Biology 5868 Ecotoxicology. Risk Assessment of Contaminants

Transcription

1 Biology 5868 Ecotoxicology Risk Assessment of Contaminants 2009

2 Ecological Risk Assessment Risk assessment is the product of a shotgun wedding between science and the law. William Ruckelshaus (first head of the EPA, 1970).. technical support for decision making under uncertainty. (Bernstein, 1996) Requirements to initiate an ERA: - a decision to be made - uncertainty concerning outcomes

3 Why Risk Assessment? Risk-based environmental decisions: 1) should we permit x? (e.g. use of a new chemical, release of an effluent, increased harvest) 2) What should we do about x? (e.g. remediate, treat, ignore) 3) Should we do x, y, or z? (e.g. which pest management method poses the least risk?) ERAs processes and methods; used to develop, organize and present scientific information so that it is relevant to decision-making ERAs are scientific inputs to the question of regulating contaminants. Other inputs are generated by: - stakeholder concerns - availability of technical solutions - benefits - equity - costs - legal mandates - political issues

4 Risk and Risk Assessment Risk: The probability (or likelihood) of some adverse consequence occurring to an exposed human or to an exposed ecological entity. (Newman & Unger) - combination of severity (nature and magnitude) and probability of effects

5 Risk, Benefit, and Cost Possible considerations for taking an action; - e.g. remediation of a contaminated site include: Risks: - risk of ecological injury from the contaminants - risk from the remedial action itself Benefits: - e.g. reduced contaminant risks to fish Costs: Consideration of cost subject to different laws } Whose risks, benefits, costs? e.g. for pesticide: - manufacturer - user - public

6 Comparative Risk Assessment Confluence of Scientific and Social Realms Comparison of alternative actions e.g. pesticide registration - accept (register) - accept with modifications (registration with restrictions) - reject (do not register) What about considering the consequences of non-registration on current pesticide use? Comparison of risks/benefits of alternative approaches to a range of alternatives - both risk and benefits must be examined - a relatively low-risk alternative action may be undesirable because it offers little or no benefit - common units problem is involved - if alternatives involve disparate risks and benefits, they many not be directly comparable - temporal integration of expected benefits must be assessed - net benefits must be monotized to yield a cost-benefit analysis

7 Alternatives/Compliments to Risk Assessment Rule-based management - e.g. TMDL - often based on driving forces other than science Precautionary principle: In the absence of mitigating evidence, assume that the effects of any agent (e.g. chemical, compound, stressor) is or will be negative; regulate to avoid effects. - many alternative definitions/practices - strictest require definitive proof of safety (implausible to impossible) - least strict require bias towards protection when making a decision; least hazardous alternative should be selected Monitoring environmental status and trends - e.g. EMAP (Environmental Monitoring and Assessment Program, EPA), National Status and Trends Program (NOAA) - generate data or analyze existing data - concerned with broad patterns of common conditions (not specific adverse effects)

8 Alternatives/Compliments to Risk Assessment Life cycle assessment - cradle to grave assessment of manufactured materials - good for determining best alternatives; e.g. paper v. plastic, coal v. nuclear power Technology-based rules - specify particular technology or set of approved technologies for treatment or remediation Best practices, rules, or guidance - e.g. smokestack emissions of NOx reduced to best possible quality by available technology - e.g. chemical release to be as low as reasonably achievable Adaptive management - try it and see if it works approach - alternative actions treated as experimental treatments Prohibition - certain classes of materials may be banned; e.g. CFCs - certain practices may be banned; e.g. offshore sewage waste dumping

9 ERA Protocol Discussion between Risk Assessor and Manager Problem Formulation Gather Data, Verify, and Monitor Exposure Risk Ecological Effects ERA proper Discussion of Results between Risk Assessor and Manager Risk Management

10 Problem formulation - identification of: - ecosystem potentially at risk - stressor characteristics - ecological effects - endpoint selection Also: - input from data acquisition - verification protocols - monitoring protocols Problem Formulation Discussion between risk assessor and risk manager; e.g. - contrasting societal goals/scientific reality - setting boundaries for scope - consolidating goals Products of problem formulation: 1. Assessment and measurement endpoints. 2. Risk hypotheses. 3. Conceptual models. Discussion between Risk Assessor and Manager Gather Data, Verify, and Monitor Exposure Problem Formulation Risk Ecological Effects

11 Products of Problem Formulation Assessment endpoints: valued ecological entity to be protected. - surrogates often used Measurement endpoints: qualities to be measured to assess effects to the assessment endpoint (see N&U Table 13.1) Risk hypothesis: clear statement of postulated or predicted effects Conceptual models include: - pathways of exposure - possible response (effects) - linkages between assessment endpoints with stressors - areas of uncertainty or concern

12 Anylysis - of Exposure Exposure: interaction of stressors with receptors Data from problem formulation evaluated: how is exposure likely to occur? - strength and limitations of data - ecosystem and receptor characteristics Assessment of hazard due to exposure, including - concentrations of contaminants - tissue levels - physical changes (e.g. body weight) - exposure potential of critical biological components Gather Data, Verify, and Monitor Qualitative information regarding the strength of evidence - potential magnitude of risk - descriptions of uncertainties in estimates and conclusions Exposure Stressor characteristics: - physical; e.g. increased temperature - chemical; e.g. pesticides, effluents, including dose/concentration, duration, timing, frequency - biological; e.g. introduction of new species, fertilizer Problem Formulation Risk Ecological Effects

13 Analysis - Ecological Effects Effects characterization determination of the potential and type of ecological effects anticipated; links with assessment endpoints - bioaccumulation, biodegradation, etc. - dose-response tests, etc. - effects at different levels of biological organization Problem Formulation Strength of evidence; level of confidence Gather Data, Verify, and Monitor Exposure Risk Ecological Effects Stressor-response profile - how effects change with varying stressor levels

14 Risk Integration and evaluation of exposure and effects information: - combine ecological effects with environmental concentrations = likelihood of effects Risk combination of exposure and resultant effects expressed as a probability - expressed as a hazard quotient (HQ): HQ = E RfD (for humans) E exposure RfD reference dose Gather Data, Verify, and Monitor - for non-humans: expected environmental concentration HQ = concentration producing unacceptable effect HQs: > 1 = high risk ~ 1 = potential risk < 1 = low risk Uncertainty can be reduced by collecting additional data Exposure Problem Formulation Risk Ecological Effects NOTE risk management decisions do not require absence of uncertainty - attempts normally made to quantify and communicate uncertainty

15 US EPA Framework for ERA Discussion between Risk Assessor and Manager Problem Formulation Gather Data, Verify, and Monitor Exposure Risk Ecological Effects Discussion of Results between Risk Assessor and Manager Risk Management