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Issues in Risk Assessment (1993)
Commission on Life Sciences (CLS)

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. "Risk Assessment Has Many Uses." Issues in Risk Assessment. Washington, DC: The National Academies Press, 1993.

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Issues in Risk Assessment

In his summary, Dr. Johnson suggested that much better communication is needed between ecologists and the public and between ecologists and economists. Ecologists need to educate the public about the importance of preservation and must learn which aspects of nature the public values most highly. Economists need help from ecologists in educating people about the interactions between natural and human systems and in understanding motives for nonuse values. Ecologists need economists to help them understand both what people care about and how intensely they care. Ecologists also need economists to communicate effectively with risk managers who face competing demands for budgetary and regulatory resources.

RISK ASSESSMENT AND THE REGULATORY PROCESS

W. Cooper and D. W. North

Risk Assessment Has Many Uses

Because there are many uses for risk assessment, many forms of risk assessment are needed. The methodological approach and the level of detail in each form might differ a great deal, depending on the purpose for which risk assessment is carried out.

For strategic planning and setting priorities, it might be appropriate to conduct risk assessments that rely on expert judgment for direct assessments of relative risk. An example of the use of such an approach is the ecological risk portion of the recent EPA Science Advisory Report on Reducing Risk (EPA, 1990). With the direct approach, risk is assessed on the basis of overall integrated judgment to summarize each of the risks being compared. Modeling and other analytical tools are not used directly, but they can play an important role in providing the basis for expert judgment. The result of the risk assessment is a set of risk rankings that reflect the judgment of the assessors. The assessment also includes a discussion of the reasoning underlying the assessments, with explanation for differences among the experts. Because the direct approach relies on expert judgment, rather than mathematical formalism such as model calculations or statistical analysis to reach conclusions, the direct approach can be perceived as lacking in scientific rigor. However, the direct approach can be carried out quickly and might

