# Control of Air Pollution From New Motor Vehicles: Proposed Heavy-Duty Engine and Vehicle Standards and Highway Diesel Fuel Sulfur Control Requirements > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A00-12952 ## Record - **Collection:** Federal Register - **Document type:** Proposed Rule - **Published:** June 2, 2000 - **Citation:** 65 FR 35430 ## Text ENVIRONMENTAL PROTECTION AGENCY 40 CFR Parts 69, 80, and 86 [AMS-FRL-6705-2] RIN 2060-AL69 Control of Air Pollution From New Motor Vehicles: Proposed Heavy-Duty Engine and Vehicle Standards and Highway Diesel Fuel Sulfur Control Requirements AGENCY: Environmental Protection Agency. ACTION: Notice of proposed rulemaking. SUMMARY: Diesel engines contribute considerable pollution to our nation's continuing air quality problems. Even with more stringent heavy-duty highway engine standards set to take effect in 2004, these engines will continue to emit large amounts of nitrogen oxides and particulate matter, both of which contribute to serious public health problems in the United States. These problems include premature mortality, aggravation of respiratory and cardiovascular disease, aggravation of existing asthma, acute respiratory symptoms, chronic bronchitis, and decreased lung function. Numerous studies also link diesel exhaust to increased incidence of lung cancer. The diesel engine is a vital workhorse in the United States, moving much of the nation's freight, and carrying out much of its farm, construction, and other labor. Diesel engine sales have grown over the last decade, so that now about a million new diesel engines are put to work in the U.S. every year. Diesels overwhelmingly dominate the bus and large truck markets and have been capturing a growing share of the light heavy-duty vehicle market over the last decade. We are proposing a comprehensive national control program that would regulate the heavy-duty vehicle and its fuel as a single system. We are proposing new emission standards that would begin to take effect in 2007, and would apply to heavy-duty highway engines and vehicles. These proposed standards are based on the use of high-efficiency catalytic exhaust emission control devices or comparably effective advanced technologies. Because these devices are damaged by sulfur, we are also proposing to reduce the level of sulfur in highway diesel fuel significantly by the middle of 2006. Diesel engines are more durable and get better fuel economy than gasoline engines, but also pollute significantly more. If this program is implemented as proposed, diesel trucks and buses will have dramatically reduced emission levels. This proposed program will bring heavy-duty diesel emissions on par with new cars. The results of this historic proposal would be comparable to the advent of the catalytic converter on cars, as the proposed standards would, for the first time, result in the widespread introduction of exhaust emission control devices on diesel engines. By 2007, we estimate that heavy-duty trucks and buses will account for as much as 30 percent of nitrogen oxides emissions from transportation sources and 14 percent of particulate matter emissions. In some urban areas, the contribution will be even greater. The standards for heavy-duty vehicles proposed in this rule would have a substantial impact on the mobile source inventories of oxides of nitrogen and particulate matter. Beginning the program in the 2007 model year ensures that emission reductions start early enough to counter the upward trend in heavy-duty vehicle emissions that would otherwise occur because of the increasing number of vehicle miles traveled each year. This proposed program would result in particulate matter and oxides of nitrogen emission levels that are 90% and 95% below current standards levels, respectively. In order to meet these more stringent standards for diesel engines, the proposal calls for a 97% reduction in the sulfur content of diesel fuel. As a result, diesel vehicles would achieve gasoline-like exhaust emission levels, in addition to their inherent advantages over gasoline vehicles with respect to fuel economy, lower greenhouse gas emissions, and lower evaporative hydrocarbon emissions. We are also proposing more stringent standards for heavy-duty gasoline vehicles. The clean air impact of this program would be dramatic when fully implemented. By 2030, this program would reduce annual emissions of nitrogen oxides, nonmethane hydrocarbons, and particulate matter by a projected 2.8 million, 305,000 and 110,000 tons, respectively. We project that these reductions and the resulting significant environmental benefits of this program would come at an average cost increase of about $1,700 to $2,800 per new vehicle in the near term and about $1000 to $1600 per new vehicle in the long term, depending on the vehicle size. In comparison, new vehicle prices today can range up to $250,000 for larger heavy-duty vehicles. The cost of reducing the sulfur content of diesel fuel would result in an estimated increase of approximately four cents per gallon. DATES: Comments: We must receive your comments by August 14, 2000. Hearings: We will hold public hearings on June 19, 20, 22, 27, and 29, 2000. See ADDRESSES below for the locations of the hearings. 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 copies of written comments (in duplicate if possible) to the contact person listed below. Send e-mail comments to diesel@epa.gov. EPA's Air Docket makes materials related to this rulemaking available for review in Docket No. A-99-06 located at U.S. Environmental Protection Agency (EPA), Air Docket (6102), Room M-1500, 401 M Street, SW, Washington, DC 20460 (on the ground floor in Waterside Mall) from 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 at (202) 260-4400. We may charge a reasonable fee for copying docket materials, as provided in 40 CFR part 2. Hearings: We will hold five public hearings at the following locations: June 19, 2000, Crowne Plaza Hotel, 1605 Broadway, New York, NY, 10019 June 20, 2000, Rosemont Convention Center, 5555 N. River Rd., Rosemont, IL 60018 June 22, 2000, Renaissance Atlanta Hotel, 590 W. Peachtree St, NW, Atlanta, GA, 30308 June 27, 2000, Hyatt Regency, 711 S. Hope Street, Los Angeles, CA, 90017 June 29, 2000, Doubletree Hotel, 3203 Quebec St., Denver, CO, 80207 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 X, “Public Participation” below for more information on the comment procedure and public hearings. FOR FURTHER INFORMATION CONTACT: Margaret Borushko, U.S. EPA, National Vehicle and Fuel Emissions Laboratory, 2000 Traverwood, Ann Arbor MI 48105; Telephone (734) 214-4334, FAX (734) 214-4816, E-mail borushko.margaret@epa.gov. SUPPLEMENTARY INFORMATION: Regulated Entities This proposed action would affect you if you produce or import new heavy-duty engines which are intended for use in highway vehicles such as trucks and buses or heavy-duty highway vehicles, or convert heavy-duty vehicles or heavy-duty engines used in highway vehicles to use alternative fuels. It would also affect you if you produce, distribute, or sell highway diesel 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 69, 80, and 86. If you have questions, call the person listed in the FOR FURTHER INFORMATION CONTACT section above. Category NAICS Codes a SIC Codes b Examples of potentially regulated entities Industry 336112 3711 Engine and truck manufacturers. 336120 Industry 811112 7533 Commercial importers of vehicles and vehicle components. 811198 7549 Industry 324110 2911 Petroleum refiners. Industry 422710 5171 Diesel fuel marketers and distributors. 422720 5172 Industry 484220 4212 Diesel fuel carriers. 484230 4213 a North American Industry Classification System (NAICS). b Standard Industrial Classification (SIC) system code. Access to Rulemaking Documents Through the Internet Today's proposal is available electronically on the day of publication from the Environmental Protection Agency Internet Web site listed below. Electronic copies of the preamble, regulatory language, Draft Regulatory Impact Analysis, and other documents associated with today's proposal are available from the EPA Office of Transportation and Air Quality (formerly the Office of Mobile Sources) Web site listed below shortly after the rule is signed by the Administrator. This service is free of charge, except any cost that you incur for connecting to the Internet. Environmental Protection Agency Web Site: http://www.epa.gov/fedrgstr/ (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 “Heavy Trucks/Busses” topic.) Please note that due to differences between the software used to develop the document and the software into which document may be downloaded, changes in format, page length, etc. may occur. Table of Contents I. A Brief Overview A. What Is Being Proposed? 1. Heavy-Duty Emission Standards 2. Fuel Quality Standards B. Why Is EPA Making This Proposal? 