Cumulative Air Emissions Risk Analysis at the MPCA Background Document

Transcription

1 Cumulative Air Emissions Risk Analysis at the MPCA Background Document Executive Summary Within the Environmental Review Process, the Minnesota Pollution Control Agency (MPCA) is required to conduct a cumulative potential effects evaluation as part of an Environmental Assessment Worksheet (EAW). The cumulative potential effects question of an EAW covers many aspects of the environment such as water quality, invasive species and air quality. For the criteria pollutants (i.e. NOx, SOx, CO, PM 10, PM 2.5, Lead, and Ozone) the analysis done to demonstrate compliance with the National Ambient Air Quality Standards is cumulative in that it includes the facility s emissions, emissions from nearby sources and accounts for background concentrations. For air toxics 1 (and certain criteria pollutants), air quality related cumulative potential effects can be assessed with information from an Air Emissions Risk Analysis (AERA), which analyzes the potential risks from on-site air toxics 1 emissions, and a Cumulative Air Emissions Risk Analysis, which analyzes the potential risks from off-site air toxics 1 emissions. Both an AERA and a Cumulative Air Emissions Risk Analysis may be performed outside the environmental review process (i.e., as part of the permitting process) in order to inform risk management decisions. Risk management decisions are made at various levels at the MPCA depending on the circumstance. The AERA process has health risk goals which are designed to identify those sources, source groups, pollutants and associated exposure pathways that clearly do not pose unacceptable risks or hazards to the public as a result of on-site emissions. Risk goals for cumulative risks are under discussion. In the MPCA risk management process, both the quantitative and qualitative risk assessment results from the AERA and Cumulative Air Emissions Risk Analysis are integrated with other considerations including the inherent limitations of the analysis. Scope The three main objectives of this document are to discuss: The Environmental Quality Board (EQB) regulatory requirement to consider the cumulative potential effects of related or anticipated future projects when deciding the need for an Environmental Impact Statement How the MPCA is implementing this requirement, particularly in light of the Minnesota Supreme Court s decision in Citizens Advocating Responsible Development (CARD) vs. Kandiyohi County. The role of MPCA technical staff and risk managers in informing and/or guiding risk-based decision making for air regulatory and environmental review processes inclusive of cumulative air emissions risk analyses. This document also contains a summary of MPCA s methods for conducting a cumulative air emissions risk analysis and refers the reader to a companion document (How to Conduct a Cumulative Air Emissions Risk Analysis). Cumulative Air Emissions Risk Analysis Applicability A cumulative air emissions risk analysis should be conducted for an EAW in which air emissions are considered. For facilities not completing an EAW, but who are completing an AERA, Agency staff make a determination on a case-by-case basis as to which facilities will complete a cumulative air emissions risk analysis. These decisions are influenced by the following factors: Proposed project emissions (typically greater than 100 tons per year) Data availability and quality Proximity of receptors Presence and location of nearby sources Emissions of nearby sources Ambient air concentrations based on monitoring data This list is not exhaustive and additional information may be considered. 1 Air Toxics is defined for this document using the definition in the AERA Guidance 2007 as A category of substances in the air that are known or suspected of causing cancer or other health problems. MPCA risk assessment staff consider criteria pollutants that are assessed for potential human health effects beyond the Federal and State regulatory criteria pollutant analyses as air toxics (e.g. NO 2 is analyzed as an air toxic with respect to a Minnesota Department of Health acute health index; lead is analyzed as an air toxic with respect to a chronic reference concentration; PM 2.5 should at a minimum be qualitatively discussed for health effects, etc.). aq9-20 March 2009 Minnesota Pollution Control Agency 520 Lafayette Rd. N., St. Paul, MN TTY or Available in alternative formats

2 Regulatory Framework for Cumulative Air Emissions Risk Analyses When determining the need for an environmental impact statement during the environmental review process, Minn. R , subp. 7, item B, states that the Responsible Governmental Unit (RGU) must consider specific factors identified in the rule to decide whether a project has the potential for significant environmental effects. One of these factors is the cumulative potential effects of related or anticipated future projects. The RGU is to identify any past, present or reasonably foreseeable future projects that may interact with the project described in the EAW in such a way as to cause cumulative potential effects. Furthermore, the RGU is asked to describe the nature of the cumulative potential effects and summarize any other available information relevant to determining whether there is potential for significant environmental effects due to cumulative potential effects. In the Minnesota Supreme Court CARD Decision, the Court described how an RGU should apply the rule criterion on cumulative potential effects for determining when to order an Environmental Impact Statement (EIS). Briefly, the court identified the following items that should be included in a cumulative effects analysis as a part of an EAW (Taken from Justice Anderson s Opinion in the CARD decision). A cumulative potential effects inquiry under Minn. R , subp. 7, requires