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Section 6: Risk Assessment

  • Page ID
    316738
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    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:

    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:
      1. 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).
      2. Dose-Response Assessment
        • Carcinogenic (cancer) risk assessment involves two steps:
          1. Perform qualitative evaluation of all epidemiology studies, animal bioassay data, and biological activity.
          2. 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.
      3. 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:
          1. Characterize the point of exposure setting and exposure scenario.
          2. Identify exposure pathways.
          3. Quantify the exposure.
        • Exposure models are commonly used because actual exposure measurements are often not available.
      4. 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.

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