Science and Judgment in Risk Assessment (1994) / Chapter Skim
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Appendix A: Risk Assessment Methodologies: EPA
Appendix A: Risk Assessment Methodologies: EPA
Pages 287-350
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From page 287... ...
APPENDIXES NOTE: The following appendixes have been typeset from a variety of original sources. The typographical appearance of the originals, as well as the editorial content and style, has been preserved wherever possible.
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APPENDIX A Risk Assessment Methodologies: EPA's Responses to Questions from the National Academy of Sciences DISCLAIMER This document was prepared primarily by the staff of the Pollutant Assessment Branch within the Office of Air Quality Planning and Standards. Some of the responses that describe future risk assessment procedures and policies represent the opinions of the authors within the Office of Air Quality Planning and Standards and do not necessarily represent the U.S.
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Risk Characterization and Treatment of Uncertainty 310 S Some Differences Between Past and Present Risk Assessments 312 C
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297 IV. Pr10rit~st10a of Dam Gathering (Question 4)
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292 Figure SCIENCE AND JUDGMENT IN RISK ASSESSMENT LIST OF FIGURES 1 Title m Regulatory Flow....................... 2 Chronology of Title m Implementation Page ..295 ..296 3 Risk Assessment Guidelines Development Process 307 4 Hazard Assessment Document Development 309 5 Integration of Exposure Assessment into Risk Assessment Process 310 6 Identification, Assessment, and Regulation of Hazardous Air Pollutants 315 7 Chronology of Section 112 Regulatory Policy Development .....................................................................................
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316 .328 ..332 6 Data on Hazardous Air Pollutants 334
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I.B Regulatory Flow and Chronology of Title III Implementation Regulation under Title m is comprised of two major steps: the application of technology-based emission standards to categories of major stationary industrial sources, followed by the evaluation of residual risks and the development of further standards, as necessary, to insure that public health is being protected with an ample margin of safety. Affected source categories are identified based on emissions of listed pollutants.
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c. Hazard Ranking: A hazard ranking is the relative comparison of information identified in individual pollutant hazard assessments.
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It is typically conducted for individual sources, but the results may also be aggregated across an industrial source category. This level of analysis requires the most extensive collection of data and analytical resources.
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~.~ I.E Title III Risk-Related Provisions Several provisions of Title III contain requirements for risk or hazard assessment. Beginning on the following page, Table 1 summarizes these provisions.
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303 c y HE ._ y :c y ._ = lo 3 ._ 2 7 ._ e C .C ..
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304 :q c me ._ y 7 :o .~ .= ._ A = of .
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and associated threshold quantities - pollutant petition process included - establishment of Chemical Safety Board - development of regulatory program - report to Congress on use of hazard assessments, May '92 -promulgation of pollutant list and threshold quantities, Nov '92 - report to Congress on regulatory recommendations, Nov '92 - identification of potential for death, injury, serious adverse effect(s) QRA a,d,e 1 Levels of Anaylsis: HA, Hazard Assessment; HR, Hazard Ranking; RR, Risk Ranking; QRA, Quantitative Risk Assessment, as described in Section I.C.
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of the National Academy of Sciences in 1983. This process was described in a book entitled "Risk Assessment in the Federal Government: Managing the Process" and identified risk assessments as containing one or more of the following four components: hazard identification, dose-response assessment, exposure assessment, and risk characterization.
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Il.B.2 Hazard Assessment Document Development Hazard Assessment Documents (HADs) were commissioned at the request of EPA's Office of Air Quality Planning and Standards (OAQPS)
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The process is diagrammed below in Figure 4. TI.B.3 Exposure Methodology The first systematic exposure assessments of hazardous air pollutants (HAPs)
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Review by CARPS, OHEA, ORD ~ No ad verse enacts: Pubileh Tier ~ document O.cleJon not to list as HAP ' D.clelon not to llet as HAP D.clelon not to develop HAD No adverse effects: , TIER 111 ~ Prepare full HAD Rewlew by SAB and with tall public comment I I F'ubilsh HAD i FIGURE 4 Hazard Assessment Document Development. promote consistency among various exposure assessment activities that are carried out by the Agency.
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guidelines. The new guidelines incorporate developments in the exposure assessment field since 1986, both including the previous work and adding several topics not covered previously.
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In the early 1980's risk estimates were used largely to rank source categories by their estimated potential risks. As experience was gained with risk assessments and the perceived need of risk managers to have more information to make more informed decisions increased, the national source category approach evolved into plant-by-plant and, in some cases, emission point-by-emission point analyses.