a Responsible Governmental Unit to inquire whether a proposed project, which may not individually have the potential to cause significant environmental effects, could have a significant effect when considered along with other projects that (1) are already in existence or planned for the future; (2) are located in the surrounding area; and (3) might reasonably be expected to affect the same natural resources. The MPCA s Cumulative Risk Analysis Approach The MPCA developed an approach to meet the intent of the environmental review rules and be consistent with the Minnesota Supreme Court s CARD decision. The rationale and the methodology for the MPCA s approach are described below and in the How to Conduct a Cumulative Air Emissions Risk Analysis companion document. Objectives for conducting cumulative air emissions risk analysis The primary objective of the cumulative air emissions risk analysis is to answer the general questions posed by the EAW process, regardless of why the analysis is being done. More specifically, the cumulative air emissions risk analysis process is designed to identify those sources, source groups, pollutants and associated exposure pathways that clearly do not pose unacceptable risks or hazards to the public as a result of cumulative emissions. The MPCA uses its general authorities often in the development of permits and in enforcement actions. Staff requires information, records, data, testing, monitoring, reports and similar submittals to ensure that staff has complete information before making recommendations. Many permits contain facility specific conditions based on the MPCA s general authority to prevent pollution and to protect human health and the environment. The MPCA s general authorities are important tools to insure that MPCA staff has the flexibility to respond to individual situations. In addition, the cumulative air emissions risk analysis supports two MPCA 2008 Strategic Goals: Minnesota s outdoor air quality will meet environmental and human health benchmarks for toxic and other air pollutants. Minnesota reduces its contribution to regional, national and global air pollution. Approach development The MPCA considered the term natural resources (as mentioned by Justice Anderson) and determined that in light of the CARD decision, human receptors are natural resources. A cumulative air emission risk analysis can include evaluations of individual human receptors and/or a population. As a result, all air pollutants and their sources that could potentially cause human health effects need to be considered in the decision for whether there is the potential for significant environmental effects due to cumulative impacts. This broadens the EAW projects definition when considering the potential for significant effects to include all sources of air emissions that could potentially act upon the same human receptors. In developing an approach, the MPCA examined EPA guidance on cumulative risk assessment, relevant literature and past MPCA practices. The EPA does not provide specific guidance on conducting analyses for cumulative potential effects in environmental review or permitting decisions. However, EPA does provide documents describing tools for use in cumulative risk assessments. The EPA s Framework for Cumulative Risk Assessment and EPA s Cumulative Risk Resource Document include descriptions of models, sources to include, criteria for initiating and scoping a cumulative risk analysis. Excerpts from EPA s Framework are provided in Appendix C of this document. Page 2 of 12

3 Consistent with many components of EPA s Framework, the MPCA developed the following subset of EPA s more comprehensive list as components to be considered in a cumulative air emissions risk analysis. The quantitative analysis of the components listed below depends on the specific project, its location, availability of information and emission levels. The project proposers may include other components not listed below that they deem relevant. Components to be considered in a cumulative air emissions risk analysis (The italicized components are also evaluated in MPCA s AERA process for the project.) Multiple pollutants acting by the same mode of action and causing the same effect Multiple media and exposure routes, including food exposures from air pollutants Multiple sources including: On-site: o Existing facility o Proposed project o Vehicle tailpipe emissions and dust suspension (case by case) Off-site: o o o o Vehicle tailpipe emissions and dust suspension (case by case) Point sources that could impact receptors within ten (10) km of a facility Area sources (as defined by MPCA s emissions inventory) that could impact receptors within ten (10) km of a facility Ambient background air concentrations related to sources not associated with sources listed above (e.g. anthropogenic) Summary of approach methodology In the development of this approach, MPCA considered data quality and availability, tool, method, time and resource availability among other technical factors. Much of the methodology for conducting a cumulative air emissions risk analysis fundamentally builds on information used in the AERA process. For example, the pollutant specific health benchmarks used in the cumulative air emissions risk analysis are the same as those used in the AERA process. As in the AERA, the cumulative air emissions risk analysis can be iterative, starting with a conservative screening evaluation (i.e., worst-case scenarios) that identifies pollutants and issues that may require more refined analyses. Pollutants can be excluded from further analysis at any point throughout the refinement process if it is demonstrated that individual excess lifetime cancer risks are less than one in a million (10-6 ) and non-cancer hazard quotients are less than 0.1. The MPCA addresses components from cumulative air emissions