Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 367
Science and Decisions: Advancing Risk Assessment Appendix E Environmental Protection Agency Program and Region Responses to Questions from the Committee In January 2007 the NRC committee sent EPA a list of questions (see below) to gather additional information on their risk assessment practices. EPA responses were provided by the Office of Air and Radiation (OAR); Office of Prevention, Pesticides, and Toxic Substances (OPPTS), Region 2; and the Office of Solid Waste and Emergency Response (OSWER); and the Office of Water (OW). The EPA responses do not represent the views of the committee on these issues. QUESTIONS FOR EPA FROM THE NRC COMMITTEE Give an example of a risk assessment from your office that you would consider an example of “best practice,” and an example of a risk assessment that you think could have been improved (and if so, how). What improvement in EPA risk assessment practices would you find particularly helpful in the short term (2-5 years) and in the longer term (10-20 years)? If these improvements were to be implemented, how do you foresee the changes impacting your office? Please describe the risk assessment paradigm(s) used by your office. Do these paradigms adequately address environmental problems faced by the country? If not, how might current paradigms be modified or new paradigms identified to address these problems? Describe problems that arise when using risk assessment to support regulatory decision making. Do you encounter similar problems when using risk assessment in non-regulatory decisions? Please provide specific examples to illustrate your points. How would you recommend improving the presentation of EPA risk assessments for decision-making?
OCR for page 368
Science and Decisions: Advancing Risk Assessment How have you addressed and communicated uncertainty in risk assessments? Please discuss the adequacy of default assumption choices, and efforts to use alternatives to these default assumptions. Please describe the ways in which children and potentially unique or vulnerable populations are specifically considered in your office’s risk assessments. Please provide examples. AGENCY RESPONSES TO QUESTIONS OFFICE OF AIR AND RADIATION (OAR) Current Practice Statutory basis/current approach and paradigms for risk assessment (specific to each program office) Examples and best practices Gaps and problems Uncertainty analysis Examples Communication of risk and uncertainty Sensitive and vulnerable subpopulations (e.g., children, elderly, tribes, endangered species) Examples of physical attributes and unique exposures that impact risk Problems and challenges Challenges for risk assessment in a regulatory process Examples Problems and challenges General Comment The 2004 Agency document “An Examination of EPA Risk Assessment Principles and Practices” (EPA 2004a) provides a good resource for understanding the Agency as well as OAR’s approach to risk assessment. Consistent to the focus of the NAS committee charge this response does not address ecological risk assessment. Protection of ecosystems from adverse impacts from of air pollution is an important mission of our Office and we could provide additional information in this area if requested. There are two programs within OAR that best illustrate the use of risk assessment in our Office. First, are assessment activities that support the development of national ambient air quality standards (NAAQS) for the 6 “criteria” air pollutants, and, second, those conducted in consideration of emissions controls for hazardous air pollutants (HAPs or air toxics). National Ambient Air Quality Standards (NAAQS) The “criteria” air pollutants are the six pollutants—ozone, particulate matter, carbon monoxide, nitrogen dioxide, sulfur dioxide and lead—the presence of which in the ambient air results from numerous or diverse sources, and for which there are established public health concerns at historic ambient levels. These pollutants have been extensively studied
OCR for page 369
Science and Decisions: Advancing Risk Assessment over time and health-based National Ambient Air Quality Standards (NAAQS) have been developed for each. Human exposure and/or health risk assessments and ecological risk assessments are performed during the periodic reviews of these standards. The process under which exposure and/or risk assessments are performed for the criteria pollutants is largely driven by statutory language and legislative history and involves substantial external peer and public review. Each NAAQS review includes a full review of the underlying scientific database which supports the quantitative exposure and/or risk assessments (for an example, see the Air Quality Criteria for Ozone and Other Photochemical Oxidants [EPA 2008a]). The health-effects databases for criteria pollutants are generally very rich and include: epidemiological studies of normal exposures to the ambient mix of air pollutants, controlled-human exposure studies, and animal studies (short- and long-term exposures). Risk assessments for criteria air pollutants also benefit from extensive exposure related information including monitoring data and well developed exposure models. Hazard characterization involves a weight-of-evidence approach, using all relevant information and considering the nature and severity of effects, patterns of human exposure, nature and size of sensitive populations, the kind and degree of uncertainties, and the consistency or coherence across all types of available evidence. “Dose”-response evaluations are based on the nature of available evidence from human studies, generally with no discernable thresholds (effects observed at current ambient concentrations). For example, for PM, ambient concentration-response functions are employed, for ozone, exposure-response and concentration-response relationships are used and for CO and lead, internal dose-metrics are used. When ambient concentration-response functions are used, simulations of “just meeting” alternative standards are used to examine levels of risk. When exposure or internal dose-response metrics are used, exposure modeling is relied upon that includes air quality monitoring/modeling and simulations of “just meeting” alternative standards, pollutant concentrations within relevant microenvironments (home, yard, car, office), amount of time in different microenvironments and level of exertion (time-activity and breathing rate data), population demographics (census data, commuting patterns), probabilistic assessment (including uncertainty and variability), and sensitivity analyses. This modeling provides the ability to identify, and characterize exposure distributions for sensitive and/or at risk groups. Risk characterization for criteria pollutants includes both qualitative and quantitative approaches. There is an integration of evidence on acute and chronic health effects (strengths, weaknesses, uncertainties). Expert judgments are made on adversity of effects (severity, duration, frequency). There are qualitative and quantitative assessments of population exposures of concern and/or risks to public health. The risk characterizations are primarily based on available evidence from human studies and “real-world” air quality and exposure analyses; no need for traditional “uncertainty” or “safety” factors. Risk assessments and characterizations for criteria pollutants, while considering the general population, include focus on the susceptible and/or the more highly exposed subpopulations (e.g., asthmatics and children are groups focused on in the current ozone NAAQS review). However, exposures and risks do not focus on maximum exposed individuals or maximum individual risk given the legislative history indicating that standards are to protect most of the sensitive population group but not the most sensitive individual. Uncertainty in criteria pollutant risk assessments is routinely addressed using probabilistic assessment (including uncertainty and variability) and sensitivity analyses. For an example of the type of exposure and risk assessments conducted for the NAAQS reviews see the final OAQPS Staff Paper for Ozone (EPA 2008b) and the human exposure, health risk assessment, and exposure, risk and impacts assessment for vegetation technical support documents (EPA 2008c).
