Role of Human Health Science Assessments in EPA’s Risk Assessment Paradigm

EPA's framework for assessing and managing risks to human health from environmental contaminants reflects the risk assessment and risk management paradigm set forth by the National Academy of Sciences (NRC) in 1983. The framework is illustrated below.

The 1983 NRC report identified four steps integral to any risk assessment:

• Hazard Identification is the process of determining whether exposure to a chemical can cause an increase in the incidence of specific adverse health effects (e.g., cancer, birth defects). 
• Dose-Response Assessment describes how the likelihood and severity of adverse health effects (the responses) are related to the amount and condition of exposure to a chemical (the dose provided). The quantitative relationships identified in this step are used to derive reference values for noncancer effects and potency estimates for cancer effects. 
• Exposure Assessment is the process of measuring or estimating the magnitude, frequency, and duration of human exposure to a chemical in the environment, or estimating future exposures for a chemical that has not yet been released.
• A Risk Characterization conveys the risk assessor's judgment as to the nature and presence or absence of risks, along with information about how the risk was assessed, where assumptions and uncertainties still exist, and where policy choices will need to be made.

ORD’s portfolio of human health science assessments focus on hazard identification and/or dose-response assessment, as summarized below.