Risk Assessment and 09/13/07. Learning Objectives. Nature of Risk. Risk Assessment and Environmental Policy. Gene Schroder, PhD

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1 Risk Assessment and Environmental Policy Risk Assessment and Environmental Policy Gene Schroder, PhD the dichotomy that exist between the perceptions of the public and the experts on which risks are important presents and enormous challenge to a pluralistic, democratic country. Learning Objectives Compare environmental health risks with other risks. Review the process of risk assessment. Present concepts of relative risk assessment. Relate environmental policy to environmental risks. Nature of Risk What is risk? The possibility of loss or injury Risk assessment - "the characterization of the potential adverse health effects of human exposures to environmental hazards" (NRC, 1983) May be broadly based (risks of exposure to ozone or lead in air) or local (risks associated with living near a superfund site). May be retrospective or prospective (e.g. asbestos exposure; new pesticide) 1

2 Risk Assessment A risk assessment for a toxic pollutant combines results of studies on the health effects of various animal and human exposures to the pollutant with results of studies that estimate the level of people's exposures at different distances from the source of the pollutant. We Deal With Risk Daily Personal Activities: motorcycling = 2,000 deaths/100,000 persons at risk/year (2%) fire fighting = 80 deaths/100,000/yr (0.08%) motor vehicle accidents = 24 deaths/100,000/yr (0.024%) 024%) personal activities that affect health (smoking, drinking, food, exercise etc.) Accidents of Nature: Lightning kills 0.05 people/yr/100,000 ( %) Risk from meteorite hits per 100,000 or ( %) Estimating Risks from Toxic Substances Estimates of Common Risks Exposures to Toxic Substances - estimates based on animal studies not actual human deaths in most instances. Cancer risk from chlorinated drinking water 0.8/100,000/yr (0.0008%) How is this risk estimate different from the above? Previous data were based on observed incident rates Based on adverse effects from animal studies using various chlorinated compounds Result is a worst-case estimate (upper bound). Assumes there is no safe dosage This is an average attributed risk. (no particular high or low risk group is identified) Source: Should We Risk It? D. Kammen and D. Hassenzahl Princeton Univ. Press,

3 Strength of Association Quality of Risk Estimates Source: Risk Assessment for Toxic Air Pollutants: A Citizen's Guide - EPA 450/ ,March 1991 Dealing with uncertainty in complex systems Big Picture Direction and magnitude of process What data are missing? What assumptions must be made? Qualitative Analysis of Existing Data Make needed assumptions Arrive at detailed quantitative solution (model) Evaluate Robustness of Conclusions How sensitive to assumptions? Where new data needed? Intuitive Modeling Intuitive Modeling Source: Should We Risk It? D. Kammen and D. Hassenzahl Princeton Univ. Press, 1999 Source: Should We Risk It? D. Kammen and D. Hassenzahl Princeton Univ. Press,

4 Intuitive Modeling Intuitive Modeling Source: Should We Risk It? D. Kammen and D. Hassenzahl Princeton Univ. Press, 1999 Source: Should We Risk It? D. Kammen and D. Hassenzahl Princeton Univ. Press, 1999 Intuitive Modeling Which of the graphs best represent Linear Convex Concave Threshold the the number the the number of leaks of of accidents of carcinomas space a sewer shuttle a driver line a surfer accidents as has, a function is as likely a as function a to of function get the of as number total a of of years cumulative functioin total it has number been of miles total in of service driven? missions lifetime without hours flown? maintenance the sun? or replacement? Source: Should We Risk It? D. Kammen and D. Hassenzahl Princeton Univ. Press, 1999 Non-cancer Health Risks Cancer not the only risk from environmental chemicals (immune, hormonal, developmental, reproductive) These endpoints are usually regulated by determining the no effect (NOEC or NOEL) level in animals and applying a safety margin (X10) (Reference dose). Unlike carcinogens, these regulations assume a safe level of exposure. Risks of 10-6 (one in a million / lifetime) are not worth regulating. Average lifetime risk of cancer is about 33%. 4

5 Health Effects of Air Pollutants The National Academy of Sciences Paradigm for Risk Assessment Hazard Identification Dose-Response Relationships Exposure Analysis Risk Characterization Source: Risk Assessment for Toxic Air Pollutants: A Citizen's Guide - EPA 450/ ,March 1991 Risk Assessment Process Hazard Identification Hazard Identification - to determine whether the available scientific data describe a causal relationship between an environmental agent and demonstrated injury to human health or the environment. In humans observed injury (birth defects, cancer, etc.) In the environment ( fish kills, defoliation, etc.) Possible causal factors identified (workplace, food, water) Evidence that observed effects can result from exposure to causal factors Good environmental epidemiology Source: Risk Assessment for Toxic Air Pollutants: A Citizen's Guide - EPA 450/ ,March