OCR for page 370
Science and Decisions: Advancing Risk Assessment Risk assessments for criteria pollutants generally include quantitative sensitivity analyses of exposure and health risk estimates as mentioned above, and also include qualitative discussion of contributing uncertainties. Key Issues and Challenges Key issues and challenges in carrying out quantitative risk assessments for criteria pollutants have included: (1) how to appropriately reflect and characterize model uncertainty, especially with respect to the shape and location of concentration-response relationships for which epidemiological studies are often failing to discern population thresholds, even at ambient levels approaching background levels; and (2) how to appropriately address and consider multi-pollutant health effect models and to disentangle the likely interaction among air pollutants, many of which are correlated and come from common sources (e.g., combustion of fossil fuels) in causing various health effects. In the area of exposure analysis, these challenges include how to use the human activity data base which consists of over 20,000 individual daily diaries to construct human activity sequences over months or an entire year. There is very little longitudinal data, so it is difficult to know if we are appropriately taking into account the repeated activities that individuals engage in. There also are few exposure field studies that include representative population sampling that would allow evaluation of the regulatory exposure models used by EPA in its NAAQS assessments. In addition, there are challenges in determining how “just meeting” hourly or daily standards will affect the overall distribution of pollutant concentrations across all hours and days. For non-threshold pollutants, the choice of method used in simulating attainment can have potentially large impacts on the estimated risks. Hazardous Air Pollutants The hazardous air pollutants (HAPs or “air toxics”) are 187 substances listed in CAA (e.g., benzene, methylene chloride, cadmium compounds, etc.) which have been associated with, or for which data suggest, the potential for serious adverse health and/or environmental effects, and for which there are specific source-based statutory requirements. Although several HAPs have substantial health and/or ecological effects data bases, most others have very limited data, much of it based solely on knowledge of health effects on exposed animals rather than humans. HAPs are regulated through source-oriented technology and risk-based emissions standards. HAP risk assessments are performed for consideration of risk-based emissions standards (residual risk standards) for source categories for which technology-based controls have already been applied (a good example of which may be found in the docket supporting the proposed residual risk rule for the source category called “Halogenated Solvent Cleaners” (look in ICF International 2006). Rather than focusing on the risks associated with exposure to an individual chemical, these risk assessments commonly examine cumulative risks associated with exposures resulting from the combination of pollutants emitted by a particular type of industry. By statutory language and regulatory history, these risk assessments include both a maximum individual risk (i.e., presuming an individual were exposed to the maximum level of a pollutant for a lifetime), as well as a characterization of a representative population risk. HAP risk assessments may also be performed for other programmatic purposes. For example, national-scale assessments have been performed based on the 1996 and 1999 emissions inventories as part of the National Air Toxics Assessment (NATA) activities (EPA
OCR for page 371
Science and Decisions: Advancing Risk Assessment 2002a, 2003a). As another example, risk assessments may be performed to support decisions on petitions to list or delist individual HAPs or source categories from Clean Air Act regulatory consideration. The scope of HAP risk assessments varies with the characteristics of the pollutants and sources being assessed. Inhalation and, as appropriate, other routes of exposure are assessed, and both chronic and acute time scales are considered. Ecological risks are also considered for residual risk decision-making. Routinely, a tiered approach is employed for efficiency, with lower tiers using simpler, more conservative tools and assumptions to identify important sources and pollutants, and higher tiers using more refined tools and site-specific data to determine where emission controls may be appropriate. Lower-tier risk assessments generally support decisions not to regulate or assist decisions to focus resources on a small number of stressors and sources for next iteration. They alone generally do not support decisions to mandate additional control of emissions. Such decisions, which can have significant economic implications, usually require more refined assessment. Hazard and dose-response assessments for HAPs generally rely on the most current existing assessments that have undergone scientific peer review and public review. The dose-response metrics used are acute or chronic reference concentrations (RfCs), and cancer inhalation unit risk (IUR) estimates. The sources for these values include U.S. EPA (e.g., IRIS), U.S. ATSDR, California EPA, etc. The common qualities across the sources employed are: development under a defined scientific process, use of independent external peer review, and a reflection of the state of knowledge at the time of the assessment. Risk assessments for HAPs routinely include, as a first step, derivation of risk estimates for conservative exposure scenarios (e.g., continuous lifetime exposure). Where this first step suggests risks in a range of potential concern, more refined assessments which utilize more of the available data are performed. The most refined assessments attempt to provide a probabilistic distribution of risk (including uncertainty and variability) and sensitivity analyses. The use of probabilistic assessments is currently limited to certain exposure assessment variables (i.e., those describing daily activity and long-term migration behaviors), and does not typically include variables describing emission rates, release conditions, meteorology, fate and transport, or dose-response. Consideration of the most exposed receptors (individuals) is accomplished by estimating chronic exposures at the Census block level and acute exposures at the offsite location with the highest 1-hour concentration. OAR in its HAPs assessment is a user of Hazard/Dose response information (e.g., such as that produced under the IRIS program). Thus, consideration of sensitive subpopulations is considered in so far as it is explicitly built into the dose-response metrics that EPA uses to estimate risk (i.e., where data supporting such distinctions are available). Unit risk estimates typically incorporate protective low-dose extrapolation assumptions and are based on statistical upper confidence limits. Reference concentrations employ uncertainty factors that account for differences among species, within human populations, and database deficiencies (e.g., failure to identify no-effect doses and absence of chronic studies). These uncertainty factors are intended to ensure that the reference concentration represents an exposure that is likely to be without appreciable risk of adverse effects in human populations, including sensitive sub-populations. Risk assessments for HAPs may include quantitative sensitivity analyses of exposure as mentioned above, and also include qualitative discussion of contributing uncertainties. However, the dose response information provided in IRIS (or other sources of dose response information) typically does not have information suitable quantitative analysis of either uncertainty or variability.
OCR for page 372
Science and Decisions: Advancing Risk Assessment Key Issues and Challenges Key issues and challenges in carrying out risk assessments for hazardous air pollutants include both lack of data and how to appropriately reflect and characterize uncertainty and variability in assessments. As described above, risk assessments for the HAP program decisions routinely address multiple pollutant exposure and risk for multiple similar sources. Limitations associated with current assessments may contribute to uncertainties in resultant risk estimates. Examples of these are listed below as areas where improvements in risk assessment methods, tools or inputs might lead to reduced uncertainty in risk estimates. As described above, the single greatest challenge in risk analysis for most hazardous air pollutants is the need to rely primarily on animal or limited human data for the development of hazard and dose response assessments. The interpretation and implications of such data for potential risk is typically one of the greatest sources of uncertainty in such assessments. One of the significant sources of uncertainty to risk assessments is the source characterization, including emissions estimates. This is particularly true for source categories that have large numbers of sources and where “representative” data may not exist. For modeling purposes, source data should include site-specific release parameter/characterization information as well as better source emission estimates. For example, such parameters include map coordinates, release heights and temperatures, emissions data measured or estimated (and approved) directly by the facilities, annual and maximum hourly emission rates, and quantitative estimates of the uncertainties associated with each. We are limited in methods to consider the effects on source-specific exposure of longer-term population mobility. While such data on migration behavior on a local scale are available, they have not been developed into tools or analyses that are readily applicable to our risk assessment methods. Atmospheric deposition data, which would contribute to improved/enhanced assessment of non-inhalation exposures and risk, are limited. Methods for estimating and presenting uncertainty in a manner easily understood by decision makers are limited. Use of the Agency’s traditional exposure-response assessments (e.g., cancer unit risk factors and RfCs) contribute to our limitations with regard to incorporating quantitative uncertainty and variability of response into risk estimates. Limitations with regard to spatial coverage of air toxics monitoring networks affect performance evaluation capabilities for local-scale air modeling used in HAP risk assessments. Our ability to evaluate mixtures and potential interactions (other than that provided under EPA’s current mixtures guidance) is limited. Because of the number of hazardous air pollutants emitted from the many sources considered and the time required for updating the hazard and dose-response assessments, the development of those updated assessments can not kept up with the need to make regulatory decisions. Thus, OAR is often confronted with making such decisions with out the benefit of final IRIS assessments.