1. Heavy-Duty Vehicles Contribute to Serious Air Pollution Problems 2. Technology-Based Solutions 3. Basis for Action Under the Clean Air Act C. Putting This Proposal In Perspective 1. Diesel Popularity 2. Past Progress and New Developments 3. Tier 2 Emissions Standards 4. Mobile Source Air Toxics Rulemaking 5. Nonroad Engine Standards and Fuel 6. Actions in California 7. Retrofit Programs 8. Actions in Other Countries II. The Air Quality Need and Projected Benefits A. Overview B. Public Health and Welfare Concerns 1. Ozone and Its Precursors a. Health and Welfare Effects From Short-Term Exposures to Ozone b. Current and Future Nonattainment Status With the 1-Hour Ozone NAAQS i. Ozone Predictions Made in the Tier 2 Rulemaking and Other Information on Ozone Attainment Prospects ii. Areas At Risk of Exceeding the 1-Hour Ozone Standard iii. Conclusion c. Public Health and Welfare Concerns from Prolonged and Repeated Exposures to Ozone 2. Particulate Matter a. Health and Welfare Effects i. Particulate Matter Generally ii. Special Considerations for Diesel PM b. Potential Cancer Effects of Diesel Exhaust c. Noncancer Effects of Diesel Exhaust d. Attainment and Maintenance of the PM 10 NAAQS i. Current PM 10 Nonattainment ii. Risk of Future Exceedances of the PM 10 Standard e. Public Health and Welfare Concerns from Exposure to Fine PM f. Visibility and Regional Haze Effects of Ambient PM g. Other Welfare Effects Associated with PM h. Conclusions Regarding PM 3. Other Criteria Pollutants 4. Other Air Toxics a. Benzene b. 1,3-Butadiene c. Formaldehyde d. Acetaldehyde e. Acrolein f. Dioxins 5. Other Environmental Effects a. Acid Deposition b. Eutrophication and Nitrification c. POM Deposition C. Contribution From Heavy-Duty Vehicles 1. NO X Emissions 2. PM Emissions 3. Environmental Justice D. Anticipated Emissions Benefits 1. NO X Reductions 2. PM Reductions 3. NMHC Reductions 4. Additional Emissions Benefits a. CO Reductions b. SO X Reductions c. Air Toxics Reductions E. Clean Heavy-Duty Vehicles and Low-Sulfur Diesel Fuel Are Critically Important for Improving Human Health and Welfare III. Heavy-Duty Engine and Vehicle Standards A. Why Are We Setting New Heavy-Duty Standards? B. Technology Opportunity for Heavy-Duty Vehicles and Engines C. What Engine and Vehicle Standards Are We Proposing? 1. Heavy-Duty Engine Standards a. Federal Test Procedure b. Not-to-Exceed and Supplemental Steady-State Test c. Crankcase Emissions Control 2. Heavy-Duty Vehicle Standards a. Federal Test Procedure b. Supplemental Federal Test Procedure 3. Heavy-Duty Evaporative Emission Standards D. Standards Implementation Issues 1. Alternative Approach To Phase-In 2. Implementation Schedule for Gasoline Engine and Vehicle Standards E. Feasibility of the Proposed New Standards 1. Feasibility of Stringent Standards for Heavy-Duty Diesel a. Meeting the Proposed PM Standard b. Meeting the Proposed NO X Standard c. Meeting the Proposed NMHC Standard d. Meeting the Crankcase Emissions Requirements e. The Complete System 2. Feasibility of Stringent Standards for Heavy-Duty Gasoline 3. Feasibility of the Proposed Evaporative Emission Standards F. Need for Low-Sulfur Diesel Fuel 1. Diesel Particulate Filters and the Need for Low-Sulfur Fuel a. Inhibition of Trap Regeneration Due to Sulfur b. Loss of PM Control Effectiveness c. Increased Maintenance Cost for Diesel Particulate Filters Due to Sulfur 2. Diesel NO X Catalysts and the Need for Low-Sulfur Fuel a. Sulfate Particulate Production for NO X Control Technologies b. Sulfur Poisoning (Sulfate Storage) on NO X Adsorbers c. Sulfur Impacts on Catalytic Efficiency 3. What About Sulfur in Engine Lubricating Oils? G. Fuel Economy Impact of Advanced Emission Control Technologies 1. Diesel Particulate Filters and Fuel Economy 2. NO X Control Technologies and Fuel Economy 3. Emission Control Systems for 2007 and Net Fuel Economy Impacts H. Future Reassessment of Diesel NO X Control Technology I. Encouraging Innovative Technologies IV. Diesel Fuel Requirements A. Why Do We Believe New Diesel Fuel Sulfur Controls Are Necessary? B. What New Sulfur Standard Are We Proposing for Diesel Fuel? 1. Why Is EPA Proposing a 15 ppm Cap and Not a Higher or Lower Level? 2. Why Propose a Cap and Not an Average? 3. Should the Proposed 15 ppm Cap Standard Also Have an Average Standard? 4. Why We Believe Our Diesel Fuel Sulfur Program Should Be Year-round and Nationwide C. When Would the New Diesel Sulfur Standard Go Into Effect? D. Why We Believe the Proposed Diesel Sulfur Standard is Technologically Feasible 1. What Technology Would Refiners Use? 2. Are These Technologies Commercially Demonstrated? 3. Are There Unique Concerns for Small Refiners? 4. Can Refiners Comply with an April 1, 2006 Start Date? 5. Can a 15 ppm Cap on Sulfur be Maintained by the Distribution System? 6. What are the Potential Impacts of the Proposed Sulfur Change on Lubricity, Other Fuel Properties, and Specialty Fuels? a. What Is Lubricity and Why Might It be a Concern? b. Voluntary Approach for the Maintenance of Fuel Lubricity c. What Are the Possible Impacts of Potential Changes in Fuel Properties Other Than Sulfur on the Materials Used in Engines and Fuel Supply Systems? d. What Impact Would the 15 ppm Cap Have on Diesel Performance Additives? e. What Are the Concerns Regarding the Potential Impact on the Availability and Quality of Specialty Fuels? E. Who Would Be Required to Meet This Proposed New Diesel Sulfur Standard? F. What Might Be Done To Encourage the Early Introduction of Low-Sulfur Diesel Fuel? V. Economic Impact A. Cost for Diesel Vehicles to Meet Proposed Emissions Standards 1. Summary of New System and Operating Costs 2. New System Costs for NO X and PM Emission Control 3. Operating Costs Associated With NO X and PM Control B. Cost for Gasoline Vehicles to Meet Proposed Emissions Standards 1. Summary of New System Costs 2. Operating Costs Associated with Meeting the Heavy-Duty Gasoline Standard C. Benefits of Low-Sulfur Diesel Fuel for the Existing Diesel Fleet D. Cost of Proposed Fuel Change 1. Refinery Costs 2. Cost of Possibly Needed Lubricity Additives 3. Distribution Costs E. Aggregate Costs F. Cost Effectiveness 1. What Is the Cost Effectiveness of This Proposed Program? 2. Comparison With Other Means of Reducing Emissions G. Does the Value of the Benefits Outweigh the Cost of the Proposed Standards? 1. What Is the Purpose of This Benefit-Cost Comparison? 2. What Is Our Overall Approach to the Benefit-Cost Analysis? 3. What Are the Significant Limitations of the Benefit-Cost Analysis? 4. How Will the Benefit-Cost Analysis Change From the Tier 2 Benefit-Cost Analysis? 5. How Will We Perform the Benefit-Cost Analysis? 6. What Types of Results Will Be Presented in the Benefit-Cost Analysis? VI. Alternative Program Options A. What Other Fuel Implementation Options Have We Considered? 1. What Are the Advantages and Disadvantages of a Phase-in Approach to Implementing the Low Sulfur Fuel Program? a. Availability of Low Sulfur Diesel Fuel b. Misfueling c. Distribution System Impacts d. Uncertainty in the Transition to Low Sulfur e. Cost Considerations Under a Phase-in Approach 2. What Phase-in Options Is EPA Seeking Comment on in Today's Proposal? a. Refiner Compliance Flexibility i. Overview of Compliance Flexibility ii. What Are the Key Considerations in Designing the Compliance Flexibility? iii. How Does This Compliance Flexibility Relate to the Options for Small Refiner Flexibility? iv. How Would the Averaging, Banking and Trading Program Work? v. Compliance, Recordkeeping, and Reporting Requirements b. Refiner-Ensured Availability c. Retailer Availability Requirement 2. Why Is a Regulation Necessary to Implement the Fuel Program? 3. Why Not Just Require Low-Sulfur Diesel Fuel for Light-Duty Vehicles and Light-Duty Trucks? 4. Why Not Phase-Down the Concentration of Sulfur in Diesel Fuel Over Time as Was Done With Gasoline in the Tier 2 Program? B. What Other Fuel Standards Have We Considered In Developing This Proposal? 1. What About Setting the 15 ppm Sulfur Level as an Average? a. Emission Control Technology Enablement Under a 15 ppm Average Standard b. Vehicle and Operating Costs for Diesel Vehicles to Meet the Proposed Emissions Standards with a 15 ppm Average Standard c. Diesel Fuel Costs Under a 15 ppm Average Standard d. Emission Reductions Under a 15 ppm Average Standard e. Cost Effectiveness of a 15 ppm Average Standard 2. What About a 5 ppm Sulfur Level? 3. What About a 50 ppm Sulfur Level? 4. What Other Fuel Properties Were Considered for Highway Diesel Fuel? C. Should Any States or Territories Be Excluded from this Rule? 1. What Are the Anticipated Impacts of Using High-Sulfur Fuel in New and Emerging Diesel Engine Technologies if Areas Are Excluded From This Rule? 2. Alaska a. Why is Alaska Unique? b. What Flexibilities Are We Proposing for Alaska? c. How Do We Propose to Address Alaska's Petition Regarding the 500 ppm Standard? 3. American Samoa, Guam, and the Commonwealth of Northern Mariana Islands a. Why are We Considering Excluding American Samoa, Guam, and the Commonwealth of Northern Mariana Islands? b. What Are the Relevant Factors? c. What Are the Options and Proposed Provisions for the Territories? D. What About the Use of JP-8 Fuel in Diesel Equipped Military Vehicles? VII. Requirements for Engine and Vehicle Manufacturers A. Compliance With Standards and Enforcement B. Certification Fuel C. Averaging, Banking, and Trading D. Chassis Certification E. FTP Changes to Accommodate Regeneration of Aftertreatment Devices F. On-Board Diagnostics G. Supplemental Test Procedures H. Misfueling Concerns I. Light-Duty Provisions J. Correction of NO X Emissions for Humidity Effects VIII. Requirements For Refiners, Importers, and Fuel Distributors A. Compliance and Enforcement 1. Overview 2. What Are the Requirements for Refiners and Importers? a. General Requirements b. Dyes and Markers 3. What Requirements Apply Downstream? a. General Requirements b. Use of Used Motor Oil in Diesel-Fueled New Technology Vehicles c. Use of Kerosene and Other Additives in Diesel Fuel 4. What Are the Proposed Testing and Sampling Methods and Requirements? a. Testing Requirements and Test Methods b. Sampling Methods 5. What Are the Proposed Recordkeeping Requirements? 6. Are There Any Proposed Exemptions Under This Subpart? 7. Would California Be Exempt From the Rule? 8. What Are the Proposed Liability and Penalty Provisions for Noncompliance? a. Presumptive Liability Scheme of Current EPA Fuels Programs b. Affirmative Defenses for Liable Parties c. Penalties for Violations 9. How Would Compliance With the Diesel Sulfur Standards Be Determined? B. Lubricity C. Would States Be Preempted From Adopting Their Own Sulfur Control Programs for Highway Diesel Fuel? D. Refinery Air Permitting E. Provisions for Qualifying Refiners 1. Allow Small Refiners to Continue Selling 500 ppm Highway Diesel 2. Temporary Waivers Based on Extreme Hardship Circumstances 3. 