# Control of Emissions of Hazardous Air Pollutants from Mobile Sources > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A00-18640 ## Record - **Collection:** Federal Register - **Document type:** Proposed Rule - **Published:** August 4, 2000 - **Citation:** 65 FR 48058 ## Text ENVIRONMENTAL PROTECTION AGENCY 40 CFR Parts 80 and 86 [AMS-FRL-6839-2] Control of Emissions of Hazardous Air Pollutants from Mobile Sources AGENCY: Environmental Protection Agency (EPA). ACTION: Notice of proposed rulemaking. SUMMARY: A range of compounds known as hazardous air pollutants are emitted from motor vehicles and fuels and are known or suspected to have serious health impacts. This document describes EPA's program to address emissions of hazardous air pollutants from mobile sources. In this document, we develop a framework to construct a national mobile source air toxics program and propose additional controls on gasoline to prevent increases in emissions of benzene. We also describe a plan to continue to conduct research and analysis on mobile source air toxics and make a commitment to revisit the issue of mobile source air toxics controls in a 2004 rulemaking. More specifically, we look at the various compounds that are emitted by motor vehicles and identify those compounds that should be considered Mobile Source Air Toxics (MSATs). Our list of 21 MSATs includes various volatile organic compounds (VOCs) as well as metal compounds and diesel exhaust. We then evaluate the effectiveness of current controls in reducing on-highway emissions of these MSATs. Our analysis shows that the programs we currently have in place or have recently proposed are expected to yield significant reductions of mobile source air toxics. Between 1990 and 2020, these programs are expected to reduce on-highway emissions of benzene, formaldehyde, 1,3-butadiene, and acetaldehyde by 75 percent or more. In addition, we expect to see on-highway diesel PM emission reductions of over 90 percent. We then consider whether there are additional air toxics controls that should be put in place at this time to further reduce on-highway MSAT inventories. With regard to fuels-based controls, we are proposing a gasoline benzene control program that requires refiners to maintain the current levels of over-compliance with RFG and anti-dumping toxics requirements. Because the proposed standard for each refinery is the same as the 1998-1999 average gasoline benzene level for that refinery, EPA currently anticipates that the proposed standards would impose only negligible costs, if any. With regard to additional vehicle-based controls, we conclude that it is not appropriate at this time to propose more stringent standards than the technology forcing standards found in our recently adopted Tier 2 and recently proposed HD2007 rule standards. Finally, because of our concern about the potential future health impacts of exposure to the public of air toxics from the remaining emissions from mobile sources in the future, including emissions from nonroad equipment and fuels, we propose to continue our toxics-related research activities, in conjunction with other activities currently being conducted by the Agency. These include our National Air Toxics Activities (NATA) and the National Air Toxics Program: The Integrated Urban Strategy (UATS). Under this strategy, EPA will continue to improve our understanding of emissions inventories, assessments of exposure, and the need for and appropriateness of additional mobile source air toxics controls for on-highway and nonroad sources. Based on the information developed through this research, EPA is proposing to conduct a future rulemaking to evaluate whether such additional mobile source air toxic controls should be adopted. This rulemaking would be completed no later than 2004. DATES: Comments: We must receive your written comments on this document by September 20, 2000. Hearings: We will hold a public hearing on August 21, 2000, in Romulus, Michigan. The hearing will begin at 10 am and will continue until all testifiers have spoken. ADDRESSES: Comments: You may send written comments in paper form and/or by e-mail. We must receive them by the date indicated under DATES above. Send paper and/or e-mail copies of written comments (in duplicate if possible) to the contact person listed below. Docket: EPA's Air Docket makes materials related to this rulemaking available for review in Public Docket No. A-2000-12 at the following address: U.S. Environmental Protection Agency (EPA), Air Docket (6102), Room M-1500 (on the ground floor in Waterside Mall), 401 M Street, S.W., Washington, D.C. 20460 between 8 a.m. to 5:30 p.m., Monday through Friday, except on government holidays. You can reach the Air Docket by telephone at (202) 260-7548, and by facsimile (202) 260-4400. We may charge a reasonable fee for copying docket materials, as provided in 40 CFR part 2. Hearings: We will hold a public hearing at the Crowne Plaza Detroit-Metro Airport Hotel, 8000 Merriman Road, Romulus, Michigan 48174. We request that parties who want to testify at a hearing notify the contact person listed below ten days before the date of the hearing. Please see section IX, “Public Participation” below for more information on the comment procedure and public hearings. FOR FURTHER INFORMATION CONTACT: Carol Connell, U.S. EPA, National Vehicle and Fuels Emission Laboratory, 2000 Traverwood, Ann Arbor, MI 48105; Telephone (734) 214-4349; FAX: (734) 214-4816; E-mail: connell.carol@epa.gov SUPPLEMENTARY INFORMATION: Regulated Entities This proposed action would affect you if you produce new motor vehicles, alter individual imported motor vehicles to address U.S. regulation, or convert motor vehicles to use alternative fuels. It would also affect you if you produce, distribute, or sell gasoline motor fuel. The table below gives some examples of entities that may have to follow the proposed regulations. But because these are only examples, you should carefully examine the proposed and existing regulations in 40 CFR parts 80 and 86. If you have questions, call the person listed in the FOR FURTHER INFORMATION CONTACT section above. Category NAICS codes 1 SIC codes 2 Examples of potentially regulated entities Industry 336111 3711 Motor Vehicle Manufacturers. 336112 336120 Industry 336311 3592 Alternative Fuel Vehicle Converters. 336312 3714 422720 5172 454312 5984 811198 7549 541514 8742 541690 8931 Industry 811112 7533 Commercial Importers of Vehicles and Vehicle Components. 811198 7549 541514 8742 Industry 324110 2911 Petroleum Refiners. Industry 422710 5171 Gasoline Marketers and Distributors. 422720 5172 Industry 484220 4212 Gasoline Carriers. 484230 4213 1 North American Industry Classification System (NAICS). 2 Standard Industrial Classification (SIC) system code. Access to Rulemaking Documents through the Internet: Today's document is available electronically on the day of publication from the Office of the Federal Register Internet Web site listed below. Electronic copies of the preamble, regulatory language and other documents associated with today's proposal are available from the EPA Office of Transportation and Air Quality Web site listed below shortly after the rule is signed by the Administrator. This service is free of charge, except any cost that you already incur for Internet connectivity. Federal Register Web Site: http://www.epa.gov/docs/fedrgstr/epa-air/ (Either select a desired date or use the Search feature) Office of Transportation and Air Quality (OTAQ) Web Site: http://www.epa.gov/otaq (Look in “What's New” or under the specific rulemaking topic) Please note that due to differences between the software used to develop the document and the software into which the document may be downloaded, changes in format, page length, etc., may occur. Outline of this Preamble I. Introduction A. Background B. Brief Overview of Air Toxics C. Basic Components of Today's Proposal 1. Identification of Mobile Source Air Toxics 2. Assessment of Emission Benefits from Current Standards 3. Consideration of Additional Controls at This Time 4. Technical Analysis Plan and Future Rulemaking 5. Nonroad Air Toxics D. EPA's Statutory Authority for Proposing Today's Action E. Motor Vehicle Air Toxics Studies F. Other Air Toxics Activities 1. Integrated Urban Air Toxics Strategy 2. National Air Toxics Assessment II. What Are the Mobile Source Air Toxics? A. Introduction B. The Methodology Used to Identify Our List of Mobile Source Air Toxics 1. Identifying Pollutants Emitted From Mobile Sources 2. Using IRIS to Identify Pollutants With Potential Adverse Health Effects C. List of Mobile Source Air Toxics D. How Our List of MSATs Compares to Other Lists or Sources of Data on Toxics E. Diesel Health Assessment Document F. Diesel Exhaust and Diesel Particulate Matter III. How Are Motor Vehicle Emission Control Programs Reducing MSAT Emissions? A. Baseline Inventories B. Impacts of Motor Vehicle Emission Controls on Emissions Inventories 1. Description of Emission Control Programs 2. Emission Reductions From Control Programs C. Summary IV. Evaluation of Additional Motor Vehicle-based Controls A. MSATs and Motor Vehicle-based Controls B. EPA's Motor Vehicle-based Emission Control Program 1. Light-duty Vehicles 2. Heavy-duty Vehicles C. Feasibility of More Stringent Vehicle-based Standards to Reduce MSATs 1. Light-duty Vehicles 2. Heavy-duty Vehicles 3. Conclusion V. Evaluation of Additional Fuel-based Controls A. What Current Gasoline Programs Control Toxics Emissions? B. Why Is EPA Focusing on Benzene? C. Given the Existing Over-compliance, Why Is EPA Considering Additional Gasoline Benzene Controls? D. What Type of Gasoline Control Program Is EPA Proposing Today? E. Will the Proposed Benzene Standards Pre-Empt State Benzene Controls? F. What Are the Expected Impacts of EPA's Proposed Program? G. Determination of the Need for Future Controls Deferred to Technical Analysis Plan and Future Rulemaking H. What Are the Details of Today's Proposed Program? 1. Standards and Dates 2. Entities Subject to the Proposed Regulation 3. California Gasoline 4. Proposed Baseline Development and Submittal Requirements 5. Flexibility Provisions 6. Downstream Standards 7. Sampling and Testing 8. Recordkeeping and Reporting Requirements 9. Exemptions for Research, Development, and Testing 10. Liability and Penalty Provisions for Noncompliance I. Toxics Performance Standard VI. Nonroad Sources of MSAT Emissions A. Nonroad MSAT Baseline Inventories B. Impacts of Current Nonroad Mobile Source Emission Control Strategies 1. Description of the Emission Control Programs 2. Emission Reductions From Current Programs C. Gaps in Nonroad Mobile Source Data D. Summary VII. Technical Analysis Plan to Address Data Gaps and Reopening of Rulemaking A. Technical Analysis Plan to Address Data Gaps B. Commitment for Further Rulemaking VIII. Public Participation A. Comments and the Public Docket B. Public Hearings IX. Administrative Requirements A. Administrative Designation and Regulatory Analysis B. Regulatory Flexibility Act C. Paperwork Reduction Act D. Intergovernmental Relations 1. Unfunded Mandates Reform Act 2. Executive Order 13132: Federalism 3. Executive Order 13084: Consultation and Coordination With Indian Tribal Governments E. National Technology Transfer and Advancement Act F. Executive Order 13045: Children's Health Protection X. Statutory Provisions and Legal Authority I. Introduction A. Background The 1990 Clean Air Act Amendments provide a key part of the foundation for our current national air toxics program. The Act provides a statutory framework designed to characterize, prioritize, and address the serious impacts of hazardous air pollutants (HAPs) on the public health and the environment through a strategic combination of regulatory approaches, partnerships, ongoing research and assessments, risk initiatives, and education and outreach. Since 1990, our national air toxics control program for stationary sources has consisted primarily of technology-based emissions standards to reduce emissions of toxic air pollutants from major stationary sources, as required in section 112(d) of the Act. These actions have resulted, or are projected to result, in substantial reductions in HAP emissions. Mobile source regulatory actions have also resulted in significant reductions of air toxics since 1990. In general, these mobile source air toxic reductions have been achieved through the implementation of controls put in place primarily to achieve attainment of the National Ambient Air Quality Standards (NAAQS) for ozone, particulate matter (PM), and carbon monoxide (CO). For example, hydrocarbon controls for motor vehicles to reduce ozone formation also reduce emissions of gaseous air toxics such as benzene, 1,3-butadiene, and formaldehyde. Mobile source PM controls on diesel engines have considerably reduced diesel exhaust emissions as well. Additional toxics reductions have been achieved through fuel controls, including the federal reformulated gasoline (RFG) program, and through refiner over-compliance with toxics requirements of our RFG and conventional gasoline programs. Today's proposal takes our mobile source toxics control program a step further by considering more specifically the contribution mobile sources make to national inventories of specific air toxics and by evaluating the appropriateness of setting additional standards to reduce contributions from on-highway vehicles. In performing our analysis of additional controls, we will follow the requirements specified in section 202(l)(2) of the Act: these motor vehicle or motor fuel standards must “reflect the greatest degree of emission reduction achievable through the application of technology which will be available, taking into consideration the standards established under [section 202(a)], the availability and costs of the technology, and noise, energy, and safety factors, and lead time.” Our program is also consistent with the National Air Toxics Program: The Integrated Urban Strategy (also called the Urban Air Toxics Strategy, or UATS) published July 19, 1999 (64 FR 38706). With this background, we now turn to an overview of today's proposal. Section I of this preamble will give you a brief overview of our proposal and the rationale for proposing it. Subsequent sections expand on the identification of mobile source air toxics (MSATs), the impact of current and proposed motor vehicle emission control programs on MSAT emissions, and the evaluation of additional control programs for motor vehicles and their fuels. Additional sections deal with the contribution of nonroad engines to MSAT inventories and our plan to continue to evaluate MSAT emissions and evaluate the appropriateness of setting additional air toxics control standards in the future. The final sections deal with several subjects, including opportunities for public participation. B. Brief Overview of Air Toxics Before proceeding to a summary of today's action, we want to provide a brief overview of air toxics: what they are, their general health and environmental effects, and their sources. Today's action addressing motor vehicle air toxics occurs in the context of extensive earlier air toxics work, primarily relating to stationary sources of these pollutants. These topics are discussed in more detail later in this proposal and in the draft TSD. • What are air toxics? Air toxics, which are also known as “hazardous air pollutants” or HAPs, are those pollutants known or suspected to cause cancer or other serious health or environmental effects. They include pollutants like benzene found in gasoline, perchloroethylene emitted from dry cleaners, methylene chloride used as an industrial solvent, heavy metals like mercury and lead, polychlorinated biphenyls (PCBs), dioxins and some pesticides. While the harmful effects of air toxics are of particular concern in areas closest to where they are emitted, they can also be transported and affect other geographic areas. Some can persist for considerable time in the environment and/or bioaccumulate in the food chain. • What are the sources of air toxics? There are literally millions of sources of air toxics, including: major stationary sources 1 such as large industrial complexes like chemical plants, oil refineries and steel mills; small (area) stationary sources 2 such as dry cleaners, gas stations, and small manufacturers; and mobile sources such as cars, trucks, buses, and nonroad vehicles such as construction and farm equipment. 