OCR for page 373
Science and Decisions: Advancing Risk Assessment Future Directions: Addressing Gap, Limitations, and Needs Both the Criteria and Hazardous air pollutant program operate under the risk assessment paradigm developed by the NRC in its 1983 “Red Book” report. The overall approach to risk assessment in the Hazardous Air pollutant program has also been guided by the 1994 NRC report, “Science and Judgment,” which, for example, outlined a tiered approach to the assessment of risk from toxics air emissions from affected sources. We believe the basic paradigm for risk assessment remains sound. In developing recommendations for improvements, we ask that the Committee consider that the agency must operate within mandated timeframes and growing resource constraints. Thus, any guidance on prioritization of recommendations or on those circumstances where potentially more resource intensive approaches are suggested, would be useful. The “key issues and challenges” discussions in Part I of this submission (for both the NAAQS process and hazardous air pollutants) provide useful insight into areas where the Committee might focus in looking at future directions and needs. In addition to those points we would add the following few comments: The issue of needed data and tools for improving NAAQS assessments are to some extent addressed in the NAAQS review process. Of particular note is the role played by our external scientific review group, the Clean Air Scientific Advisory Committee (CASAC), that explicitly identifies policy-relevant research needs to improve our capabilities for the next cycle of review. This has led to a continuous improvement in our assessment capabilities. Within the NAAQS program the application of additional methods for uncertainty analysis (e.g. expert elicitation) has particular promise in this program. However, the Agency is still in an early stage of considering how best to incorporate such approaches into its assessments, where appropriate, and how to consider such assessments relative to data driven assessments. Whatever approaches are adopted to characterize uncertainties, it is important to communicate how much weight to accord across the distribution of exposure and/or risk estimates, and not simply provide lower and upper uncertainty bounds. OFFICE OF PREVENTION, PESTICIDES AND TOXIC SUBSTANCES (OPPTS) Current Practice: Risk Assessment at the EPA Statutory Basis/Current Approach and Paradigms for Risk Assessment (Specific ro Each Program Office) A response to this question can be found at our websites (EPA 2008d,e) along with current practices and recommendations to improve risk assessment (EPA 2002b, 2007a, 2008f). Very briefly, as an example, the passage of the 1996 Food Quality Protection Act requires that EPA consider, among other things, the best available data and information on the following: aggregate exposure to the pesticide (including exposure from food, water, and residential pesticide uses to a single pesticide), cumulative effects from other pesticides sharing a common mechanism of toxicity (including exposure from food, water, and residential pesticide uses to a multiple pesticides), whether there is an increased susceptibility from exposure to the pesticide to infants and children, and whether the pesticide produces an effect in humans similar to an effect produced by a naturally occurring estrogen, or other endocrine effects. Like other EPA offices, OPPTS relies on the basic 4 component NAS paradigm from the
OCR for page 374
Science and Decisions: Advancing Risk Assessment Red Book/Science and Judgment) (NRC 1983, 1994) in assessing aggregate and cumulative risks (hazard, dose response, exposure assessment and risk characterization). OPPTS follows EPA approaches for risk assessment described in Agency risk assessment guidelines. In order to reduce the application of default assumptions and default uncertainty/extrapolation factors, in the areas of animal to human extrapolation and high to low dose extrapolation, OPPTS has used physiologically based pharmacokinetic (PBPK) models, data-derived uncertainty factors, and mode of action data, and human biomonitoring data in their risk assessments. OPPTS has been a leader in developing and implementing newer and sophisticated approaches and tools such as probabilistic methods for assessing exposures in food, water, and from residential pathways. Key examples of the implementation of all of these approaches include the Organophosphate Pesticide (OP) and N-methyl carbamate cumulative risk assessments (EPA 2002c, 2007b), PFOA draft risk assessment (EPA 2005a), and draft lead risk assessment (EPA 2007c). It should be noted that not all assessments need to be of the same depth and scope. We use an iterative and tiered process that considers exposure and sensitivity analyses to balance resources against the need to refine the assessment and reduce uncertainty where appropriate. Uncertainty Analysis OPPTS uses sensitivity analyses in the exposure component of risk assessments, particularly in those assessments that inform or support potentially consequential actions (e.g., pesticides and major industrial compounds). As noted below, OPPTS is working closely with ORD to develop more advanced methods of quantitative uncertainty analysis (e.g., 2-dimensional Monte Carlo). For example, OPPTS and ORD are planning to discuss science issues surrounding the implementation of 2-dimensional Monte Carlo into ORD’s SHEDs model (Stochastic Human Exposure and Dose Simulation Model) with the FIFRA Science Advisory Panel in 2007. Current methods for the hazard component provide some quantitative measure of experimental data variability. For example, in the cumulative risk assessments for the OP and N-methyl carbamate pesticides, OPPTS quantified upper and lower confidence bounds on potency estimates for each chemical. For those risk assessments that utilize PBPK models, uncertainty/sensitivity analysis of the input parameters can be performed. Currently, however, uncertainty due to missing toxicological data is qualitatively described and established methods for quantifying that uncertainty are lacking. Sensitive and Vulnerable Subpopulations (e.g., Children, Elderly, Tribes, Endangered Species) A response to this question can be extracted from NCEA’s Framework for Children’s Health Risk Assessment (EPA 2006) and the RAF document on the RfD/RfC methodology (EPA 2002b) which OPPTS uses as guidance. For pesticides, it should be noted however, that the FQPA includes the statutory requirement of an additional 10X safety factor to protect infants and children. This 10X factor can only be reduced or removed if it is determined that the hazard and exposure analyses are protective of infants and children. OPP’s guidance for implementing the FQPA factor can also be found via the web (EPA 2002d). OPP also assesses the potential effect of pesticides to non-target species, including federally listed threatened and endangered species (listed species) and habitat deemed critical to their survival. The assessment is conducted consist with scientific methodology described in EPA’s Overview Document (EPA 2004b) and endorsed by the U.S. Fish and Wildlife Service
OCR for page 375
Science and Decisions: Advancing Risk Assessment and National Marine Fisheries Service (FWS/NMFS 2004). This assessment results in an “effects determination” for a species—a determination of whether a particular pesticide’s use has “no effect,” is “not likely to adversely affect,” or is “likely to adversely affect” the listed species on a geographically specific basis. Consistent with Departments of Interior and Commerce regulations governing federal agency responsibilities relative to listed species, EPA consults with the U.S. Fish and Wildlife Service and National Marine Fisheries Service (the Services), as appropriate, for any determination other than “no effect.” Consultation and resulting input from the Services, informs OPPs decision on whether changes to the pesticide’s registration are necessary to ensure protection of federally listed threatened or endangered species and their critical habitat. Challenges for Risk Assessment in a Regulatory Process There are many challenges for risk assessment in a regulatory process. One key issue is the training of staff to implement new tools (e.g., MOA analyses) and prepare risk characterizations that provide transparent weight of evidence analyses. Another one is accounting for missing toxicological data via quantitative uncertainty analyses and to move the evaluation of toxicological effects into probabilistic and multi- endpoint analyses. Lastly, an important overall direction for OPPTS is to improve and refine how we integrate all available and relevant toxicology, human studies/epidemiology, biomonitoring, and exposure information into a paradigm that balances resources with the needs of the risk assessment (i.e., sustainable). Future Directions: Addressing Gap, Limitations, and Needs Issues to Be Addressed: Needed Improvements and Recommendations Short-term: 2-5 years OPPTS is working closely with ORD to develop more advanced methods of quantitative uncertainty analysis (e.g., 2-dimensional Monte Carlo) and incorporating these into exposure models. As knowledge expands, these methods will need further refinement and improvements. There is a need to continue to promote the development of PBPKmodels and other approaches which allow for the replacement of default assumptions uncertainty/extrapolation and to develop methods to quantify uncertainty and variability for the hazard/effects component of risk assessment. Long-term: 10-20 years Replacement or reduction of animal testing and moving toward an “integrated” risk paradigm by improving QSAR approaches, developing methods for interpreting and incorporating “omics” data, in silico, etc approaches into risk analyses. Address Media-Specific Needs for Risk Assessment, For Example: Do Current Paradigms Adequately Address Environmental Problems Faced by the Country? See above response to short and long term needs. OPPTS continues to develop and use alternatives to defaults by incorporating PBPK modeling and data derived uncertainty fac-
OCR for page 376
