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Research Programs: Human Health Risk
Risk Assessment Process
Human Health Risk
Through risk assessments, researchers seek to understand the fundamental processes that underlie human health problems that are caused by pollutants in the environment. Risk assessments address questions of exposure and the adverse outcomes associated with exposure. The resultant information provides sound scientific guidance to decision-makers about what actions need to be taken and why.
4 Steps in the Process of Risk Assessment1:
1. Hazard Identification
- Does exposure to a certain substance cause an adverse health effect? What is the nature of the adverse effect?
- What evidence relates exposure to an adverse effect?
2. Dose-Response Assessment
- What is the relationship between exposure or dose and the incidence and severity of the adverse health effect?
- How is this relationship influenced by factors such as the intensity and pattern of exposure or age and lifestyle?
- How can extrapolations be made between animal responses (observed through experiments) and human responses (resulting from real-life exposures) or between high-dose responses (observed in the laboratory) and low-dose responses (resulting from environmental exposures)?
3. Exposure Assessment
- What is the intensity, frequency, and duration of individuals' exposure to a substance?
- How much of the substance in question is emitted into the environment; what happens to it once it is in the environment; and how are people exposed to it?
4. Risk Characterization
- How much of a pollutant can individuals be exposed to before their health is affected? How likely is this effect?
- Are certain subpopulations of people more at risk than others?
- What is the risk to the people who are most exposed?
There are many uncertainties in the process of risk assessment because of limitations in the available data and because of the complex interactions between the sources and environmental concentrations of contaminants, the dose received at the site within a person where the effect is induced, and variability in people's responses. These uncertainties result in the use of default assumptions, simplified approaches, and uncertainty factors. The result of these assumptions and simplifications, which are designed/intended to be protective of human health, may overestimate the risk associated with exposure to a particular level of a pollutant. This may result in overly stringent standards and unnecessarily burdensome costs. Conversely, oversimplifying the risk assessment may underestimate risks to some groups such as children or the elderly or another particularly vulnerable group-a different type of cost which is too high to pay.
EPA's human health research is based on the belief that the public interest can best be served by sound science that improves our understanding of the health consequences of pollutants and that, in turn, reduces uncertainties in the risk assessment process.
Read more about EPA's human health research efforts.
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