1 Major stationary sources are sources that emit, or have the potential to emit, 10 tons per year or more of any one HAP or 25 tons per year or more of a combination of HAPs. 2 Area sources are those stationary sources that are not major sources. • What health and environmental effects do air toxics cause? Hazardous air pollutants can cause many ill health effects. Many of these substances are known or suspected to be human carcinogens. Some of these chemicals are known to have negative effects on people's respiratory, neurological, immune, or reproductive systems. Some chemicals pose particular hazards to people with preexisting illnesses, or those of a certain age or stage in life, such as children or the elderly. • What are mobile source air toxics? We use the term “mobile source air toxics,” or “MSATs,” to signify those air toxics are emitted by nonroad engines and motor vehicles. Section 202(l) of the Act, which addresses controls for hazardous air pollutants from motor vehicles and motor vehicle fuels, does not specify which pollutants are to be evaluated as air toxics, other than benzene, formaldehyde, and 1,3-butadiene. As a result, the first thing a mobile source air toxics control program must do is develop a list of compounds to be addressed. Using the methodology described in section II of this proposal, we have identified 21 mobile source air toxics (MSATs), listed in Table I-1 below. Of our 21 MSATs, thirteen (those marked with an asterisk in Table I-2) are also included on the list of urban HAPs for the Urban Air Toxics Strategy (see below). Of the remainder, all but one are specifically identified in the CAA section 112(b) HAP list. Diesel exhaust is not included in these other two lists because this pollutant was not included by Congress in the section 112(b) HAP list and, consequently, was not included in the group of pollutants that were considered for inclusion in the urban HAP list. It is, however, a pollutant that we identified in the UATS as a concern in urban areas. Table I-1.—List of Mobile Source Air Toxics (MSATs) Acetaldehyde a Diesel Exhaust MTBE. Acrolein a Ethylbenzene Naphthalene. Arsenic compounds a Formaldehyde a Nickel compounds. a Benzene a n-Hexane POM (Sum of 7 PAHs) a 1,3-Butadiene a Lead compounds a Styrene. Chromium compounds a Manganese compounds a Toluene. Dioxin/Furans a Mercury compounds a Xylene. a Also on the list of urban HAPs for the Urban Air Toxics Strategy. • How are air toxics from mobile sources formed? Mobile source air toxics come from four sources. First, some air toxics are present in fuel and are emitted to the air when it evaporates or passes through the engine as unburned fuel. Benzene, for example, is a component of gasoline. Cars emit small quantities of benzene in unburned fuel, or as vapor when gasoline evaporates. Second, mobile source air toxics are formed through engine combustion processes. A significant amount of automotive benzene comes from the incomplete combustion of compounds in gasoline such as toluene and xylene that are chemically very similar to benzene. Like benzene itself, these compounds occur naturally in petroleum and become more concentrated when petroleum is refined to produce high octane gasoline. Diesel exhaust emissions, as well as formaldehyde, acetaldehyde, and 1,3-butadiene, are also by-products of incomplete combustion. Third, some compounds, like formaldehyde and acetaldehyde, are also formed through a secondary process when other mobile source pollutants undergo chemical reactions in the atmosphere. Finally, metal air toxics result from engine wear or from impurities in oil or gasoline. They can also be present in fuel additives. • What are the Urban HAPs? The urban HAPs are the 33 compounds that have been identified by the Agency in the Urban Air Toxics Strategy (UATS) 3 as those HAPs posing the greatest threat to human health in the largest number of urban areas. These compounds are a subset of the 188 compounds listed in section 112(b) of the Clean Air Act. The 33 urban HAPs are as follows: 3 National Air Toxics Program: The Integrated Urban Strategy; Notice (64 FR 38706-38740 (19 July 1999)). Table I-2.—List of Urban HAPs for the Urban Air Toxics Strategy Acetaldehyde Coke oven emissions Mercury compounds Acrolein 1,2-dibromomethane Methylene chloride (dichloromethane). Acrylonitrile 1,2-dichloropropane (propylene dichloride) Nickel compounds. Arsenic compounds 1,3-dichloropropene Polychlorinated biphenyls (PCBs). Benzene Ethyl dichloride (1,2-dichloroethane) Polycyclic organic matter (POM). Beryllium compounds Ethylene oxide Quinoline. 1,3-Butadiene Formaldehyde 1,2,7,8-tetrachlorodibenzo-p-dioxine (and cogeners and TCDF cogeners). Cadmium compounds Hexachlorobenzene 1,2,2,2-tetrachloroethane. Carbon tetrachloride Hydrazine Tetrachloroethylene (perchloroethylene). Chloroform Lead compounds Trichloroethylene. Chromium compounds Manganese compounds Vinyl chloride. C. Basic Components of Today's Proposal Many motor vehicle and fuel emission control programs of the past have reduced air toxics. EPA has recently created or proposed several programs that further reduce air toxics emissions from a wide variety of mobile sources. These include our reformulated gasoline (RFG) program, which has substantially reduced mobile source air toxics in certain areas of the country, our national low emission vehicle (NLEV) program, our Tier 2 motor vehicle emissions standards and gasoline sulfur control requirements, and our recently proposed heavy-duty engine and vehicle standards and on-highway diesel fuel sulfur control requirements. In addition, certain other mobile source control programs have been specifically aimed at reducing toxics emissions ( i.e. , our lead phase-out programs). While these mobile source standards were put in place primarily to reduce ozone and particulate matter inventories through VOC and diesel PM controls, and thereby to help states and localities come into attainment with the National Ambient Air Quality Standards (NAAQS), they have reduced and will continue to reduce on-highway emissions of gaseous air toxics very significantly. 4 By 2020, these programs are expected to reduce 1990 levels of on-highway emissions of benzene by 75 percent, formaldehyde by 87 percent, 1,3-butadiene by 75 percent, and acetaldehyde by 82 percent. 4 Included among the numerous chemicals that make up total VOC emissions—that thus are reduced when VOCs are reduced—are several gaseous toxics ( e.g. , benzene, formaldehyde, 1,3-butadiene, and acetaldehyde). In addition, we have issued or proposed regulations to control diesel particulate matter (diesel PM) emissions from mobile sources, including the recent light- and heavy-duty vehicle programs mentioned above. By 2020, we expect to see on-highway diesel PM emission reductions of 94 percent from 1990 levels. Nevertheless, there is a continuing public health concern about the ambient levels of several key air toxics. Today's proposal therefore contains a plan to address mobile sources of these air toxics. We begin by considering the different kinds of emissions from motor vehicles and identifying a list of compounds that should be considered Mobile Source Air Toxics (MSATs). We then evaluate the effectiveness of current and proposed controls in reducing on-highway emissions of these MSATs. We then consider whether there are additional air toxics controls that should be put in place at this time to reduce on-highway MSAT inventories even more. Based on this assessment, we are proposing standards that will require individual refiners to maintain their current gasoline benzene content levels. Finally, we describe a process to conduct research and analysis to continue to assess the need for and feasibility of additional mobile source air toxics controls. We are proposing to conduct another rulemaking to be completed by December 2004, based on the additional research and analysis we conduct and any additional information that becomes available in that timeframe. That future rulemaking would re-evaluate the various decisions on motor vehicle and fuel air toxics controls made in this rulemaking. 1. Identification of Mobile Source Air Toxics There are hundreds of different compounds and elements that are known to be emitted from passenger cars, on-highway trucks, and various types of nonroad equipment. Today's action identifies a list of pollutants known to be emitted from motor vehicles or their fuels and considered by EPA to pose potential adverse human health risks. This list is not intended to be a fixed one; additional compounds may be added to the list, in a future rulemaking, as we learn more about the pollutants emitted from mobile sources and the health effects of those pollutants. Similarly, compounds may be removed from the list if new information on the pollutants emitted by mobile sources or their health effects supports a different conclusion. Based on the available data, we are proposing a list of 21 mobile source air toxics (MSATs). We are requesting comment both on the list we have developed and on our approach to developing that list. 2. Assessment of Emission Benefits From Current Standards Once we identified the MSATs, we were able to assess the impact that current and future mobile source controls will have on national emissions inventories of these pollutants. Today's action describes how our current mobile source emission control programs are expected to reduce these emissions. The very good news is that, by 2020, we expect existing programs like the reformulated gasoline (RFG) program, national low emission vehicle (NLEV) program, Tier 2 motor vehicle emissions standards and gasoline sulfur control requirements (Tier 2), and our recently proposed heavy-duty engine and vehicle standards and on-highway diesel fuel sulfur control requirements (HD2007 rule), to significantly reduce on-highway emissions of key air toxics. Between 1990 and 2020, these programs are expected to reduce on-highway emissions of benzene by 75 percent, formaldehyde by 87 percent, 1,3-butadiene by 75 percent, and acetaldehyde by 82 percent. In addition, we expect to see on-highway diesel PM emission reductions of 94 percent. 3. Consideration of Additional Controls at This Time Although we anticipate substantial reductions in emissions of key toxic pollutants by 2020, the serious health effects associated with many of these compounds lead us to evaluate whether additional controls are appropriate at this time. For the purpose of our analysis, we divide potential control measures into two broad categories: vehicle-based controls and fuel-based controls. Vehicle-based controls include programs that would reduce evaporative and exhaust emissions from vehicles and engines. Fuel-based controls explore how changing fuel formulation can reduce air toxic emissions. The only toxics control program we are proposing today is fuel-based. Specifically, we are proposing to require refiners and importers to maintain the gasoline benzene content of the fuel they produce or import at the current benzene levels of such gasoline for the foreseeable future. We are also seeking comment on whether additional volumes of gasoline produced above the volumes produced in a baseline year should be subject to a different benzene standard. The overall goal of this program is to ensure that benzene emissions due to gasoline fuel benzene do not increase above current emission levels. The details of this program are discussed in section V below, as well as the various vehicle and fuel controls EPA has considered. With regard to vehicle-based air toxics controls, EPA believes that it is not appropriate at this time to propose additional motor vehicle or fuel based controls under section 202(l)(2), beyond the controls currently adopted or proposed by the Agency. This is based on consideration of the technical feasibility, cost, and other factors relevant to a proposal of further controls at this time. EPA is also proposing a regulatory provision providing for a future rulemaking that would determine, based on the information available at that time, whether additional motor vehicle or fuel controls would be appropriate under section 202 (l)(2) to control emissions of hazardous air pollutants from motor vehicles and their fuels. Finally, the rulemaking would consider the contribution of nonroad engines to emissions of air toxics and whether controls that reduce these emissions along with motor vehicle emissions are appropriate under the Act. 4. Technical Analysis Plan and Future Rulemaking We believe our evaluation to date of the need for, and appropriateness of, additional mobile source toxics control measures provides adequate support for today's proposal. At this time, EPA is also engaged in other toxics-related research activities through the NATA activities and the UATS described below. This emerging information will help us in further evaluating potential additional mobile source air toxics controls in the future. In light of this ongoing work, we are proposing to conduct a Technical Analysis Plan as described in section VII below. This Plan would coordinate work within the Agency in several key areas, including development of emission factors for nonroad sources, analysis of toxics exposures in microenvironments, and examination of additional fuel- and vehicle-based air toxics controls for both motor vehicles and engines and nonroad engines. This work would be fully coordinated with the new work with NATA and the UATS. This will allow us to take full advantage of what is collectively learned and provide a solid basis for future rulemaking. The results of this research and analysis would form the basis of a future rulemaking, as discussed below. 