Science and Decisions: Advancing Risk Assessment tors, mode of action data, probabilistic exposure modeling, and biomonitoring data. For example, As an alternative to the RfD, OPPTS also uses characterization of risk for specific age groups and evaluates exposures across different durations of exposure (e.g., single day to lifetime). REGION 2 AND THE OFFICE OF SOLID WASTE AND EMERGENCY RESPONSE Introduction This report is primarily based on Chapter 5 of EPA’s Office of the Science Advisor’s Staff Paper titled: “Risk Assessment Principles and Practices” (EPA 2007a). The Chapter provides information regarding current practices for site and chemical specific risk assessments in EPA’s Office of Solid Waste and Emergency Response (OSWER). As described on the OSWER homepage (EPA 2008g): OSWER provides policy, guidance and direction for the Agency’s solid waste and emergency response programs. We develop guidelines for the land disposal of hazardous waste and underground storage tanks. We provide technical assistance to all levels of government to establish safe practices in waste management. We administer the Brownfields program which supports state and local governments in redeveloping and reusing potentially contaminated sites. We also manage the Superfund program to respond to abandoned and active hazardous waste sites and accidental oil and chemical releases as well as encourage innovative technologies to address contaminated soil and groundwater. This chapter provides a perspective on site-specific risk assessments conducted within the Superfund program. Current Practice Statutory Basis/Current Approach and Paradigms for Risk Assessment (Specific to Each Program Office) The Superfund Program To understand the Superfund program and its application in OSWER and the Regions it is important to first take a look at the legislation that governs this regulatory program. The Comprehensive Environmental Response Compensation and Liability Act (CERCLA) was enacted in 1980 and is commonly referred to as the Superfund program. The Act was amended in 1986 under the Superfund Amendments and Reauthorization Act of 1986. These laws require that action selected to remedy hazardous waste sites be protective of human health and the environment. The National Oil and Hazardous Substances Pollution Contingency Plan, or NCP, establishes the overall approach for determining appropriate remedial action at Superfund sites across the country and mandates that a risk assessment is performed to characterize current and potential threats to human health and the environment (40 CFR § 300.430 (d)(4)). The preamble to the NCP (55 Fed. Reg. 8709) provides more detail on the general goals and approach for Superfund risk assessments. The Superfund process involves a number of steps as shown in Figure E-1 from site discovery, listing on the National Priorities List (NPL), Remedial Investigation and Feasibility Study (RI/FS), Record of Decision (ROD) to final NPL deletion. Within the Superfund program, the range of activities at sites includes Removal Actions where actions are necessary in a short timeframe and longer remedial investigations of complex sites. This discus-
OCR for page 377
Science and Decisions: Advancing Risk Assessment FIGURE E-1 Community involvement activities at NPL sites. Source: EPA 2001a. sion will concentrate primarily on the latter type of investigation, i.e., sites that are on the NPL. Currently, across the country, there are 1,557 current and deleted sites on the NPL. The NPL is the list of national priorities among the known releases or threatened releases of hazardous substances, pollutants, or contaminants throughout the United States and its territories. The NPL is intended primarily to guide the EPA in determining which sites warrant further investigation. Further details regarding the Superfund program are available on the Superfund homepage (EPA 2008h). At each site risk assessments are developed to assess both human health and ecological risks during the RI/FS. The risk information is used to determine whether remedial action is needed at the site. All decisions at Superfund sites must meet the nine criteria provided in Table E-1. The Threshold Criteria that must be met at all sites are protection of public health and the environment and meeting the Applicable or Relevant and Appropriate Requirements (ARARs) or statutory requirements. Risk assessment plays a critical role in determining that these criteria are met. Risk Assessment in the Superfund Program The Superfund program uses risk assessment to determine whether remedial action is necessary at a specific site and to determine the levels of remedial action where actions are required. The program protects human health and the environment from current and potential future threats posed by uncontrolled hazardous substances releases. Decisions at Superfund sites involve consideration of cancer risks, non-cancer health hazards, and site-specific information associated with both current and future land use conditions. Consideration of future land use and future risks is included in the risk assessment because CERCLA mandates that remedies are protective in the long-term. The human health and ecological risk assessments developed at sites follow peer-reviewed guidelines, policies and guidance specific to the OSWER program as well as those for the Agency. The OSWER documents regarding risk assessment are available online (EPA
OCR for page 388
Science and Decisions: Advancing Risk Assessment FIGURE E-2 The framework for ecological risk assessment (Modified from EPA 1998). Office of Water operates under several pieces of enabling legislation. We have obligations under the following: Safe Drinking Water Act (Amended 1996) Clean Water Act Food Quality Protection Act (1996) (FQPA) Beaches Environmental and Coastal Health Act (BEACH Act) (2000) Coastal Zone Management Act Endangered Species Act FQPA amended the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) in 1996; this was specifically to highlight risks to children from pesticides. As pesticides are found in drinking water source waters, OW adopts the risk assessments done under FQPA by the Office of Pesticides Programs, at least as far as hazard identification and dose response; exposure assessment will differ given the purview of the legislation under which the risk assessment is conducted. The BEACH act is a 2000 amendment to the Clean Water Act (CWA). These changes set new requirements for recreational criteria and standards for coastal areas and the Great Lakes. The Endangered Species Act requires that EPA engage in consultation with the U.S. Fish and Wildlife Service on any actions which may affect endangered plant or animal species. The major pieces of enabling legislation for water programs are the CWA and the Safe
OCR for page 389
Science and Decisions: Advancing Risk Assessment FIGURE E-3 Conditions for regulation under SDWA 1996. Drinking Water Act (SDWA) as amended in 1996. SDWA deals with all uses of water from the tap, but only tap water (albeit from source to last public connection). Under SDWA, EPA establishes a list of chemical and microbial contaminants for potential regulation. EPA is obliged to revise this list on a regular basis; furthermore, EPA must make regulatory decisions on five agents on the list every five years. The bases for regulation are illustrated in Figure E-3. In order to regulate a contaminant in drinking water, EPA must establish the following: the contaminant can adversely affect public health; the contaminant occurs or is likely to occur in public water systems at levels that can affect public health; and there is a meaningful opportunity for public health improvement as a result of the regulation. In answering these questions OW conducts quantitative risk assessments to determine nonenforceable Maximum contaminant level goals (MCLGs). OW then sets enforceable Maximum contaminant levels (MCLs) as close as technically feasible to the MCLGs after taking costs into consideration. SDWA also requires that EPA conduct a Health Risk Reduction and Cost Analysis (HRCCA) for each proposed rule. There are seven elements of the HRRCA Quantifiable and non-quantifiable health risk reduction benefits; Quantifiable and non-quantifiable health risk reduction benefits form reduction in co-occurring contaminants; Quantifiable and non- quantifiable costs; Incremental costs and benefits; Effects of the contaminant on the general population as well as sensitive subpopulations including infants, children, pregnant women, the elderly, individuals with a history of serious illness or others that may be at greater risk; Any increase in health effects as a result of compliance including co-occurring contaminants;
OCR for page 390
Science and Decisions: Advancing Risk Assessment The quality and extent of information, the uncertainties in the analyses and factors with respect to the degree and nature of the risk. After completion of the HRCCA, analysis of technical feasibility of contaminant control, and determining appropriate monitoring, OW may propose and promulgate a National Primary Drinking Water Rule (NPDWR). These rules must be reviewed every six years by OW to determine if there is sufficient reason (e.g. new data, new risk assessment methods) to revise the rule. The CWA provides broad outlines for controlling discharges to ambient waters from point sources of pollution and diffuse sources of contamination (e.g. run-off from agricultural lands, mining sites, etc). CWA requires that States and authorized Tribes designate uses for waterbodies (such as drinking water source water, fishable/swimable waterbody). The States then are required to take specific actions to ensure that those uses are attained; such as setting standards, issuing permits, defining total maximum daily loads of a contaminant to a water body. Under CWA, OW publishes ambient water quality criteria (AWQC) for both human health and aquatic life. These are risk assessments that the States and Tribes may choose to adopt; EPA determines whether State or Tribal standards are scientifically justified. In deriving national AWQC, OW follows EPA published methodologies including the Methodology for Deriving Ambient Water Quality Criteria for the Protection of Human Health (EPA 2000), and the Guidelines for Deriving Numerical National Water Quality Criteria for the Protection of Aquatic Organisms and Their Uses (EPA 1985). The latter document is being updated. The Human Health Methodology is being expanded through Technical Support Documents. A series of technical documents deals with bioaccumulation through aquatic food webs, as human health criteria specifically identify consumption of contaminated seafood as a pathway in exposure assessment. The Human Health Methodology also describes the concept of relative source contribution (RSC), a method for apportioning the “allowable risk” such as an RfD over all plausible routes of exposure. OW also applies the RSC in calculating MCLGs under SDWA. For example in the risk assessment for chloroform, inhalation of vapors and concentrations in foods were considered in developing the MCLG. Ultimately the EPA default process had to be used in the chloroform RSC, as there were insufficient data on which to base a specific value. Other examples of best practices can be seen in the economic analyses in support of NPDWRs such as the 2005 Long Term 2 Enhanced Surface Water Treatment Rule (LT2) and the 2006 Groundwater Rule (GWR). Both of these rules were based on assessment of human risk from a variety of microbial contaminants including protozoa, bacteria and viruses. Uncertainty Analysis Regarding the presentation of alternative risk estimates SDWA says the following: The Administrator shall, in a document made available to the public in support of a regulation promulgated under this section, specify, to the extent practicable: Each population addressed by any estimate of public health effects; The expected risk or central estimate of risk for the specific populations; Each appropriate upper-bound or lower-bound estimate of risk … (OW; SDWA § 300g-1 (b)(3)). OW describes areas of uncertainty and variability in the risk assessment documents
