Science and Decisions Advancing Risk Assessment (2009) / Chapter Skim
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Appendix D: Environmental Protection Agency Response to Recommendations from Selected NRC Reports: Policy, Activity, and Practice
Appendix D: Environmental Protection Agency Response to Recommendations from Selected NRC Reports: Policy, Activity, and Practice
Pages 299-366
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From page 299... ...
For a full picture on any topic of interest, the committee advises readers to begin with pages cited in the table and to look beyond those citations for related information. Note also that several National Research Council recommendations and EPA policy statements cover multiple topics (such as both "risk characterization" and "uncertainty" or both "models" and "defaults")
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300 SCIENCE AND DECISIONS: ADVANCING RISK ASSESSMENT • Aggregate and Cumulative Risk • Default Assumptions and Options • Distinguishing and Linking Risk Assessment and Risk Management • Distinguishing Science and Science Policy • Exposure Assessment (and Methods Validation) • Health-Risk and Toxicity Assessment for Cancer and Other End Points • Inference Guidelines • Interagency and Outside Collaboration • Iterative Approach to Risk Assessment • Models and Model Validation • Peer Review and Expert Panels • Priority-Setting and Data-Needs Management • Problem Formulation and Ecologic Risk Assessment • Public Review and Comment; Public Participation • Risk Characterization • Risk Communication in Relation to Risk Management • Uncertainty Analysis and Characterization • Variability and Differential Susceptibility
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In addition, the Science and conditions; (2) Develop exposure models Policy Council will support workshops and methods suitable for EPA and the for risk assessors and managers to public to assess aggregate and cumulative discuss implementation opportunities and risk, including mathematical and statistical problems, and solutions." relationships among sources of environmental contaminants, their environmental fate, and EPA 2000a Supplementary Guidance for pathway specific concentrations; models Conducting Health Risk Assessment of linking dose and exposure from biomarker Chemical Mixtures at xiv: This guidance data; and approaches to assess population updates the 1986 agencywide guidance on based cumulative risk, including those chemical mixtures and "describes more involving exposure to stressors other than 301 continued
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analysis, and (3) risk characterization…Research and GAO 2006 at 49: "The branch of the Office development needs are also discussed, of Air Quality Planning and Standards that including understanding the timing of regulates hazardous air pollutants employs exposure and its relationship to effects; the Multiple Pathways of Exposure model to
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[It] includes approach; using biomarkers; considering procedures to estimate human exposures and hazards presented by nonchemical stressors; health risks that result from the transfer of methods for combining different types of pollutants from the air to soil and surface risk; and development of default values water bodies and the subsequent uptake of for cumulative risk assessments, among the pollutant by plants, animals, and humans.
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From page 304... ...
authorities to reduce air toxics emissions from all sources, including major industrial sources, smaller stationary sources, and mobile sources such as cars and trucks. By integrating activities under different parts of the Act, EPA can better address cumulative public health risks and adverse environmental impacts posed by exposures to multiple air toxics in areas where the emissions and risks are most significant." EPA 2004a: Air Toxics Risk Assessment Reference Library at 14-1: The guidance states that "multipathway risk assessment may be appropriate generally when air toxics that persist and which also may bioaccumulate and/or biomagnify are present in releases.
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From page 305... ...
Some may travel great distances, and linger for long periods of time in the environment." The guidance provides information on planning, scoping, problem formulation, data analysis, and risk characterization. EPA 2002a Guidance on cumulative risk assessment of pesticide chemicals that have a common mechanism of toxicity: Provides "guidance to OPP scientists for evaluating and estimating the potential human risks associated with such multichemical and multipathway exposures to pesticides.
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From page 306... ...