5. Nonroad Air Toxics While section 202(l)(2) of the Act specifies that we set standards to control hazardous air pollutants from motor vehicles and motor vehicle fuels, we believe it is also necessary to discuss nonroad sources in today's proposal, making it a comprehensive mobile source air toxics program, for two important reasons. First, today's proposal is intended to be a companion piece to EPA's Urban Air Toxics Strategy. As described above, the Urban Air Toxics Strategy is intended to address air toxics inventories in urban areas. Because both on-highway and nonroad engines contribute to those inventories, it is important to address both categories in a comprehensive strategy to reduce urban air toxics. Second, currently available data suggests that nonroad sources contribute approximately the same amount to national inventories of key air toxics as on-highway sources. Therefore, a comprehensive control strategy must include nonroad sources. Section 213 of the Act allows us to control emissions from those classes or categories of new nonroad engines that cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare. To the extent emissions of MSAT from these engines is found to cause or contribute to air pollution problems, EPA may decide to adopt further nonroad controls in the future, as specified in section 213 of the Act. At the same time, while we are including nonroad sources in our discussions of inventory impacts and expected reductions from current nonroad emission control strategies, we are not proposing new emission control standards for these engines in this proposal. This is because we are lacking relevant data that are required to assess the appropriateness of additional MSAT controls. These include speciation data for some categories of nonroad engines, geographic dispersion of emissions, and information, including cost information, about technologies that can reduce these emissions further. Our Technical Analysis Plan, described below, would help us obtain the data we need to consider and in the future evaluate whether additional nonroad air toxics controls are needed and appropriate. D. EPA's Statutory Authority for Proposing Today's Action We are proposing today's action under the authority of section 202(l) of the Clean Air Act. The gasoline benzene standards in today's action are proposed under section 211(c) of the Clean Air Act. Section 202(l) of the Act consists of two parts. Section 202(l)(1) calls on EPA to study the need for and feasibility of controlling toxic air pollutants associated with motor vehicles and motor vehicle fuels. That study is to focus on those categories of emissions that pose the greatest risk to human health or about which significant uncertainties remain. The Act specifies that, at a minimum, the study focus on emissions of benzene, formaldehyde, and 1,3-butadiene. Section 202(l)(2) instructs us to set standards to control hazardous air pollutants from motor vehicles, motor vehicle fuels, or both. These standards, which may be revised from time to time, are to reflect the greatest degree of emission reduction achievable through the application of technology which will be available, taking into consideration the motor vehicle standards established under section 202(a) of the Act, the availability and cost of the technology, and noise, energy and safety factors, and lead time. The regulations are to apply, at a minimum, to benzene and formaldehyde emissions. We completed the study required under section 202(l)(1) in April 1993. The report, entitled “Motor Vehicle-Related Air Toxics Study,” is available on our website (http://www.epa.gov/otaq/toxics.htm). Specific pollutants or pollutant categories discussed in this report include benzene, formaldehyde, 1,3-butadiene, acetaldehyde, diesel particulate, gasoline particulate, gasoline vapors, and selected metals. The emissions and exposure aspects of this report were recently updated in November 1999 for several of the air toxics covered in the 1993 study. That report, entitled “Analysis of the Impacts of Control Programs on Motor Vehicle Toxics Emissions and Exposure in Urban Areas and Nationwide,” is also available on our website, and is described in more detail in section I.E., below. We sought peer review comments on both the 1993 and 1999 studies. We considered the 1993 comments in developing the 1999 document and will consider the 1999 comments in developing our future activities (e.g., in the development of version 4 of the Hazardous Air Pollutant Exposure Model, HAPEM4). Today's action is pursuant to section 202(l)(2). In this action, we identify a list of MSATs and discuss the impacts of existing mobile source emission control programs on their emissions. In a separate rulemaking, the HD2007 rule, we are proposing stringent emission standards that would lead to significant reductions of the gaseous and PM components in diesel exhaust emissions. In today's proposal, we are proposing standards to maintain the benzene content of gasoline fuel at 1998-1999 levels for volumes produced in that time period. We are also seeking comment on whether additional volumes of gasoline produced above the volumes produced in a baseline year should be subject to a different benzene standard. Today's proposal is based on all the information EPA has available at this time. EPA recognizes that there are various gaps in the data, and that further analysis and evaluation would be useful in evaluating the appropriateness of and need for additional future controls on motor vehicles or their fuels. Given the important contribution of mobile sources to the national inventory of air toxics, we are proposing a plan to conduct this additional work in the near future. The results of this additional research would form the basis for a future rulemaking to re-evaluate the question of whether additional controls on motor vehicles and nonroad engines or their fuels are appropriate under the Act based on all of the information available to the Agency at that time. E. Motor Vehicle Air Toxics Studies In 1993, EPA released a study of motor vehicle-related air toxics in compliance with section 202(l)(1) of the Clean Air Act. 5 The study provided estimates of motor vehicle emissions of several pollutants believed to pose the greatest risk to public health. Using these estimates of emissions, the study modeled the exposure and risk attributable to motor vehicle emissions and projected emissions, exposures, and risk for the year 2010. 5 EPA, 1993. Motor Vehicle-Related Air Toxics Study. Report No. EPA 420-R-93-005. This report can be accessed at http://www.epa.gov/otaq/toxics.htm. Peer review of this study was completed in 1994. 6 The comments from the peer review included suggestions for improving EPA's exposure modeling and risk assessment methodology. In response to these comments, EPA updated its exposure model for motor vehicle-related air toxics. Also, since 1993, significant new information on vehicle emission rates has been developed as part of the Auto/Oil program, the development of the Complex Model for reformulated gasoline, CARB test programs, and other sources, and much more is known about the impact of fuel properties on toxic emissions. Furthermore, EPA has developed new programs, such as the NLEV and Tier 2 standards, which have significant effects on projections of toxic emissions and exposure. Finally, EPA has released an updated cancer risk assessment for benzene, a draft reassessment for 1,3-butadiene, and a draft assessment for diesel exhaust emissions. 7, 8, 9, 6 Peer review comments on the 1993 study can be accessed at http://www.epa.gov/otaq/toxics.htm. 7 EPA 1998. Environmental Protection Agency, Carcinogenic Effects of Benzene: An Update, National Center for Environmental Assessment, Washington, DC. 1998. This report can be accessed at http://www.epa.gov/ncea/benzene.htm. 8 EPA 1998. Environmental Protection Agency, Health Risk Assessment of 1,3-Butadiene. EPA/600/P-98/001A, February 1998. This report can be accessed at http://www.epa.gov/ncea/butadiene.htm. 9 EPA 1999. Health Assessment Document for Diesel Emissions: SAB Review Draft. EPA/600/8-90/057D Office of Research and Development, Washington, D.C. The document is available electronically at www.epa.gov/ncea/diesel.htm. In light of all of this new information that has been developed since 1993, and in response to peer review comments, EPA has updated the estimates of emissions and exposure contained in the 1993 study. 10 The Agency is making further efforts to improve its understanding of toxic emissions, exposure, and risk associated with on-highway vehicles, nonroad equipment, and other sources as part of the National Air Toxics Assessment (NATA) process discussed below. 10 Analysis of the Impacts of Control Programs on Motor Vehicles Toxics Emissions and Exposure in Urban Areas and Nationwide (Volumes 1 and 2), November 1999. EPA420-R-99-029/030. In the above air toxics studies, there are limitations in how ranges of exposures are modeled or characterized. For instance, the screening models the Agency has used do not consider “hotspots” for elevated air toxics concentrations. For this reason, EPA has not been able to conduct a complete exposure assessment. The Agency also needs to do more work on considering the costs and performance levels of pollution controls on air toxics. These activities would be included in the proposed Technical Analysis Plan discussed later in this preamble. F. Other Air Toxics Activities As we developed and prepared today's mobile source air toxics program, we worked in the context of two other important activities that are ongoing at the Agency. These are EPA's Integrated Urban Air Toxics Strategy (UATS) development and the National Air Toxics Assessment (NATA) activities. Because these two programs are also important parts of our efforts to reduce toxic emissions from all sources, this section contains a brief summary of their key components. Interested readers are encouraged to visit EPA's Toxics website for more information about these programs (www.epa.gov/otaq/toxics.htm). 1. Integrated Urban Air Toxics Strategy EPA's Urban Air Toxics Strategy (the UATS) focuses on reducing the human health threats of air toxics in urban areas. In urban areas, toxic air pollutants raise special concerns because sources of emissions and people are concentrated in the same geographic areas, leading to large numbers of people being exposed to the emissions of many HAPs from many sources. In the UATS, EPA outlines future actions that we plan to take to reduce emissions of air toxics and improve our understanding of the health threats posed by air toxics in urban areas. The over-arching goal for the UATS is to reduce cancer and noncancer risks associated with air toxics in urban areas. Also, because air toxics in urban areas may threaten the health of some people more than others, depending on factors such as where they live in relation to toxic sources, we intend to characterize exposure and risk distributions both geographically and demographically. This will include particular emphasis on highly exposed individuals (such as those in geographic hot spots) and specific population subgroups (e.g., children, the elderly, and low-income communities). The overall UATS goals are: (1) To reduce by 75 percent from 1990 levels the risk of cancer associated with air toxics from stationary sources (both large and small commercial and industrial sources); (2) to substantially reduce the noncancer health effects (e.g., birth defects and reproductive effects) associated with air toxics from small commercial and industrial sources; and (3) to address disproportionate impacts in certain areas (e.g., highly-exposed individuals in toxics “hot spots”) or experienced by certain populations (e.g., children, the elderly, or minority and low-income communities). As a first step in the UATS, EPA identified 33 of the 188 Section 112(b) toxic air pollutants that EPA concluded pose the greatest threat to public health in the largest number of urban areas (see Table I-2, above). It should be noted that while diesel exhaust emissions are not included as a specific pollutant in the list of 33 urban HAPs, many of the hazardous constituents of diesel exhaust emissions are included among them, and it is a pollutant that we identified in the UATS as a concern in urban areas. The UATS outlines several steps that EPA will take to reduce urban air toxics and address risks, and as a part of the UATS, EPA has prepared an Action Plan. The key components of the Action Plan are as follows: • Achieve reductions through regulatory actions and related projects. The strategy presents a framework for reducing air toxic emissions from all types of sources found in urban areas, including mobile sources, major industrial sources, and smaller stationary sources. Today's proposal contains mobile source-specific toxics regulations. We are also developing programs to reduce emissions from several area source categories (i.e., smaller commercial and industrial operations), and plan to complete regulations to address the new 13 sources identified in the UATS by 2004. Regulations are already under development or exist for the 16 other area source categories listed in the UATS. • Collaborate with interested parties. We are working with state, local, and tribal agencies, environmental groups, environmental justice communities, and affected industries, including small businesses, to assure that any actions under the UATS are responsive to health concerns while promoting fairness, encouraging urban redevelopment, and minimizing regulatory burdens. • Education and outreach efforts. We will make an effort to inform stakeholders about the UATS and get their input into designing programs to implement it. 2. National Air Toxics Assessment National Air Toxics Assessment (NATA) activities are an important component of the UATS and EPA's overall goal of reducing exposure to air toxics. These assessment activities include air toxics monitoring, emissions inventory development, exposure modeling, research activities, and risk assessment. Over time, these activities will help us set program priorities, characterize risks, and track progress toward reducing exposure to air toxics. Specifically, our current NATA activities include expanding air toxics monitoring, improving and periodically updating emissions inventories, periodically conducting national- and local-scale air quality, multimedia and exposure modeling, characterizing risks associated with air toxics exposures, and continued research on health and environmental effects and exposures to both ambient and indoor sources of air toxics. As part of these NATA activities, EPA is now conducting an initial national screening-level assessment to demonstrate our approach to characterizing air toxics risks nationwide. This initial screening-level assessment will help to characterize the potential health risks associated with inhalation exposures to the 33 urban HAPs and diesel exhaust emissions. 