risk analyses qualitatively or more quantitatively, depending on the specifics of the project and the available data. For specific direction on how to conduct a site specific analysis, refer to the How to Conduct a Cumulative Air Emissions Risk Analysis document on the Cumulative Air Emissions Risk Analysis website ( The cumulative air emissions risk analysis includes consideration of two general categories of air toxics emissions sources: on-site and off-site. AERA risk results from the on-site existing and proposed emissions sources (including fugitive dust from mobile sources) can be used directly in the cumulative air emissions risk analysis. These risk results are typically from modeled air concentrations. The inclusion of on-site vehicle tailpipe emissions in AERA risk calculations should be decided upon on a case by case basis and is distinct from Prevention of Significant Deterioration (PSD) requirements. The inclusion or exclusion of a quantitative analysis of a specific off-site source can depend on the following factors: population density, proximity of existing facility and receptors to nearby point and area sources, local traffic counts and the potential increase in traffic counts associated with proposed project, availability and quality of data and other potential driving factors. The inclusion or exclusion of off-site point sources in a cumulative air emissions risk analysis is discussed in the EAW language in terms of geography and timing. The MPCA s interpretation of these terms is discussed below, and is the basis for the inclusion or exclusion of off-site point sources. Page 3 of 12

4 Timing Based on the EAW language, the project proposers are asked to include any point sources that are existing air emissions sources at the time of the submission of permit or environmental review materials. A historical facility that has closed down operation and is no longer emitting air pollutants should not be included as a point source in the cumulative air emissions risk analysis. Risks from historically emitted pollutants should be included as risks from monitored data. Potential future projects should be included as point sources for consideration in the cumulative air emissions risk analysis if the facility/project has submitted plans, a permit application or environmental review materials to the State of Minnesota or a more local jurisdiction. Geography Geography is the other area of consideration for the inclusion of projects/facilities in a cumulative air emissions risk analysis. The development of methodology to determine this spatial extent is described in the How to Conduct a Cumulative Air Emissions Risk Analysis document on the Cumulative Air Emissions Risk Analyses website ( The major factors contributing to the inclusion or exclusion of an off-site source on the basis of geography are: distance to receptors of interest, emission rates, dispersion characteristics and the pollutants emitted. Quantitative representation of off-site air toxics sources can be derived from either modeled air concentrations and/or ambient monitoring data. Off-site point sources of air toxics need to be considered in the cumulative air emissions risk analysis within ten kilometers of the proposed project s receptors of maximum impact. Guidance for the quantitative assessment of off-site non-point and mobile sources is under discussion. For some projects, MPCA s statewide cumulative risk modeling results (MNRiskS) can also be used to represent off-site sources based on estimates from emissions inventory information. Each source category can be distinguished and added or subtracted at will. In addition to off-site point sources, MNRiskS modeling includes mobile source and area source emissions. The mobile and area source emissions included in MNRiskS are from the Minnesota emissions inventory and include general flowing traffic. MNRiskS does not contain idling vehicle emissions. When possible, it is most informative to separate results from different sources so that the stakeholders have a more complete picture of potential cumulative risks. This also provides a more complete picture for making risk management decisions. Cumulative air emissions risk analysis limitations Ingestion-based risks from off-site sources are not currently quantitatively assessed in the cumulative air emissions risk analysis process with the exception of cumulative risks from the fish ingestion pathway, e.g. the MPCA Mercury Risk Evaluation Method (MMREM). There are methodological challenges such as source apportionment associated with cumulative ingestion-based risk analyses. The uncertainty associated with these challenges could be propagated with the summation of multiple pathways, routes and endpoints. The MPCA is working on quantifying cumulative risks that take into account background levels of persistent and bioaccumulative toxics from the fish ingestion pathway using Industrial Risk Assessment Program (IRAP-h) view, the MMREM and the MPCA Fish Pollutant Accumulation Spreadsheet System (F- PASS) models. Other issues not addressed by the cumulative air emissions risk analysis are: indoor air quality, pollutants not measured by ambient air monitors (unless modeled), pollutants without health benchmarks, chemical transformation, pollutant interaction effects (e.g. synergistic toxicity, antagonistic absorption, etc.), occupational exposures, personal microenvironmental exposure, etc. Given these limitations, especially when ambient monitoring data is used exclusively to assess off-site risks, these results could be under predictions of risks. Other aspects of the risk assessment process could lead to an over prediction of risk. Risk Management Decisions Risk management is a distinctly different process from risk assessment. It can generally be described as the process by which policy actions to deal with the hazards identified in the risk assessment process are chosen. Risk managers consider scientific evidence and risk estimates, along with statutory, engineering, economic, social and political factors, in evaluating alternative regulatory options and choosing among those options (NRC, 1983). Page 4 of 12