50 ppm Sulfur Cap for Small Refiners IX. Standards and Fuel for Nonroad Diesel Engines X. Public Participation A. Submitting Written and E-mail Comments B. Public Hearings XI. Administrative Requirements A. Administrative Designation and Regulatory Analysis B. Regulatory Flexibility Act 1. Potentially Affected Small Businesses 2. Small Business Advocacy Review Panel and the Evaluation of Regulatory Alternatives C. Paperwork Reduction Act D. Intergovernmental Relations 1. Unfunded Mandates Reform Act 2. 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 G. Executive 13132: Federalism XII. Statutory Provisions and Legal Authority I. A Brief Overview This proposal covers the second of two phases in a comprehensive nationwide program for controlling emissions from heavy-duty engines (HDEs) and vehicles. It builds upon the phase 1 program we proposed last October (64 FR 58472, October 29, 1999). That action reviewed and proposed to confirm the 2004 model year emission standards set in 1997 (62 FR 54693, October 21, 1997), proposed stringent new emission standards for gasoline-fueled heavy-duty vehicles (HDVs), and proposed other changes to the heavy-duty program, including provisions to ensure in-use emissions control. Today's proposal takes the provisions of the October 1999 proposal as a point of departure. This second phase of the program looks beyond 2004, based on the use of high-efficiency exhaust emission control devices and the consideration of the vehicle and its fuel as a single system. In developing this proposal, we took into consideration comments received in response to an advance notice of proposed rulemaking (ANPRM) published in May of last year (64 FR 26142, May 13, 1999), and comments we received in response to our discussion of future standards in the heavy-duty 2004 standards proposal last October. We welcome comment on all facets of this proposal and its supporting analyses, including the levels and timing of the proposed emissions standards and diesel fuel quality requirements. We ask that commenters provide any technical information that supports the points made in their comments. This proposed program would result in particulate matter (PM) and oxides of nitrogen (NO X ) emission levels that are 90% and 95% below current standards levels, respectively. In order to meet these more stringent standards for diesel engines, the proposal calls for a 97% reduction in the sulfur content of diesel fuel. This proposal would make clean diesel fuel available in time for implementation of the light-duty Tier 2 standards. The heavy-duty engine standards would be effective starting in the 2007 model year and the low sulfur diesel fuel needed to facilitate the standards would be widely available by the middle of 2006. As a result, diesel vehicles would achieve gasoline-like exhaust emission levels, in addition to their inherent advantages over gasoline vehicles with respect to fuel economy, lower greenhouse gas emissions, and lower evaporative hydrocarbon emissions. We are also proposing more stringent standards for heavy-duty gasoline vehicles. The standards proposed would result in substantial benefits to public health and welfare and the environment through significant reductions in emissions of NO X , PM, nonmethane hydrocarbons (NMHC), carbon monoxide (CO), sulfur oxides (SO X ), and air toxics. We project that by 2030, this proposed phase 2 program would reduce annual emissions of NO X , NMHC, and PM by 2.8 million, 305,000 and 110,000 tons, respectively. Especially in the early years of this program, large reductions in the amount of direct and secondary PM caused by the existing fleet of heavy-duty vehicles would occur because of the improvement in diesel fuel quality. A. What Is Being Proposed? There are two basic parts to this proposal: (1) New exhaust emission standards for heavy-duty highway engines and vehicles, and (2) new quality standards for highway diesel fuel. The systems approach of combining the engine and fuel standards into a single program is critical to the success of our overall efforts to reduce emissions, because the emission standards would not be feasible without the fuel change. This is because the emission standards, if promulgated, are expected to result in the use of high-efficiency exhaust emission control devices that would be damaged by sulfur in the fuel. This proposal, by providing extremely low sulfur diesel fuel, would also enable cleaner diesel passenger vehicles and light-duty trucks. This is because the same pool of highway diesel fuel also services these light-duty diesel vehicles, and these vehicles can employ technologies similar to the high-efficiency heavy-duty exhaust emission control technologies that would be enabled by the fuel change. We believe these technologies are needed for diesel vehicles to comply with our recently adopted Tier 2 emissions standards for light-duty highway vehicles (65 FR 6698, February 10, 2000). We believe that this systems approach is a comprehensive way to enable promising new technologies for clean diesel affecting all sizes of highway diesel engines and, eventually, diesel engines used in nonroad applications too. The fuel change, in addition to enabling new technologies, would also produce emissions and maintenance benefits in the existing fleet of highway diesel vehicles. These benefits would include reduced sulfate and sulfur oxides emissions, reduced engine wear and less frequent oil changes, and longer-lasting exhaust gas recirculation (EGR) components on engines equipped with EGR. Heavy-duty gasoline vehicles would also be expected to reach cleaner levels due to the transfer of recent technology developments for light-duty applications, and the recent action taken to reduce sulfur in gasoline as part of the Tier 2 rule. The basic elements of the proposal are outlined below. Detailed provisions and justifications for our proposal are discussed in subsequent sections. 1. Heavy-Duty Emission Standards We are proposing a PM emissions standard for new heavy-duty engines of 0.01 grams per brake-horsepower-hour (g/bhp-hr), to take full effect in the 2007 HDE model year. We are also proposing standards for NO X and NMHC of 0.20 g/bhp-hr and 0.14 g/bhp-hr, respectively. These NO X and NMHC standards would be phased in together between 2007 and 2010, for diesel engines. The phase-in would be on a percent-of-sales basis: 25 percent in 2007, 50 percent in 2008, 75 percent in 2009, and 100 percent in 2010. Because of the more advanced state of gasoline engine emissions control technology, gasoline engines would be fully subject to these standards in the 2007 model year, although we request comment on phasing these standards in as well. A potential delay in the implementation date of the gasoline engine and vehicle standards to the 2008 model year arising from issues connected with the 2004 model year standards is discussed in section III.D.2. In addition, we are proposing a formaldehyde (HCHO) emissions standard of 0.016 g/bhp-hr for all heavy-duty engines, to be phased in with the NO X and NMHC standards, and the inclusion of turbocharged diesels in the existing crankcase emissions prohibition, effective in 2007. Proposed standards for complete HDVs would be implemented on the same schedule as for engine standards. For certification of complete vehicles between 8500 and 10,000 pounds gross vehicle weight rating (GVWR), the proposed standards are 0.2 grams per mile (g/mi) for NO X , 0.02 g/mi for PM, 0.195 g/mi for NMHC, and 0.016 g/mi for formaldehyde. 1 For vehicles between 10,000 and 14,000 pounds, the proposed standards are 0.4 g/mi for NO X , 0.02   g/mi for PM, 0.230 g/mi for NMHC, and 0.021 g/mi for formaldehyde. These standards levels are roughly comparable to the proposed engine-based standards in these size ranges. Note that these standards would not apply to vehicles above 8500 pounds that we classify as medium-duty passenger vehicles as part of our Tier 2 program. 1 Vehicle weight ratings in this proposal refer to GVWR (the curb weight of the vehicle plus its maximum recommended load of passengers and cargo) unless noted otherwise. Finally, we are proposing to revise the evaporative emissions standards for heavy-duty engines and vehicles, effective on the same schedule as the gasoline engine and vehicle exhaust emission standards. The proposed standards for 8500 to 14,000 pound vehicles are 1.4 and 1.75 grams per test for the 3-day diurnal and supplemental 2-day diurnal tests, respectively. Slightly higher standards levels of 1.9 and 2.3 grams per test would apply for vehicles over 14,000 pounds. These proposed standards represent more than a 50 percent reduction in the numerical standards as they exist today. 2. Fuel Quality Standards We are proposing that diesel fuel sold to consumers for use in highway vehicles be limited in sulfur content to a level of 15 parts per million (ppm), beginning June 1, 2006. This proposed sulfur standard is based on our assessment of how sulfur-intolerant advanced exhaust emission control technologies will be, and a corresponding assessment of the feasibility of low-sulfur fuel production and distribution. We are seeking comment on voluntary options for providing refiners with flexibility in complying with the low sulfur highway diesel fuel program. In addition, we request comment on some potential flexibility provisions to assist small refiners in complying with the program. With minor exceptions, existing compliance provisions for ensuring diesel fuel quality that have been in effect since 1993 would remain unchanged (55 FR 34120, August 21, 1990). B. Why Is EPA Making This Proposal? 