11 While such a broad-scale assessment is necessarily limited in the scope of the risks that it can assess quantitatively, and by the uncertainties inherent in the various types of data and methods currently available, it represents an important step in characterizing air toxics risks nationwide. Our initial national, screening-level air toxics assessment includes four major steps: 11 For an explanation of the connection between diesel exhaust, which is one of our MSATs, and diesel PM, see section II.F. • Compiling a national emissions inventory of 1996 air toxics emissions from outdoor sources of air toxics emissions. • Estimating 1996 air toxics ambient concentrations across the continental United States (and Puerto Rico and the Virgin Islands) for the 33 urban HAPs and diesel PM. —Model evaluation comparing ambient concentrations with available monitored values. • Estimating 1996 population exposures across the continental United States (and Puerto Rico and the Virgin Islands) to the 33 urban HAPs and diesel PM. • Characterizing potential public health risks due to inhalation of these 33 urban HAPs. In describing what NATA will include, it is also important to note the potentially important sources and pathways of risks to public health that are beyond the scope of this quantitative assessment. For example, while we recognize that indoor sources of air toxics emissions likely contribute substantially to the total exposures that people experience for a number of these HAPs, assessing these indoor sources of exposure cannot be done on a national scale at this time. Further, for a subset of these HAPs ( i.e., those that persist and bioaccumulate in the environment), dietary exposures (e.g., eating contaminated fish) likely contribute much more to the total risk associated with exposure to these pollutants than do the inhalation exposures that will be addressed in this assessment. These and other important aspects of total population exposures to air toxics will be addressed more fully over time as part of our NATA activities as more comprehensive data and assessment tools become available. Additionally, NATA activities include other key activities that will support further risk characterizations on the local and national level in the future. These include: • Developing and implementing a plan to characterize the concentrations of ambient air toxics through an expanded monitoring network. Data from existing state and local air monitoring programs will be compiled to summarize our current knowledge about ambient concentrations of air toxics. Existing ambient air toxics monitoring data will be compiled and summarized and then used as a “reality check” on model output. • Improving existing monitoring networks, guided by data analysis and model predictions, to improve the collection of ambient concentration data for future model evaluations. As the monitoring program matures, trend sites will be established to assess the effectiveness of all of our air toxics control programs. • Evaluating air toxics on a more local scale (e.g., an urban area) using more refined air quality modeling tools that factor in specific local information such as terrain (e.g., mountainous or flat) and local weather patterns. The results of national and local-scale modeling can be compared to provide a more complete context for the evaluation of air toxics. • Comparing air toxics inventories from 1990 and 1996 on a toxicity-weighted basis to help inform future assessments of progress toward meeting the risk reduction goals. • Recommending tools to state, local and tribal regulatory agencies for evaluating air toxics concentrations, exposures and risk. This will include a comparison of the results from national-scale models to those from more local-scale models. While there continue to be significant uncertainties and gaps in methods, models, and data that limit our ability to assess risks to public health and the environment associated with exposures to air toxics, continued research will enable future assessment activities, both at the national screening-level and at more local refined levels, to yield improved assessments of cumulative air toxics risks. II. What Are the Mobile Source Air Toxics? A. Introduction There are hundreds of different compounds and elements that are known to be emitted from passenger cars, on-highway trucks, and various nonroad equipment. Several of these compounds may have adverse effects on human health and welfare. In recognition of this fact, Congress instructed EPA, in section 202(l)(2) of the Act, to set emission control standards for hazardous air pollutants from motor vehicles and their fuels. Except for benzene and formaldehyde (specifically mentioned in 202(l)(2)), the Act does not specify the compounds that should be included in such a control program. Therefore, the first step in developing a mobile source air toxics control program is to identify the compounds that should be treated as hazardous air pollutants for purpose of section 202(l)(2). Since EPA data suggests that nonroad engines and vehicles emit the same pollutants, EPA will identify this list as a list of mobile source air toxics (MSATs). 12 EPA has used the methodology described below to develop this list of MSATs. 12 We have chosen to call our list of toxics a mobile sources list to acknowledge that nonroad sources may also contribute emissions of these pollutants. For purposes of section 202(l)(2), each of the MSATs would be considered a “hazardous air pollutant from motor vehicles and motor vehicle fuels.” B. The Methodology Used To Identify Our List of Mobile Source Air Toxics EPA developed the list of MSATs by first compiling all available recent (i.e., less than 10 years old) studies which speciated emissions from motor vehicles and their fuels. We then compared the list of compounds in EPA's Integrated Risk Information System (IRIS) database to the speciated lists of compounds in these studies. IRIS is a database of compounds that identifies EPA's consensus scientific judgment on the characterization of the potential adverse health effects that may result from a lifetime or acute exposure to various substance. IRIS may also indicate that based on the current data a compound can be found to have “evidence of noncarcinogenicity” i.e., the compound does not cause cancer. By comparing the list of compounds in IRIS to these emission speciation studies, we generated a list of 21 compounds. An evaluation of the potential for adverse health effects reflected in IRIS and in the ongoing agency scientific assessments of these compounds indicates that the potential for adverse health effects from exposure to these compounds warrants inclusion as a MSAT. It is important to note that inclusion on the list is not itself a determination by EPA that emissions of the compound in fact present a risk to public health or welfare, or that it is appropriate to adopt controls to limit the emissions of such a compound from motor vehicles or their fuels. The purpose of the list is more as a screening tool—it identifies those compounds emitted from motor vehicles or their fuels, and where the available information about their potential for adverse health or welfare effects indicates that further evaluation of emissions controls is appropriate. In conducting any such further evaluation, pursuant to sections 202(a) or 211(c) of the Act, EPA would consider whether emissions of the compound cause or contribute to air pollution which may reasonably be anticipated to endanger the public health or welfare. Such an evaluation would also consider the appropriate level of any controls, based on the criteria established in section 202(l)(2). Inclusion of a compound on the MSAT list does not decide these issues, but instead identifies those compounds for which such an evaluation would appear to be warranted. EPA also compared its universe of known compounds emitted from motor vehicles against other lists or sources of information on toxic substances, and did not identify any additional substance that we believe should be listed at this time. EPA believes this process allows for re-evaluation of the MSAT list in the future, as information is learned about additional compounds or new information is learned about the 21 compounds. Compounds may be added to or removed from the list in a rulemaking. EPA invites comment on an alternative listing approach whereby any compound emitted from motor vehicles or their fuels that is listed under section 112(b) would be considered a MSAT. Additional compounds not on the section 112(b) list, such as diesel exhaust, would be considered a MSAT where EPA has sufficient scientific evidence, such as an EPA health assessment or similar analysis, indicating a potential for adverse effects on public health or welfare that would warrant inclusion on the list. 1. Identifying Pollutants Emitted From Mobile Sources In identifying a list of MSAT, EPA first compiled all available recent studies which speciated emissions from motor vehicles and their fuels. To do this, EPA reviewed a number of databases that contain information on the various species of compounds emitted from motor vehicles and their fuels. It is difficult to get a precise picture of these emissions due to the variety and number of databases in the literature. This is particularly true for hydrocarbon (HC) speciation databases. Most toxic air pollutants are hydrocarbons by their chemical nature and thus will be detected only if the HCs are chemically separated and identified (speciated). Many test programs that characterize vehicle emissions identify only total hydrocarbons (THC) without separating out the individual species of hydrocarbons and many use different test methods. The issue is further complicated by the limited availability of these databases for certain vehicle classes. We have recent (less than ten years old) speciation profiles for emissions from light-duty gas vehicles (LDGV), heavy-duty diesel vehicles (HDDV), heavy-duty gasoline vehicles (HDGV), gasoline powered nonroad engines, and turbine engine aircraft. 13 Data for other vehicle and engine types (e.g., light-duty diesel engines and nonroad diesel engines) either do not exist or are outdated (more than 10 years old) and thus are judged not to be representative of current emissions. However, it is unlikely that the lack of recent data for these vehicle and engine types would result in the absence of compounds from the list, since the combustion process is similar to vehicle and engine types for which we do have data. Forty-four speciation studies were found that met this age criteria. All of these speciation profiles attempt to accomplish more or less the same objective: separating and identifying the compounds that comprise the hydrocarbon portion and particulate phase of mobile source emissions. 13 See appendix I, chapter 2 of the TSD. With regard to alternative-fueled vehicles, most of the compounds included in their exhaust are included on our list of MSATs (e.g., formaldehyde, acetaldehyde). It should be noted that, depending on their fuel, these vehicles may also emit unburned ethanol and methanol, which were not included in our speciation data. Low level ethanol mixtures (10% ethanol and 90% gasoline) are widely used in the United States. Higher level ethanol mixtures (e.g., 85% ethanol) are used as alternative fuel sources in a small number of flexible fuel vehicles. However, there is a paucity of data on potential inhalation effects of ethanol, and the compound is not listed in IRIS. Thus it is not included on the list of MSATs. EPA requests comment on whether it should be included. Methanol is also a promising alternative fuel for motor vehicles, and a small number of flexible fuel vehicles operate on a methanol mixture (e.g., 85% methanol). Inhalation of methanol at high concentrations (greater than 1000 ppm) has caused birth defects in rats and mice and at low levels can cause symptoms such as eye irritation, headaches, dizziness, and nausea. Methanol is highly toxic by oral exposure routes and is listed in IRIS. Because of the small numbers of vehicles using methanol currently in use, EPA requests comment on whether this compound should also be included in our MSAT list. EPA requests comment on our list of compounds associated with motor vehicles and their fuels provided here. 2. Using IRIS To Identify Pollutants With Potential Adverse Health Effects The Integrated Risk Information System (IRIS) is an EPA database of scientific information that contains the Agency consensus scientific positions on potential adverse health effects that may result from lifetime (chronic) or short-term (acute) exposure to various substances found in the environment. 14 IRIS currently provides health effects information on over 500 specific chemical compounds. The information contained in the IRIS database includes an EPA finding for each compound that: (1) there is a health hazard, either cancer or noncancer, associated with exposure to the compound, (2) the compound is noncarcinogenic based on current data, or (3) the data is insufficient to determine if the compound is a hazard. 14 EPA IRIS Database, http://www.epa.gov/ngispgm3/iris/index.html IRIS contains chemical-specific summaries of qualitative and quantitative health information. IRIS information may include the reference dose (RfD) for noncancer health effects resulting from oral exposure, the reference concentration (RfC) for noncancer health effects resulting from inhalation exposure, and the carcinogen assessment for both oral and inhalation exposure. Combined with information on specific exposure situations, the summary health hazard information in IRIS may be used in evaluating potential public health risks from environmental contaminants. Before a substance is listed on the IRIS database, it goes through a thorough scientific evaluation. This consensus and review process, managed by EPA's Office of Research and Development (ORD), consists of (1) an annual Federal Register announcement of the IRIS agenda and a call for scientific information from the public on the selected chemical substances, (2) a search of the current literature, (3) development of health assessment and draft IRIS summaries, (4) internal EPA peer review, (5) external peer review, (6) Agency consensus review and management approval within EPA, (7) preparation of final IRIS summaries and supporting documents, and (8) entry of summaries and supporting documents into the IRIS database. C. List of Mobile Source Air Toxics By comparing the list of compounds in IRIS to the motor vehicle emissions identified in the speciation studies, we identified 21 MSAT. This list is set out in Table II-1. Each of these pollutants are known, probable, or possible human carcinogens (Group A, B or C) or were considered by the Agency to pose a risk of adverse noncancer health effects. 