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

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. "Credibility is Crucial." Issues in Risk Assessment. Washington, DC: The National Academies Press, 1993.

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Issues in Risk Assessment

assessment is being prepared. Interested and affected groups should be informed in advance about the risk assessment. They should have the opportunity to express their concerns and contribute information to the risk assessment process while the process is being carried out.

Issues that seem obvious to the expert scientists participating in the risk assessment might not be obvious to laypersons, but it is important for both to understand each other if there is to be effective bridging between the scientific knowledge available to the experts and the concerns of the public. As one working-group participant expressed it, "if risk assessment opens up a dialogue, then it serves an appropriate objective."

Communication between modelers, risk assessors, and managers should be mutual, iterative, timely, and flexible. Risk assessments will be valuable as support to the risk management process only if the assessments address the right problem and if the managers who are the users of the products of risk assessment understand them. One suggestion offered at the workshop is that an agency assign someone the task of being the translator, or liaison, between the group that has carried out the risk assessment and the users of the risk assessment.

Credibility is Crucial

Risk assessments will be useful to the extent that they are perceived to be effective in accomplishing a difficult task: summarizing what science can tell us about the possible consequences to an ecological system. If a risk assessment is perceived to be incomplete or biased toward a particular point of view, it will not be trusted for risk management decision-making. It is therefore essential that a risk assessment be a comprehensive and balanced summary of the applicable science.

How can comprehensiveness and balance be achieved? The recommendations on health risk issues from the 1983 report appear equally applicable to ecological risk issues:

  • Regulatory agencies should take steps to establish and maintain a clear conceptual distinction between assessment of risks and the consideration of risk management alternatives; that is, the scientific findings and policy judgments embodied in risk assessments should be explicitly distinguished from the politi-

Page
335
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 335
Issues in Risk Assessment assessment is being prepared. Interested and affected groups should be informed in advance about the risk assessment. They should have the opportunity to express their concerns and contribute information to the risk assessment process while the process is being carried out. Issues that seem obvious to the expert scientists participating in the risk assessment might not be obvious to laypersons, but it is important for both to understand each other if there is to be effective bridging between the scientific knowledge available to the experts and the concerns of the public. As one working-group participant expressed it, "if risk assessment opens up a dialogue, then it serves an appropriate objective." Communication between modelers, risk assessors, and managers should be mutual, iterative, timely, and flexible. Risk assessments will be valuable as support to the risk management process only if the assessments address the right problem and if the managers who are the users of the products of risk assessment understand them. One suggestion offered at the workshop is that an agency assign someone the task of being the translator, or liaison, between the group that has carried out the risk assessment and the users of the risk assessment. Credibility is Crucial Risk assessments will be useful to the extent that they are perceived to be effective in accomplishing a difficult task: summarizing what science can tell us about the possible consequences to an ecological system. If a risk assessment is perceived to be incomplete or biased toward a particular point of view, it will not be trusted for risk management decision-making. It is therefore essential that a risk assessment be a comprehensive and balanced summary of the applicable science. How can comprehensiveness and balance be achieved? The recommendations on health risk issues from the 1983 report appear equally applicable to ecological risk issues: Regulatory agencies should take steps to establish and maintain a clear conceptual distinction between assessment of risks and the consideration of risk management alternatives; that is, the scientific findings and policy judgments embodied in risk assessments should be explicitly distinguished from the politi-

OCR for page 336
Issues in Risk Assessment cal, economic, and technical considerations that influence the design and choice of regulatory strategies. Before an agency decides whether a substance [ecosystem stressor] should or should not be regulated, … a detailed and comprehensive written risk assessment should be prepared and made publicly accessible … An agency's risk assessment should be reviewed by an independent science advisory panel before any major regulatory action or decision not to regulate. In those recommendations, it might be appropriate to replace "regulatory" language with more general terms relevant to the broad range of decision alternatives available for the management of ecological risks. However, the principles embodied in the recommendations can be applied essentially unchanged: to promote credibility, establish and maintain the conceptual distinction between risk assessment and risk management; place risk assessments in a written, publicly accessible form; and subject them to peer review by outside scientists.