OCR for page 391
Science and Decisions: Advancing Risk Assessment supporting our regulatory and other risk management decisions. Some of these analyses included quantitative estimates of uncertainty and variability; this is most commonly done for exposure data. Recent economic analyses done in support of SDWA include assessments of uncertainty in occurrence or exposure data (for example, LT2, the arsenic NPDWR, GWR). Discussion of uncertainty in dose response assessment was published in the context of these rules as well. In addition OW discussed uncertain the effectiveness of drinking water treatment (LT2) as well as uncertainty in the measurements or indicators used in risk-targeted regulatory strategies (LT2 and GWR). These analyses are peer-reviewed and subject to public comment before publication of the final economic analysis. OW has published sensitivity analyses and presentations of alternative risk estimates; for example in the Regulatory Impact Analysis (RIA) supporting the Arsenic NPDWR. Note that the preamble to this rule also included an extensive discussion of uncertainty in the dose response data and modeling. OW has also used published uncertainty analyses; for example, the assessment of variability in pharmacokinetic parameters presented by NRC (2000) was incorporated into the reference dose for methylmercury used in the AWQC (EPA 2001f). OW uses default procedures and assumptions as indicated in EPA documents including the 2005 Cancer Guidelines and Supplemental Guidance (EPA 2005c,d) and the Staff Paper (EPA 2004a). OW has also published analyses that permit the use of distributional approaches to exposure assessment; for example, analyses of Continuing Study of Food Intake by Individuals (CSFII) data on consumption of water from public water systems, in beverages and so on. This report also supports the use of 2l/day for adult exposure assessment as a reasonable default when distributional approaches are not warranted (EPA 2004c). Sensitive and Vulnerable Subpopulations (e.g., Children, Elderly, Tribes, Endangered Species) The SDWA Amendments mandate that EPA consider risks to groups within the general population that are identified as being at greater risk of adverse health effects; these include children, the elderly, and people with serious illness (Safe Drinking Water Act ). To this end OW includes consideration of appropriate susceptible populations in the risk assessment documents supporting risk management. This is always described in the preamble to regulations (for, example Disinfection By-products Stage 1). For example specific consideration of immunocompromised persons was highlighted in the Long Term Enhanced Surface Water Treatment Rules. OW specifically recommends that States and authorized Tribes use waterbody specific population and exposure data in their derivation of criteria and standards. OW recommends use of default exposure factors only in absence of any relevant data (EPA 2000). OW is conscious of Native American and other traditional lifestyles that may result in exposure parameters different from those considered to be the norm. The American Indian Environmental Office (AEIO/OW) and EPA Tribal Science Council are among the groups pursuing these issues. Challenges for Risk Assessment in a Regulatory Process Under the SDWA, costs vs. benefits of regulation are a factor in the choice to regulate or not as well as in the limits set by an MCL. An illustration of the methods and challenges of benefits assessment is the RIA for the arsenic NPDWR. It should be noted that identified but not quantified, and quantified but not monetized, benefits are difficult to characterize and compare with monetized benefits. Given that the standard non-linear low dose extrapola-
OCR for page 392
Science and Decisions: Advancing Risk Assessment tion procedure, calculation of an RfD, does not provide an estimate of risk, this is a major challenge. In the GWR economic analysis, OW made the case using a semi-quantitative approach that monetized benefits might be more than five-fold greater than those used, if bacterial disease could be better quantified. Under the Clean Water Act, OW publishes AWQC for human health; these risk assessments do not consider the cost or technological feasibility of meeting these criteria. However, demonstration of quantifiable, monetized benefits has become increasingly important in the acceptance of any risk management choice. The problem of assessing benefits of an ecosystem remains a very serious one. The major problem in conduct of OW risk assessments is insufficient resources. Chief among the resource lack is the lack of data. None of the enabling legislation for water programs provide a means to require that ecological or health effect data be generated. OW can establish requirements for monitoring of various kinds, depending on the law, but there is no way to acquire health effects data. There is further a requirement in SDWA that data serving as the basis for regulation be peer-reviewed and publicly available. OW risk assessments are most often limited by paucity of usable data on health effects and occurrence of contaminants in food and water. Data to support microbial dose response assessment are lacking and are likely not to be forthcoming. New human challenge studies are extremely unlikely to be conducted, and even if available may not be usable by EPA given recent restrictions on use of human studies. Those studies that are complete may not be applicable to assessment of exposure in the general population for these reasons. The studies administered laboratory strains of microbes; that is healthy infectious organisms grown or concentrated from specific hosts. Environmental organisms are of more diverse origin and may be more or less potent than laboratory strains. Challenge studies are conducted in healthy volunteers, usually one gender, and only of a limited age range (typically 20-50). Another challenge in assessing microbial pathogens is lack of data and models on secondary transmission. Dynamic disease transmission modeling is developing as a useful tool. Time is also a limited resource. SDWA risk assessments must be done to deadlines for regulation proposal, promulgation and review. For both CWA and SDWA actions, there are often court-ordered deadlines to be met. OW may not delay these actions to await data generation or method development. Under SDWA OW is concerned with contaminant mixtures in drinking water in response to requirements of the Safe Drinking Water Act Amendments of 1996, including mixtures of DBPs and of Contaminant Candidate List chemicals (e.g., organotins, pesticides, metals, pharmaceuticals). Information and methods are being developed to better evaluate the toxic mode of action, the risk posed by drinking water mixtures, exposure estimates for mixtures via multiple routes, and the relative effectiveness of advanced treatment technologies (EPA 2003c,d). Whole-mixture studies are routinely used in ecological risk assessments. The Agency has developed subchronic toxicity tests for whole aqueous effluents and for contaminated ambient waters, sediments, and soils (EPA 1989b, 1991c, 1994a). Furthermore, the effects of mixtures in aquatic ecosystems are evaluated using bioassessment techniques that are equivalent to epidemiology, but more readily employed (Barbour et al. 1999). Similar bioassessment methods are sometimes used at Superfund sites (EPA 1994b). These empirical approaches to assessing ecological risks from mixtures are employed in National Pollutant
OCR for page 393
Science and Decisions: Advancing Risk Assessment Discharge Elimination System permitting and the development of Total Maximum Daily Loads, and are often used in Superfund baseline ecological risk assessments. Many uncertainty analyses account for parameter uncertainty, but ignore model uncertainty. When only one model can reasonably explain or be fit to the data, then there is need only to account for uncertainty in that specific model’s parameter values. For example, a dose-response relationship might be known to be exponential, and data are used to estimate and characterize uncertainty about the exponential model’s single parameter (r). If it is uncertain whether the model is exponential, beta-Poisson, or some other form, then the data are used to characterize uncertainty about the model as well as the models’ parameter values. In OW’s GWR and LT2 rules, model uncertainty was explored in sensitivity analyses; these showed that the choice of model did not significantly alter the results. Dealing with model uncertainty may be a significant challenge in future analyses under these conditions: (a) data do not clearly point to a single preferred model; or (b) the regulatory outcome or estimate is sensitive to model choice. Future Directions: Addressing Gaps, Limitations, and Needs The 1983 NRC paradigm for human health risk assessment for chemicals and radiation remains adequate. The 1998 paradigm for ecological risk assessment remains adequate. We look forward to a federal peer-reviewed, published microbial risk assessment paradigm. Water programs need improved dose response methods, in particular for microbial disease causing agents. While OW would like to see increased use of data from “omic” technologies, there is an enormous amount of work in that field to be done before such use will be either practical or will stand the test of the courts. Probably the first accepted use of “omics” in water programs will be in microbial source tracking and in rapid detection of contaminants (rather than in risk assessment). Improved and accepted methods for quantifying ecological benefit, and human health benefits (beyond value of a statistical life), will be immediately useful. Means to assess the utility and the lessons learned from various types of uncertainty analyses will be immediately useful, as will improved methods for communicating uncertainty to both decision makers and the (litigious) public. The major limitations in applying any new risk assessment methods will be lack of data (particularly health and ecological effects data); and degree of acceptance of new methods by stakeholders. REFERENCES ATSDR (Agency for Toxic Substances and Disease Registry). 1996. ATSDR Public Health Assessment Guidance Manual. Agency for Toxic Substances and Disease Registry, Atlanta, GA. ATSDR (Agency for Toxic Substances and Disease Registry). 2001. Summary Report for the ATSDR Soil-Pica Workshop, June 2000, Atlanta, GA. Prepared by Eastern Research Group, Lexington, MA. Contract No. 205-95-0901. Task Order No. 29. March 20, 2001 [online]. Available: http://www.atsdr.cdc.gov/NEWS/soilpica.html [accessed Jan. 30, 2008]. Barbour, M.T., J. Gerritsen, B.D. Snyder, and J.B. Stribling. 1999. Rapid Bioassessment Protocols for Use in Streams and Wadeable Rivers: Periphyton, Benthic Macroinvertebrates and Fish, 2nd Ed. EPA 841-B-99-002. Office of Water, U.S. Environmental Protection Agency, Washington, DC [online]. Available: http://www.epa.gov/owow/monitoring/rbp/ [accessed Jan. 31, 2008]. Behrman, L.E., and V.C. Vaughan, III. 1983. Nelson Textbook of Pediatrics, 12 Ed. Philadelphia, PA: W.B. Saunders.