1. Heavy-Duty Vehicles Contribute to Serious Air Pollution Problems As will be discussed in detail in section II, emissions from heavy-duty vehicles contribute greatly to a number of serious air pollution problems, and will continue to do so into the future absent further controls to reduce these emissions. First, heavy-duty vehicles contribute to the health and welfare effects of ozone, PM, NO X , SO X , and volatile organic compounds (VOCs), including toxic compounds such as formaldehyde. These adverse effects include premature mortality, aggravation of respiratory and cardiovascular disease (as indicated by increased hospital admissions and emergency room visits, school absences, work loss days, and restricted activity days), changes in lung function and increased respiratory symptoms, changes to lung tissues and structures, altered respiratory defense mechanisms, chronic bronchitis, and decreased lung function. Ozone also causes crop and forestry losses, while PM also causes damage to materials, and soiling. Second, both NO X and PM contribute to substantial visibility impairment in many parts of the U.S. Third, NO X emissions from heavy-duty trucks contribute to the acidification, nitrification and eutrophication of water bodies. Millions of Americans live in areas with unhealthful air quality that currently endangers public health and welfare. Without emission reductions from the proposed standards for heavy-duty vehicles, there is a significant risk that an appreciable number of areas across the country will violate the 1-hour ozone national ambient air quality standard (NAAQS) during the period when these standards will take effect. Furthermore, our analysis shows that PM 10 concentrations in 10 areas with a combined population of 27 million people face a significant risk of exceeding the PM 10 NAAQS without significant additional controls in 2007 or thereafter. Under the mandates and authorities in the Clean Air Act, federal, State, and local governments are working to bring ozone and particulate levels into compliance with the 1-hour ozone and PM 10 NAAQS through State Implementation Plan (SIP) attainment and maintenance plans, and to ensure that future air quality reaches and continues to achieve these health-based standards. The reductions proposed in this rulemaking would play a critical part in these important efforts. Emissions from heavy-duty vehicles account for substantial portions of the country's ambient PM and NO X levels. (NO X is a key precursor to ozone formation). By 2007, we estimate that heavy-duty vehicles will account for 29 percent of mobile source NO X emissions and 14 percent of mobile source PM emissions. These proportions are even higher in some urban areas, such as in Albuquerque, where HDVs contribute 37 percent of the mobile source NO X emissions and 20 percent of the mobile source PM emissions. The PM and NO X standards for heavy-duty vehicles proposed in this rule would have a substantial impact on these emissions. By 2030, NO X emissions from heavy-duty vehicles under today's proposed standards would be reduced by 2.8 million tons, and PM emissions would decline by about 110,000 tons, dramatically reducing this source of NO X and PM emissions. Urban areas, which include many poorer neighborhoods, can be disproportionately impacted by HDV emissions, and these neighborhoods would thus receive a relatively larger portion of the benefits expected from new HDV emissions controls. Over time, the relative contribution of diesel engines to air quality problems will go even higher if diesel-equipped light-duty vehicles become more popular, as is expected by some automobile manufacturers. In addition to its contribution to PM inventories, diesel exhaust PM is of special concern because it has been implicated in an increased risk of lung cancer and respiratory disease in human studies. The EPA draft Health Assessment Document for Diesel Emissions is currently being revised based on comments received from the Clean Air Scientific Advisory Committee (CASAC) of EPA's Science Advisory Board. The current EPA position is that diesel exhaust is a likely human carcinogen and that this cancer hazard applies to environmental levels of exposure. 2 In the draft Health Assessment Document for Diesel Emissions, EPA provided a qualitative perspective that the upper bounds on environmental cancer risks may exceed 10 −6 and could be as high as 10 −3 . Several other agencies and governing bodies have designated diesel exhaust or diesel PM as a “potential” or “probable” human carcinogen. In addition, diesel PM poses nonmalignant respiratory hazards to humans, not unlike, in some respects, hazards from exposure to ambient PM 2.5 , to which diesel PM contributes. State and local governments, in their efforts to protect the health of their citizens and comply with requirements of the Clean Air Act (CAA or “the Act”), have recognized the need to achieve major reductions in diesel PM emissions, and have been seeking Agency action in setting stringent new standards to bring this about. 3 2 Environmental Protection Agency (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 3 For example, see letter dated July 13, 1999 from John Elston and Richard Baldwin on behalf of the State and Territorial Air Pollution Program Administrators and the Association of Local Air Pollution Control Officials (docket A-99-06, item II-D-78). 2. Technology-Based Solutions Although the air quality problems caused by diesel exhaust are formidable, we believe they can be resolved through the application of high-efficiency emissions control technologies. As discussed in detail in section III, the development of diesel emissions control technology has advanced in recent years so that very large emission reductions (in excess of 90 percent) are possible, especially through the use of catalytic emission control devices installed in the vehicle's exhaust system (and integrated with the engine controls). These devices are often referred to as “exhaust emission control” or “aftertreatment” devices. Exhaust emission control devices, in the form of the well-known catalytic converter, have been used in gasoline-fueled automobiles for 25 years, but have had only limited application in diesel vehicles. Because the Clean Air Act requires us to set heavy-duty engine standards that reflect the greatest degree of emission reduction achievable through the application of available technology (subject to a number of criteria as discussed in section I.B.3), this notice proposes these standards, and proposes a justification for their adoption based on the air quality need, their technological feasibility, costs, and other criteria listed in the Act (see section III of this document). As part of this proposal, we are also proposing changes to diesel fuel quality in order to enable these advanced technologies (section IV). Heavy-duty gasoline engines would also be able to reach the significantly cleaner levels envisioned in this proposal by relying on the transfer of recent technology developments for light-duty applications, given the recent action taken to reduce sulfur in gasoline (65 FR 6698, February 10, 2000). We believe the proposed standards would require the application of high-efficiency PM and NO X exhaust emission controls to heavy-duty diesel vehicles. High-efficiency PM exhaust emission control technology has been available for several years, although engine manufacturers have generally not needed this technology in order to meet our PM emission standards. This technology has continued to improve over the years, especially with respect to durability and robust operation in use. It has also proven extremely effective in reducing exhaust hydrocarbon emissions. Thousands of such advanced-technology systems are now in use in fleet programs, especially in Europe. However, as discussed in detail in section III, these advanced-technology systems are very sensitive to sulfur in the fuel. For the technology to be viable and capable of meeting the proposed standards, we believe, based on information currently available, that it will require diesel fuel with sulfur content at the 15 ppm level. Similarly, high-efficiency NO X exhaust emission control technology will be needed if heavy-duty vehicles are to attain the proposed standards. We believe this technology, like the PM technology, is dependent on 15 ppm diesel fuel sulfur levels to be feasible, marketable, and capable of achieving the proposed standards. High-efficiency NO X exhaust emission control technology has been quite successful in gasoline direct injection engines that operate with an exhaust composition fairly similar to diesel exhaust. However, as discussed in section III, application of this technology to diesels has some additional challenges and so has not yet gotten to the field trial stage. We are confident that the certainty of low-sulfur diesel fuel that would be provided by promulgation of the proposed fuel standard would allow the application of this technology to diesels to progress rapidly, and would result in systems capable of achieving the proposed standards. However, we acknowledge that our proposed NO X standard represents an ambitious target for this technology, and so we are asking for comment on the appropriateness of a technology review of diesel NO X exhaust emission controls. The need to reduce the sulfur in diesel fuel is driven by the requirements of the exhaust emission control technology that we project would be needed to meet the proposed standards. The challenge in accomplishing the sulfur reduction is driven by the feasibility of needed refinery modifications, and by the costs of making the modifications and running the equipment. In consideration of the impacts that sulfur has on the efficiency, reliability, and fuel economy impact of diesel engine exhaust emission control devices, we believe that controlling the sulfur content of highway diesel fuel to the 15 ppm level will be necessary. Furthermore, although the refinery modifications and process changes needed to meet a 15 ppm restriction are expected to be substantial, we propose that this level is both feasible and cost effective. However, we are asking for comment on various concepts to provide implementation flexibility for refiners. 