This is discussed, observations, and/or scientific theory." for example, when conducting screening analyses: "For complete or potential exposure EPA 1996 Proposed Carcinogen Risk pathways identified in the exposure pathway Assessment Guidelines at 61 FR 18000: evaluation, the screening analysis may involve
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EPA 2000b Risk Characterization Handbook at 21: Directs risk assessors to "describe the uncertainties inherent in the risk assessment and the default positions used to address these uncertainties or gaps in the assessment." 307 continued
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. Choices made surface-area assumption with body weight about using data or default options in the to the 0.75 power)
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Third, we must communicate to the public what we are doing, why we are doing it in risk management terms, and how the risk management approach will improve the way that EPA carries out its mission." EPA 1986 Guidelines for Carcinogen Risk 309 Assessment at 51 FR 33993: "Regulatory continued
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From page 310... ...
Thus, regulatory decisions are usually based on GAO 2006 at 29: "The Office of Air and a combination of the technical analysis Radiation recognized the need for planning used to develop the risk assessment and and developed planning guidance as part of information from other fields." its Air Toxics Risk Assessment Reference Library, issued in 2004. EPA acknowledged in EPA 2002b Lessons Learned from its 2004 staff paper that it needs to continue Planning and Scoping Environmental Risk to stress the importance of concerted and Assessments at vi: Was developed "to conscious planning with risk assessors and provide early feedback to agency scientists risk managers before a risk assessment is and managers regarding our experiences started.
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From page 311... ...
. This handbook is also meant to be a catalyst to encourage agency managers to adopt formal planning and scoping as part of EPA's culture, especially when conducting significant and/or unique environmental assessments." EPA 1998, Ecological Risk Assessment Guidelines at 13: "The characteristics of an ecological risk assessment are directly determined by agreements reached by risk managers and risk assessors during planning dialogues.
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Information needs/data for other members of the ‘team' to conduct their analyses (e.g., economic, social, or legal analyses) ." Distinguishing NRC 1983 at 153: "Before an agency EPA 1996 Proposed Carcinogen Assessment Science and decides whether a substance should or Guidelines at 61 FR 17968: "The default Science Policy should not be regulated as a health hazard, to include benign tumors observed in a detailed and comprehensive written risk animal studies in the assessment of animal assessment should be prepared and made tumor incidence is they have the capacity publicly accessible.
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From page 313... ...
Also: "Interagency and public understanding would be served by the EPA 1998 Ecological Risk Guidelines at preparation and release of a report on 110: The risk-assessment report should the science-policy issues and decisions discuss "science policy judgments or default that affect EPA's risk-assessment and risk- assumptions used to bridge information management practices." gaps and the basis for these assumptions." EPA 2005a Carcinogen Risk Assessment Guidelines, at 70 FR 17774: "The agency considered both the advantages and disadvantages to extending recommended, age dependent adjustment factors for carcinogenic potency to carcinogenic agents for which the mode of action remains unknown EPA decided to recommend these factors only for carcinogens acting through a mutagenic mode of action based on a combination of analysis of available data and long-standing science policy positions which govern the Agency's overall approach to carcinogen risk assessment." Also at 17808: "Important features [of the risk characterization] include the constraints of available data and the state of knowledge, significant scientific issues, and significant science and science policy choices that were made when alternative interpretations of data exist." Exposure NRC 1994 at 217: "The committee EPA 1992ad Guidelines for Exposure Assessment endorses the EPA's use of bounding Assessment, sec.
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From page 314... ...
First, the only thing it, and not a vague estimate ‘somewhere the bounding estimate can establish is a above the 90th percentile,' is responsive to level to eliminate pathways from further the language in CAAA-90 calling for the consideration. It cannot be used to make a calculation of risk to ‘the individual most determination that a pathway is significant exposed to emissions.'" (that can only be done after more (Directed to Air Program)
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From page 315... ...
NRC 1994 at 218: "EPA should use the EPA 2005a Guidelines for Carcinogen Risk mean of current life expectancy as the Assessment at 71 FR 17801: "Unless there assumption for the duration of individual is evidence to the contrary in a particular residence time in a high-exposure area, case, the cumulative dose received over or a distribution of residence times which a lifetime, expressed as average daily accounts for the likelihood that changing exposure prorated over a lifetime, is residences might not result in significantly recommended as an appropriate measure of lower exposure. Similarly, EPA should use exposure to a carcinogen." a conservative estimate for the number of hours a day an individual is exposed, EPA 1992ad Sec.