Page
331
Front Matter (R1-R18)
Executive Summary (1-2)
USE OF THE MAXIMUM TOLERATED DOSE IN ANIMAL BIOASSAYS FOR CARCINOGENICITY (3-8)
THE TWO-STAGE MODEL OF CARCINOGENESIS (9-9)
A PARADIGM FOR ECOLOGIC RISK ASSESSMENT (10-12)
Issues In Risk Assessment Use Of Maximum Tolerated Dose in Animal Bioassays for Carcinogenicity (13-14)
BACKGROUND (15-17)
SCOPE OF REPORT (18-20)
DEFINITIONS AND BACKGROUND (21-23)
CORRELATIONS (24-32)
RELATIONSHIP BETWEEN TOXICITY AND CARCINOGENICITY OBSERVED AT MTD (33-42)
QUALITATIVE INFORMATION (43-48)
QUANTITATIVE INFORMATION (49-52)
OPTION 1 (53-53)
OPTION 2 (54-54)
OPTION 3 (55-56)
Option 4A (57-58)
Option 4B (59-60)
5 Conclusions and Recommendations (61-66)
REFERENCES (67-78)
BACKGROUND (79-79)
DEFINING AND DETERMINING THE MTD (80-90)
Appendix B Organizing Subcommittee (91-92)
Appendix C Federal Liaison Group (93-94)
Appendix D Workshop Program (95-96)
Appendix E Workshop Attendees (97-110)
1. INTRODUCTION (111-112)
2.1 Measures of Carcinogenic Potency (113-115)
2.2 Carcinogenic Potency Database (CPDB) (116-116)
2.3 Variation in Carcinogen Potency (117-118)
2.4 Classification of Carcinogens (119-120)
3.1 Empirical Correlations (121-124)
3.2 Range of Possible TD50 Values (125-125)
3.3 Analytical Correlations (126-127)
3.4 Model Dependency (128-129)
3.5 Genotoxic vs. Nongenotoxic Carcinogens (130-130)
4.1 Predictions Based on the MDT (131-131)
4.2 Predictions Based on Mutagenicity and Acute Toxicity (132-134)
5.1 Correlation Between Upper Bounds On the Low Dose Slope and MTD (135-135)
5.2 Correlation Between q1* and the TD50 (136-138)
5.3. Preliminary Estimate of Risk (139-139)
6. INTERSPECIES EXTRAPOLATION (140-140)
6.1 Extrapolation from Rats to Mice (141-143)
6.2 Extrapolation from Rodents to Humans (144-145)
7. CONCLUSIONS (146-148)
8. ACKNOWLEDGEMENTS (149-149)
9. REFERENCES (150-159)
ANNEX A: MAXIMUM LIKELIHOOD METHODS FOR FITTING THE WEIBULL MODEL (160-161)
ANNEX B. SHRINKAGE ESTIMATORS OF THE DISTRIBUTION OF CARCINOGENIC POTENCY (162-163)
ANNEX C: ADJUSTMENT OF POTENCY VALUES FOR LESS THAN LIFETIME EXPOSURE (164-165)
ANNEX D: CORRELATION BETWEEN TD50 AND MTD (166-168)
ANNEX E: CORRELATION BETWEEN TD50S FOR RATS AND MICE (169-172)
Appendix G Informal Search for ''Supercarcinogens" (173-174)
CRITERIA AND CANDIDATE CHEMICALS (175-176)
DATA (177-180)
RESULTS (181-181)
DISCUSSION (182-184)
Issues in Risk Assessment The Two-Stage Model Of Carcinogenesis (185-186)
INTRODUCTION (187-187)
BIOLOGIC CONSIDERATIONS (188-189)
THE TWO-STAGE MODEL (190-195)
APPLICATIONS OF THE TWO-STAGE MODEL TO ANIMAL DATA (196-211)
Data Needs (212-212)
Criteria for Adoption (213-213)
Prospects (214-214)
CONCLUSIONS AND RECOMMENDATIONS (215-216)
REFERENCES (217-222)
BIOLOGICAL FACTORS IN TWO-STAGE MODELS (223-225)
TWO-STAGE MODEL OF CLONAL EXPANSION (226-227)
APPLICATION OF THE TWO-STAGE MODEL TO ANIMAL DATA (228-232)
Appendix B Workshop Program (233-234)
Appendix C Workshop Federal Liaison Group (235-236)
TOPIC GROUP MEMBERS (237-238)
Appendix E Workshop Organizing Task Group (239-240)
Isuees In Risk Assessment A Paradigm for Ecological Risk Assessment (241-242)
1 Introduction (243-246)
2 Scope of Ecological Risk Assessment (247-248)
COMPONENTS OF THE 1983 FRAMEWORK (249-250)
CONSISTENCY OF CASE STUDIES WITH THE 1983 FRAMEWORK (251-253)
INTEGRATION OF ECOLOGICAL RISK INTO THE 1983 FRAMEWORK (254-254)
DEFINITION OF FRAMEWORK COMPONENTS FOR ECOLOGICAL RISK ASSESSMENT (255-258)
EXTRAPOLATION ACROSS SCALES (259-260)
QUANTIFICATION OF UNCERTAINTY (261-261)
VALIDATION OF PREDICTIVE TOOLS (262-262)
VALUATION (263-264)
5 Conclusions (265-266)
6 Recommendations (267-268)
REFERENCES (269-272)
Appendix A Workshop Participants (273-278)
Appendix B Workshop Organizing Subcommittee and Federal Liaison Group (279-280)
Appendix C Workshop Introduction (281-282)
TERRY F. YOSIE BUILDING ECOLOGICAL RISK ASSESSMENT AS A POLICY TOOL (283-285)
D. WARNER NORTH: RELATIONSHIP OF WORKSHOP TO NRC'S 1983 RED BOOK REPORT (286-288)
MICHAEL SLIMAK: U.S. ENVIRONMENTAL PROTECTION AGENCY ACTIVITIES IN ECOLOGICAL RISK ASSESSMENT (289-292)
CASE STUDY 1: TRIBUTYLTIN RISK MANAGEMENT IN THE UNITED STATES (293-293)
Discussion (294-294)
CASE STUDY 2: ECOLOGICAL RISK ASSESSMENT FOR TERRESTRIAL WILDLIFE EXPOSED TO AGRICULTURAL CHEMICALS (295-296)
CASE STUDY 3A: MODELS OF TOXIC CHEMICALS IN THE GREAT LAKES: STRUCTURE, APPLICATIONS, AND UNCERTAINTY ANALYSIS (297-298)
CASE STUDY 3B: ECOLOGICAL RISK ASSESSMENT OF TCDD AND TCDF (299-299)
Discussion (300-300)
CASE STUDY 4: RISK ASSESSMENT METHODS IN ANIMAL POPULATIONS: THE NORTHERN SPOTTED OWL AS AN EXAMPLE (301-301)
Discussion (302-302)
CASE STUDY 5: ECOLOGICAL BENEFITS AND RISKS ASSOCIATED WITH THE INTRODUCTION OF EXOTIC SPECIES FOR BIOLOGICAL CONTROL OF A... (303-303)
Discussion (304-304)
CASE STUDY 1: UNCERTAINTY AND RISK IN AN EXPLOITED ECOSYSTEM: A CASE STUDY OF GEORGES BANK (305-306)
Discussion (307-308)
Generic Issues (309-309)
Analysis of Case Studies (310-310)
DOSE-RESPONSE ASSESSMENT (311-311)
Selection of End Points (312-312)
Consideration of Nonlinearities And Discontinuities (313-313)
Understanding the Stressor (314-314)
Additions to the 1983 Paradigm Needed for Ecological Risk Assessment (315-315)
Modeling Needs for Stress-Response Relationships (316-316)
Methods of Measuring Stressors for Ecological Exposure Assessment (317-317)
Definition of Risk Characterization (318-318)
Components of Risk Characterization (319-319)
Organization and Presentation (320-320)
Differences from and Similarities To the 1983 Report (321-321)
Application to the Case Studies (322-323)
Agricultural Chemicals (324-324)
Northern Spotted Owl (325-325)
General Discussion: Models and Risk Assessment (326-326)
Uncertainties Identified In the Case Studies (327-327)
Implications of Uncertainty for Ecological Risk Assessment (328-328)
VALUATION (329-330)
Risk Assessment Has Many Uses (331-332)
Different Risk Assessment Methods Are Suited to Different Risk Assessment Needs (333-333)
Risk Assessors and Risk Managers Need to Communicate (334-334)
Credibility is Crucial (335-336)
Appendix G Contemplations on Ecological Risk Assessment (337-342)
Appendix H Workshop Summary (343-346)
Appendix I References for Appendixes (347-350)
Appendix J Workshop Program (351-356)