3. Basis for Action Under the Clean Air Act Section 202(a)(1) of the Act directs us to establish standards regulating the emission of any air pollutant from any class or classes of new motor vehicles or engines that, in the Administrator's judgment, cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare. Section 202(a)(3) requires that EPA set standards for heavy-duty trucks that reflect the greatest degree of emission reduction achievable through the application of technology which we determine will be available for the model year to which the standards apply. We are to give appropriate consideration to cost, energy, and safety factors associated with the application of such technology. We may revise such technology-based standards, taking costs into account, on the basis of information concerning the effects of air pollution from heavy-duty vehicles or engines and other sources of mobile source related pollutants on the public health and welfare. Section 202(a)(3)(C) requires that promulgated standards apply for no less than three years and go into effect no less than 4 years after promulgation. This proposal has been developed in conformance with these statutory requirements. We believe the evidence provided in section III and the draft Regulatory Impact Analysis (RIA) indicates that the stringent technology-forcing standards proposed today are feasible and reflect the greatest degree of emission reduction achievable in the model years to which they apply. We have given appropriate consideration to costs in choosing these standards. Our review of the costs and cost-effectiveness of these proposed standards indicate that they would be reasonable and comparable to the cost-effectiveness of other emission reduction strategies that have been required or could be required in the future. We have also reviewed and given appropriate consideration to the energy factors of this rule in terms of fuel efficiency and effects on diesel production and distribution, as discussed below, as well as any safety factors associated with these proposed standards. The information regarding air quality and the contribution of heavy-duty engines to air pollution in section II and the Draft RIA provides strong evidence that emissions from such engines significantly and adversely impact public health or welfare. First, there is a significant risk that several areas will fail to attain or maintain compliance with the NAAQS for 1-hour ozone concentrations or PM 10 concentrations during the period that these proposed new vehicle and engine standards would be phased into the vehicle population, and that heavy-duty engines contribute to such concentrations, as well as to concentrations of other NAAQS-related pollutants. Second, EPA currently believes that diesel exhaust is a likely human carcinogen. The risk associated with exposure to diesel exhaust includes the particulate and gaseous components. Some of the toxic air pollutants associated with emissions from heavy-duty vehicles and engines include benzene, formaldehyde, acetaldehyde, dioxin, acrolein, and 1,3-butadiene. Third, emissions from heavy-duty engines contribute to regional haze and impaired visibility across the nation, as well as acid deposition, POM deposition, eutrophication and nitrification, all of which are serious environmental welfare problems. Based on this evidence, EPA believes that, for purposes of section 202(a)(1), emissions of NO X , VOCs, SO X and PM from heavy-duty trucks can reasonably be anticipated to endanger the public health or welfare. In addition, this evidence indicates that it would not be appropriate to modify the technology based standards pursuant to section 202(a)(3)(B). EPA believes that it is required under section 202(a)(3)(A) to set technology based standards that meet the criteria of that provision, and is not required to make an affirmative determination under section 202(a)(1). Instead EPA is authorized to take air quality into consideration under section 202(a)(3)(B) in deciding whether to modify or not set standard under section 202(a)(3)(A). In this case, however, EPA believes the evidence would fully support a determination under section 202(a)(1) to set standards, and a determination not to modify such standards under section 202(a)(3)(B). In addition, there is significant evidence that emissions from heavy-duty trucks contribute to levels of ozone such that large segments of the national population are expected to experience prolonged exposure over several hours at levels that present serious concern for the public health and welfare. The same is true for exposure to fine PM. These public health and welfare problems are expected to occur in many parts of the country, including areas that are in compliance with the 1-hour ozone and PM 10 NAAQS (PM 10 is particulate matter that is 10 microns or smaller). This evidence is an additional reason why the controls proposed today are justified and appropriate under the Act. While EPA sees this as additional support for this action, EPA also believes that the evidence of air pollution problems summarized above and described in greater detail elsewhere is an adequate justification for this rule independent of concern over prolonged exposure to ozone levels. Section 211(c) of the CAA allows us to regulate fuels where emission products of the fuel either: (1) Cause or contribute to air pollution that reasonably may be anticipated to endanger public health or welfare, or (2) will impair to a significant degree the performance of any emission control device or system which is in general use, or which the Administrator finds has been developed to a point where in a reasonable time it would be in general use were such a regulation to be promulgated. This proposal meets each of these criteria. The discussion of the first test is substantially the same as the above discussion for the heavy-duty engine standards, because SOx emissions from heavy-duty diesel vehicles are due to sulfur in diesel fuel. The substantial adverse effect of high diesel sulfur levels on diesel control devices or systems expected to be used to meet the heavy-duty standards is discussed in depth in section III.F and in the Draft RIA. In addition, our authority under section 211(c) is discussed in more detail in appendix A to the draft RIA. C. Putting This Proposal in Perspective There are several helpful perspectives to establish in understanding the context for this proposal: the growing popularity of diesel engines, past progress and new developments in diesel emissions control, Tier 2 light-duty emission standards and other related EPA initiatives (besides the above-discussed rulemaking for highway heavy-duty engine emission standards in 2004), and recent actions and plans to control diesel emissions by the States and in other countries. 1. Diesel Popularity The diesel engine is increasingly becoming a vital workhorse in the United States, moving much of the nation's freight, and carrying out much of its farm, construction, and other labor. Diesel engine sales have grown impressively over the last decade, so that now about a million new diesel engines are put to work in the U.S. every year. Unfortunately, these diesel engines emit large quantities of harmful pollutants annually. Furthermore, although diesel emissions in this country come mostly from heavy-duty trucks and nonroad equipment, an additional source may grow out of auto manufacturers' plans to greatly increase the sales of diesel-powered light-duty vehicles (LDVs) and especially of light-duty trucks (LDTs), a category that includes the fast-selling sport-utility vehicles, minivans, and pickup trucks. These plans reflect the continuation of an ongoing dieselization trend, a trend recently most evident in the growing popularity of diesel-powered light heavy-duty trucks (8500 to 19,500 pounds). Diesel market penetration is working its way from larger to smaller highway applications and to a broader array of nonroad equipment applications. Finally, especially in Europe where diesels have already gained a broad consumer acceptance, the diesel engine is increasingly viewed as an attractive technology option for reducing emissions of gases that contribute to global warming, because it has greater operating efficiency than a gasoline engine. 