5 In the MPCA risk management process, both the quantitative and qualitative risk assessment results are integrated with other considerations such as policy, legal concerns, economics, analysis limitations and practicality of implementing risk reduction activities. Risk management decisions are made at various levels at the MPCA depending on the circumstance. For example, staff may make mitigation recommendations, yet more complex issues may involve MPCA Board decisions. Cumulative risk goals The EPA guidance for conducting air toxics analyses and making risk management decisions at the facility and communityscale level considers a range of acceptable cancer risks from one in a million to one in ten thousand. The EPA s choice in risk goal depends on a number of factors for example: risk estimates for individuals and the number of people at different risk levels. For non-carcinogenic pollutants, EPA considers a reference level that is developed based on data from laboratory animal or human epidemiology studies, and to which uncertainty factors are applied. The reference level is usually an exposure level below which there are not likely to be any adverse effects from exposure to the pollutant. Exposures above the reference level may have some potential for causing adverse effects. A more complete discussion of EPA s guidance on risk-based decision making is provided as Appendix A of this document. MPCA generally follows EPA s guidance in comparing acceptable risk thresholds to incremental risks 2 estimated for specific projects. The MPCA and Minnesota Department of Health (MDH) collaboratively agree to a cancer risk of one in 100,000 (from an individual facility) and a facility hazard index of 1 as threshold criteria above which further analysis or mitigation should be pursued. These facility based risk thresholds were adopted for project incremental risks without background. In the context of cumulative air emissions risk analysis, thresholds for cumulative risk decisions are still being developed. Several conceptual starting points include: the acceptance of EPA s cancer risk range of one in a million to one in ten thousand; using a hazard index of one for similar non-cancerous human health systemic effects; or developing acceptable risk increments for each source contributing to risk at a selected receptor (similar to the PSD process). In situations where cumulative air emissions risk analysis results exceed thresholds, the MPCA considers options such as mitigation strategies, further model refinement, and/or off-set plans. 2 Incremental risk is the amount of risk that is contributed by the proposed project. Page 5 of 12

6 Appendix A Environmental Protection Agency on Risk Management The US Environmental Protection Agency (EPA) has developed an Air Toxics Risk Assessment (ATRA) reference library 3 (EPA, 2004) for conducting air toxics analyses at the facility and community scale. This library provides information on the fundamental principles of risk-based assessment for air toxics and how to apply those principles in different settings as well as strategies for reducing risk at the local level. The following information is from Volume 1 Technical Resource Manual, Part V. Risk-Based Decision Making 4, and specifically from Chapter 27 on Risk Management; Section 27.4, Use of Risk Estimates in Decision Making 5. Use of risk estimates in decision-making Decision-makers have a number of options when deciding what types of risk estimates to consider as inputs to risk management decisions. Estimates of human health risk generally fall into two categories, estimated cancer risk and the estimated noncancer hazard magnitude of exposure concentration or dietary intake greater than a pre-established reference exposure level), as described in more detail in Chapters 13 and 22. Non-cancer hazard may be considered for both acute (short-term) and chronic (longer-term) exposures. In some cases, ecological risk may be a factor in decision-making. In some situations, risk managers may choose to consider EPA s approach for assessing an ample margin of safety. For cancer risks, EPA generally considers incremental risk (or probability) of cancer for an individual potentially exposed to one or more air toxics. In protecting public health with an ample margin of safety, EPA strives to provide maximum feasible protection against risks to health from Hazardous Air Pollutants (HAP)s by (1) protecting the greatest number of persons possible to an individual lifetime risk level no higher than (one in one million) and (2) limiting to no higher than approximately (one in ten thousand) the estimated risk that a person living near a source would have if exposed to the maximum pollutant concentrations for 70 years. These goals are described in the preamble to the benzene National Emissions Standards for Hazardous Air Pollutants (NESHAP) rulemaking (54 Federal Register 38044, September 14, 1989) and are the goals incorporated by Congress for EPA s residual risk program under Clean Air Act (CAA) section 112(f). Exhibit 27-4 (below) describes some of the key steps in the development of the to carcinogenic risk range. For non-carcinogenic substances, on the other hand, risk managers may consider a reference level that is developed based on data from laboratory animal or human epidemiology studies (see Chapter 12), and to which uncertainty factors are applied. The reference level is usually an exposure level below which there are not likely to be any adverse effects from exposure to the chemical. Exposures above the reference level may have