15 EPA requests comment on the appropriateness of the compounds on the list of compounds associated with motor vehicles and their fuels provided here as well as the need to consider other hazardous or toxic air pollutants for inclusion on the list. 15 A further discussion of the potential cancer and noncancer risks, and other dose-response information for each MSAT can be found in chapter 3 of the TSD. It is difficult to identify the specific form of metals being emitted in motor vehicle exhaust because the databases only report the total amount of metal compound identified. As a result, we have chosen to list the entire group of metal compounds if any compound of the metal has been detected in motor vehicle exhaust and any compound of the metal is listed in IRIS as potentially causing adverse human health effects. For example, if we assume most chromium (Cr) emissions for mobile sources are unidentified as to the species, we would present the emissions as total chromium and not attempt to allocate these emissions because of the lack of accurate metal speciation information in most cases. When we assess the range of potential health impacts associated with exposure to chromium compounds, we consider the health effects associated with each compound for which we have information. For chromium, the most toxic form in IRIS is Cr+6; hence the health impacts described for chromium compounds include these most serious effects even though it is highly unlikely that all motor vehicle emissions are Cr+6. EPA believes this listing approach is a reasonable, health-protective way to handle the uncertainty surrounding motor vehicle emissions of metals. We also recognize that this is not an appropriate methodology for assessing the actual health risks of the entire group of metal compounds emitted from motor vehicles. Table II-1.—Proposed List of Mobile Source Air Toxics (MSATs) Acetaldehyde Diesel Exhaust MTBE.\c\ Acrolein Ethylbenzene Naphthalene. Arsenic Compound \a\ Formaldehyde Nickel Compounds.\a\ Benzenen n-Hexane POM.\d\ 1,3-Butadiene Lead Compounds \a\ Styrene. Chromium Compounds \a\ Manganese Compounds \a\ Toluene. Dioxin/Furans \b\ Mercury Compounds \a\ Xylene. a Although the different species of the same metal differ in their toxicity, the onroad mobile source inventory contains emissions estimates for total compounds of the metal identified in particulate speciation profiles ( i.e., the sum of all forms). b This entry refers to two large groups of chlorinated compounds. In assessing their cancer risks, their quantitative potencies are usually derived from that of the most toxic, 2,3,7,8-tetrachlorodibenzodioxin. c MTBE is listed due to its potential inhalation air toxics effects and not due to ingestion exposure associated with drinking water contamination. d Polycyclic Organic Matter includes organic compounds with more than one benzene ring, and which have a boiling point greater than or equal to 100 degrees centigrade. A group of seven polynuclear aromatic hydrocarbons, which have been identified by EPA as probable human carcinogens (benz(a)anthracene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, chrysene, 7,12-dimethylbenz(a)anthracene, and indeno(1,2,3-cd)pyrene) are sometimes used as a surrogate for the larger group of POM compounds. D. How Our List of MSATs Compares to Other Lists or Sources of Data on Toxics There are other sources that provide information characterizing the cancer and noncancer health effects associated with exposure to air toxics. In identifying our MSAT list we relied upon the health effects data from the EPA IRIS database because it represents EPA's scientific consensus opinion on the health effects associated with exposure to various pollutants. We also compared our emissions speciation data to four other lists of toxic air pollutants to confirm that our MSAT list is reasonable. The four lists of toxic air pollutants are: the Clean Air Act (CAA) section 112(b) list of hazardous air pollutants; California EPA (CalEPA) list of toxic air contaminants (TAC); U.S. Department of Health and Human Service Agency for Toxic Substances and Disease Registry (ATSDR) list of Minimal Risk Levels (MRLs); and International Agency for Research on Cancer (IARC) monographs on cancer. Comparing these four lists against the emissions speciation studies, we identified two additional compounds not included on our list of 21 MSAT “ propionaldehyde and 2,2,4-trimethylpentane. Both the Cal EPA TAC list and the CAA section 112(b) HAP list contain these compounds. At this time EPA is not including propionaldehyde or 2,2,4-trimethylpentane in the list of MSATs because EPA has not drawn a conclusion on the potential adverse health effects associated with exposure to these pollutants. We request comment on whether these two compounds should be included on our MSAT list and, if so, why. Comments should include scientific information on the potential health effects of these pollutants. E. Diesel Health Assessment Document One of the key features of today's program is that we are proposing to designate diesel exhaust as a mobile source air toxic. The following paragraphs describe the most current information regarding the EPA's assessment of the health effects of exposure to diesel exhaust and provide information regarding actions by other agencies to evaluate the hazard associated with exposure to diesel exhaust. EPA determined a reference concentration in 1993 to minimize noncancer health effects resulting from exposure to diesel exhaust. EPA has summarized available information to characterize the cancer and noncancer health effects from exposure to diesel exhaust emissions in the draft Health Assessment Document for Diesel Emissions (the Assessment). This information is also presented in the TSD. The key components of the current draft Assessment are: (1) information about the chemical components of diesel exhaust and how they can influence toxicity, (2) the cancer and noncancer health effects of concern for humans, and (3) the possible impact or risk to an exposed human population. EPA is currently revising the Assessment based on a February 2000 review by the Agency's Science Advisory Board (SAB) Clean Air Scientific Advisory Committee (CASAC). A revised Assessment is expected to be available for peer review and public comment in late July 2000. The Assessment will be reviewed by CASAC late in 2000. The updated Assessment will inform the Technical Analysis Plan described in today's proposed program. The proposed finding in EPA's draft Health Assessment Document, under review by CASAC, is that diesel exhaust is a likely human carcinogen in the lung at environmental levels of exposure and that exposure to diesel exhaust can pose a noncancer health hazard. The concern for the cancer and noncancer health hazard resulting from diesel exhaust exposure is widespread. Several national and international agencies have designated diesel exhaust or diesel particulate matter as a “potential” or “probable” human carcinogen. The International Agency for Research on Cancer (IARC) considers diesel exhaust “probably carcinogenic to humans”. Based on IARC findings, the State of California identified diesel exhaust in 1990 as a chemical known to the State to cause cancer and has listed diesel PM as a toxic air contaminant. The National Institutes for Occupational Safety and Health has classified diesel exhaust a “potential occupational carcinogen.” The Department of Health and Human Services (DHHS) recently designated diesel exhaust particulates as “reasonably anticipated to be a human carcinogen” in its Ninth Report on Carcinogens. F. Diesel Exhaust and Diesel Particulate Matter Diesel exhaust include gaseous and particulate components. Gaseous components of diesel exhaust include organic compounds, nitrogen-containing compounds, sulfur compounds, carbon monoxide, carbon dioxide, water vapor, and excess air (nitrogen and oxygen). Among these gaseous organic compounds are benzene (a known human carcinogen), formaldehyde, acetaldehyde, and 1,3-butadiene (possible or probable human carcinogens). Particulate components include many organic compounds that are mutagenic as well as several trace metals (including chromium, manganese, mercury and nickel) that may have general toxicological significance (depending on the specific species). In addition, small amounts of dioxins have been measured in diesel exhaust, some of which may partition to the particle phase. Because diesel exhaust is a mixture of particles and gases, the choice of a measure of exposure ( i.e., dosimeter) is important. EPA believes that exposure to whole diesel exhaust is best described, as many researchers have done over the years, by diesel particulate concentrations expressed in units of mass concentration ( e.g., μg/m 3 ). The choice of this dosimeter implies that the contribution of the gaseous components and diesel particulate constituents to toxicity are related by diesel particulate mass. This assumption is consistent with historic practice, but can only be validated when there is a better understanding of the toxicological mode of action for diesel exhaust. While some of the cancer and noncancer hazard may be associated with exposure to the gaseous component of diesel exhaust, studies suggest that the particulate component plays a substantial role in carcinogenicity and noncancer effects. Investigations show that diesel particles (the elemental carbon core plus the adsorbed organics) induce lung cancer at high doses and that the particles, independent of the gaseous compounds, elicit an animal lung cancer response. The presence of non-diesel elemental carbon particles, as well as the organic-laden diesel particles, correlate with an adverse inflammatory effect in the respiratory system of animals. Additional evidence suggesting the importance of the role of particulate matter in diesel exhaust includes the observation that the extractable particle organics collectively produce cancer and adverse mutagenic toxicity in laboratory experiments. Given the available information, we are proposing to list diesel exhaust as a mobile source air toxic pollutant. We invite scientific and policy rationales for listing only the particulate component of diesel exhaust as an MSAT. III. How Are Motor Vehicle Emission Control Programs Reducing MSAT Emissions? In the previous section we identified the 21 MSATs. We now turn to an evaluation of the impact of existing and planned controls on inventories of those air toxics by examining the emissions inventories and estimated reductions expected to be achieved by our various mobile source control programs. The data and information available on emissions of these 21 MSATs vary considerably. While we have baseline inventory data for all of the MSATs except napthalene, we do not have inventory projections for all of them. Therefore, we are examining the projected impacts of our current and proposed mobile source control program by groupings of air toxics. More specifically, we have projections of future emissions for five gaseous toxics (benzene, formaldehyde, 1,3-butadiene, acetaldehyde, MTBE) and for diesel PM 16 and we present these in this section. However, we do not have emissions projections for the remaining gaseous toxics (acrolein, POM, styrene, toluene, xylene, ethylbenzene, naphthalene, and n-hexane), but because these compounds are part of VOCs, we believe it is reasonable to utilize VOC emissions inventory projections to track the expected impact of our control programs on these other gaseous MSATs. Finally, we also do not have emissions inventory projections for the metals on the MSAT list (arsenic compounds, chromium compounds, mercury compounds, nickel compounds, manganese compounds, and lead compounds) or for dioxins/furans. While metal emissions and dioxin/furans emissions are associated with particles, and it is possible that they track PM emissions to some extent, we do not have good data on these relationships. Therefore, we are not presenting emission projections for these compounds in this document. 16 In this notice the emissions inventory for diesel exhaust is looked at in terms of diesel PM, as that is what we have measured to date. Thus, even though we are proposing to list diesel exhaust as an MSAT, all emissions inventory and trends numbers are stated in terms of diesel PM. As we describe in the following discussion, there have been and will continue to be significant reductions in MSAT emissions as a result of implemented, promulgated, and proposed regulations. By 2020, we project on-highway emissions of gaseous toxics such as benzene, formaldehyde, 1,3-butadiene, and acetaldehyde, to decrease by 75 percent or more from 1990 levels as a result of our mobile source control programs up to and including our Tier 2 control program and our recently proposed heavy-duty engine and vehicle standards and on-highway diesel fuel sulfur control requirements (HD2007 rule). Under these current and proposed controls we expect on-highway diesel PM emissions to be reduced by more than 90 percent by 2020, as compared with 1990 levels. Nonroad engines and equipment also contribute substantially to levels of MSAT emissions and have only in recent years been subject to emission standards. Since nonroad engines are not subject to the same stringent controls as on-highway vehicles, the reductions from these sources are more moderate than those for on-highway sources. The discussion in this section consists of two parts. First, we describe current inventories of MSAT emissions. Next, we describe how our on-highway emission control programs will reduce them. Interested readers should refer to chapter 4 of our Technical Support Document for more detailed information about the methodology we used to compile these inventories and the results of our analysis. We consider the impacts of our nonroad engine control programs on MSAT emissions in section VI of this preamble. A. Baseline Inventories We developed inventory estimates for several gaseous MSATs (acetaldehyde, benzene, 1,3-butadiene, formaldehyde, MTBE) and also for diesel PM as part of the 1999 study, “Analysis of the Impacts of Control Programs on Motor Vehicle Toxic Emissions and Exposure in Urban Areas and Nationwide,” described in Section I.E, above (hereafter referred to as the 1999 EPA Motor Vehicle Air Toxics Study, or the 1999 Study). 