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(2) If data on the distribution of doses are not available, but data on the parameters used to calculate the dose are available, a simulation (such as an exposure model or Monte Carlo simulation)
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and the possible routes by which people at risk pesticides cumulative risk guidance (EPA might be exposed, and this should be done 2002a) for related discussion.
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This will facilitate systematic consideration of multiroute exposures in designing and measuring compliance with Clean Air Act requirements." (Directed to air program) NRC 1994 at 140: "EPA should explicitly Note: Nothing in the 1992 exposure consider the inclusion of noninhalation assessment guidelines prevents an assessor pathways, except where there is prevailing from considering these pathways.
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From page 319... ...
." based on physical, chemical and biological information that helps to explain key events in an agent's influence on tumor development. The entire range of information developed in the assessment is reviewed to arrive at a reasoned judgment." NRC 1994 at 141: "EPA should continue EPA 1996 Proposed Carcinogen Risk Note: It is not clear whether EPA has worked to use the results of studies in mice and Assessment Guidelines at 61 FR 17976: with NTP or other entities on the question of rats to evaluate the possibility of chemical "The default assumption is that positive testing species other than mice and rats.
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From page 320... ...
The agency See section 5.4 of the guidelines for more should seek international agreement on a complete details." classification system." EPA 1996 Proposed Guidelines for NRC 1994 at 10: "EPA should develop a Carcinogen Risk Assessment at 61 FR two-part scheme for classifying evidence 17985: "Hazard classification uses three on carcinogenicity that would incorporate categories of descriptors for human both a simple classification and a narrative carcinogenic potential.
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From page 321... ...
However, uncertainty about the potency estimate should be described." And at 17802: Assessments should discuss the significant uncertainties encountered in the analysis, distinguishing, if possible, among model uncertainty, parameter uncertainty, and human variation. NRC 1994 at 13: "In the analysis of EPA 1996 Proposed Guidelines for animal bioassay data on the occurrence of Carcinogen Risk Assessment at 126: "In multiple tumor types, the cancer potencies analyzing animal bioassay data on the should be estimated for each relevant occurrence of multiple tumor types, these tumor type that is related to exposure, and guidelines outline a number of biological the individual potencies should be summed and other factors to consider.
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From page 322... ...
Summing incidences would result in a higher risk estimate, a step that appears unnecessary without more reason." EPA 2005a Guidelines for Carcinogen Risk Assessment at 71 FR 17801: "When multiple estimates can be developed, all datasets should be considered and a judgment made about how best to represent
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From page 323... ...
, GAO 2006 at 38: "Since 1994, EPA has "EPA should enhance and expand the changed the IRIS assessment process in references in the data files on each several ways. For example, each IRIS file chemical and include information on risk- now contains a discussion of the key studies, assessment weaknesses for each chemical as well as a description of the decisions and and the research needed to remedy such default assumptions used in the assessment.
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From page 324... ...
To date, EPA has fallen considerably short of this goal. According to a program official, EPA completed 8 IRIS assessments in 2005, plans to complete 16 in 2006, and has approximately 75 assessments under way." "In 2004, the IRIS program also initiated a review of available scientific literature for the 460 chemicals in the database that are not under active reassessment to determine whether a reassessment based on new literature could significantly change existing
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From page 325... ...
As part of its National Air Toxics Assessment -- an ongoing comprehensive evaluation of hazardous air pollutants in the United States -- EPA assessed 32 air pollutants plus particulate matter in diesel exhaust in 1996. The national assessment is designed to identify air pollutants with the greatest potential to harm human health, and the results will help set priorities for collecting additional data.
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They include a framework to assess risks to human default options, which are essentially health that help make risk assessments more policy judgments of how to accommodate consistent. For example, some risk assessors uncertainties.