OCR for page 394
Science and Decisions: Advancing Risk Assessment Calabrese, E.J., R. Barnes, E.J. Stanek, III, H. Pastides, C.E. Gilbert, P. Veneman, X.R. Wang, A. Lasztity, and P.T. Kostecki. 1989. How much soil do young children ingest: An epidemiologic study. Regul. Toxicol. Pharmacol. 10(2):123-137. Calabrese, E.J., E.J. Stanek, and C.E. Gilbert. 1991. Evidence of soil-pica behavior and quantification of soil ingestion. Hum. Exp. Toxicol. 10(4):245-249. CDC (Centers for Disease Control and Prevention). 1991. Preventing Lead Poisoning in Young Children. U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, Atlanta, GA. October 1, 1991 [online]. Available: http://wonder.cdc.gov/wonder/prevguid/p0000029/p0000029.asp [accessed Jan. 30, 2008]. Charney, E., J. Sayre, and M. Coulter. 1980. Increased lead absorption in inner city children: Where does the lead come from? Pediatrics 65(2):226-231. Chiang, A. 1998. A Seafood Consumption Survey of the Laotian Community of West Contra Costa County, CA. Oakland, CA: Asian Pacific Environmental Network. Davis, S., P. Waller, R. Buschbom, J. Ballou, and P. White. 1990. Quantitative estimates of soil ingestion in normal children between the ages of 2 and 7 years: Population-based estimates using aluminum, silicon, and titanium as soil tracer elements. Arch. Environ. Health 45(2):112-122. EPA (U.S. Environmental Protection Agency). 1985. Guidelines for Deriving Numerical National Water Quality Criteria for the Protection of Aquatic Organisms and Their Uses. EPA 822/R-85-100. U.S. Environmental Protection Agency, Office of Research and Development, Environmental Research Laboratories, Duluth, MN, Narragansett, RI, and Corvallis, OR [online]. Available: http://www.epa.gov/waterscience/criteria/85guidelines.pdf [accessed Jan. 30, 2008]. EPA (U.S. Environmental Protection Agency). 1988. Guidance for Conducting Remedial Investigations and Feasibility Studies under CERCLA. Interim Final. OSWER Directive 9355.3-01. EPA/540/G-89/004. Office of Emergency and Remedial Response, U.S. Environmental Protection Agency, Washington, DC. October 1988 [online]. Available: http://rais.ornl.gov/homepage/GUIDANCE.PDF [accessed Jan. 30, 2008]. EPA (U.S. Environmental Protection Agency). 1989a. Risk Assessment Guidance for Superfund, Vol. 1. Human Health Evaluation Manual (Part A). EPA/540/1-89/02. Office of Emergency and Remedial Response, U.S. Environmental Protection Agency, Washington, DC. December 1989 [online]. Available: http://www.epa.gov/oswer/riskassessment/ragsa/pdf/rags-vol1-pta_complete.pdf [accessed Jan. 30, 2008]. EPA (U.S. Environmental Protection Agency). 1989b. Short-Term Methods for Estimating the Chronic Toxicity of Effluents and Receiving Waters to Freshwater Organisms, 2nd Ed. EPA 600/4-89/001. Environmental Monitoring Systems Laboratory, U.S. Environmental Protection Agency, Cincinnati, OH. EPA (U.S. Environmental Protection Agency). 1991a. Risk Assessment Guidance for Superfund, Vol. I: Human Health Evaluation Manual, Supplemental Guidance, “Standard Default Exposure Factors.” Interim Final. OSWER Directive 9285.6-03. PB91-921314. Office of Emergency and Remedial Response, U.S. Environmental Protection Agency, Washington, DC. March 25, 1991 [online]. Available: http://www.epa.gov/oswer/riskassessment/pdf/OSWERdirective9285.6-03.pdf [accessed Jan. 30, 2008]. EPA (U.S. Environmental Protection Agency). 1991b. Role of the Baseline Risk Assessment in Superfund Remedy Selection Decisions. OSWER Directive 9355.0-30. Memorandum to Directors: Waste Management Division, Regions I, IV, V, VII, VIII; Emergency and Remedial Response Division, Region II; Hazardous Waste Management Division, Regions III, VI, IX; and Hazardous Waste Division, Region X, from Don R. Clay, Assistant Administrator, Office of Solid Waste and Emergency Response, U.S. Environmental Protection Agency, Washington, DC. April 22, 1991 [online]. Available: http://www.epa.gov/oswer/riskassessment/pdf/baseline.pdf [accessed Jan. 30, 2008]. EPA (U.S. Environmental Protection Agency). 1991c. Methods for Measuring the Acute Toxicity of Effluents and Receiving Waters to Freshwater and Marine Organisms, 4th Ed. EPA-600/4-90/027. Office of Research and Development, U.S. Environmental Protection Agency, Washington, DC. September 1991. EPA (U.S. Environmental Protection Agency). 1992. Guidelines for Exposure Assessment. EPA/600/Z-92/001. Risk Assessment Forum, U.S. Environmental Protection Agency, Washington, DC. May 1992 [online]. Available: http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=15263 [accessed Oct. 10, 2007]. EPA (U.S. Environmental Protection Agency). 1994a. ECO Update: Catalog of Standard Toxicity Tests for Ecological Risk Assessment. EPA 540-F-94-013. Pub. 9345.0-051. Office of Solid Waste and Emergency Response, Washington, DC. Intermittent Bulletin 2(2) [online]. Available: http://www.epa.gov/swerrims/riskassessment/ecoup/pdf/v2no2.pdf [accessed Jan. 30, 2008]. EPA (U.S. Environmental Protection Agency). 1994b. ECO Update: Field Studies for Ecological Risk Assessment. EPA 540-F-94-014. Pub. 9345.0-051. Office of Solid Waste and Emergency Response, Washington, DC. Intermittent Bulletin 2(3) [online]. Available: http://www.epa.gov/swerrims/riskassessment/ecoup/pdf/v2no3.pdf [accessed Jan. 30, 2008].