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OCR for page 331
Issues in Risk Assessment In his summary, Dr. Johnson suggested that much better communication is needed between ecologists and the public and between ecologists and economists. Ecologists need to educate the public about the importance of preservation and must learn which aspects of nature the public values most highly. Economists need help from ecologists in educating people about the interactions between natural and human systems and in understanding motives for nonuse values. Ecologists need economists to help them understand both what people care about and how intensely they care. Ecologists also need economists to communicate effectively with risk managers who face competing demands for budgetary and regulatory resources. RISK ASSESSMENT AND THE REGULATORY PROCESS W. Cooper and D. W. North Risk Assessment Has Many Uses Because there are many uses for risk assessment, many forms of risk assessment are needed. The methodological approach and the level of detail in each form might differ a great deal, depending on the purpose for which risk assessment is carried out. For strategic planning and setting priorities, it might be appropriate to conduct risk assessments that rely on expert judgment for direct assessments of relative risk. An example of the use of such an approach is the ecological risk portion of the recent EPA Science Advisory Report on Reducing Risk (EPA, 1990). With the direct approach, risk is assessed on the basis of overall integrated judgment to summarize each of the risks being compared. Modeling and other analytical tools are not used directly, but they can play an important role in providing the basis for expert judgment. The result of the risk assessment is a set of risk rankings that reflect the judgment of the assessors. The assessment also includes a discussion of the reasoning underlying the assessments, with explanation for differences among the experts. Because the direct approach relies on expert judgment, rather than mathematical formalism such as model calculations or statistical analysis to reach conclusions, the direct approach can be perceived as lacking in scientific rigor. However, the direct approach can be carried out quickly and might

OCR for page 332
Issues in Risk Assessment provide extremely important guidance to nontechnical decision-makers, especially in the absence of any other form of integrated comparison among risks that are competing for scarce resources. In particular, such methods permit regulatory agencies to set priorities and research budgets in a proactive fashion. Such activities can counter the tendency to set priorities and research expenditures based on recent crises and public pressures—reaction to the pollutant of the month—rather than a comprehensive overview of competing risks. Risk assessment is most often viewed as a quantitative process that is used to support specific risk management and resource management program decisions and policies. Among the biggest policy issues that involve ecological risk are acid deposition and global climate alteration. Neither of those was formally presented in the workshop, but participants in this work group frequently brought them up as examples of the most complex problems for ecological risk assessment. Application to problems of this scale is a massive undertaking. The six case studies were selected to be representative of major ecological issues of concern to government agencies. The case studies illustrate the complexities and uncertainties that the agencies must deal with on such issues. Participants observed that a complete risk assessment was not presented for any of the case studies. Yet, for each case study, a massive amount of information and analysis was described. At the local level, analytical resources are rarely available to deal with such a large amount of detail. But local communities and agency offices must deal with problems, such as remediation of hazardous waste sites, management of wildlife resources, and many other small-scale matters. Risk assessment can provide scientific support to state or local agencies that are responsible for managing risk issues but lack the scientific and analytical resources of large federal agencies. Citizens groups might also have a strong interest in risk issues, but lack scientific capabilities and resources to carry out research and analysis. Risk assessment databases and monitoring efforts carried out by federal agencies to obtain baseline data can be useful to state, local, and citizens groups. Examples include the EPA-maintained IRIS database on toxic substances and the EMAP program the EPA is developing to obtain and make available data on ecological systems. Risk assessment can provide guidance for identifying needed data and research. Such needs often become obvious when a risk assessment has