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Appendix A presents additional information on EPA's risk assessment guidelines for developmental toxicity. As tools develop in the area of noncancer risk assessment along with expansion of existing data bases, quantitative presentation of risk assessments similar to analyses conducted for potential carcinogenic risks may be possible.
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Some of these concerns are: · assessing residual risk from multiple pollutants rather than individual pollutants within a source category · determining the approach appropriate to evaluating risk to the most exposed individual · assessing noncancer health risks · determining the risks from less than chronic exposure, especially acute exposures · factoring population mobility and activity patterns into the risk assessment process · identifying sensitive populations · assessing ecological risks While these may not be new concerns, the CAA of 1990 has focused greater attention on these issues. II.C Examples of Past Assessments II,C.1 Problem Definition Exposure to HAP emissions may result in a variety of adverse health effects considering both cancer and noncancer endpoints.
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In addition to toxicity data, other information that is typically included in a hazard assessment include data on a chemical's environmental fate, transport, or persistence in the environment. If the data are sufficient, a hazard assessment presents a profile of a chemical's toxicity, potential health and environmental risk, and related chemical characteristics.
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Identification of Problem Candide~ Pollutant Dcf~nition 1 ' | Health I | Source l 4.~sment Amassment T ..._. External Review 1 ScienceAdvisory NAPCTAC Board Source Category Risk Ranking Listing ~ Proposal of Standards _ Public Comment Period Promulgation of Standards flatted Assessmen t Risk Ranking Quantitative Risk Assessment Quantitative R:SJC Assessment FIGURE 6 Identification, Assessment, and Regulation of HAPs.
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316 SCIENCE AND JUDGMENT IN RISK ASSESSMENT TABLE 2 1984-1987 Hazardous Air Pollutant Decisions POLLUTANT ACTION CITATION Acrylonitrile State Referral 50FR24319; June 10, 1985 1,3-Butadiene Intent-to-List 50FR41466; October 10, 1985 Cadmium Intent-to-List 50FR42000; October 16, 1985 Carbon Tetrachloride Intent-to-List 50FR32621; August 13, 1985 Chlorofluorocarbon 113 Not-to-Regulate 50FR24313; June 10, 1985 Chlorinated Benzenes Not-to-Regulate 50FR32628; August 13, 1985 Chloroform Intent-to-List 50FR39626; September 27, 1985 Chloroprene Not-to-Regulate 50FR39632; September 27, 1985 Chromium Intent-to-List 50FR24317; June 10, 1985 Coke Oven Emissions Listing Notice 49FR36560; September 18, 1984 Copper Not-to-Regulate 52FR5496; February 23, 1987 Epichlorohydrin Not-to-Regulate 50FR24575; June 11, 1985 Ethylene Dichloride Intent-to-List 50FR41994; October 16, 1985 Ethylene Oxide Intent-to-List 50FR40286; October 2, 1985 Hexachlorocyclopentadiene Not-to-Regulate 50FR40154; October 1, 1985 Manganese Not-to-Regulate 50FR32627; August 13, 1985 Methyl Chloroform Not-to-Regulate 50FR24314; June 10, 1985 Methylene Chloride Intent-to-List 50FR42037; October 17, 1985 Municipal Waste Advance Notice of 52FR25399; July 7, 1987 Combustion Emissions Proposed Rule making Naphthalene Nickel Perchloroethylene Phenol Polycyclic Organic Matter Toluene Trichloroethylene Not-to-Regulate Not-to-Regulate Intent-to-List Not-to-Regulate Not-to-Regulate Not-to-Regulate Intent-to-List Vinylidene Chloride Not-to-Regulate Zinc/Zinc Oxide . Not-to-Regulate *
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The regulation of benzene also spans a period during which the methods for quantitatively estimating risks from exposure to airborne carcinogens evolved, and the appropriate role of such estimates in the decision process was hotly debated within, as well as outside, the EPA. For these reasons, benzene represents an interesting and illuminating case study of quantitative risk assessment and its use in determining the appropriate level of control under Section 112.
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In the benzene listing notice the following year, EPA announced the conduct of a benzene health risk assessment and indicated that the "relative risk to the public" would be considered in judging "the degree of control which can and should be required". The risk assessment, containing the original unit risk estimate for benzene, was subsequently published in January 1979 (Appendix F - Benzene Population Risk)
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These estimates were then combined with the unit risk estimate to yield cancer risk estimates. In the first benzene standards, estimates of maximum individual lifetime risk and annual incidence were calculated.