2. Past Progress and New Developments Since the 1970's, highway diesel engine designers have employed numerous strategies to meet our emissions standards, beginning with smoke controls, and focusing in the 1990's on increasingly stringent NO X , hydrocarbon, and PM standards. These strategies have generally focused on reducing engine-out emissions and not on exhaust emission controls, although low-efficiency oxidation catalysts have been applied in some designs to reduce PM (and even their effectiveness has been limited by sulfur in the fuel). On the fuel side, we set quality standards that provided emissions benefits by limiting the amount of sulfur and aromatics in highway diesel fuel beginning in 1993 (55 FR 34120, August 21, 1990). Our most recent round of standard setting for heavy-duty highway diesels occurred in 1997 (62 FR 54693, October 21, 1997), effective with the 2004 model year. These standards were recently reviewed in a proposed rulemaking (64 FR 58472, October 29, 1999), which proposed to confirm them. These actions will result in engines that emit only a fraction of the NO X , hydrocarbons, and PM produced by engines manufactured just a decade ago. We consider this an important first phase of our current initiative to reconcile the diesel engine with the environment. Nevertheless, certain characteristics inherent in the way diesel fuel combustion occurs have prevented achievement of emission levels comparable to those of today's gasoline-fueled vehicles. Although diesel engines provide advantages in terms of fuel economy, durability, and evaporative emissions, and have inherently low exhaust emissions of hydrocarbons and carbon monoxide, controlling NO X emissions is a greater challenge for diesel engines than for gasoline engines, primarily because of the ineffectiveness of three-way catalysis in the oxygen-rich and relatively cool diesel exhaust environment. Similarly, PM emissions, which are inherently low for properly operating gasoline engines, are more difficult to control in diesel engines, because the diesel combustion process tends to form soot particles. The challenge is somewhat complicated by the fact that historical diesel NO X control approaches tend to increase PM, and vice versa, but both are harmful pollutants that need to be controlled. Considering the air quality impacts of diesel engines and the potential for growth of diesels in the lighter-duty portion of the market, it is imperative that progress in diesel emissions control continue. Fortunately, encouraging progress is now being made in the design of exhaust emission control devices for diesel applications, driven in part by the challenge presented by the stringent Tier 2 standards for light-duty vehicles. As discussed in detail in section III, promising new exhaust emission control technologies for NO X , PM, and hydrocarbon reduction show potential for a major advancement in diesel emissions control of a magnitude comparable to that ushered in by the automotive catalytic converter in the 1970's. However, changes in diesel fuel quality will be needed to enable these high-efficiency exhaust emission control devices. With these promising technologies, diesel vehicles have potential to achieve gasoline-like exhaust emission levels, in addition to their inherent advantages over gasoline vehicles with respect to fuel economy, lower greenhouse gas emissions, and lower evaporative hydrocarbon emissions. 3. Tier 2 Emissions Standards Auto manufacturers' design plans for new light-duty diesel vehicle models will be greatly affected by our recent adoption of stringent new emission standards for light-duty highway vehicles (referred to as “Tier 2” standards) that will phase in between 2004 and 2009. These Tier 2 standards will require significant improvements in electronic engine controls and catalysts on gasoline vehicles. (We anticipate that these advances will be transferred over to heavy-duty gasoline vehicles in meeting the standards proposed in this document). The Tier 2 NO X and PM standards (that apply equally to gasoline and diesel vehicles) are far more challenging for diesel engine designers than the most stringent light- or heavy-duty vehicle standards promulgated to date, and so will require the use of advanced emission control technologies. However, the low sulfur highway diesel fuel proposed in this notice would make it possible for designers to employ advanced exhaust emission control technologies in these light-duty applications, and the timing of the proposed fuel change provides for the use of these devices in time to satisfy Tier 2 phase-in requirements. The Tier 2 program phases in interim and final standards over a number of years, providing manufacturers the option of delaying some of their production of final Tier 2 designs until later in the phase-in. For vehicles up to 6000 lbs GVWR (LDVs) and light light-duty trucks (LLDTs)), the interim standards begin in 2004 and phase out by 2007, as they are replaced by the final Tier 2 standards. For vehicles between 6000 and 8500 lbs ( heavy light-duty trucks (HLDTs)), the interim standards begin in 2004 and phase out by 2009 as they are replaced by the final Tier 2 standards. A new category of vehicles between 8,500 and 10,000 lbs, medium-duty passenger vehicles (MDPVs), will follow the same phase-in schedule as HLDTs. Our assessment in the Tier 2 final rule is that the interim standards are feasible for diesel vehicles without a need for fuel quality changes. Manufacturers can take advantage of the flexibilities provided in the Tier 2 program to delay the need for light-duty diesels to meet the final Tier 2 levels until late in the phase-in period (as late as 2007 for LDVs and LLDTs, and 2009 for HLDTs and MDPVs). However, low sulfur fuel is expected to be needed for diesel vehicles designed to meet the final NO X and PM standards, because these vehicles are likely to employ light-duty versions of the sulfur-sensitive exhaust emission control technologies discussed in Section III. The gasoline quality changes and light-duty gasoline engine developments that will result from the Tier 2 rule would also help make it feasible for heavy-duty gasoline engines to meet the standards proposed in this document. 4. Mobile Source Air Toxics Rulemaking Passenger cars, on-highway trucks, and nonroad equipment emit hundreds of different compounds and elements. Several of these are considered to be known, likely, or possible human carcinogens. These include diesel exhaust, plus several VOCs such as acetaldehyde, benzene, 1,3-butadiene, formaldehyde, and acrolein. Trace metals may also be present in heavy-duty diesel engine emissions, resulting from metals in fuels and lubricating oil, and from engine wear. Several of these metals have carcinogenic and mutagenic effects. These and other mobile source air toxics are already controlled under existing programs established under Clean Air Act sections 202(a) (on-highway engine requirements), 211 (the fuel requirements), and 213 (nonroad engine requirements). Although these programs are primarily designed for control of criteria pollutants, especially ozone and PM 10 , they also achieve important reductions in air toxics through VOC and hydrocarbon controls. In addition to these programs, section 202(l)(2) of the Act directs us to consider additional controls to reduce emissions of hazardous air pollutants from motor vehicles, their fuels, or both. Those standards are to reflect the greatest degree of emission reduction achievable through the application of technology which will be available, taking into account existing standards, costs, noise, energy, and safety factors. We anticipate that this section 202(l)(2) rulemaking, which we expect to propose in July 2000 and finalize in December 2000, will consist of three parts. First, we will identify a list of hazardous air pollutants emitted from motor vehicles and determine which of these endanger human health and welfare. Diesel particulate matter will be considered as part of this determination because, as discussed in section II, human epidemiological studies have suggested that diesel exhaust is associated with increased risk of adverse respiratory effects and lung cancer. Second, we will consider more comprehensively the contribution of mobile sources to the nation's air toxics inventory and evaluate the toxics benefits of existing and proposed emission control programs. The benefits of the program proposed in today's action will be included in this analysis. Finally, we will consider whether additional controls are appropriate at this time, given technological feasibility, cost, and the other criteria specified in the Act. 5. Nonroad Engine Standards and Fuel Although this proposal covers only highway diesel engines and fuel, it is clear that potential requirements for nonroad diesel engines and fuel are related. It is expected that nonroad diesel fuel quality, currently unregulated, may need to be controlled in the future in order to reduce the large contribution of nonroad engines to NO X and PM inventories. Refiners, fuel distributors, states, environmental organizations, and others have asked that we provide as much information as possible about the future specifications for both types of fuel as early as possible. We do plan to give further consideration to further control of nonroad engine emissions. As discussed below in section IX, an effective control program for these engines requires the resolution of several major issues relating to engine emission control technologies and how they are affected by fuel sulfur content. The many issues connected with any rulemaking for nonroad engines and fuel warrant serious attention, and we believe it would be premature today for us to attempt to propose resolutions to them. We plan to initiate action in the future to formulate thoughtful proposals covering both nonroad diesel fuel and engines. 6. Actions in California The California Air Resources Board (ARB) and local air quality management districts within California are also pursuing measures to better control diesel emissions. Key among these efforts is work resulting from the Board's designation of particulate emissions from diesel-fueled engines as a toxic air contaminant (TAC) on August 27, 1998. TACs are air pollutants that may cause or contribute to an increase in death or serious illness or may pose a present or future hazard to human health. The TAC designation was based on research studies showing that emissions from diesel-fueled engines may cause cancer in animals and humans, and that workers exposed to higher levels of emissions from diesel-fueled engines are more likely to develop lung cancer. The ARB has now begun a public process to evaluate the need to further reduce the public's exposure to organic gases and PM emissions from diesel-fueled engines, and the feasibility and cost of doing so. 4 This evaluation is being done in consultation with the local air districts, affected industries, and the public, and will result in a report on the appropriate degree of control. Based on this report, if cost effective measures are identified that will reduce public exposure, then specific control measures applicable in California will be developed in a public process. 