Decembers, 1995
EPA-SAB-EC-COM-96-001
The Honorable Carol Browner
Administrator
United States Environmental Protection Agency
401 M Street, SW
Washington, DC 20460
Subject: Science Advisory Board Commentary on Hazard Identification
Dear Ms. Browner:
Recently, different committees of the SAB have provided advice to Agency programs on
the hazard identification step of the risk assessment process that has been interpreted as being
contradictory. Specifically, during their May 4 & 5, 1995 meeting, the Clean Air Scientific
Advisory Committee (CASAC) noted that consideration of existing dose-response information
about particulate loading should have been considered in the hazard evaluation of diesel emissions
(EPA-SAB-CASAC-LTR-95-003). However, in their report on the Agency's Reproductive
Toxicity Risk Assessment Guidelines (EPA-SAB-EHC-95-014), the Environmental Health
Committee (EHC) expressed concern over the Agency's proposal to consider dose-response
information during the hazard identification phase of risk assessment. The EHC comments were
interpreted by some in the Agency as contradictory to what the CASAC was advising and to what
the EHC had advised in an earlier report on the Agency's Developmental Toxicity Risk
Assessment Guidelines (EPA-SAB-EHC-90-013).
In an attempt to clarify this situation, the Executive Committee has generated this
commentary, using input from selected members of both CASAC and EHC. We want to clarify
our thinking on this important issue in order to assist Agency scientists as they prepare to address
the same issue in the Cancer Risk Assessment Guidelines that will be coming to the SAB for
review later this fiscal year.
Commentary:
The National Academy of Sciences (NAS) risk assessment framework, described in the
1983 "Decision Making in the Federal Government: Managing the Process", has proven a useful
and durable tool for assessing risk. It identifies easily understandable and recognizable steps for
assessing risk and using the results for decision-making. In 1994, the National Academy of
Sciences report, "Science and Judgment in Risk Assessment", recommended that EPA and others
should broaden the types of information considered in the hazard identification phase of risk
assessment. The SAB supports EPA's intent to expand the hazard identification and evaluation
phase to include additional data. However, we recommend that the phases of the hazard
identification process remain clearly discernable rather than simply being combined into an overall
hazard characterization. Specifically, assessment of hazard should include a weight of evidence
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evaluation of available experimental and epidemiological data.
The hazard identification should continue to be essentially qualitative in nature and should
focus on the following where data are available: overall consistency of data, nature of the effects
observed, relevance of the effect(s) to human health, mechanisms of action if known, pattern of
dose-response relationships in the studies reviewed, and pharmacokinetic data where appropriate
(especially in terms of qualitative differences in metabolic pathways between species). In contrast,
the dose-response analysis step evaluates in quantitative terms the relationship between dose or
exposure and severity or probability of effect in humans.
The SAB emphasizes the importance of conducting a hazard identification in cases in
which data are not available to carry out the dose-response analysis and further steps of the risk
assessment process. This approach is preventive in nature and gives impetus for follow-up by the
research community and the Agency.
In conclusion, expanding the hazard identification step to include more information while
retaining the step-wise approach laid out in 1983 provides for a more in-depth initial analysis of
potential risk that is consistent with prevention and has the significant benefits of promoting
consistency and clarity in the risk assessment process.
Closing:
We appreciate the opportunity to clarify the thinking of the Board on this matter and look
forward to your response.
Sincerely,
Dr. Genevieve Matanoski, M.D., Chair
Science Advisory Board
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