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The EPA accepted voluntary remand of the 1984-85 standards and issued a new proposal in July 1988, consistent with the vinyl chloride opinion. Given the requirement for a determination of "safe", the importance of the quantitative risk assessment took on even greater emphasis.
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standards, EPA is required to evaluate residual risks, applying the decision criteria used in the final benzene rules, to determine whether the technology-based rules provide an ample margin of safety to protect public health. Risk assessment will continue to play an important role in the implementation of this and other provisions of Section 112 and the importance of appropriate methodologies and characterization of uncertainties cannot be understated.
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The Report to Congress requires the following information: · contribution of atmospheric deposition to total pollution loading · environmental and public health effects · sources of the pollutants · contribution of HAPs to water quality violations To accomplish this, it will be necessary to: · conduct atmospheric deposition monitoring for source identification and model validation · conduct atmospheric transport and deposition modeling to include direct and indirect pathways · develop emission inventories as input to models · evaluate adverse effects of air toxics on public health and the environment
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The quantification of noncancer risks from exposure to inhaled hazardous air pollutants currently focuses on the derivation of inhalation reference concentrations (RfCs)
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The Eddies are defined as the estimated dose associated with a lifetime increased cancer risk of logo. Threshold pollutants are ranked by either their composite scores (CS)
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This score, along with other factors such as efficiency of grouping like sources for a particular regulation, availability of control technology information, and the specific nature of adverse health effects associated with a source category, is then used to assist in the scheduling of regulations. The Lesser Quantity Emission Rate project is an example of a risk ranking assessment because of the use of exposure assessment and data on health effects.
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The major consequence of this analysis would be a redefinition of some sources as major sources if their emission rates of HAPs exceed the assigned LQER. II.D.5 Quantitative Risk Assessment With regard to quantitative risk assessment activities, two current CAArelated activities address the use of refined modeling techniques with site-specific data to quantify risks associated with both long- and short-term exposure to hazardous air pollutants from stationary sources.
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Residual Risk Evaluation Under Section 112(f) of the CAA, EPA is required to assess the risks associated with a regulated source category within 8 years of the MACT standard promulgated for that category.
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If effects occur at one hour exposure, predict one hour concentrations/exposures. For cancer, estimate annual average values that are assumed to persist 70 years (the averaging time of unit risk factor)
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Table 3 presents data sources and assumptions that were generally used in previous exposure assessments. The source category deletion and residual risk evaluation provisions in Title III place a much greater focus on source and individual exposures associated with an often complex mixture of source types and pollutants.
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will be integrated with the models to improve the predicted ambient concentrations by incorporation of topography and land use information to aid in selection of appropriate meteorological data and the location of area source categories In addition, GIS will allow OAQPS to more accurately locate areas where people may reside than is currently possible using U.S. Bureau of Census data alone (See Appendix V, GIS - Application to Exposure Assessment)
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This table may be used to quickly determine whether a given scenario may be modeled at any particular tier based on available site-specific data. Within each tier, cancer unit risk estimates, chronic noncancer concentration thresholds, and acute concentration thresholds are required to convert concentration predictions into cancer risks, chronic noncancer risks, and acute noncancer risks, respectively.
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risks additive, site classification, noncancer risks building dimensions additive for downwash calculation Tier 3 emission rate, stack concentrations at cancer risks height, actual each receptor point, additive, noncancer fenceline and release long-term cancer risks additive point locations, risk estimates, stack velocity, stack chronic noncancer temperature, stack hazard index diameter, rural/urban estimates at each site classification, receptor point, local meteorological annual hazard index data, receptor exceedance rate at locations for each receptor concentration predictions, frequency and duration of short term (intermittent) releases
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III.A Introduction The EPA has compiled currently available data on the hazardous air pollutants (HAPs) in developing strategies for implementing various provisions conta~ned in Title III of the Clean Air Act.
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334 SCIENCE AND JUDGMENT IN RISK ASSESSMENT TABLE 6 Cu~rent Data on the HAPs CAS Chemical Name # ~M ~ C T 1991 1990 1989 1988 Y E A ~Emis Emis Emis Fmi~ 2 4 7 10 (T/yr)
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APPENDIX A 335 IUR OUR EPA RfC IARC Exp. Gencdc Toxicity Data Rcprl per per WOE mg/m3 WOE Asses.