4 Regularly updated information on this effort can be obtained at a website maintained by the ARB staff: www.arb.ca.gov/toxics/diesel/diesel.htm The ARB also recently adopted stringent new emission requirements for urban transit buses and is considering similar requirements for school buses. 5 This program is aimed at encouraging the use of clean alternative fuels and high-efficiency diesel emission control technologies. Their program includes requirements for zero-emissions buses, fleet average NO X levels, and retrofits for PM control, as well as model year 2007 NO X and PM standards levels of 0.2 and 0.01 g/bhp-hr, respectively (equal to the levels proposed in this document). It also requires that all diesel fuel used by transit agencies after July 1, 2002 must meet a cap of 15 ppm sulfur. This is the same as the sulfur level proposed in this document, but in batch amounts and on a much earlier schedule to support the ARB's proposed PM retrofit schedule. 5 “Notice of Public Hearing To Consider the Adoption of a Public Transit Bus Fleet Rule and Emission Standards For New Urban Buses”, California ARB, November 30, 1999, and ARB Resolution 00-2, dated February 24, 2000. California's urban bus program is focused on only a portion of the highway diesel fleet and fuel, characterized by short-range trips and captive fuel supplies. The large amount of interstate truck traffic in California and the fact that these trucks can travel many miles between refuelings would dramatically reduce the effectiveness of a more comprehensive State program, and would also subject California businesses to competitive disadvantages. As a result, the ARB has stressed the need for action at a Federal level, and is depending on our efforts to control HDV NO X and PM emissions and to regulate diesel fuel. We agree that a national program is appropriate to ensure the effectiveness of such a program. 7. Retrofit Programs Many States facing air quality improvement challenges have expressed strong interest in programs that would reduce emissions from existing highway and nonroad diesel engines through the retrofitting of these engines with improved emission control devices. The urban bus program proposed by the California ARB includes such a retrofit requirement as one of its major components (see section I.C.6). These retrofit programs are appealing because the slow turnover of the diesel fleet to the new low-emitting engines makes it difficult to achieve near-term air quality goals through new engine programs alone. Some of the exhaust emission control technologies discussed in this proposal are especially appealing for use in retrofits because they can be fitted to an existing vehicle as add-on devices without major engine modifications, although some of the more sophisticated systems that require careful control of engine parameters may be more challenging. Because of the uncertainty at this time in how and when such programs may be implemented, this proposal does not calculate any benefits from them. Nevertheless, we believe that this proposed program can enable the viability of these retrofit technologies. We expect that large emission benefits from the existing fleet could be realized as a result of the fuel changes we are proposing here, combined with retrofit versions of the technologies that would be developed in response to the proposed engine standards. These benefits would be especially important in the early years of the program when new vehicles standards are just beginning to have an impact, and when States and local areas need to gain large reductions to attain air quality goals. 8. Actions in Other Countries There is substantial activity taking place in many countries of the world related to the regulation of diesel fuel and engines. The large light-duty vehicle market share enjoyed by diesels in many European countries has helped to stir innovation in dealing with diesel emissions problems. Advanced emissions control technologies are being evaluated there in the in-use fleet and experience gained from these trials is helping to inform the diesel emissions control discussion in the U.S. In addition, several European countries have low sulfur diesel fuel, with maximum sulfur levels varying from 10 to 50 ppm, and so experience gained from the use of these fuels, though not completely transferable to the U.S. situation, also helps to inform the discussion. European Union countries will limit sulfur in diesel fuel to 50 ppm by 2005, and even more aggressive plans are being discussed or implemented. The United Kingdom made a rapid conversion to 50 ppm maximum sulfur diesel fuel last year by offering tax incentives. This change occurred with much smaller refinery investments than had been predicted, and some refinery production there is actually at levels well below the 50 ppm cap. Germany is moving forward with plans to introduce a 10 ppm sulfur cap for diesel fuel by 2003, also via tax incentives, and is attempting to get the 50 ppm specification that was adopted by the European Commission revised downward to the 10 ppm cap level. One European country has had extensive experience with the transition to low sulfur diesel fuel. In the early 1990's, Sweden decided to take advantage of the environmental benefits of 10 ppm sulfur/low aromatics fuel by introducing it with a reduction in the diesel fuel tax. The program has been quite successful, and in excess of 90 percent of the road fuel used there is of this 10 ppm maximum sulfur class. 6 The ability of the Swedish fuel distributors to maintain these low sulfur levels at the fuel stations has also been quite good. 6 Memo from Thomas M. Baines to Docket A-99-06, October 29, 1999, Docket #A-99-06, Item II-G-12. Section VII.H discusses how differences between the future fuel specifications in the U.S. and those in Canada and Mexico may affect the emissions control program proposed in this document. II. The Air Quality Need and Projected Benefits A. Overview Heavy-duty vehicle emissions contribute to air pollution with a wide range of adverse health and welfare impacts. Emissions of VOC, CO, NO X , SO X , and PM from HD vehicles contribute a substantial percentage to ambient concentrations of ozone, PM, sulfur and nitrogen compounds, aldehydes, and substances known or considered likely to be carcinogens. VOC and diesel PM emissions include some specific substances known or suspected to cause cancer, and diesel exhaust emissions are associated with non-cancer health effects. These ambient concentrations in turn cause human health effects and many welfare effects including visibility reductions, acid rain, nitrification and eutrophication of water bodies. Emissions from heavy-duty vehicles, which are predominantly diesel-powered, account for substantial portions of the country's ambient PM and ground-level ozone levels. (NO X is a key precursor to ozone formation). By 2007, we estimate that heavy-duty vehicles would account for 29 percent of mobile source NO X emissions, and 14 percent of mobile source PM emissions. These proportions are even higher in some urban areas, such as New York and Los Angeles. Urban areas, which include many poorer neighborhoods, can be disproportionately impacted by HDV emissions because of heavy traffic in and out of densely populated urban areas. Of particular concern is human epidemiological evidence linking diesel exhaust to an increased risk of lung cancer. Based on information provided in the draft Health Assessment Document for Diesel Emissions 7 and other sources of information, we believe that emissions from heavy-duty diesel vehicles contribute to air pollution that warrants regulatory attention under section 202(a)(3) of the Act. 7 EPA is revising this draft document in response to comments by the CASAC. Thirty-six metropolitan areas with a total population of 111 million people have recently violated or are currently violating the 1-hour ozone NAAQS, and have ozone modeling or other factors which indicate a risk of NAAQS violations in 2007 or beyond. Another six areas with 11 million people have recently experienced ozone concentrations within 10 percent of exceeding the NAAQS between 1996 and 1998 and have some evidence of a risk of future violations. Ten PM 10 nonattainment areas with 27 million people face a significant risk of experiencing particulate matter levels that violate the PM 10 standard during the time period when this proposal would take effect. Without reductions from these proposed standards, there is a significant risk that an appreciable number of these areas would violate the 1-hour ozone and PM 10 standards during the time period when these proposed standards would apply to heavy-duty vehicles. Under the mandates and authorities in the Clean Air Act, federal, State, and local governments are working to bring ozone and particulate levels into compliance with the 1-hour ozone and PM 10 NAAQS through SIP attainment and maintenance plans, and to ensure that future air quality continues to achieve these health-based standards. The reductions proposed in this rulemaking would assist these efforts. The proposed heavy-duty vehicle and engine emission standards, along with the diesel fuel sulfur standard proposed today, would have a dramatic impact in reducing the large contribution of HDVs to air pollution. The proposed standards would result in substantial benefits to public health and welfare through significant annual reductions in emissions of NO X , PM, NMHC, carbon monoxide, sulfur dioxide, and air toxics. For example, we project a 2 million ton reduction in NO X emissions from HD vehicles in 2020, which would increase to 2.8 million tons in 2030 when the current HD vehicle fleet is completely replaced with newer HD vehicles that comply with these proposed emission standards. When coupled with the emission reductions projected to result from the Phase 1 (model year 2004) HDV standards, the emission reductions from heavy-duty vehicles are projected to be as large as the substantial reductions the Agency expects from light-duty vehicles as a result of its recently promulgated Tier 2 rulemaking. B. Public Health and Welfare Concerns The following subsections present the available information on the air pollution situation that is likely to exist without this rule for each ambient pollutant. We also present information on the improvement that would result from this rule. The Agency's analysis and this proposal are supported by the numerous letters received from States and environmental organizations calling for significant emission reductions from heavy-duty vehicles in order to enable these areas to achieve and sustain clean, healthful air. 8 8 Letters from States and environmental organizations are located in the docket for this proposal. 