, or even fluctuations in the economy.
EPA’s Exposure Research improves risk assessment through:
- Characterizing pollution sources;
- Developing environmental fate and transport computer models that can be used to quantify how risk management options are likely to affect exposures;
- Developing and enhancing measurement methods for pollutants and exposure indicators; and
- Developing exposure models that reflect individual behaviors and microenvironments.
Exposure measurements, methods, and models also are important in:
- Determining whether a pollutant or stressor represents an unacceptable risk;
- Selecting the most appropriate approaches to reduce risk; and
- Tracking compliance with environmental regulations and achieving environmental goals.
Assessing environmental exposure involves a number of elements:
- Characterizing sources of pollution, including mobile sources such as automobiles; point sources such as industrial plants; and non-point sources such as agricultural run-off and land-management practices.
- Understanding and modeling the processes that control the distribution, transport, transformation, and fate of these pollutants or stressors as they move through the environment from sources to "receptors" (humans, plants, animals or ecosystems exposed to stressors).
- Characterizing actual exposure, including measuring and modeling how humans and ecosystems come into contact with pollutants or stressors. Studying environmental exposure involves consideration of both the pollutant-stressor and the "receptor" (e.g., the human or ecosystem which is exposed), together with duration of exposure. For this reason, exposure assessments require a variety of efforts, including:
- Measuring and modeling pollutants and stressors in various media — for example, measuring pollutant levels in the food people eat, the water they drink, the air they breathe, and the things they touch; and
- Profiling the behavior patterns of people or animals that affect their exposure — including characterizing the daily activities of people (the what, when, where and how long) that bring them into contact with pollutants.
- Assessing the effectiveness of an exposure, including making measurements that provide evidence that "receptors" have been exposed. EPA’s exposure research includes: determination and modeling of uptake or transfer efficiencies; modeling of dose to target organs; characterizing indicators of exposure, like measuring biological markers of exposure in people or animals; identifying antibodies in humans resulting from exposure to pathogens; characterizing changes in wetlands or forest cover; and measuring changes in the composition of ecosystems.
EPA’s exposure scientists work closely with scientists across a host of other disciplines, including toxicology, chemistry, and geology, as well as with research staff in a multitude of other federal agencies, states, industry, utilities, universities, and non-profit organizations around the world.
Research and Technical Support for Regulatory Programs
EPA exposure scientists provide a wide range of research and regulatory technical support to EPA program and regional offices, states, and foreign governments. In particular, EPA’s Exposure Research Program provides substantial support in regulatory monitoring methods, waste site characterization, computer modeling of pollutant transport and fate, remote sensing, monitoring network design, environmental indicators, and design of exposure assessment studies. EPA uses a variety of mechanisms to communicate its research products to program offices, the public, and the international community.