17 We addressed these five gaseous MSATs and diesel PM because we had detailed information on the emission impacts of emission control technologies, fuel properties, and other parameters for these compounds. 17 Analysis of the Impacts of Control Programs on Motor Vehicles Toxics Emissions and Exposure in Urban Areas and Nationwide (Volumes 1 and 2), November 1999. EPA420-R-99-029/030. This report can be accessed at http://www.epa.gov/otaq/toxics.htm. The 1999 EPA Motor Vehicle Air Toxics Study provides 1990 and 1996 estimates of emissions for these compounds. The 1990 baseline represents estimated emissions before any of the programs added by the 1990 Clean Air Act Amendments were implemented. The 1996 estimates reflect toxics emissions with some of the new Clean Air Act programs in place, such as Phase 1 of the RFG program. We present emission estimates for these years in Table III-1. Note that since completion of the Study, we have updated our estimates of diesel PM emissions; these updated estimates are presented in Table III-1. It should also be noted that these estimates are only for on-highway vehicles. Table III-1.—Annual Emission Summary for the Total U.S. for Selected Air Pollutants, On-Highway Vehicles Only [Short tons a per year] Compound 1990 baseline emissions 1996 emissions 1,3-butadiene 36,000 22,000 Acetaldehyde 41,000 27,000 Benzene 257,000 165,000 Formaldehyde 139,000 80,000 Diesel PM b 235,000 180,000 MTBE 55,000 65,000 a In this notice we report emissions in terms of short tons as opposed to metric tons. One short ton is 2,000 pounds. To convert to metric tons, multiply short tons by 0.9072. Note that all emissions and percentages in this and subsequent tables are rounded. b The 1996 diesel PM estimate is based on the Tier 2 rulemaking inventories, updated to reflect the Updated Tier 2 Emissions Inventory for light-duty diesel exhaust and the proposed 2007 heavy-duty engine rule for heavy-duty diesel exhaust. For 1990, we used estimates from EPA's Trends Report for that year, as described below. The 1996 National Toxics Inventory (NTI) prepared in connection with the Agency's NATA 18, 19 activities, described above, also contains emission estimates for 1,3-butadiene, acetaldehyde, benzene, formaldehyde and MTBE. The 1996 NTI emission estimates for these compounds differ slightly from those generated in the 1999 Study, due largely to revisions made to the NTI based on state comments. Since diesel exhaust are not included on the list of 112(b) hazardous pollutants, which is the focus of the 1996 NTI, diesel PM estimates have not been compiled there. 18 - 19 [Reserved]. The 1996 National Toxics Inventory (NTI) prepared in connection with the Agency's NATA activities, described above, also contains emission estimates for 1,3-butadiene, acetaldehyde, benzene, formaldehyde and MTBE. The 1996 NTI emission estimates for these compounds differ slightly from those generated in the 1999 Study, due largely to revisions made to the NTI based on state comments. Since diesel exhaust are not included on the list of 112(b) hazardous pollutants, which is the focus of the 1996 NTI, diesel PM estimates have not been compiled there. The 1996 NTI also contains 1996 emissions estimates for several other MSATs, and includes data for nonroad 20 as well as on-highway sources. We present these data in Table III-2. We also indicate the on-highway and nonroad percentages of the national inventories for these MSATs (the total national inventories include emissions from on-highway and nonroad mobile sources, major and area stationary sources, and other sources such as forest fires). Between the 1999 EPA Motor Vehicle Air Toxics Study and the 1996 NTI, we have baseline inventory data for all of the 21 MSATs except mercury compounds and naphthalene. 21 22 20 The nonroad inventory in the 1996 NTI includes emissions data for aircraft, commercial marine vessel, locomotives, and other nonroad engines. Note that under the Clean Air Act definition, nonroad does not include aircraft. For convenience, in this notice the term “nonroad” will include aircraft except where otherwise noted. It should be noted that the NONROAD model, on which the estimates for nonroad engines other than locomotive, commercial marine vessels, and aircraft are based, is still draft, and the emissions estimates based on this model are subject to change. 21 [Reserved]. 22 Naphthalene emissions are not reported in the 1996 NTI separately from 16-PAH. Since diesel exhaust emissions are not included in the list of 112(b) hazardous pollutants that is the focus of the 1996 NTI, diesel PM emissions estimates have not been compiled there. See Chapter 3 of the TSD for the explanation of the linkage between diesel exhaust and diesel PM. Table III-2.—1996 On-Highway and Nonroad Emission Inventories of Proposed MSATs 1996 NTI (Short Tons) Compound On-Highway Tons Percent of total national emissions (percent) Nonroad Tons Percent of total national emissions (percent) Mobile sources Tons Percent of total national emissions (percent) 1,3-Butadiene a 23,500 42 9,900 18 33,400 60 Acetaldehyde a 28,700 29 40,800 41 69,500 70 Acrolein a 5,000 16 7,400 23 12,400 39 Arsenic Compounds a 0.25 0.06 2.01 0.51 2.26 0.57 Benzene a 168,200 48 98,700 28 266,900 76 Chromium Compounds a 14 1.2 35 3 49 4.2 Dioxins/Furans a, b 0.0001 0.2 N.A. N.A. 0.0001 0.2 Ethylbenzene 80,800 47 62,200 37 143,000 84 Formaldehyde a 83,000 24 86,400 25 169,400 49 Lead Compounds a 19 0.8 546 21.8 565 22.6 Manganese Compounds a 5.8 0.2 35.5 1.3 41.3 1.5 Mercury Compounds a 0.2 0.1 6.6 4.1 6.8 4.2 MTBE 65,100 47 53,900 39 119,000 86 n-Hexane 63,300 26 43,600 18 106,600 44 Napthalene N.A. N.A. N.A. N.A. N.A. N.A. Nickel Compounds a 10.7 0.9 92.8 7.6 103.5 8.5 POM (as sum of 7 PAH) a 42.0 4 19.3 2 61.3 6 Styrene 16,300 33 3,500 7 19,800 40 Toluene 549,900 51 252,200 23 802,100 74 Xylene 311,000 43 258,400 36 569,400 79 a Indicates also on the list of urban HAPs for the Integrated Urban Air Toxics Strategy. b Mass given in tons of TEQ (toxic equivalency quotient). The EPA Office of Research and Development (ORD) has recently developed an inventory for dioxin and dioxin-like compounds using different methods than those used in the NTI. For 1995, the EPA-ORD estimate of on-highway emissions of dioxin compounds is 0.00005 tons TEQ, comprising 1.5 percent of the national inventory in that year. The above inventory data reflect certain interesting characteristics of mobile source air toxics emissions. First, mobile sources account for the majority of the national inventory of three of the gaseous MSATs that are included on the urban HAP list. These three are 1,3-butadiene (60 percent), acetaldehyde (70 percent), and benzene (76 percent). Mobile sources account for 39 percent of the national inventory of acrolein, and 49 percent of the national inventory of formaldehyde, two other gaseous urban HAPs. All of these MSATs are formed as part of the combustion process. In addition, benzene is also released through evaporative emissions from gasoline. Second, with regard to the other MSATs that are included on the urban HAP list, the mobile source contribution generally is small (arsenic compounds, chromium compounds, manganese compounds, nickel compounds, POM, and dioxins/furans). The sole exception is lead compounds. Mobile sources contribute 23 percent to national inventories of lead compound emissions, due primarily to nonroad sources and, more specifically, to the use of a lead-additive package used to boost the octane of aviation gasoline. 23 The mobile source contribution to the other metals on the urban HAP list comes primarily from engine wear, some fuel additives, or impurities in engine oil. 23 Aviation gasoline is used by a relatively small number of aircraft, those with piston engines, which are generally used for personal transportation, sightseeing, crop dusting, and similar activities. With regard to the gaseous MSATs that are not included on the urban HAP list (ethylbenzene, MTBE, n-hexane, styrene, toluene, and xylene), mobile source contributions are high because of the presence of these compounds in gasoline. In addition, mobile sources account for almost all of diesel PM emissions. As shown in Table III-1, above, we estimate that 1996 on-highway diesel PM emissions are approximately 180,000 tons. We estimate that 1996 nonroad diesel PM emissions are approximately 346,000 tons, as discussed in section VI of this document. 24 24 Note that the nonroad diesel PM emissions estimate is still draft and is subject to change. B. Impacts of Motor Vehicle Emission Controls on Emission Inventories 1. Description of Emission Control Programs Many of the programs that we have put in place since the passage of the 1990 Clean Air Act Amendments to achieve attainment of the National Ambient Air Quality Standards (NAAQS) for ozone, PM and CO have also reduced MSAT and diesel PM emissions. For example, measures to control hydrocarbons from motor vehicles are also effective in controlling gaseous toxics. In addition, certain programs address air toxics directly, such as the RFG program and the gasoline lead phase-out. In this section we briefly describe several categories of mobile source emission control measures that have helped reduce inventories of these harmful compounds. These programs include: • More stringent vehicle standards and test procedures. The 1990 Clean Air Act Amendments set specific emission standards for hydrocarbons and for PM. Air toxics are present in both of these pollutant categories. As vehicle manufacturers develop technologies to comply with the hydrocarbon and particulate standards (e.g., more efficient catalytic converters), we expect air toxics to be reduced as well. Since 1990, we have developed a number of programs to address exhaust and evaporative hydrocarbon emissions and PM emissions. Some of the key programs are the Tier 1 and NLEV standards for light-duty vehicles and trucks; enhanced evaporative emissions standards; the supplemental federal test procedures (SFTP); urban bus standards; and heavy-duty diesel and gasoline standards for the 2004/2005 time frame. • Recent motor vehicle/fuel control initiatives. Two of our recent initiatives to control emissions from motor vehicles and their fuels are the Tier 2 control program and our recently proposed 2007 heavy-duty engine rule. Together these two initiatives define a set of comprehensive standards for light-duty and heavy-duty motor vehicles and their fuels. In both of these initiatives, we treat vehicles and fuels as a system. The Tier 2 control program establishes stringent tailpipe and evaporative emission standards for light-duty vehicles and a reduction in sulfur levels in gasoline fuel beginning in 2004. The proposed 2007 heavy-duty engine rule proposes stringent exhaust emission standards for heavy-duty engines and vehicles for the 2007 model year as well as reductions in diesel fuel sulfur levels starting in 2006. • Limits on gasoline volatility. Volatility is a measure of how easily a liquid evaporates. As described earlier, some toxics such as benzene are present in gasoline and get into the air when gasoline evaporates. We imposed limits on gasoline volatility in the early 1990s to control evaporative emissions of both hydrocarbon and toxic compounds (most air toxics are hydrocarbons, so programs designed to reduce hydrocarbon emissions also reduce air toxics). • Reformulated gasoline. The 1990 Clean Air Act Amendments required reformulated gasoline to be introduced in the nation's most polluted cities beginning in 1995. From 1995 through 1999, these gasolines were required to provide a minimum 16.5 percent reduction in air toxics emissions over typical 1990 gasolines, increasing to a 21.5 percent minimum reduction beginning in the year 2000. The air toxics reductions have been achieved mainly by further reducing gasoline volatility and by reducing the benzene, aromatics, sulfur, and olefin content of the gasoline. • Phase-out of lead in gasoline. One of the first programs was the removal of lead from gasoline. The lead phase out began in the mid-1970s. It was completed January 1, 1996 when lead was banned from motor vehicle gasoline. The removal of lead from gasoline has essentially eliminated on-highway mobile source emissions of this highly toxic substance. • Ensuring emissions are controlled while vehicle actually used. Many of our vehicle standards require certification of new engines and vehicles, but ensuring continued performance of emission controls can be difficult. The Clean Air Act establishes several programs to make sure vehicle emission controls are functioning properly in actual use. These programs include requirements for periodic emission inspections (I/M, or inspection and maintenance programs) and for computerized diagnostic systems that alert drivers and mechanics to malfunctioning emission controls. We encourage the interested reader to refer to chapter 1 of our TSD for more detailed information about these programs. 2. Emission Reductions From Control Programs We expect the mobile source emissions control programs described above to have beneficial impacts on the national inventories of MSATs. The remainder of this section summarizes our MSAT inventory projections. First, we present an overview of our inventory methodologies. Next, we present the results of our inventory projections. We encourage interested readers to refer to chapter 4 of our TSD for a more detailed discussion of these projections and how we developed them. The inventory projections in this section are for on-highway vehicles only, since we have the most complete information for this category of mobile sources. Projections of nonroad MSAT emissions are included in section VI of this preamble. a. Overview of Inventory Sources We have developed inventory projections for five gaseous MSATs, for VOC, and for diesel PM for the years 2007 and 2020 under our current and proposed control programs. These programs include the national low-emission vehicle (NLEV) program, the reformulated gasoline (RFG) program, the 2004 heavy-duty diesel and gasoline engine standards, the Tier 2/Sulfur controls, and our recently proposed heavy-duty engine and vehicle standards and on-highway diesel fuel sulfur control requirements (HD2007 rule). The inventory projections for the five gaseous toxics are based on the 1999 EPA Motor Vehicle Air Toxics Study, and data from a spreadsheet model developed in support of the proposed 2007 heavy-duty engine rule. 25 The 1999 Study estimated on-highway motor vehicle air toxics emissions for ten urban areas (Atlanta, Chicago, Denver, Houston, Minneapolis, New York City, Philadelphia, Phoenix, Spokane, and St. Louis) and 16 geographic regions. These areas were selected to reflect the range of potential fuels, temperatures, and I/M programs observed in the U.S. The estimation methodology used in the 1999 Study was similar to that used in our original 1993 Motor Vehicle Related Air Toxics Study. In our approach, the MOBILE model is used to generate total organic gas (TOG) emissions from on-highway motor vehicles by vehicle class and model year. Toxics fractions, developed as a percentage of the toxic compound of interest contained in TOG emissions, are then applied to the MOBILE-based TOG emission rates (reported in grams per mile) to arrive at toxics emission rates (reported in grams per mile or milligrams per mile). These toxics fractions are developed as a function of vehicle class ( e.g. , light-duty, heavy-duty), fuel type ( e.g. , gasoline or diesel), fuel composition, and technology type ( e.g. , non-catalyst, catalyst). 