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

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. "Risk Assessors and Risk Managers Need to Communicate." Issues in Risk Assessment. Washington, DC: The National Academies Press, 1993.

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Issues in Risk Assessment

learned from ecological risk assessments is that the power of an expensive test to reject or confirm a hypothesis should be evaluated before data collection. If the data are unlikely to provide a basis for rejecting or confirming a hypothesis important to the risk assessment, then it might not be worth the expense to obtain the data.

As the volume of risk assessments grows, it will be particularly important to ensure quality and consistency. Development and use of formal guidelines, training of risk assessors, and communication of examples of good risk assessment practice will help agencies and organizations to ensure quality and consistency in their applications.

Consistency and flexibility must be balanced appropriately in the risk assessment process. Consistency motivates doing risk assessments for similar situations in a similar and predictable way. Flexibility motivates departures from a standard risk assessment approach when scientific information indicates that differences are important for the proper assessment of risk. In practice, it might be appropriate to have standard or default procedures that are used when scientific information is not sufficient to motivate a different approach, and provisions for innovative exceptions that are supported by applicable scientific information.

Risk assessment should not become too rigid. Its purpose is to summarize and communicate applicable science to meet the needs of policy makers. That task by its very nature requires flexibility and creativity, not reliance on formulas or cookbook recipes evolved from past practice.

Risk Assessors and Risk Managers Need to Communicate

Managers responsible for ecological systems must be responsive to the public, and risk assessors should recognize that their task supports risk management. Risk assessment can help risk managers to explain the basis for their decisions to interested and potentially affected groups. Risk assessment, therefore, has an important function as communication.

As was stressed in a recent National Research Council report on risk communication (NRC, 1989), such communication should be two-way. To ensure that communication is effective and that public concerns are addressed, it is generally useful to involve the public while the risk

Page
334
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 334
Issues in Risk Assessment learned from ecological risk assessments is that the power of an expensive test to reject or confirm a hypothesis should be evaluated before data collection. If the data are unlikely to provide a basis for rejecting or confirming a hypothesis important to the risk assessment, then it might not be worth the expense to obtain the data. As the volume of risk assessments grows, it will be particularly important to ensure quality and consistency. Development and use of formal guidelines, training of risk assessors, and communication of examples of good risk assessment practice will help agencies and organizations to ensure quality and consistency in their applications. Consistency and flexibility must be balanced appropriately in the risk assessment process. Consistency motivates doing risk assessments for similar situations in a similar and predictable way. Flexibility motivates departures from a standard risk assessment approach when scientific information indicates that differences are important for the proper assessment of risk. In practice, it might be appropriate to have standard or default procedures that are used when scientific information is not sufficient to motivate a different approach, and provisions for innovative exceptions that are supported by applicable scientific information. Risk assessment should not become too rigid. Its purpose is to summarize and communicate applicable science to meet the needs of policy makers. That task by its very nature requires flexibility and creativity, not reliance on formulas or cookbook recipes evolved from past practice. Risk Assessors and Risk Managers Need to Communicate Managers responsible for ecological systems must be responsive to the public, and risk assessors should recognize that their task supports risk management. Risk assessment can help risk managers to explain the basis for their decisions to interested and potentially affected groups. Risk assessment, therefore, has an important function as communication. As was stressed in a recent National Research Council report on risk communication (NRC, 1989), such communication should be two-way. To ensure that communication is effective and that public concerns are addressed, it is generally useful to involve the public while the risk