some potential for causing adverse effects. This concept may also be applied generally to ecological risks. Risk estimate options generally revolve around estimates of individual risk, the number of people at different risk levels (population risk), and occasionally include the expected incidence of disease in the entire population. Risk estimates can be derived for the current population as currently distributed in an area or for a population size and geographic distribution that might occur in the future; similarly, they may focus on risk estimates for persons currently exposed or possible risks calculated for a hypothetical individual located where exposures are expected to be relatively high. It is important to note that risk estimates should strive to take into account both indoor and outdoor exposure to toxics, when possible. Risk to a specified individual. Most risk assessments focus on estimating individual risk rather than the incidence of adverse effects (e.g., numbers of predicted cancer cases per year) in a population. There are two general estimates of individual risk: High-end risk estimates seek to determine a plausible worst case situation among all of the individual risks in the population. This estimate is meant to describe an individual who, as a result of where they live and what they do, experiences the highest level of exposure within some reasonable bounds. Reasonable maximum risk estimates are often defined conceptually as above the 90th percentile of the population (4) but not at a higher exposure level than the person exposed at the highest level in the population. When calculated using deterministic methods, the high-end individual is calculated by combining upper-bound and mid-range exposure factors (e.g., an average body weight, but high-end ingestion rate) so that the result represents an exposure scenario that is both protective and reasonable, but not higher than the worst possible case Page 6 of 12

7 Central-tendency risk estimates seek to determine a reasonable average or mid-range situation among all of the individual risks in the population. Many risk management decisions related to exposure to radioactive substances (e.g., in nuclear power plants) are based on central-tendency risk estimates. Note that, when calculating deterministic risk estimates, both a high end and central tendency estimate of risk give the risk manager some sense of the range of risks in the population. When risks to a population are developed using probabilistic methods, this becomes a moot point, since the result is a distribution of risks across the population, which necessarily includes information about the full variability of risk across the population including both high and central tendency risks. See Chapter 31 6 for more information on probabilistic approaches to risk assessment. Risk to the total population. Whether or not risk to the total population is considered by EPA may depend on the regulatory authority provided by the CAA. For example, Section 112(k) of the CAA requires EPA to develop an Urban Air Toxics Strategy to reduce HAPs from area sources to achieve a 75 percent reduction in cancer incidences attributable to such sources. Two general types of descriptors are used for population risk. One, sometimes termed population at risk is derived by determining the number of people in a population with a particular individual risk level (e.g., 1,340,000 people are exposed at the level, and 320 people are exposed at the level ). This is a useful estimate of the variability of risk in a population. Incidence, another descriptor used for population risk, is an estimate of the total number (incidence) of adverse effects in a population over a specified time period (e.g., a period of 70 years). A screening approach to deriving this estimate for a 70-year period involves multiplying the estimate of individual risk (central tendency and/or reasonable maximum) by the number of persons for which that risk estimate was predicted. For example, in a population of 200 million persons, an individual cancer risk of (i.e., one in ten thousand) for everyone in the population would translate to an incidence of hundreds or thousands of excess cancer cases over a 70-year period (depending on the exposure assumptions). However, in a small population (e.g., a town of 200 persons), the same individual cancer risk to everyone would translate to an excess incidence of cancer of less than one over a 70-year period. Present versus future scenarios. Risks may be characterized using present or future scenarios. Use of present scenarios involves predicting risks associated with the current exposures to individuals (or populations) that currently reside in areas where exposures are predicted to occur. For example, a current population risk estimate would use the existing population within some specified area. The resultant risk estimates are associated with the presumption that the current exposure conditions exist for the current population over the period of time associated with the assessment (e.g., into the future). Use of future population scenarios involves estimating risks associated with exposure conditions to individuals that might reside, at some future point, in areas where potential exposures may occur (e.g., if a housing development were built on currently vacant land). Potential risk. Risks may be sometimes be characterized for hypothetical exposures. For example, in a screening air toxics modeling application, a potential risk estimate may be derived using the location where the maximum modeled exposure concentration occurs, regardless of whether there is a person there or not. This estimate may be considered along with the predicted individual risk associated with a currently populated area, such as the MIR, which reflects risk associated with the maximum exposure concentration at an