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In addition, the Office of Air preparing human health risk assessments. and Radiation created the Air Toxics Risk More specifically, several risk assessors Assessment Reference Library that provides noted that the carcinogen guidelines provide information on how to analyze the risks a useful framework for preparing risk from hazardous air pollutants." assessments.
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See tables of contents in the of hazard identification, dose-response guidelines listed as references in this table assessment, and risk characterization and for scope and contents of each guideline. should require assessors to show that they have considered all the necessary components in each step.
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cancer risk-assessment guidelines issued The process followed by the • in 2005: "In 1996, the Agency published government for adoption of inference proposed revisions to EPA's 1986 cancer guidelines should ensure that the guidelines for public comment. Since the resulting guidelines are uniform 1996 proposal, the document has undergone among all responsible agencies and are extensive public comment and scientific peer consistently adhered to in assessing the review, including three reviews by EPA's risks of individual hazards.
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According to an agency official, the forum is designed as a venue where staff can meet and discuss common risk assessment issues across program offices. One of the forum's main contributions to risk assessment at EPA has been the issuance of a series of risk assessment guidelines.
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Because of diverse problems in estimating different means of exposure (e.g., through food, drinking water and consumer products) , separate guidelines may be needed for each." NRC 1994 at 266: "EPA should recognize EPA 1986d Guidelines for Carcinogen that the conduct of risk assessment does Risk Assessment at 51 FR 33993: These not require any specific methodologic guidelines describe the general framework approach and that it is best seen not as a to be followed in developing an analysis of number or even a document, but as a way carcinogenic risk and salient principles to to organize knowledge regarding potentially be used in evaluating the quality of data hazardous activities or substances and to and in formulating judgments concerning facilitate the systematic analysis of the the nature and magnitude of the cancer risks that those activities or substances hazard.
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From page 332... ...
A key difference between these toxicological assessments and the ones in EPA's IRIS database is that ATSDR includes chronic cancer and noncancer effects, as well as acute effects, while IRIS generally includes only chronic cancer and noncancer effects." GAO 2006 at 35: "Since 1994, EPA has strengthened and formalized collaboration with a range of other federal researchers to better leverage its limited research dollars and foster the development of data to improve human health risk assessments. Specifically, EPA has developed relationships with agencies such as the National Institute for Environmental Health Sciences (NIEHS)
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As a result, what may be a priority chemical in one program office may not be a priority in another, thereby hindering timely collaboration. Furthermore, a couple of risk assessors found collaboration challenging because they could not find the right person in another office to communicate with on a specific issue." 333 continued
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A few risk assessors suggested that a central library of risk assessment information would facilitate collaboration and avoid duplicating work already done by others. Specifically, one risk assessor said EPA could provide centralized databases of work conducted by different agencies and organizations, such as chemical-specific toxicity data, specific exposure or other values, and points of contact at each office." GAO 2006 at 37: "The Office of Pollution Prevention and Toxics has two programs to work with industry to develop data on contaminants that can be used to better understand risks.
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The remaining 3 chemicals in the pilot program have no sponsors." Iterative NRC 1994 at 14: "EPA should develop the EPA 1998 Ecological Risk Guidelines at GAO 2006 at 30: "Some program offices Approach to ability to conduct iterative risk assessments 92: "If risks are not sufficiently defined have also adopted an iterative -- or Risk Assessment that would allow improvements to be to support a management decision, risk tiered -- approach to risk assessment.
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The assessment. This will lead to an improved analysis, not all risk characterizations can degree of refinement is based on the type understanding of the relationship between or should be equal in coverage or depth." of decision, the available resources, and the risk assessment and risk management and needs of the risk manager.
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committee will provide advice concerning also conduct research on alternative the development of guidelines and a vision methods and models that might represent EPA 1994a at 4, Model Validation of the selection and use of models at the deviations from the default options to for Predictive Exposure Assessments: agency.
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From page 338... ...