OCR for page 395
Science and Decisions: Advancing Risk Assessment EPA (U.S. Environmental Protection Agency). 1996. Soil Screening Guidance: User’s Guide, 2nd Ed. OSWER Pub. 9355.4-23. EPA540/R-96/018. Office of Solid Waste and Emergency Response, Washington, DC. July 1996 [online]. Available: http://www.epa.gov/superfund/health/conmedia/soil/pdfs/ssg496.pdf [accessed Jan. 30, 2008]. EPA (U.S. Environmental Protection Agency). 1997a. Exposure Factors Handbook, Vols. 1-3. EPA/600/P-95/002F. Office of Research and Development, National Center for Environmental Assessment, U.S. Environmental Protection Agency, Washington, DC [online]. Available: http://www.epa.gov/ncea/efh/ [accessed June 3, 2007]. EPA (U.S. Environmental Protection Agency). 1997b. Policy for Use of Probabilistic Analysis in Risk Assessment at the U.S. Environmental Protection Agency. U.S. Environmental Protection Agency, Washington, DC. May 15, 1997 [online]. Available: http://www.epa.gov/osa/spc/pdfs/probpol.pdf [accessed June 3, 2007]. EPA (U.S. Environmental Protection Agency). 1998. Guidelines for Ecological Risk Assessment. EPA/630/R-95/002F. Risk Assessment Forum, U.S. Environmental Protection Agency, Washington, DC [online]. Available: http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=12460 [accessed June 3, 2007]. EPA (U.S. Environmental Protection Agency). 1999a. Risk Assessment Guidance for Superfund: Vol. I—Human Health Evaluation Manual (Supplement to Part A): Community Involvement in Superfund RiskAassessments. EPA 540-R-98-042. Office of Solid Waste and Emergency Response, U.S. Environmental Protection Agency, Washington, DC. March 1999 [online]. Available: http://www.epa.gov/oswer/riskassessment/ragsa/pdf/ci_ra.pdf [accessed Jan. 31, 2008]. EPA (U.S. Environmental Protection Agency). 1999b. Superfund Risk Assessment and How You Can Help [videotape]. EPA-540-V-99-002. Office of Solid Waste and Emergency Response, U.S. Environmental Protection Agency, Washington, DC. September. EPA (U.S. Environmental Protection Agency). 2000. Methodology for Deriving Ambient Water Quality Criteria for the Protection of Human Health. EPA-822-B-00-004. Office of Water, Office of Science and Technology, Washington, DC. October 2000 [online]. Available: http://www.epa.gov/waterscience/criteria/humanhealth/method/complete.pdf [accessed Jan. 31, 2008]. EPA (U.S. Environmental Protection Agency). 2001a. Community Involvement Activities Diagram. Superfund, U.S. Environmental Protection Agency. January 2001 [online]. Available: http://www.epa.gov/superfund/community/pdfs/pipeline.pdf [accessed Feb. 1, 2008]. EPA (U.S. Environmental Protection Agency). 2001b. Risk Assessment Guidance for Superfund (RAGS), Volume III, Part A: Process for Conducting Probabilistic Risk Assessment. EPA 540-R-02-002. Office of Emergency and Remedial Response, U.S. Environmental Protection Agency, Washington, DC [online]. Available: http://www.epa.gov/oswer/riskassessment/rags3a/ [accessed Oct 10, 2007]. EPA (U.S. Environmental Protection Agency). 2001c. Comprehensive Five-Year Review Guidance. EPA 540-R-01-007. Office of Emergency and Remedial Response, U.S. Environmental Protection Agency, Washington, DC. June 2001 [online]. Available: http://www.epa.gov/superfund/accomp/5year/guidance.pdf [accessed Jan. 31, 2008]. EPA (U.S. Environmental Protection Agency). 2001d. Record of Decision: Alcoa (Point Comfort)/Lavaca Bay Site Point Comfort, TX. CERCLIS #TXD008123168. Superfund Division, Region 6, U.S. Environmental Protection Agency. December 2001 [online]. Available: http://www.epa.gov/region6/6sf/pdffiles/alcoa_lavaca_final_rod.pdf [accessed Jan. 31, 2008]. EPA (U.S. Environmental Protection Agency). 2001e. Risk Assessment Guidance for Superfund: Vol. I—Human Health Evaluation Manual (Part D, Standardized Planning, Reporting, and Review of Superfund Risk Assessments). Final. Publication 9285.7-47. Office of Emergency and Remedial Response, U.S. Environmental Protection Agency, Washington, DC [online]. Available: http://www.epa.gov/oswer/riskassessment/ragsd/tara.htm [accessed Oct. 11, 2007]. EPA (U.S. Environmental Protection Agency). 2001f. Water Quality Criterion for the Protection of Human Health: Methylmercury. Final. EPA-823-R-01-001. Office of Water, Office of Science and Technology, U.S. Environmental Protection Agency, Washington, DC. January 2001 [online]. Available: http://www.epa.gov/waterscience/criteria/methylmercury/merctitl.pdf [accessed Jan. 31, 2008]. EPA (U.S. Environmental Protection Agency). 2002a. Technology Transfer Network: 1996 National-Scale Air Toxics Assessment. U.S. Environmental Protection Agency [online]. Available: http://www.epa.gov/ttn/atw/nata/ [accessed Aug. 19, 2008]. EPA (U.S. Environmental Protection Agency). 2002b. A Review of the Reference Dose and Reference Concentration Processes. EPA/630/P-02/002F. Risk Assessment Forum, U.S. Environmental Protection Agency, Washington, DC. December 2002 [online]. Available: http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=55365 [accessed Jan. 4, 2008].
OCR for page 396
Science and Decisions: Advancing Risk Assessment EPA (U.S. Environmental Protection Agency). 2002c. Organophosphate Pesticides: Revised Cumulative Risk Assessment. Office of Pesticide Programs, U.S. Environmental Protection Agency. June 10, 2002 [online]. Available: http://www.epa.gov/pesticides/cumulative/rra-op/ [accessed Feb. 4, 2008]. EPA (U.S. Environmental Protection Agency). 2002d. Determination of the Appropriate FQPA Safety Factor(s) in Tolerance Assessment. Office of Pesticide Programs, U.S. Environmental Protection Agency, Washington, DC. February 28, 2002 [online]. Available: http://www.epa.gov/oppfead1/trac/science/determ.pdf [accessed Jan. 25, 2008]. EPA (U.S. Environmental Protection Agency). 2002e. Child-Specific Exposure Factors Handbook. Interim Report. EPA-600-P-00-002B. National Center for Environmental Assessment, Office of Research and Development, U.S. Environmental Protection Agency, Washington, DC. September 2002 [online]. Available: http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=5514 [accessed Feb. 1, 2008]. EPA (U.S. Environmental Protection Agency). 2003a. Technology Transfer Network 1999 National-Scale Air Toxics Assessment: 1999 Assessment Result [online]. Available: http://www.epa.gov/ttn/atw/nata1999/nsata99.html [accessed Aug. 19, 2008]. EPA (U.S. Environmental Protection Agency). 2003b. Human Health Toxicity Values in Superfund Risk Assessments. OSWER Directive 9285.7-53. Memorandum to Superfund National Policy Managers, Regions 1-10, from Michael B. Cook, Director /s/ Office of Superfund Remediation and Technology Innovation, Office of Solid Waste and Emergency Response, U.S. Environmental Protection Agency, Washington, DC. December 5, 2003 [online]. Available: http://www.epa.gov/oswer/riskassessment/pdf/hhmemo.pdf [accessed Feb. 1, 2008]. EPA (U.S. Environmental Protection Agency). 2003c. Developing Relative Potency Factors for Pesticide Mixtures: Biostatistical Analyses of Joint Dose-Response. EPA/600/R-03/052. National Center for Environmental Assessment, Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, OH. September 2003. EPA (U.S. Environmental Protection Agency). 2003d. The Feasibility of Performing Cumulative Risk Assessments for Mixtures of Disinfection By-Products in Drinking Water. EPA/600/R-03/051. National Center for Environmental Assessment, Office of Research and Development, U.S. Environmental Protection Agency, Cincinnati, OH. June 2003 [online]. Available: http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=56834 [accessed Jan. 31, 2008]. EPA (U.S. Environmental Protection Agency). 2004a. An Examination of EPA Risk Assessment Principles and Practices. EPA/100/B-04/001. Office of the Science Advisor, U.S. Environmental Protection Agency, Washington, DC [online]. Available: http://www.epa.gov/OSA/pdfs/ratf-final.pdf [accessed June 3, 2007]. EPA (U.S. Environmental Protection Agency). 2004b. Overview of the Ecological risk Assessment Process in the Office of Pesticide Programs: Endangered and Threatened Species Effects Determinations. Office of Prevention, Pesticides and Toxic Substances, Office of Pesticides Programs, U.S. Environmental Protection Agency, Washington, DC. September 23, 2004 [online]. Available: http://www.epa.gov/oppfead1/endanger/consultation/ecorisk-overview.pdf [accessed Feb. 1, 2008]. EPA (U.S. Environmental Protection Agency). 2004c. Estimated Per Capita Water Ingestion and Body Weight in the United States—An Update. EPA-822-R-00-001. Office of Water, Office of Science and Technology, U.S. Environmental Protection Agency, Washington, DC. October 2004 [online]. Available: http://www.epa.gov/waterscience/criteria/drinking/percapita/2004.pdf [accessed Jan. 31, 2008]. EPA (U.S. Environmental Protection Agency). 2005a. Draft Risk Assessment of the Potential Human Health Effects Associated with Exposure to Perfluorooctanoic Acid and Its Salts. Office of Pollution Prevention and Toxics, U.S. Environmental Protection Agency. January 4, 2005 [online]. Available: http://www.epa.gov/oppt/pfoa/pubs/pfoarisk.pdf [accessed Feb. 4, 2008]. EPA (U.S. Environmental Protection Agency). 2005b. Integrated Exposure Uptake Biokinetic Model for Lead in Children (IEUBKwin v1.0 build 264). Software and Users’ Manuals, U.S. Environmental Protection Agency, Washington, DC. December 2005 [online]. Available: http://www.epa.gov/superfund/lead/products.htm [accessed Jan. 31, 2008]. EPA (U.S. Environmental Protection Agency). 2005c. Guidelines for Carcinogen Risk Assessment. EPA/630/P-03/001F. Risk Assessment Forum, U.S. Environmental Protection Agency, Washington, DC. March 2005 [online]. Available: http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=116283 [accessed Feb. 7, 2007]. EPA (U.S. Environmental Protection Agency). 2005d. Supplemental Guidance for Assessing Susceptibility for Early-Life Exposures to Carcinogens. EPA/630/R-03/003F. Risk Assessment Forum, U.S. Environmental Protection Agency, Washington, DC. March 2005 [online]. Available: http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=160003 [accessed Jan. 4, 2008].