25 This spreadsheet model can be found in EPA Air Docket A-99-06, Item II-B-31. We do not have detailed emissions data for gaseous MSATs other than the five gaseous MSATs examined in the 1999 Study. However, we expect the trend for other gaseous MSATs, including acrolein, POM, styrene, xylene, toluene, ethylbenzene, naphthalene, and n-hexane, to follow that of VOC, since all of these compounds are VOCs. Therefore, to estimate projected inventory impacts from mobile source emission control programs, we use VOC inventories. We believe this is appropriate because all of these compounds are constituents of VOCs, and we expect their inventories to decrease in proportion to decreases in overall VOC emissions. We recognize that some gaseous MSATs may not decrease at the same rate as VOCs overall. Without having more detailed emission data for each of the MSATs, however, we are unable to project how those rates may differ. We request comment on this approach, and on how to develop inventory projections for the other gaseous MSATs. Our VOC and diesel PM emission estimates are derived from several sources. The 1996 and later values for light-duty vehicles are based on the Tier 2 rulemaking inventories, updated to reflect the Updated Tier 2 Emissions Inventory spreadsheet. 26 The 1996 and later values for heavy-duty engines and vehicles are based on data from a spreadsheet model developed in support of the proposed 2007 heavy- duty engine rule. 27 The 1990 VOC emission estimate is based on the 1999 EPA Motor Vehicle Air Toxics Study, 28 and the 1990 diesel PM is from EPA's Trends Report. 29 26 Details of this approach can be found in a memorandum by Harvey Michaels to Docket A-2000-12 titled “Adjustment to the Tier 2 Air Quality Inventory for the Mobile Source Air Toxics Proposed Rule”. 27 This spreadsheet model can be found in EPA Air Docket A-99-06, Item II-B-31. 28 The analysis methodology is described in a memorandum from Meredith Weatherby, Eastern Research Group, to Rich Cook, EPA, entitled “Estimating of 1990 VOC and TOG Emissions” in EPA Air Docket A-2000-12. 29 EPA, 2000. National Air Pollution Emission Trends, 1900-1998 (March 2000). Office of Air Quality Planning and Standards, Research Triangle Park, NC. Report No. 454/R-00-002. We are not reporting inventory trends for the metals on our list of MSATs (arsenic compounds, chromium compounds, mercury compounds, nickel compounds, manganese compounds, and lead compounds) or for dioxins/furans. Metals in mobile source exhaust can come from fuel, fuel additives, engine oil, engine oil additives, or engine wear. Formation of dioxin and furans requires a source of chlorine. Thus, while metal emissions and dioxin/furan emissions are associated with particles, there are a number of other factors that contribute to emission levels. While it is possible that these compounds track PM emissions to some extent, we do not have good data on these relationships. b. Emission Reductions Table III-4 presents the annual emission projections for on-highway vehicles in the years 2007 and 2020 for five gaseous toxics, VOC, and diesel PM with our current and proposed on-highway control programs. Table III-4.—Annual Fifty-State Emissions Summary for Selected Air Pollutants With Tier 2 and Proposed Heavy-Duty 2007 Controls On-Highway Vehicles Only From 1990 to 2020 [Thousand short tons per year] Compound 1990 1996 2007 2020 Benzene 257 165 86 65 Acetaldehyde 41 27 14 8 Formaldehyde 139 80 35 17 1,3 Butadiene 36 22 11 9 MTBE a 55 65 25 18 VOC 7,585 4,819 2,662 1,838 Diesel PM 235 180 82 15 a These estimates do not include consideration of EPA's examination of options to phase down or otherwise control the use of MTBE under the Toxic Substances Control Act, or legislative authority that EPA has asked Congress to provide the Agency to address MTBE use in gasoline. Table III-5 summarizes the percent reductions we expect in on-highway emissions of gaseous MSATs, VOC, and diesel PM from 1990 and 1996 levels in 2007 and 2020 as a result of our current and proposed on-highway control programs. Table III-5.—Summary of Fifty-State Percent Emission Reductions With Tier 2 and Proposed Heavy-Duty 2007 Controls On-Highway Vehicles Only in 2007 and 2020 From 1990 or 1996 Compound Reduction in 2007 From 1990 From 1996 Reduction in 2020 From 1990 From 1996 Benzene 67 48 75 61 Acetaldehyde 65 47 82 73 Formaldehyde 75 55 87 78 1,3 Butadiene 69 49 75 60 MTBE a 54 61 67 72 VOC 65 45 76 62 Diesel PM 65 48 94 92 a These estimates do not include consideration of EPA's examination of options to phase down or otherwise control the use of MTBE under the Toxic Substances Control Act, or legislative authority that EPA has asked Congress to provide the Agency to address MTBE use in gasoline. The results of this analysis show that on-highway emissions of the five gaseous MSATs examined are expected to decline by approximately 75 percent by 2020 from 1990 levels with our existing and proposed controls. For some gaseous MSATs, the reductions are even greater. For example, we project both formaldehyde and acetaldehyde emissions will decrease by over 80 percent by 2020 from 1990 levels with our current and proposed controls. Likewise, VOC inventories from on-highway vehicles are projected to decrease as much as 75 percent between 1990 and 2020 and we assume that other gaseous toxics would decrease by approximately 75 percent as well. Finally, diesel PM emissions are expected to decline by over 90 percent by 2020 from 1990 levels. Though these air toxics emissions reductions are substantial, we are not certain whether or not more control in the future is warranted for the remaining emissions from these air toxics. They have the potential to present serious health impacts to the public under certain circumstances that we have not been able to investigate fully. We also believe there is merit in considering further vehicle and fuel controls for both highway and nonroad sources for addressing the remaining emissions given the ever-changing nature of pollution control technology. These controls would be considered as part of our proposed Technical Analysis Plan outlined in section VII. C. Summary In this section, we presented our inventory projections for MSATs. These projections, which are limited to on-highway mobile sources, show that with our current and proposed emission control programs up to and including Tier 2 and our recently proposed 2007 heavy-duty engine rule, on-highway emissions of gaseous MSATs are expected to decline by approximately 75 percent by 2020 from 1990 levels, and on-highway emissions of diesel PM are expected to decline by over 90 percent by 2020 from 1990 levels. These reductions will result from the more stringent VOC and PM controls that we have put into place over the last decade or have recently adopted (Tier 2) or proposed (HD2007). IV. Evaluation of Additional Motor Vehicle-based Controls This section discusses the relationship between EPA's vehicle-based control programs and the control of MSATs, the impact of our most recent efforts to control VOCs, and the need for additional control of MSATs. A. MSATs and Motor Vehicle-based Controls The majority of gaseous MSATs are hydrocarbons that are primarily the result of incomplete combustion of petroleum fuels (a small amount of raw fuel may also pass through the engine unburned). Technologies used to reduce exhaust hydrocarbons also reduce MSAT hydrocarbon species. This is true whether control is achieved through engine or component modifications, add-on devices, or the use of aftertreatment devices such as oxidation or three-way catalysts. We are not aware of vehicle or engine technologies that selectively reduce MSATs without reducing other hydrocarbons to a similar degree. The other major source of hydrocarbon emissions from motor vehicles are fuel vapors. These emissions occur when components of the liquid fuel (gasoline or diesel) evaporate when onboard the vehicle. The emissions are normally separated into refueling emissions and evaporative emissions (hot soak, diurnal, and running losses). The nature and amount of potential MSATs associated with fuel vapors depend primarily on the fuel composition and the temperatures involved. Gasoline is volatile and evaporates at normal ambient temperatures, while diesel fuel is relatively non-volatile. Thus evaporative emissions are only an issue for gasoline-fueled vehicles (or vehicles using volatile alternative fuels such as methanol). Evaporative and refueling emissions are controlled by eliminating sources of potential liquid and vapor leaks within the vehicle fuel system and venting any vapors to an activated carbon canister or similar device. Activated carbon effectively adsorbs most hydrocarbon compounds, including the common evaporative-related MSATs. Particulate matter emissions from motor vehicles are primarily composed of partially burned carbon and hydrocarbons from the fuel and engine oil, and to a lesser degree, metals and other inorganic compounds from contaminants or additives in the fuel or engine oil, or products of engine wear in the oil. Since our PM exhaust emission standards apply without regard to the source of the PM, manufacturers must account for all of these emissions. Manufacturers have significantly reduced PM emissions associated with unburned fuel and engine oil through combustion system and engine modifications. B. EPA's Motor Vehicle-Based Emission Control Program To understand the relationship between the Agency's current emission control program for on-highway vehicles and the control of MSATs, it is important to first understand the structure and scope of our current emission control programs. EPA's emission control program for on-highway vehicles has historically been divided into two broad vehicle/engine categories that we regulate: “light-duty” (vehicles 8,500 pounds gross vehicle weight rating (GVWR) or less) and “heavy-duty” (vehicles above 8,500 pounds GVWR). 30 Within these light-duty and heavy-duty categories, we further distinguish vehicles and sometimes establish different emission limits based on vehicle size or other factors. For example, within the light-duty category, in the past we have often had different programs for light-duty vehicles and light-duty trucks. 30 EPA recently created the new category of “medium-duty passenger vehicles” (MDPVs) that includes passenger vehicles over 8,500 pounds GVWR. 1. Light-Duty Vehicles Before our regulations, cars emitted more than 9 grams per mile (gpm) HC in exhaust emissions. Our HC emission standards in the 1970s and 1980s cut these levels by more than an order of magnitude, to a level of 0.41 gpm in 1980. In 1991, we finalized Tier 1 controls for light-duty vehicles and light-duty trucks to be phased in from 1994 to 1996 (56 FR 25724). In 1998, we developed an innovative, voluntary nationwide program to make new cars, called National Low Emission Vehicles (NLEV), significantly cleaner than Tier 1 cars (63 FR 926). The NLEV program went into effect in the Northeast states in 1999 and will go into effect in the rest of the country in 2001. Table IV-1 illustrates the declining exhaust standards through the NLEV program that have resulted in HC reductions in the 1970s through the 1990s and are expected to result in future reductions. 31 In December 1999, the Agency finalized the Tier 2/sulfur rule establishing light-duty requirements that will be phased-in beginning with the 2004 model year. A more detailed discussion of the Tier 2 program follows in section C. 31 Our programs achieve VOC reductions through standards that limit HC, NMHC, or NMOG. Table IV-1. Hydrocarbon (HC) Exhaust Emission Standards for Light-Duty Vehicles (gpm) Year 1970 1972 1975 1980 1994 2001 HC 2.2 3.4 1.5 0.41 0.31 1 0.09 2 1 The 1994 standard is an nonmethane hydrocarbon (NMHC) standard. 2 The 2001 standard is an nonmethane organic gas (NMOG) standard. Our existing regulations contain test procedures to measure evaporative hydrocarbon emissions during a simulated parking event (diurnal emissions) and immediately following a drive (hot soak emissions). In 1993, we finalized more stringent evaporative emission test procedures which apply to light-duty and heavy-duty gasoline vehicles. These procedures were fully phased in by 1999 (58 FR 16002). The 1993 rule also addressed fuel spitback during refueling with a vehicle test to ensure that no spillage occurs when a vehicle is refueled at a rate of up to 10 gallons (37.9 liters) per minute. The Tier 2 rule included even more stringent requirements. We have also finalized on-board refueling vapor recovery (ORVR) requirements for light-duty gasoline vehicles (59 FR 16262, April 6, 1994), and proposed to extend ORVR to heavy-duty gasoline vehicles between 8,500 and 10,000 lbs GVWR (64 FR 58471, October 29, 1999). ORVR is a nationwide program for capturing refueling emissions by collecting vapors from the vehicle gas tank and storing them in the vehicle during refueling. The fuel vapors are then purged into the engine air intake to be burned while the vehicle is being driven. 2. Heavy-Duty Vehicles Table IV-2 summarizes the hydrocarbon and PM standards for heavy-duty engines. Also shown in the table are estimates of emission rates from uncontrolled engines. Not shown in the table are the standards in our recently proposed 2007 heavy-duty rulemaking. 32 In that NPRM we proposed exhaust emission standards of 0.14 NMHC and 0.01 PM for all heavy-duty engines. 32 65 FR 35429, June 2, 2000. Table IV-2.—HC and PM Exhaust Emissions and Standards for Heavy-Duty Engines Gasoline (Otto-Cycle) Exhaust HC Diesel Exhaust HC Exhaust PM Uncontrolled Emissions 10-13 g/bhp-hr 4 g/bhp-hr 0.7 g/bhp-hr Current Standards 1.1 g/bhp-hr a 1.3 g/bhp-hr 0.10 g/bhp-hr 2004/5 Standards 0.25 g/bhp-hr b 0.4 g/bhp-hr c 0.10 g/bhp-hr a Current standard is 1.9 g/bhp-hr for Otto-cycle vehicles over 14,000 GVWR. b Standard has been proposed as a 2005 NMHC+NOx standard; level shown is estimated equivalent NMHC standard. c Standard is a 2004 NMHC+NOx standard; level shown is estimated equivalent NMHC standard. C. Feasibility of More Stringent Vehicle-Based Standards To Reduce MSATs Section III of this proposal highlights the very significant reduction in toxics emissions that have been achieved as a result of EPA's on-highway emission control programs. Most recently, the Agency has finalized the Tier 2/sulfur requirements which will require manufacturers to incorporate the latest light-duty emission controls. EPA has also proposed new heavy-duty engine and vehicle standards and on-highway diesel fuel sulfur control requirements that would also result in large emission reductions. 