For example, in its plan for GAO 2006 at 43: "EPA is beginning research on hazardous air pollutants, EPA to embrace such new risk assessment established a long-term goal to reduce methodologies as probabilistic risk assessment uncertainties in risk assessments through and mode of action analysis. Probabilistic methods, data, and models of acute and risk assessment characterizes the variability chronic exposures and exposures through or uncertainty in risk estimates as the multiple pathways at both the national and range or distribution of the number of regional levels." times each possible outcome will occur.
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From page 339... ...
For risk assessments of hazardous air pollutants, GIS can display and analyze data during planning, scoping, and problem formulation, during the exposure assessment, and during the characterization of risks. GIS can also help communicate information to risk managers and other stakeholders." 339 continued
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In both cases, the observed range of data will be modeled by curve fitting in the absence of supporting data for a biologically based or case specific model." Peer Review NRC 1983 at 156: "An agency's risk EPA 1992b, 1994c Peer Review Policy GAO 2006 at 26: "In addition to enhancing and Expert assessment should be reviewed by an Memorandum: "Major scientifically and its scientific leadership, EPA has also Panels independent scientific advisory panel technically based work products related increased its reliance on research advisory before any major regulatory action or to agency decisions normally should be groups since 1994." decision not to regulate. Peer review may peer reviewed.
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From page 341... ...
" and "administrative journals; and 111 were products that were mechanisms for EPA pre-dissemination deemed, usually because of their repetitive review of information products." or routine nature, not to be candidates for peer review. Dividing 111 ‘peer review not EPA 2003c A Summary of General needed' products by the 859 sum, we see Assessment Factors for Evaluating the that nearly 90 percent of our scientific and Quality of Scientific and Technical technical work products receive internal or Information at iv: Was "intended to external peer review" (p.
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From page 342... ...
. The manual discusses EPA's role in managing and coordinating the data-quality system, including developing a quality-management plan, and "planning, directing, and conducting assessments of the effectiveness of the quality system being applied to environmental data operations and reporting results to senior management." NRC 1994 at 8: "EPA should continue to Risk Assessment Forum–sponsored risk use the Science Advisory Board and other assessment guidelines and forum reports are expert bodies.
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From page 343... ...
scientific basis of risk assessment and to arise, and to insure that Agency consensus make explicit the underlying assumptions on such issues is incorporated into the and policy ramifications of the different appropriate risk assessment guidelines. The inference options in each component of Forum will also provide Agency scientists the risk assessment process.
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." maintains a database of dose-response values [Directed to air program] developed by various sources, including IRIS, ATSDR, and the California Environmental Protection Agency, as an aide for its risk assessors.
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For example, in its National Human Exposure Assessment Survey (NHEXAS) program, which was completed in 1998, ORD collected human exposure data from hundreds of subjects from several areas of the country.
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From page 346... ...
The process must have The Agency is engaged in several activities an appropriately diverse participation or that involve working with stakeholders. representation of the spectrum of interested Experience from these activities will and affected parties, of decision makers, provide the solid basis for engaging and of specialists in risk analysis, at each interested and affected parties in risk step." assessment and risk management issues." EPA 1998 Guidelines for Ecological Risk Assessment at 13: "The characteristics of an ecological risk assessment are directly determined by agreements reached by risk managers and risk assessors during planning dialogues.
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From page 347... ...
Some additional discussion concerning interactions among risk assessors, risk managers, and interested parties was added, particularly to section 2 (planning) ." NRC 1996 at 6: "The analytic-deliberative EPA 1998 at 13: States that "during process leading to a risk characterization planning, risk managers and risk assessors should include early and explicit attention are responsible for coming to agreement to problem formulation; representation on the goals, scope, and timing of a risk of the spectrum of interested and affected assessment and the resources that are parties at this early stage is imperative.