actual residence or in a census block with a non-zero population (see Chapter 11 7 ). Exhibit 27-4: development of the to carcinogenic risk range The 1970 Clean Air Act (CAA) established Section 112 to deal with hazardous air pollutants. Once the EPA Administrator had identified such a pollutant and listed it, he/she was directed to set emission standards for sources emitting it at levels that would provide an ample margin of safety to protect the public health. The regulation of benzene pursuant to Section 112 illustrates the evolution of risk based decision making for carcinogens and the consideration of the ample margin of safety. The EPA listed benzene as a HAP in June 1977 and indicated that the relative risk to the public would be considered in judging the degree of control which can and should be required. In 1980, the first round of benzene standards followed the proposed procedures in EPA s 1979 draft airborne carcinogen policy, which reflected a technology-based approach to emission standard development with a limited role for quantitative risk assessment in establishing priorities and ensuring that the residual risks following the application of best available technology (BAT) were not unreasonable Page 7 of 12

8 In 1984, after weighing all factors, EPA made several changes to the proposed benzene rules, arguing that the risks were too small to warrant Federal regulatory action. These decisions were promptly challenged by the Natural Resources Defense Council, who argued about the uncertainties in the risk estimates and the inappropriate consideration of cost in regulatory decisions made under Section 112. The issues raised were similar to litigation already pending on amendments to the original vinyl chloride standards. On July 28, 1987, Judge Robert Bork, writing for the D.C. Circuit Court of Appeals, remanded the vinyl chloride amendments to EPA, finding that the Agency had placed too great an emphasis on technical feasibility and cost rather than the provision of an ample margin of safety as required by the statute. The opinion also laid out a process for making decisions, consistent with the requirements of the law. The Bork opinion held that EPA must first determine a safe or acceptable level considering only the potential health impacts of the pollutant. Once an acceptable level was identified, the level could be reduced further, as appropriate and in consideration of other factors, including cost and technical feasibility to provide the required ample margin of safety. The Court also held, however, that safe did not require a finding of risk free and that EPA should recognize that activities such as driving a car or breathing city air may not be considered unsafe. In September of 1989, after proposing several options and receiving considerable public comment, EPA promulgated emission standards for several categories of benzene sources. EPA argued for the consideration of all relevant health information and established presumptive benchmarks for risks that would be deemed acceptable. The goal, which came to be known as the fuzzy bright line, is to protect the greatest number of persons possible to an individual lifetime risk no higher than one in 1,000,000 and to limit to no higher than approximately one in 10,000 the estimated maximum individual risk. The selection of even fuzzy risk targets placed greater emphasis on the development and communication of risk characterization results. Source: National Academy of Sciences Science and Judgment in Risk Assessment (The Blue Book).(2) Page 8 of 12

9 Appendix B Environmental Protection Agency on Background Exposures Framework for cumulative risk assessment In 2003 US Environmental Protection Agency (EPA) published a Framework for Cumulative Risk Assessment 8. The Framework is part of a long term effort to develop cumulative risk assessment guidance. The report identifies the basic elements of the cumulative risk assessment process and provides flexible structure for conducting and evaluating cumulative risk assessment, and for addressing scientific issues related to cumulative risk. The following excerpt is from Appendix C: Some Thoughts on Background Exposures 9. When looking at aggregate exposures or cumulative risks of citizens, background exposures to specific chemicals are no less real than the exposures to pollution usually studied for regulatory purposes. Whereas in historical single-chemical assessments conducted for limiting pollution, background sources of the chemical were often irrelevant to the questions being asked of the assessment (or ignored as having negligible effect on risk), background sources in cumulative risk assessments are rarely irrelevant 10. Background concentrations can be categorized as either naturally occurring, that is, chemicals that are naturally present in the environment before it was influenced by humans, or anthropogenic, that is, present in the environment due to historical human-made sources. Naturally occurring background chemicals may be either localized or ubiquitous. Anthropogenic background sources can be either localized from a point source or generalized from unidentified sources or nonpoint sources. Assessments of morbidity incidence and death rates, market basket surveys, and pesticide residue surveys also provide information that can be reflective of background chemical concentrations as well as overt pollution. Background issues extend across all media, beyond regulated sources, and beyond direct exposure. Many chemicals are naturally present in the environment (e.g., soils, water, vegetation, and other biota) and are consequently part of dietary, dermal, and inhalation exposures. In some cases, naturally occurring substances may be present at levels that exceed health-based or risk-based regulatory standards (e.g., drinking water standards) or other levels established to protect