Risk Assessment Introduction • Environmental regulations and the resultant activities are designed to address environmental M5: Overview of Urban Water threats to human (public) and ecological health. • Question: Risk Assessment – How did we decide that particular activities and/or pollutant loads cause an environmental health problem that requires addressing? Shirley Clark • Much of this discussion is based on the following sources: Penn State - Harrisburg – Guidelines for Ecological Risk Assessment (Published on May 14, 1998, Federal Register 63(93):26846-26924) – Introduction to Chemical Exposure and Risk Assessment Risk Assessment Overview Risk Assessment Flow Charts • Based on two elements: characterization of effects and characterization of exposure. • These focus the three phases of risk assessment: – problem formulation, – analysis, and – risk characterization. 1
Risk Assessment Overview • Problem formulation: – Identify purpose, define problem, develop plan for analyzing and characterizing risk. – Two products: assessment endpoints and conceptual models. • Analysis: – Guided by the products of problem formulation. – Evaluate data to determine how, and if, exposure to stressors is likely to occur (characterization of exposure) and, given this exposure, the potential and type of effects that can be expected (characterization of effects). – Two profiles as products: one for exposure and one for stressor response. Risk Assessment Overview Questions Addressed by Risk Managers and Risk Assessors • Risk characterization: Questions principally for risk managers to answer : • – Integrate exposure and stressor-response profiles risk estimation process. – Product: risk description, including an interpretation of adversity (whether the • What is the nature of the problem and the best scale for the effects of the exposure are negative) and descriptions of uncertainty and assessment? lines of evidence. • What are the management goals and decisions needed, and how will risk assessment help? • Iterative process, especially as one phase exposes a data gap that requires action! • What are the ecological values (e.g., entities and ecosystem characteristics of concern)? • Monitoring data – important input to all phases of a risk assessment. • What are the policy considerations (law, corporate stewardship, – Drive need for risk assessment by identifying changes in ecological and/or health condition. societal concerns, environmental justice, intergenerational equity)? – Used to evaluate a risk assessment’s predictions. • What precedents are set by similar risk assessments and previous decisions? • The reference (US EPA 1998) from which much of this section is drawn • What is the context of the assessment (e.g., industrial site, national makes a distinction between risk managers and risk assessors. The text park)? box below highlights the differences in the two positions through the list • What resources (e.g., personnel, time, money) are available? of questions that are of interest to each. • What level of uncertainty is acceptable? • Each risk assessment is constrained by the availability of valid data and scientific understanding, expertise, time, and financial resources. 2
Questions Addressed by Risk Managers Problem Formulation and Risk Assessors • Problem formulation: process of generating and • Questions principally for risk assessors to answer: evaluating preliminary hypotheses about why effects have occurred, or may occur, from human activities. • What is the scale of the risk assessment? • What are the critical ecological endpoints and ecosystem • Early in problem formulation, the objectives are refined. and receptor characteristics? • Then the nature of the problem is evaluated and a plan • How likely is recovery, and how long will it take? for analyzing data and characterizing risk is developed. • What is the nature of the problem: past, present, future? • What is the state of knowledge of the problem? • Three products: (1) assessment endpoints that • What data and data analyses are available and adequately reflect management goals and the appropriate? ecosystem they represent, (2) conceptual models that • What are the potential constraints (e.g., limits on describe key relationships between a stressor and expertise, time, availability of methods and data)? assessment endpoint or between several stressors and assessment endpoints, and (3) an analysis plan. Problem Formulation Integration of Available Information • • Adequacy determined by how well available information on stressor sources and characteristics, exposure opportunities, characteristics of the humans or ecosystem(s) potentially at risk, and effects are integrated and used. Initial evaluations � generation of preliminary conceptual models or • assessment endpoints � lead assessors to seek other types of available information not previously recognized as needed. • When data is limited, the limitations of conclusions, or uncertainty, from the risk assessment must be clear in the risk characterization. • Reason behind risk assessment influences what information is available at the outset and what information should be collected. – Example, risk assessment can be initiated because a known or potential stressor may enter the environment. In that case, the risk assessors will seek data on the effects that have been associated in the past with that exposure. 3
What’s Different When Stressors, Effects, Back to the scenario… or Values Drive the Process? • Values-initiated assessment. – The value is stream health and desire to ensure that it currently • When concerned about stressors, information about stressor and maintains, and will continue to maintain, the designated use (drinking source focuses assessment. water source, fishable/swimmable, or agricultural/industrial). – Objectives based on determining how the stressor may contact and – Assume that the stream is designated as fishable/swimmable. In the affect possible receptors. United States, the US EPA has set the water quality criteria for – This leads to developing conceptual models and selecting assessment aquatic life. This document can be referenced at the following URL: endpoints. http://www.epa.gov/waterscience/criteria/nrwqc-2006.pdf. • When responding to observed effect, endpoints are normally – Assume four pollutants were two nutrients (phosphate and nitrate) established first. and two heavy metals (lead and zinc) and the water type was – Frequently, affected ecological entities (humans, fish, and/or benthos) freshwater. Aquatic life criteria (*25 th percentile data for region): and their response define assessment endpoints. – Protection-based goals are then established, which support development of conceptual models to identify likely stressor(s). Pollutant Criteria Maximum Criterion Continuous • For value-initiated risk assessments, goals are ecological values of Concentration [CMC] ( µ µ g/L) µ µ Concentration [CCC] ( µ µ µ g/L) µ concern (species, communities, ecosystems, or places). – Assessment endpoints are measurable interpretations of the goals. Lead 65 2.5 They support identifying stressors that may be influencing the Nitrate 58* 58* assessment endpoints and describing the diversity of potential effects. This information is then captured in the conceptual model(s). Phosphate 214* 7* Zinc 120 120 Problem Formulation: Integration of Questions to Ask Concerning Source, Stressor and Exposure Characteristics, Ecosystem Available Information Characteristics, and Effects (derived in part from Barnthouse and • Information (actual, inferred, or estimated) initially Brown, 1994) integrated as a preliminary problem scope. • Source and Stressor Characteristics – Foundation for problem formulation. – Knowledge gained during scoping used to identify missing • What is the source? Is it anthropogenic, natural, point information and potential assessment endpoints source, or diffuse nonpoint? – Knowledge provides the basis for early conceptualization. • What type of stressor is it: chemical, physical, or • Predicting risks from multiple chemical, physical, and biological? biological stressors requires understanding their • Intensity of the stress (e.g., the dose/concentration of a interactions as best as is possible given current chemical, the magnitude or extent of physical disruption, information and models. the density or population size of a biological stressor)? • Risk assessments for a region or watershed, where • What is the mode of action? How does the stressor act multiple stressors are the rule, require consideration of on organisms or ecosystem functions? ecological processes operating at larger spatial scales. 4
Recommend
More recommend