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From page 348... ...
established a process that provides several opportunities EPA 1997a Memorandum: Cumulative Risk for public participation. Depending on the Assessment Guidance -- Phase I Planning potential health risks posed by a pesticide
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From page 349... ...
to take into account cumulative risk This preliminary assessment contains all issues in scoping and planning major risk of the elements of a risk assessment and assessments and to consider a broader has undergone internal review, but is not scope that integrates multiple sources, yet finalized. Notice of the opportunity to effects, pathways, stressors and populations comment is distributed to people who have for cumulative risk analyses in all cases for elected to sign up for such notifications, which relevant data are available.
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From page 350... ...
The summary effects of the evidence for each step of the process, the uncertainties in the preceding steps are estimated uncertainty of the component described in this step." parts, the distribution of risk across various sectors of the population, the assumptions contained within the estimates, and so forth." EPA 1992b Agency-wide Policy Memorandum: "Well-balanced risk characterization presents information for other risk assessors, EPA decision-makers, and the public regarding the strengths and limitations of the assessment." (NRC 1994, Appendix B)
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From page 351... ...
EPA 2000b Risk Characterization Handbook at 39: "At EPA, various risk assessment guidelines have been written to ensure a scientifically defensible and consistent approach to risk assessment. When you write the risk characterization portion of your assessment, indicate whether or not you followed the guidelines and describe the key assumptions you made during your assessment and the impact they have on the assessment outcome.
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From page 352... ...
Major assumptions, should include the distribution of risk in scientific judgments, and, to the extent the population. When the distribution of possible, estimates of the uncertainties risk is known, it is possible to estimate the embodied in the assessment are presented." risk to individuals who are most exposed to the substance in question." EPA 1996 Proposed Carcinogen Assessment Guidelines at 125: "The result of using NRC 1994 at 10: "EPA should continue straight line extrapolation is thought to be to use as one of its risk characterization an upper bound on low-dose potency to metrics, upper-bound potency estimates of the human population in most cases, but the probability of developing cancer due to as discussed in the major defaults section, lifetime exposure.
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From page 353... ...
In situations where there are alternative approaches for risk assessment that have significant biological support, the decisionmaker can be informed by the presentation of these alternatives along with their strengths and uncertainties." Risk NRC 1994 at 15: "When EPA reports EPA 1996 Proposed Carcinogen Risk GAO 2006 at 64: "Experts also said EPA Communication estimates of risk to decision-makers and Assessment Guidelines at 126: "In part risk assessments should clearly describe the in Relation the public, it should present not only point as a response to these recommendations, sufficiency of the data and the scientific to Risk estimates of risk, but also the sources and the Administrator of EPA issued guidelines basis for its choice of a default assumption, Management magnitudes of uncertainty associated with for risk characterization and required method, or model. Some experts pointed out these estimates." implementation plans from all programs that risk assessments should identify and in EPA (EPA 1995a)
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From page 354... ...
Furthermore, in individual risk assessments, EPA 1998 Ecological Risk Guidelines at the agency could more transparently identify 109-110: "When risk characterization is which critical studies would help the agency complete, risk assessors should be able avoid relying on default assumptions. to estimate ecological risks, indicate the Some experts also suggested that EPA use overall degree of confidence in the risk as case studies completed assessments for estimates, cite lines of evidence supporting which the agency had sufficient data to use the risk estimates, and interpret the models and other analytic tools rather than adversity of ecological effects.
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From page 355... ...
, EPA risk assessors should consider of a risk assessment requires a clear and only the uncertainty conditional on the explicit statement of related uncertainties." choice of the preferred models for dose response relationships, exposure, uptake, EPA 1996 Proposed Guidelines on etc." Carcinogenic Risk Assessment at 126: "In part as a response to these NRC 1994 at 13: "Quantitative recommendations [that EPA consider uncertainty characterizations conducted the limits of scientific knowledge] , the by EPA should appropriately reflect Administrator of EPA issued guidelines the difference between uncertainty and for risk characterization and required interindividual variability." implementation plans from all programs in EPA (EPA 1995b)
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From page 356... ...