human health and the environment. Because cumulative risk assessments are population based, exposures due to naturally occurring background concentrations should typically be considered important. There are several important issues related to natural or anthropogenic background concentrations in cumulative risk assessment. First, if the risks posed by background concentrations of certain chemicals are significant (and some may approach or exceed health reference levels), their exclusion from the cumulative risk estimates and characterization may seriously distort the portion of the total estimated risk thought to be posed to the population by specific evaluated source. A second issue is the problem of whether background chemical exposures can be clearly distinguished from specific sourcerelated chemicals and how to quantify these exposures. It may be important in a cumulative risk assessment to estimate background exposures separately from specific source-related exposures, so that the risk assessor can provide the community with a more complete picture of both total and known source-related risks. This also provides a clearer, more complete picture for making risk management decisions. Finally, there may be problems in identifying representative geographic areas for determining background levels for comparison. Finally, background exposures for a community or population may also include both voluntary and involuntary exposures and subsequent risks. Involuntary exposures are associated with the naturally occurring or anthropogenic background concentrations described above. Voluntary exposures, such as are associated with lifestyle decisions, are exposures due to activities such as smoking, consuming char-grilled meats with polycyclic aromatic hydrocarbons, or other choice-based exposures and may also sometimes be defined in the assessment as background exposures if they are not assessed directly in the cumulative risk assessment Several terms are used to discuss background, and there are several ways to describe different aspects of this issue. It has been suggested (defur, 2002) that a more appropriate term for present conditions is ambient, and that background should be reserved for some untouched, even pristine state or condition. Although the Technical Panel discussed this use of the word background as a pristine reference area, the discussion in this appendix is meant to more closely reflect the way the word is used in practice within EPA. It is acknowledged that not all programs or scientists even within EPA use this term to mean the same thing. 10 The word background is often used to describe exposures to chemicals or other stressors that derive From sources other than the sources being assessed. For example, in the Agency s assessment of residual risk associated with hazardous air pollutant emissions from particular categories of sources that remain after the implementation of technology-based controls, background is defined as all hazardous air pollutant exposures (via inhalation or other routes) not associated with the source(s) being assessed. At a Superfund site, background contamination refers to contamination that is not related to the site release of chemicals, as defined by Comprehensive, Environmental Response, Compensation and Liability Act (CERCLA) (P.L , December 11, 1980, as amended by P.L , August 23, 1983, and P.L , October 17, 1986). Such focusing or segregation in a risk assessment can be useful to decisions involving pollution sources covered by particular statutory authorities, but it is typical of a chemically focused assessment rather than a population-focused assessment such as a cumulative risk assessment. Page 9 of 12

10 Appendix C EPA on Cumulative Risk Assessment The US Environmental Protection Agency (EPA) s Framework for Cumulative Risk Assessment, May In response to the increasing focus on cumulative risk -the combined risks from aggregate exposures to multiple agents or stressors - EPA has begun to explore cumulative approaches to risk assessment. Cumulative risk assessment is an analysis, characterization, and possible quantification of the combined risks to human health or the environment from multiple agents or stressors. EPA will use this Framework as a basis for future guidance as EPA continues with assessment activities related to cumulative risk. The Framework for Cumulative Risk Assessment is the first step in a long-term effort to develop cumulative risk assessment guidance. Building on EPA s growing experience with cumulative risk assessment, the Framework is intended to foster consistent approaches to cumulative risk assessment in EPA, identify key issues, and define terms used in these assessments. The Framework identifies the basic elements of the cumulative risk assessment process and provides a flexible structure for conducting and evaluating cumulative risk assessment, and for addressing scientific issues related to cumulative risk. Although this Framework report will serve as a foundation for developing future guidance, it is neither a procedural guide nor a regulatory requirement within EPA, and it is expected to evolve with experience. The Framework is not an attempt to lay out protocols to address all the risks or considerations that are needed to adequately inform community decisions. Rather, it is an information document, focused on describing various aspects of cumulative risk. Examples of cumulative risk assessments Health risks associated with the aggregate exposure (via all pathways and routes) to insecticides acting by a common mode of action. Human health risks associated with outdoor inhalation exposures of the general population to 33 priority air pollutants nationwide or via all routes to all pollutants present or being released from a hazardous waste site. Human health and ecological risks associated with multiple stressors resulting from developing a site or corridor of land for transportation, infrastructure, or a stationary facility. Human health risks for a specific neighborhood associated with exposure via all routes to all pollutants present or being released from a set of adjacent sources, including several industries, two hazardous waste sites, traffic, and a municipal landfiil Page 10 of 12