6 Dose-Response Evaluation If there is reason to believe a causal relationship then the following steps are appropriate: Dose-Response Relationships - designed to establish the quantitative relationship between exposure and response. It is based on extrapolation (high level lab studies with animals to low dose human exposures). The number produced is an estimated toxicity, R (e.g /mg/kg/d) or NOEC. Dose-response Relationship for Cancer Derivation of Slope Factor In the absence of clear evidence to the contrary, EPA assumes that there are no exposures that have "zero risk" -- even a very low exposure to a cancer-causing pollutant can increase the risk of cancer (albeit a small amount). EPA also assumes that the relationship between dose and response is a straight line -- for each unit of increase in exposure (dose), there is an increase in cancer response. Source: Risk Assessment for Toxic Air Pollutants: A Citizen's Guide - EPA 450/ ,March 1991 Dose-response Relationship for Non-cancer Effects Derivation of Reference Dose A dose may exist below the minimum health effect level for which no adverse effects occur. EPA typically assumes that at low doses the body's natural protective mechanisms repair any damage caused by the pollutant, so there is no ill effect at low doses. However, for some substances, noncancer effects may occur at low doses. The dose-response relationship (the response occurring with increasing dose) varies with pollutant, individual sensitivity, and type of health effect. Source: Risk Assessment for Toxic Air Pollutants: A Citizen's Guide - EPA 450/ ,March 1991 Dose-Response Curve 6

7 Dose-Response Curve Dose-Response Curve Dose-Response Curve Exposure Analysis & Risk Characterization Source: Risk Assessment for Toxic Air Pollutants: A Citizen's Guide - EPA 450/ ,March 1991 Exposure Analysis - moves the assessment from known populations (lab studies, or epi studies) to other potentially exposed populations. Questions raised include: likely sources of the pollutant (incinerator, dump site, ground water) concentrations at the source, transport and transformation to target population actual levels of exposure Risk Characterization - to fully describe the expected risk by examining the exposure prediction for real-world conditions. Putting all the data together to estimate risk to population 7

8 Exposure Analysis Risk Characterization Source: Risk Assessment for Toxic Air Pollutants: A Citizen's Guide - EPA 450/ ,March 1991 Source: Risk Assessment for Toxic Air Pollutants: A Citizen's Guide - EPA 450/ ,March 1991 Estimating Cancer Risk The basic equation for calculating excess lifetime cancer risk is: Risk = CDI x SF Slope Factor Slope factor is derived from bioassay results at lowest effective doses. where: Risk = a unitless probability of an individual developing cancer over a lifetime; CDI = chronic daily intake or dose or LADD = lifetime average daily dose [mg/kg-day; and risk/pci] SF = slope factor, expressed in [(mg/kg-day)-1; pci/risk] Source: 8

9 Estimating Cancer Risk Risk values for carcinogens are calculated by multiplying the lifetime average daily dose (LADD), or chronic daily intake (CDI) from the exposed population times the potency or slope factor as defined in the dose-response assessment phase of the risk assessment. Let us assume an LADD of mg/kg body weight/day. We can use the potency of Aldrin (17 tumors/mg/kg body weight/day): = LADD x Slope factor = x 17 = = one in 29 An unacceptably high risk of death. What to do? How would we determine the safe CDI for Aldrin? Estimating Non-Cancer Risks The basic equation for calculating systemic toxicity (i.e., noncarcinogenic hazard) is: Noncancer Hazard Quotient = CDI/RfD where: CDI = chronic daily intake for the toxicant expressed in mg/kg-day, and RfD = chronic reference dose for the toxicant expressed in mg/kg-day. Reference Dose Reference Dose (RfD): The RfD is a numerical estimate of a daily exposure (oral, inhalation) to the human population, including sensitive subgroups such as children, that is not likely to cause harmful effects during a lifetime. RfDs are generally used for health effects that are thought to have a threshold or low dose limit for producing effects. Estimating Reference Dose Reference dose (RfD) is estimated from either the highest dose showing no effect (NOEL) or lowest dose showing significant effect (LOEL). The dose for the most sensitive endpoint is used and divided by a safety/uncertainty factor (UF) of 10. RfD = NOEL / UF NOEL LOEL Source: 9

10 Regulatory Standards Derived from Permissible Concentrations Permissible concentration is equal to: RfD x Body weight Intake x Duration x Frequency These values are used to set regulatory standards for safe drinking water maximum contaminant levels, permissible exposure limits in the workplace, and pesticide residue limits in food and feed products. Note that for those with small body weights, such as children the permissible concentration levels within the environment will have to be lower. Routes of Exposure and Other Complexities Routes of Exposure Oral Dermal Inhalation Others Duration of Exposure Acute Chronic Age of Exposed Population Complex Mixtures Source: A Simple Example Standard Values Used in Risk Assessment Assume: A job-related exposure to an airborne toxic chemical has been detected. (assume inhalation exposure) hazard assessment A review of literature shows that past studies of exposed workers showed excess cancers. hazard assessment & dose/response Based on estimated occupational exposures and inhalation studies with laboratory rats, the estimated toxicity of this chemical is 10-3 /(mg/kg/d). dose/response Monitoring of site showed average exposure was 10 years at 0.1 mg/m 3. exposure assessment 10