To ensure transparency, risk characterizations should include a statement of confidence in the assessment that identifies all major uncertainties along with comment on their influence on the assessment, consistent with the Guidance on Risk Characterization." (See "Risk Characterization" section above for other relevant policy statements in EPA risk-assessment guidelines and other sources.) NRC 1994 at 12: "EPA should conduct EPA 1997c Guiding Principles for Monte formal uncertainty analyses, which can Carlo Analysis at 1: "Such probabilistic show where additional research might analysis techniques as Monte Carlo resolve major uncertainties and where it analysis, given adequate supporting data might not." and credible assumptions, can be viable statistical tools for analyzing variability NRC 1994 at 12: "EPA should consider in and uncertainty in risk assessments and its risk assessments the limits of scientific presents an initial set of principles to guide knowledge, the remaining uncertainties, the agency in using probabilistic analysis and the desire to identify errors of either tools." overestimation or underestimation." NRC 1994 at 12: "Despite the advantages EPA 1996 Proposed Guidelines on EPA did not adopt this recommendation in of developing consistent risk assessments Carcinogen Risk Assessment at 125: "The the 1996 guidelines.
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From page 357... ...
Rather, they most of the potentially exposed, susceptible should be given risk characterizations that population, or ecosystem. EPA's highare as robust (i.e., complete and accurate)
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From page 358... ...
Central tendency and high end individual risk descriptors capture the variability in exposure, lifestyles, and other factors that lead to a distribution of risk across a population (e.g., see Guidelines for Exposure Assessment) ." Variability and NRC 1994 at 11: "Federal agencies EPA 1997d Exposure Factors Handbook: GAO 2006 at 47: "Another way EPA Differential should sponsor molecular, epidemiological, Risk assessors have used the Exposure addresses variability is through research.
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From page 359... ...
For example, one of ORD's laboratories conducted the National Human Activity Pattern Survey to provide detailed human exposure information for specific populations and allow EPA to better understand actual human exposure to pollutants in real-world situations. The survey results are stored in the Consolidated Human Activity Database to help risk assessors estimate the time that exposed people spend in various environments and their inhalation, ingestion, and dermal absorption rates while in those environments.
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From page 360... ...
through which children come into contact with chemicals. "Variability also exists with regard to susceptibility to adverse affects because of inherent differences among humans." NRC 1994 at 11: "EPA should adopt EPA 1996 Proposed Guidelines for a default assumption for differences in Carcinogen Risk Assessment at 125: susceptibility among humans in estimating "The issue of a default assumption for individual risks." human differences in susceptibility has been addressed under the major defaults discussion in section 1.3 with respect to margin of exposure analysis.
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From page 361... ...
For example, risk assessors in the Office of Air Quality Planning and Standards EPA 2000b Risk Characterization who set certain air quality standards for Handbook at 40: "The risk assessor should six principal pollutants said they consider strive to distinguish between variability and individual activity patterns for sensitive uncertainty to the extent possible (see 3.2.8 populations like children or asthmatics in for a discussion of uncertainty)
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From page 362... ...
and interindividual variability (i.e., population heterogeneity) is generally required if the resulting quantitative risk characterization is to be optimally useful for regulatory purposes, particularly insofar as risk characterizations are treated quantitatively.
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From page 363... ...
Evaluating childhood cancer and special provisions for the consideration of interindividual variability in key biologic childhood exposures resulting in cancer risks to children from pesticides. In 1995, parameters when it uses or evaluates later in life are related, but separable, EPA's Science Policy Council called for EPA various physiologic or biologically based issues." to consider the risks to infants and children risk-assessment models (or else evaluates consistently and explicitly as part of its risk some data but does not report on this EPA 2004b at 42: "Consideration of the assessments.
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From page 364... ...
1992b. Guidance on Risk Characterization for Risk Managers and Risk Assessors.
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From page 365... ...
2000b. Risk Characterization: Science Policy Council Handbook.
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From page 366... ...
2005a. Guidelines for Carcinogen Risk Assessment (Final)
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