33 This section summarizes these two new technology-forcing programs. 33 65 FR 35429, June 2, 2000. 1. Light-Duty Vehicles Finalized in December 1999, the Tier 2/sulfur requirements phase-in a single set of tailpipe emission standards that will, for the first time, apply to all passenger cars, light-duty trucks (LDTs), and larger passenger vehicles. To enable the very clean Tier 2 vehicle emission control technology to be introduced and to maintain its effectiveness, nationwide gasoline sulfur requirements were also put into place. The Tier 2 program begins in 2004 for passenger cars and light LDTs (LDTs up to 6,000 pounds GVWR), while an interim program begins in 2004 for heavy LDTs (LDTs over 6,000 pounds GVWR). For heavy LDTs and MDPVs (medium-duty passenger vehicles), the Tier 2 standards will be phased in beginning in 2008, with full compliance in 2009. Thus, when fully implemented all vehicles designed for passenger use will have to meet the stringent new emission standards. The Tier 2 program is designed to focus on reducing the ozone and particulate matter air quality impact for these vehicles. Ozone reductions will be achieved through control of nitrogen oxides and non-methane hydrocarbons. As discussed above, it is the control of NMHC through the NMOG standards that results in the control of the gaseous toxics. Control of PM emissions will occur through reductions in sulfur. The Tier 2 rule also established stringent PM standards. Because all Tier 2 standards are fuel neutral, the PM standards apply to both gasoline and diesel vehicles. The Tier 2 standards will reduce new vehicle NO X levels to an average of 0.07 grams per mile. The NMOG standards vary depending on which of the various “bins” ( i.e. , certification categories) the manufacturers choose to use in complying with the average NO X standard. However, we expect significant reductions in NMOG emissions from these vehicles as a result of the more stringent NMOG standards in the bins and the need to select bins to meet the NO X average. When fully phased-in, we expect fleet average NMOG levels below the 0.09 g/mi level. The Tier 2 rule also finalized formaldehyde standards that harmonize federal standards with the California's LEV II program. The standards are primarily of concern for vehicles fueled with methanol because formaldehyde is chemically similar to methanol and is likely to be produced when methanol is not completely burned in the engine. In order to meet strict Tier 2 standards on a fleet-wide average, manufacturers will have to use a combination of sophisticated calibration changes and emission system hardware modifications to increase and maintain high control system efficiency. They will be challenged to maintain tight air-fuel control and improved catalyst performance, especially achieving better catalyst thermal management. Minimizing the time necessary for the catalyst to reach its operating temperature will be especially critical, since the vast majority of emissions occur in the minute or less which passes before the catalyst “lights off.” Many manufacturers are going to have to depend more on the precious metal palladium for oxidation of NMOG and CO emissions, as well as the reduction of NO X , because palladium is more tolerant to high temperatures to increase in-use efficiency. The Tier 2 standards for evaporative emissions represent, for most vehicles, more than a 50-percent reduction in diurnal plus hot soak standards from those that will be in effect in the years immediately preceding Tier 2 implementation. These standards should achieve similar reductions in gaseous MSATs, especially since activated carbon preferentially absorbs larger organic molecules. Under these requirements, it is likely that manufacturers will also need to upgrade materials and both increase the reliability of fuel/vapor hose connections and fittings and reduce the number used in the system. Taken as a whole, the Tier 2 program presents the manufacturers with significant compliance challenges in the coming years. It will require the use of hardware and emission control techniques and strategies not used in the fleet today. Bringing essentially all passenger vehicles under the same emission control program regardless of their size, weight, and application is a major engineering challenge. While there may be other prototype technologies on the horizon which could potentially reduce cold-start emissions and therefore air toxics, given the cost and engineering burden associated with Tier 2, it is not appropriate to propose standards based on these technologies. We are not convinced that these technologies would be feasible and cost effective on a fleet-wide basis at this time. This is discussed in more detail in the TSD. 2. Heavy-Duty Vehicles With regard to exhaust emission standards, the 2007 heavy-duty engine standards would reduce hydrocarbon emissions to levels approaching 0.1 g/bhp-hr for both gasoline and diesel. This would result in a significant reduction even when compared to the 2004 standards. Similarly, the proposed exhaust PM standard for heavy-duty diesel engines is very stringent. The proposed value of 0.01 g/bhp-hr is a 90-percent reduction from current standards which are currently being achieved with significant combustion chamber and engine modifications. Achieving a 0.01 g/bhp-hr standard will require the use of particulate trap-oxidizers. This technology will also result in HC emission reductions. It is further worth noting that the 2007 proposal includes provisions for a closed crankcase for turbocharged diesel engines. Crankcase emissions from these engines are a significant source of MSATs (PM and hydrocarbons) which has previously remained uncontrolled. For chassis-certified gasoline-powered heavy-duty vehicles, EPA proposed that beginning in 2007 they meet exhaust hydrocarbon standards of similar stringency to those discussed above for Tier 2. These include hydrocarbon standards of 0.195 g/mi for vehicles of 8,500-10,000 lbs GVWR and 0.23 g/mi for vehicles of 10,001-14,000 lbs GVWR. Fuel quality changes will enable gasoline and diesel-powered vehicles/engines to meet the more stringent standards over their full life. As part of the Tier 2 rule, EPA promulgated provisions limiting gasoline sulfur levels to 30 ppm average and 80 ppm cap. This program phases in beginning in 2004, and will enable a new generation of vehicle emission control for heavy-duty gasoline vehicles and also improve the emission performance of the current fleet. Sulfur is a fuel contaminant, and controlling sulfur will also reduce sulfate PM emissions. The 2007 heavy-duty proposal mentioned above also includes provisions to greatly reduce the sulfur content of current on-highway diesel fuel. Not only will this reduction enable the emission control technology now under development, but it will also reduce sulfate PM emissions as was the case for gasoline. We have also proposed more stringent evaporative standards, which would force even further refinements in fuel/vapor systems. Onboard refueling vapor control is proposed to be effective for 2004 for all heavy-duty gasoline-powered vehicles. This would reduce emissions from current uncontrolled levels by 95 percent. In addition, as part of the 2007 proposal, evaporative emission standards are proposed to be reduced by 50 percent over current standards. Both refueling controls and further evaporative controls would reduce evaporative emissions of air toxics from heavy-duty vehicles even further. The proposal for 2007 heavy-duty engine and vehicle standards contains extensive analysis and discussion of the technological feasibility. This analysis demonstrates that the proposed heavy-duty standards reflect the greatest degree of emission reduction achievable through the application of technology that will be available considering costs and other relevant factors. EPA expects that the recently proposed rulemaking to establish 2007 model year standards for heavy-duty diesel engines will satisfy the criteria in section 202(a) as well as 202(l)(2) and therefore defers to the technical decisions that will be made in that rulemaking. For further information on the diesel engine proposal see 65 FR 35430 (June 2, 2000). 3. Conclusion The Tier 2 program represents a comprehensive, integrated package of exhaust, evaporative, and fuel quality standards. The Tier 2 program will achieve significant reductions in NMHC, NO X , and PM emissions from all light-duty vehicles in the program. Emission control in the Tier 2 program will be based on the widespread implementation of advanced catalyst and related control system technology. The standards are so stringent that they will require the maximum level of control technology be used. To illustrate this point, it is worth noting that about 80 percent of all emissions from a Tier 2 vehicle will occur in the first 60 seconds of operation, before the catalyst “lights-off.” Manufacturers will have to optimize their cold-start strategies and the efficiency of warmed systems to achieve the Tier 2 levels. Compliance with the Tier 2 standards will require the application of emission technology not widely used in the light-duty fleet today and in some cases the use of technological approaches still under development. Meeting the Tier 2 requirements will significantly reduce air toxics as a result of reductions in NMHC. The emission control program for heavy-duty engines and vehicles has achieved major reductions in the emissions of criteria pollutants and their precursor emissions. New stringent emissions were established for heavy-duty diesel engines in a final rule promulgated in the fall of 1997 that will take effect in 2004. In October of 1999, we published a notice proposing to reaffirm the 2004 heavy-duty diesel engine emission standards. The notice also proposed new 2004 model year emission standards and related requirements for heavy-duty Otto-cycle vehicles/engines and supplemental test requirements for heavy-duty diesel engines. We also recently announced a further initiative in control of heavy-duty vehicle/engine emissions in May 2000. This was done in the proposal to establish new heavy-duty diesel and Otto-cycle engine standards and vehicle emission standards for 2007. It also proposed new on-highway diesel fuel sulfur control requirements. V. Evaluation of Additional Fuel-based Controls In previous sections, we showed that the mobile source toxics inventory will continue to decline through 2020 due to existing programs. In this section we consider the role of fuels programs in reducing toxics emissions from mobile sources. Fuels contribute to air toxics emissions in two ways: evaporative emissions of the fuel, and exhaust emissions due to combustion of the fuel. One means of controlling toxics emissions from motor vehicles is to change the benzene content of the fuel. In this section, we discuss our investigation of additional fuel-based controls for reducing toxics emissions. We begin with a discussion of the current gasoline-based toxics control programs, including a presentation of the over-compliance arising under the federal reformulated gasoline (RFG) and anti-dumping programs. This is followed by a discussion of why we believe that gasoline benzene control is an appropriate initial focus for additional fuel controls to reduce MSATs. Next, we present our proposed anti-backsliding program for fuel benzene in both RFG and conventional gasoline (CG). As part of this discussion we address the issue of state controls of benzene levels in gasoline. We discuss potential future benzene controls that would be included as part of the investigation in our proposed Technical Analysis Plan. Finally, we discuss other fuel controls considered in EPA's development of this proposal. A. What Current Gasoline Programs Control Toxics Emissions? Current federal gasoline programs that control toxics emissions include the prohibition on leaded gasoline for highway use, the summertime volatility requirements, and the reformulated gasoline and anti-dumping programs. The first of these programs, the prohibition on leaded gasoline for use in motor vehicles, is a Clean Air Act requirement adopted in 1990 that was designed to complete the phase-out of leaded gasoline because of its contribution to national ambient lead levels. Lead is a probable human carcinogen with a variety of serious non-cancer health effects at low dose levels. The transition to unleaded gasoline began in 1974, and leaded gasoline has been banned for highway use since 1996 (see CAA Section 211(n)). Under the second program, the federal volatility requirements, every area of the continental U.S. has a maximum summertime gasoline Reid vapor pressure (RVP). RVP is a volatility measurement of gasoline. Generally speaking, a fuel with a higher RVP evaporates more quickly than a fuel with a lower RVP. Thus, by instituting a maximum summertime RVP for each area, we control evaporative emissions of the volatile components of gasoline, including benzene and other gaseous toxics. The federal reformulated gasoline (RFG) program includes, in addition to standards on VOC and NO X emissions, several requirements related to toxics. Specifically, the RFG program (covering about one-third of the gasoline sold in the country) includes standards on the benzene content of fuel as well as standards governing the overall toxics emissions associated with evaporation and combustion of the fuel. Toxics emissions covered under the RFG program include exhaust and evaporative benzene, formaldehyde, acetaldehyde, 1,3-butadiene and polycyclic organic matter (POM). Under the Phase II RFG program which began in January 2000, a refinery's or importer's annual average total toxics emissions, as measured by the Complex Model, 34 must be 21.5 percent less than the toxics emissions attributable to the statutory baseline fuel. Additionally, a refinery's or importer's annual average RFG benzene content cannot exceed 0.95 percent by volume, and no batch may exceed 1.3 percent by volume. Alternatively, no batch of RFG may have a benzene content exceeding 1.0 percent by volume. Each refinery and importer must choose annua [Text truncated at 120,000 characters. The full text is on the page linked above.] --- Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A00-18640. Public record. Not legal advice.