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

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. "6 Recommendations ." Issues in Risk Assessment. Washington, DC: The National Academies Press, 1993.

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Issues in Risk Assessment

6
Recommendations

  • The committee recommends that risk assessors, risk managers, and regulatory agencies should adopt a uniform framework for ecological risk assessment. The framework used should be general and flexible and should facilitate communication between scientists and risk managers. The objective is to systematize the regulatory process, not to specify a particular calculational procedure or data requirement. The extension of the 1983 NRC human health risk assessment framework described in this report and summarized in Figure 3-2 emphasizes the common elements of health risk and ecological risk assessment.

  • The committee recommends that state and federal agencies expand the issue of risk assessment in strategic planning and priority-setting. Those assessments can help agencies to focus their resources on critical environmental problems and uncertainties, and that focus would result in more cost effective and efficient regulatory initiatives. Assessments at this level can be principally judgment-based and need not involve explicit quantification.

  • The committee recommends that agencies support the development of improved methods of risk characterization and consistent guidelines for applying them. Improvement is needed in extrapolation of population and ecosystem effects, expression of risks in terms that are useful for decision-making and understood by the public at large, and evaluation and communication of quantitative and qualitative uncertainties.

  • EPA and other agencies, including state agencies, should institute systematic followup of risk assessments with research and monitoring to

Page
267
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 267
Issues in Risk Assessment 6 Recommendations The committee recommends that risk assessors, risk managers, and regulatory agencies should adopt a uniform framework for ecological risk assessment. The framework used should be general and flexible and should facilitate communication between scientists and risk managers. The objective is to systematize the regulatory process, not to specify a particular calculational procedure or data requirement. The extension of the 1983 NRC human health risk assessment framework described in this report and summarized in Figure 3-2 emphasizes the common elements of health risk and ecological risk assessment. The committee recommends that state and federal agencies expand the issue of risk assessment in strategic planning and priority-setting. Those assessments can help agencies to focus their resources on critical environmental problems and uncertainties, and that focus would result in more cost effective and efficient regulatory initiatives. Assessments at this level can be principally judgment-based and need not involve explicit quantification. The committee recommends that agencies support the development of improved methods of risk characterization and consistent guidelines for applying them. Improvement is needed in extrapolation of population and ecosystem effects, expression of risks in terms that are useful for decision-making and understood by the public at large, and evaluation and communication of quantitative and qualitative uncertainties. EPA and other agencies, including state agencies, should institute systematic followup of risk assessments with research and monitoring to

OCR for page 268
Issues in Risk Assessment determine the accuracy of predictions and resolve remaining uncertainties. The committee recommends that EPA and other agencies support systematic research programs to improve the credibility and utility of ecological risk assessments and draw on scientific expertise available outside the agencies themselves to develop technical guidance on the scientific content of ecological risk assessments.