Learning Objectives After completing this lesson, you will be able to: Identify the basic steps in the risk assessment process. Explain the framework for risk -based decision-making. Describe methods for identifying hazards. Explain methods for toxicity assessment, including dose-response and exposure . In this section... Topics include: 6.1: Risk Assessment 6.2: Hazard Identification 6.3: Dose-Response Assessment 6.4: Exposure Assessment 6.5: Risk Characterization What We've Covered This section made the following main points: A hazard is the capability of a substance to cause an adverse effect. A risk is the probability that the hazard will occur under specific conditions. Risk assessment is the process of determining hazard, exposure, and risk. Risk management is the process of weighing policy alternatives and deciding on the most appropriate regulatory action. There are four basic steps to risk assessment : Hazard Identification Identify or develop information suggesting or confirming whether a chemical poses a potential hazard to humans. (Quantitative) Structure Activity, or (Q)SAR methods, including computer models, help consider closely related chemicals as a group or category. Read-across involves estimating what a chemical may be like, including the presence or absence of certain properties or activities, based on one or more other chemicals. Adverse Outcome Pathways (AOPs) involve in vitro methods that evaluate changes in normal cellular signaling pathways. Other emerging methods include (Quantitative) in vitro to in vivo extrapolation, or (Q)IVIVE, Integrated Testing Strategies, and Integrated Approaches to Testing and Assessment (IATA). Dose-Response Assessment Carcinogenic (cancer) risk assessment involves two steps: Perform qualitative evaluation of all epidemiology studies, animal bioassay data, and biological activity. Quantitation of the risk for substances classified as definite or probably human carcinogens. Non-carcinogenic risk assessment includes: Acceptable Daily Intake (ADI), which divides the NOAEL by uncertainty/safety factors. Reference Dose (RfD), which divides the NOAEL or LOAEL by uncertainty/safety factors. Benchmark Dose Method (BMD), which extrapolates data to determine a point of departure (POD) that accounts for study quality. Assessments for noncancer toxicity effects, acute or short-term exposures, and occupational exposures. Exposure Assessment People are exposed to mixtures of hundreds of chemicals in everyday life. An exposure pathway describes the: Route a substance takes from its source to its endpoint. How people can be exposed to the substance. The three steps of exposure assessment are to: Characterize the point of exposure setting and exposure scenario. Identify exposure pathways. Quantify the exposure. Exposure models are commonly used because actual exposure measurements are often not available. Risk Characterization This final phase predicts the frequency and severity of effects in exposed populations. Biological and statistical uncertainties are described. For carcinogenic risks, the probability of a person developing cancer over a lifetime is estimated by multiplying the cancer slope factor for the substance by the chronic, 70-year average daily intake. For noncarcinogenic effects, the exposure level is compared with an ADI, RfD, or MRL derived for similar exposure periods.