11 Standard Inhalation Values A Simple Example Estimate dose (concentration x inhalation) 3 m mg 1 mg kg = d 70 kg d m Adjust SF for period of exposure and breathing rate kg d 10yr 250d 10m d 3 mg 70yr 365d 10.8m d Thus risk to workers is kg d = mg 6 Quality of Risk Estimates Risk Assessment/Risk Management Quality of Risk Estimates only as good as the data and assumptions. How extensive is the data base? Does it include human epidemiological data? Does the laboratory data base include test data on multiple species? Did all species respond the same? What are the scientific uncertainties? What working assumptions underlie the risk assessment? What is the overall confidence level in the risk assessment? 11

12 Uncertainties and Policy Choices Uncertainties and Policy Choices Sources of Uncertainty: Validity of basic assumptions Effects of complex exposure environments variances in scientific measurements (instruments that measure chemicals not absolutely accurate; the parameter measured may vary continuously) information gaps or lack of fundamental understanding (role of stratospheric clouds, natural responses to greenhouse gases) Regulatory decisions often cannot await final resolution of uncertainties. Policy Choices - The outcome of a risk analysis is affected by the assumptions made during the process. Different experts may have different views about what is important or how factors should be weighted. Politics will affect what experts are heard and what assumptions are used. Statutory Mandates on Risk Statutory Mandates on Risk EPA responsible for implementing about a dozen major environmental statutes. Many include specific risk management directives: Pure Risk Standards - also called zero-risk standards. Delaney clause of Federal Food, Drug and Cosmetic Act once prohibited the approval of any food additive that has been found to induce cancer in humans or animals. Very controversial. (repealed in 1998) Clean Air Act - calls for primary standards for 6 listed pollutants that protect the public health allowing an adequate margin of safety (assures protection of public health without regard to technology or cost factors). Technology-Based Standards - direct the Agency to focus on the effectiveness and cost of alternative control technologies rather than on how control actions could affect risks. Best examples are the Clean Water Act that require industries to control wastes using best available technology, best conventional technology or best demonstrated control technology. Which of these that are required consider total costs, age of equipment, processes involved, engineering and environmental factors. 12

13 Statutory Mandates on Risk Comparative Risk Analysis No Unreasonable Risk Standards - require balancing risk against benefits in making risk management decisions. The Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) requires EPA to approve and license pesticides that will cause no unreasonable adverse effects on the environment. These decisions take into account economic, social, and environmental costs and benefits. The Toxic Substances Control Act (TOSCA) requires EPA to take action if it finds a chemical substance presents or will present an unreasonable risk or injury to health or the environment. EPA must resort to some method of setting priorities. Ideally the most important problems should get the most attention. However, many forces play a critical role in directing policy: statutory mandates, considerations of costs and benefits, the state of technology, environmental equity, public values and concerns. Comparative risk analysis attempts to use objective, relevant, and fair means to set priorities. Comparative Risk Analysis Comparative Risk Analysis Process - teams of experts put together a list of problems then sort the problems by types of risk (e.g. cancer, non-cancer health, materials damage, ecological l effects ) they rank within each type by severity of effects, the likelihood of problem occurring, the number of people exposed, the result is a prioritized list of problems that are then modified by factors listed above. Funding does not reflect the results of this priority setting process. Funds set up for construction of wastewater treatment plants and superfund accounted for over 70% of the 1990 EPA budget. Only 16% was allocated toward the high risk problems (indoor radon, indoor air, stratospheric ozone, global warming received 2% in 1992). Congress also adds unfunded projects which EPA must address. 13

14 Public s Risk Perception Public s perception of risk drives environmental budget often causing spending inefficiencies. Questions you should be able to answer: How do estimates of environmental risk differ from risks of accidents? How is a possible, probable or known carcinogen defined? How do estimates of cancer and non-cancer health risk differ? What are the 4 steps in risk assessment and what do they attempt to provide? What are the most critical assumptions made in most health risk analyses? How could the risk assessment process overestimate the actual risk? Link risk assessment with policy; do the highest risk problems get the most attention? Why? Source: Environmental Science Systems and Solutions, M.L. McKinney, R.M. Schoch, West Publishing, Dealing With Environmental Uncertainty in Policymaking How do we internalize costs to health and the environment at the front end of the production/consumption cycle? If the product reflected the true cost of production, use and disposal there would be much greater incentive to conserve and protect. Market mechanisms - These mechanisms are designed to alter the pricing structure of the present market system to incorporate the longterm social and ecological costs of an economic agent s activities. Incentive-based Mechanisms Current incentive-based mechanisms include: pollution taxes, tradable pollution-discharge permits, deposit-refund systems, Newer ideas currently being researched include: Flexible environmental assurance bonding system Deposit-refund system Producer-paid performance bond 14

15 Incentive-based Mechanisms These proposals have the advantage that they: move the costs to the present where they will have the maximum impact on decisionmaking. assess the environmental and health impacts from a ecological and economic perspective to insure that the size of the bond is adequate to cover the worst-case damages. insures that the funds are used appropriately in case of a partial or complete default. applies the polluter pays principle 15