11 Appendix D Definitions: AERA: a standardized screening process used by the MPCA to assess risk to human health from toxic air emissions from a facility (on-site). Air Toxics: A category of substances in the air that are known or suspected of causing cancer or other health problems. Background: Background air quality is the general concentration of pollutants in the air, not including the pollutants contributed by the source or sources under review. Carcinogen: An agent capable of inducing a cancer response. Carcinogenic chemicals may act by initiation, promotion, and conversion. CARD: Citizens Advocating Responsible Development (CARD) vs. Kandiyohi County. In what is commonly referred to as the CARD decision, the Court described how a responsible governmental unit should apply the rule criterion on cumulative potential effects for determining whether or not to order an Environmental Impact Statement (EIS). Criteria Pollutants: The pollutants for which EPA has established national ambient air quality standards. The criteria pollutants are: particulate matter less than 10 microns in diameter (PM10), particulate matter less than 2.5 microns in diameters (PM2.5), sulfur dioxide (SO2), oxides of nitrogen (NOx), carbon monoxide (CO), ozone, and lead (Pb). Cumulative Air Emissions Risk Analysis: a standardized screening process used by the MPCA to assess risk to human health from air emissions from a facility (on-site) and off-site air toxics emissions. Cumulative Potential Effects: A cumulative potential effects inquiry under Minn. R , subp. 7, requires a Responsible Governmental Unit to inquire whether a proposed project, which may not individually have the potential to cause significant environmental effects, could have a significant effect when considered along with other projects that (1) are already in existence or planned for the future; (2) are located in the surrounding area; and (3) might reasonably be expected to affect the same natural resources. Cumulative Risk Assessment: an analysis, characterization, and possible quantification of the combined risks to human health or the environment from multiple agents, sources or stressors. EAW: Environmental Assessment Worksheet. An information gathering process that answers the question whether there may be or is potential for significant environmental impact. A part of the environmental review process that is a shorter and less detailed process than an EIS. EIS: Environmental Impact Statement. A more detailed environmental review process than an EAW. Hazard Index: The sum of more than one hazard quotient for multiple substances with the same or similar toxic endpoints. For AERA purposes, at the screening level it is assumed all noncarcinogens have the same or similar toxic endpoint. Hazard Quotient: The ratio of a single substance exposure level to an inhalation health benchmark (IHB) for that substance derived from a similar exposure period (e.g., Conc/IHB, where Conc is the air concentration for a particular contaminant, and the IHB is the inhalation health benchmark (RfC, HRV, etc.). Inhalation Health Benchmark (IHB): A chronic IHB is a concentration in ambient air at or below which a chemical is unlikely to cause an adverse health effect to the general public when exposure occurs daily throughout a person s lifetime. An acute IHB is a concentration in ambient air at or below which a chemical is unlikely to cause an adverse health effect to the general public when exposure occurs over a prescribed period of time. For implementation purposes, acute IHBs are compared to one-hour averaged concentrations. A subchronic IHB is the concentration in ambient air at or below which the chemical is unlikely to cause an adverse health effect to the general public when exposure occurs on a continuous basis over a less than lifetime exposure. For implementation purposes, subchronic IHBs are compared to a monthly averaged concentration. MNRiskS: Minnesota Risk Screening. A screening software system used by the MPCA to assess multi-pathway risks to human health from multiple source types that emit pollutants to the atmosphere. Off-site source: existing or proposed emission sources, including point sources, area sources and mobile sources. Page 11 of 12

12 On-site source: existing or proposed emissions sources (including fugitive dust from mobile sources) on a facility's property Qualitative Analysis: Refers to any pertinent information not represented by the estimated risk values generated by the RASS. The AERA qualitative analysis may include qualitative, semi-qualitative, and quantitative components. Quantitative Analysis: The estimation of cancer risks and hazard indices using the RASS. Risk: Characterizes estimated cancer risks and non cancer health endpoints. Risk Management: "...the process by which policy actions to deal with the hazards identified in the risk assessment process are chosen. Risk managers consider scientific evidence and risk estimates, along with statutory, engineering, economic, social and political factors, in evaluating alternative regulatory options and choosing among those options" (NRC, 1983) Speciation: Chemicals are often a part of a larger group or class, such as polyaromatic Toxic Endpoint: The endpoint of cancer for carcinogens or the organ or physiological system(s) affected by exposure to non-carcinogens. For carcinogenic chemicals, the organ or physiological systems are not differentiated, but all treated as a single endpoint. Page 12 of 12