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336 SCIENCE AND JUDGMENT IN RISK ASSESSMENT CAS Chemical N~e # M A C T 1991 1990 1989 1988 Y E A
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APPENDIX A IUR OUR per per ug/m3 ug/L 5 6 EPA RfC IARC E~p. WOE mg/m3 WOE Asscs.
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338 SCIENCE AND JUDGMENT IN RISK ASSESSMENT CAS Chemical Name # Colu~nn Number 106898 Epichlorohydrin (1-chloro-2,3 epoxypropane) 140885 Ethyl acrylate 100414 Ethyl benzene 51796 Ethyl carba~natc (Urethane)
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APPENDIX A 339 IUR OUR EPA RfC IARC E~p. Gencdc Tomcity Daea Rcpr/ per per WOE mg/m3 WOE Asses MVV MVT ~M Dev ug/m3 uglL Stat So G M C S E Daea 5 6 ~7 8 9 10 11 12 13 14 1.2E-6 2.8E-7 B2 UR D 1.3E-5 1.3E-3 1.3E-4 4.6E4 4.6E-5 2.2E-5 2.2E-6 4.0E-6 4.0E-7 UR B2 2.7E-8 C B2 72435 74839 74873 71556 78933 50344 74884 108101 524839 80626 1634044 75092 4.7E-1 2.1E-7 B2 101688 106898 140885 100414 51796 75003 106934 107062 151564 75218 96457 75343 107211 o 50000 o 76448 118741 87683 77474 67721 822060 680319 110543 302012 4.9E-3 8.5E-5 7647010 7664393 123319 78591 o 58899 108316 o o 57561 2.2E-4 2.5E-3 B2 2.6E-5 2.6E-6 B2 C B1 1.0E-3 2A 2B 1.0E+0 ~V 1.3E+1 2.0E" 2A 2B NV 3 2A 2B UR B2 B2 NV C D C NV 1.0E-S 7.0E-6 2.0E-1 2B 2A 2B 3 3 2B 2B 2B 7.0E-3 UR NV 3 NV 2B NV 2B B D 4.0E4 B D 3.0E4 UR D NV 3 D 5.0E-3 3 UR 3 D UR D 1.0E+0 7.0E-S 1.0E-2 UR NV 3 5.0E-1 3 UR 2B 5.0E-5 B + B + B + + B + 3 B + + 3 + + + + + + + + + + + + + + X ~s X + + + + ~$ ~ X X x X*
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APPENDIX A 341 IUR OUR EPA RfC LARC E~p. Geneiic Tox~city Data Repr/ per per WOE mg/m3 WOE Asses.
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WOE 10 Exposure Asscssmcats: A) HAPS with risk assessments done for development of Section 112 standards B)
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By Category ~ ~ Em_ ~= c_~o~ Cow B - ~~ ~= c=^og~ B1 - Ted ~= data B2 - Mediate ^= ~= ~=t aim data C - Possible ~= carom TIC - 1 - to_ ~= Icy ~ ~ - amble ~= 2B - Resale ~ c~c~g~ ~- 3 - ^1 c~s~e ~ to ~ I ~- ~ - homily not c~c~o~ic to ma_ .,
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TY.A Introduction Existing data on effects and exposure to the hazardous air pollutants (HAPs) listed under Section 112 have supported a variety of decisions under Title m of the Clean Air Act (CAA)
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The Agency anticipates that activities will begin with a ranking of HAPs that takes several factors into account. These factors include: · promulgation dates of control technology standards · estimation of the extent to which a particular HAP will contribute to risks resulting from combined HAP emissions from sources in a source category (using effects and exposure data available now)
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This narrow scope testing could include: pharmacokinetics studies, a 90 day subchronic inhalation study, or a repeat of a previous study on an endpoint to better define the dose-response relationship. TV.D Mechanisms for Obtaining Effects Data There are a variety of mechanisms that may be accessed for collecting effects data, all of which will likely be employed.
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In addition, the analyses will differ from past analyses in that they will be directed at assessing the exposure to multiple pollutants being emitted from a source in a particular source category. The EPA must begin now to develop the tools and process for obtaining the necessary data to perform residual risk analyses.
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6) Efforts to check and assure the quality of the data obtained for exposure assessments may prove to be a large part of the data gathering process.
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This does not mean that all risk assessments should look the same. But it is important that a consistent terminology be adopted, even if the terminology draws controversy, and that the risk managers understand and can communicate that understanding.
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This is particularly true in the risk assessment process, where the limitations of the current state of the science often prevent definitive answers, and can encourage continual additional data development. Reviewers of Agency risk assessments must consider the reasonable resource constraints under which the Agency operates.
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