OCR for page 397
Science and Decisions: Advancing Risk Assessment EPA (U.S. Environmental Protection Agency). 2006. A Framework for Assessing Health Risks of Environmental Exposures to Children. EPA/600/R-05/093F. National Center for Environmental Assessment, Office of Research and Development, U.S. Environmental Protection Agency, Washington, DC. September 2006 [online]. Available: http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=158363 [accessed Feb. 1, 2008]. EPA (U.S. Environmental Protection Agency). 2007a. Risk Assessment Practice. Office of Science Advisor, U.S. Environmental Protection Agency [online]. Available: http://www.epa.gov/osa/ratf.htm [accessed Aug. 19, 2008]. EPA (U.S. Environmental Protection Agency). 2007b. Revised N-Methyl Carbamate Cumulative Risk Assessment. Office of Pesticide Programs, U.S. Environmental Protection Agency. September 24, 2007 [online]. Available: http://www.epa.gov/oppsrrd1/REDs/nmc_revised_cra.pdf [accessed Feb. 4, 2008]. EPA (U.S. Environmental Protection Agency). 2007c. Lead Human Exposure and Health Risk Assessment for Selected Case Studies (Draft Report). EPA-452/D-07-001. Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, NC. July 2007 [online]. Available: http://yosemite.epa.gov/opa/admpress.nsf/68b5f2d54f3eefd28525701500517fbf/14ec9929489233f785257329006645c0!OpenDocument [accessed Feb. 4, 2008]. EPA (U.S. Environmental Protection Agency). 2007d. Cleaning Up Our Land, Water and Air. Office of Solid Waste and Emergency Response, U.S. Environmental Protection Agency [online]. Available: http://www.epa.gov/oswer/cleanup/index.html [accessed Feb. 1, 2008]. EPA (U.S. Environmental Protection Agency). 2008a. Ozone (O3) Standards Documents from Review Completed in 2008 Criteria Documents. Technology Transfer Network National Ambient Air Quality Standards, U.S. Environmental Protection Agency [online]. Available: http://www.epa.gov/ttn/naaqs/standards/ozone/s_o3_cr_cd.html [accessed Aug. 19, 2008]. EPA (U.S. Environmental Protection Agency). 2008b. Ozone (O3) Standards Documents from Review Completed in 2008–Staff Papers. Technology Transfer Network National Ambient Air Quality Standards, U.S. Environmental Protection Agency [online]. Available: http://www.epa.gov/ttn/naaqs/standards/ozone/s_o3_cr_sp.html [accessed Aug. 19, 2008]. EPA (U.S. Environmental Protection Agency). 2008c. Ozone (O3) Standards Documents from Review Completed in 2008–Technical Documents. Technology Transfer Network National Ambient Air Quality Standards, U.S. Environmental Protection Agency [online]. Available: http://www.epa.gov/ttn/naaqs/standards/ozone/s_o3_cr_td.html [accessed Aug. 19, 2008]. EPA (U.S. Environmental Protection Agency). 2008d. Office of Pollution, Prevention and Toxics, U.S. Environmental Protection Agency [online]. Available: http://www.epa.gov/oppt/ [accessed Feb. 1, 2008]. EPA (U.S. Environmental Protection Agency). 2008e. Office of Pesticides, U.S. Environmental Protection Agency [online]. Available: http://www.epa.gov/pesticides/ [accessed Feb. 1, 2008]. EPA (U.S. Environmental Protection Agency). 2008f. Cancer Guidances and Supplemental Guidance Implementation. Science Policy Council, Office of Science Advisor, U.S. Environmental Protection Agency [online]. Available: http://www.epa.gov/osa/spc/cancer.htm [accessed Aug. 21, 2008]. EPA (U.S. Environmental Protection Agency). 2008g. About EPA’s Office of Solid Waste and Emergency Response (OSWER). U.S. Environmental Protection Agency [online]. Available: http://www.epa.gov/swerrims/welcome.htm [accessed Aug. 21, 2008]. EPA (U.S. Environmental Protection Agency). 2008h. Superfund. U.S. Environmental Protection Agency [online]. Available: http://www.epa.gov/superfund/index.htm [accessed Feb. 1, 2008]. EPA (U.S. Environmental Protection Agency). 2008i. Superfund Risk Assessment. Office of Solid Waste and Emergency Response, U.S. Environmental Protection Agency [online]. Available: http://www.epa.gov/oswer/riskassessment/risk_superfund.htm [accessed Feb. 1, 2008]. FWS/NMFS (U.S. Fish and Wildlife Service and National Marine Fisheries Service). 2004. Letter to Susan B. Hazen, Principal Deputy Assistant Administrator, Office of Prevention, Pesticides and Toxic Substances, U.S. Environmental Protection Agency, Washington, DC, from Steve Williams, Director, U.S. Fish and Wildlife Service and William Hogarth, Assistant Administrator, National Marine Fisheries Service. January 26, 2004 [online]. Available: http://www.fws.gov/endangered/pdfs/consultations/Pestevaluation.pdf [accessed Feb. 1, 2008]. ICF International. 2006. Risk Assessment for the Halogenated Solvent Cleaning Source Category. Prepared for Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, NC, by ICF International, Research Triangle Park, NC. EPA Contract Number 68-D-01-052. August 4, 2006 [online]. Available: http://www.regulations.gov/search/index.jsp (EPA Docket Document ID: EPA-HQ-OAR-2002-0009-0022) [accessed Feb. 1, 2008]. NCHS (National Center for Health Statistics). 1987. Anthropometric Reference Data and Prevalence of Overweight, United States, 1976-1980. Data from the National Health and Nutrition Examination Survey. Series 11, No. 238. DHHS Publication No. (PHS) 87-1688. U.S. Department of Health and Human Services, Public Health Service, National Center for Health Statistics, Hyattsville, MD (as cited in EPA 2004a).
OCR for page 398
Science and Decisions: Advancing Risk Assessment NRC (National Research Council). 1983. Risk Assessment in the Federal Government: Managing the Process. Washington, DC: National Academy Press. NRC (National Research Council). 1994. Science and Judgment in Risk Assessment. Washington, DC: National Academy Press. NRC (National Research Council). 2000. Toxicological Effects of Methylmercury. Washington, DC: National Academy Press. Sechena, R., S. Liao, R. Lorenzana, C. Nakano, N. Polissar, and R. Fenske. 2003. Asian American and Pacific Islander seafood consumption-A community-based study in King County, Washington. J. Expo. Anal. Environ. Epidemiol. 13(4):256-266. Stanek, E.J. III, and E.J. Calabrese. 1995a. Daily estimates of soil ingestion in children. Environ. Health Perspect. 103(3):276-285. Stanek, E.J., III, and E.J. Calabrese. 1995b. Soil ingestion estimates for use in site evaluations based on the best tracer method. Hum. Ecol. Risk Assess. 1(2):133-156. Stanek, E.J., III, and E.J. Calabrese. 2000. Daily soil ingestion estimates for children at a Superfund site. Risk Anal. 20(5):627-635. TAM Consultants, Inc. 2000. Phase 2 Report: Further Site Characterization and Analysis, Vol. 2F- Revised Human Health Risk Assessment Hudson River PCBs Reassessment RI/FS. Prepared for U.S. Environmental Protection Agency, Region 2, New York, NY, and U.S. Army Corps of Engineers, Kansas City District. November 2000 [online]. Available: http://www.epa.gov/hudson/revisedhhra-text.pdf [accessed Jan. 31, 2008]. Toy, K.A., N.L. Polissar, S. Liao, and G.D. Mittelstaedt. 1996. A Fish Consumption Survey of the Tulalip and Squaxin Island Tribes of the Puget Sound Region. Tulalip Tribes, National Resources Department, Marysville, WA [online]. Available: http://www.deq.state.or.us/WQ/standards/docs/toxics/tulalipsquaxin1996.pdf [accessed Jan. 30, 2008]. van Wijnen, J.H., P. Clausing, and B. Brunekreef. 1990. Estimated soil ingestion by children. Environ. Res. 51(2):147-162.