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Risk Assessment Activities
Quantitative Risk Assessment
The public and the regulatory community are concerned with both short-term and long-term repeated chronic and environmental health risks and to humans and the environment. Chronic human health and ecological risks associated with biological, chemical, and physical substances are evaluated in a multi-step process called Quantitative Risk Assessment (QRA).
Quantitative Risk Assessment has four steps:
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Hazard Identification - What substances might be dangerous? We need to determine if the substance might be dangerous and cause negative human health and ecological effects. The evaluation of a chemical's adverse effects is largely based on experimental animal studies which are extensively peer reviewed and provide a representative correlation to adverse effects in humans and wildlife species.
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Dose-Response Assessment - How much of the substance will do how much harm? Many substances are highly toxic in large doses, but harmless or even essential to human and wildlife health at low doses. Scientists not only must estimate the potential health effects of varying amounts of exposure to the substance, but also must take into consideration: magnitude (how bad is it when exposure happens); the age, gender, and lifestyle of exposed human populations; the species, lifestage, and sensitivity of exposed wildlife populations; the intensity of the exposure (e.g. 2 grams in 8 seconds or 2 grams in 8 years); and the pathway of exposure (e.g. inhalation, skin contact, or ingestion).
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Exposure Assessment - How much of the hazard are humans and wildlife actually being exposed to? Scientists must use instruments or specialized methods of analysis, many of which have only recently been invented, to measure how much of the substance is detectable. The detectable concentration along with site specific parameters, such as the amount of time people or animals are exposed, are used to determine a total exposure dose (daily intake).
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Risk Characterization - How great is the overall risk? This step combines the results of the first three steps to evaluate the likelihood of adverse effects associated with exposure to biological, chemical, and physical substances. Both qualitative and quantitative expressions of risk are produced as well as estimates of uncertainty.
Human Health Risk Assessment is the characterization of the potential adverse health effects of human exposures to environmental hazards. Risk is estimated by combining an evaluation of human health effects data with human exposure estimates to determine the potential risk to humans from exposure to a chemical substance.
Ecological Risk Assessment evaluates the likelihood that adverse ecological effects may occur or are occurring as a result of exposure to one or more stressors. The process is used to systematically evaluate and organize data, information, assumptions, and uncertainties in order to help understand and predict the relationships between the stressors and ecological effects in a way that is useful for environmental decision making.