1. Ozone and Its Precursors a. Health and Welfare Effects From Short-Term Exposures to Ozone NO X and VOC are precursors in the photochemical reaction which forms tropospheric ozone. A large body of evidence shows that ozone can cause harmful respiratory effects including chest pain, coughing, and shortness of breath, which affect people with compromised respiratory systems most severely. When inhaled, ozone can cause acute respiratory problems; aggravate asthma; cause significant temporary decreases in lung function of 15 to over 20 percent in some healthy adults; cause inflammation of lung tissue; may increase hospital admissions and emergency room visits; and impair the body's immune system defenses, making people more susceptible to respiratory illnesses. Children and outdoor workers are likely to be exposed to elevated ambient levels of ozone during exercise and, therefore, are at greater risk of experiencing adverse health effects. Beyond its human health effects, ozone has been shown to injure plants, reducing crop yields. b. Current and Future Nonattainment Status With the 1-Hour Ozone NAAQS Exposure to levels of ozone that are not in compliance with the 1-hour ozone NAAQS are a serious public health and welfare concern. The following sections discuss the present situation and outlook regarding attainment in areas of the country where ozone levels presently fail to comply with this NAAQS, or where they have come close to failing to comply in recent years. Over the last decade, emissions have declined and national air quality has improved for all six criteria pollutants, including ozone. 9 Some of the greatest emissions reductions have taken place in densely-populated urban areas, where emissions are heavily influenced by mobile sources such as cars and trucks. For example, VOC and NO X emissions in several urban areas in the Northeast declined by 15 percent and 14 percent from 1990 to 1996. 10 However, when ozone trends are normalized for annual weather variations between 1989 and 1998, they reveal a downward trend in the early 1990's followed by a leveling off, or an upturn in ozone levels, over the past several years in many urban areas. 11 9 National Air Quality and Emissions Trends Report, 1997, US EPA, December 1998. 10 National Emissions Trends database. 11 Trends in Daily Maximum 1-hour Ozone in Selected Urban Areas, 1989-1998. Despite impressive improvements in air quality over the last decade, present concentrations of ground-level ozone continue to endanger public health and welfare in many areas. As of December, 1999, 92 million people (1990 census) lived in 32 metropolitan areas designated nonattainment under the 1-hour ozone NAAQS. 12 In addition, there are 14 areas with a 1996 population of 17 million people not currently listed as non-attainment areas because the 1-hour ozone standard was revoked for these areas (we have proposed to re-instate the standard). 13 These 14 areas are relevant to this proposal because ozone concentrations above the health-based ozone standard, should they occur, endanger public health and welfare independent of the applicability of the 1-hour standard or an area's official attainment or nonattainment status. Ozone also has negative environmental impacts. For example, exposure of vegetation to ozone can inhibit photosynthesis, and alter carbohydrate allocation, which in turn can suppress the growth of crops, trees, shrubs and other plants. 12 Memorandum to Air Docket, January 12, 2000. Information on ozone nonattainment areas and population as of December 13, 1999 from US EPA website www.epa.gov/airs/nonattn.html, USA Air Quality Nonattainment Areas, Office of Air Quality Planning and Standards. The reader should note that the 32 areas mentioned here are designated nonattainment areas, while the 36 areas noted in the overview section have recent (1995-1998) or current violations, and predicted exceedances in 2007 or 2030 based on air quality modeling or other evidence discussed in more detail later in this preamble, and in the draft RIA. 13 64 FR 57424 (October 25, 1999) The next two sections present lists of metropolitan areas, in two tables, with potential for violating the ozone standard in the future. The first section presents a table with 33 metropolitan areas that were predicted by Tier 2 modeling to have exceedances in either 2007 or 2030, and accompanying text identifies an additional nine areas for which we have other evidence of a risk of future exceedances. The second section discusses the air quality prospects for these 42 areas, which are divided into several groups. These groups are presented in Table II.B-2. i. Ozone Predictions Made in the Tier 2 Rulemaking and Other Information on Ozone Attainment Prospects In conjunction with its Tier 2 rulemaking efforts, the Agency performed ozone air quality modeling for nearly the entire Eastern U.S. covering metropolitan areas from Texas to the Northeast, and for a western U.S. modeling domain. The ozone modeling we did as part of the Tier 2 rulemaking predicted that without further emission reductions, a significant number of areas recently experiencing ozone exceedances across the nation are at risk of failing to meet the 1-hour ozone NAAQS in 2007 and beyond, even with Tier 2 and other controls currently in place. The general pattern observed from the Tier 2 ozone modeling is a broad reduction between 1996 and 2007 in the geographic extent of ozone concentrations above the 1-hour NAAQS, and in the frequency and severity of exceedances. Despite this improvement from 1996 to 2007, many ozone exceedances were predicted to occur in 2007 even with reductions from Tier 2 standards and other controls currently in place, affecting 33 metropolitan areas across the nation. Assuming no additional emission reductions beyond those that will be achieved by current control programs, 14 a slight decrease below 2007 levels in modeled concentrations and frequencies of exceedances was predicted for 2030 for most areas. Exceedances were still predicted in 2030 in most of the areas where they were predicted in 2007. 15 14 Current control programs assumed for the predictions summarized here included the Tier 2/Gasoline Sulfur program and some specific programs that are legally required but not yet fully adopted, such as the regional Ozone Transport Rule and not-yet-adopted MACT standards that will affect VOC emissions. 15 Achieving attainment with the ozone standard is only one measure of air quality improvement. EPA found that the Tier 2 program significantly lowers the model-predicted number of exceedances of the ozone standard by one tenth in 2007, and by almost one-third in 2030 across the nation (Tier 2 RIA). Although we did not model ozone concentrations for years between 2007 and 2030, we may expect that they would broadly track the national emissions trends. Based on these emission trends alone, national ozone concentrations, on average, would be projected to decline after 2007 largely due to penetration of Tier-2 compliant vehicles into the light duty vehicle fleet, but begin to increase around 2015 or 2020 due to economic growth until they reach the 2030 levels just described. However, the change in ozone levels from the expected NO X reduction is relatively small compared to the effects of variations in ozone due to meteorology. Furthermore, in some areas, where growth exceeds national averages, emissions levels would begin increasing sooner and reach higher levels in 2030. Table II.B-1 lists the 33 areas with predicted 1-hour ozone exceedances in 2007 and/or 2030 based on the Tier 2 modeling, after accounting for the emission reductions from the Tier 2 program and other controls. 16 There are areas that are not included in this table that will be discussed shortly. A factor to consider with respect to the ozone predictions in Table II.B-1 is that recent improvements to our estimates of the current and future mobile source NO X inventory have resulted in an increase in our estimate of aggregate NO X emissions from all sources by more than eight percent since the air quality modeling performed for the Tier 2 rule. The adjusted NO X inventory level in 2015 is greater than the NO X inventory used in the Tier 2 air quality analysis for 2030. If we were to repeat the ozone modeling now for the 2015 time frame, using the new emissions estimates, it would most likely predict exceedances in 2015 for all the areas that had 2030 exceedances predicted in the modeling done for the Tier 2 rulemaking. As summarized in Table II.B-1, the Tier 2 modeling predicted that there will be 33 areas in 2007 or 2030 with about 89 million people predicted to exceed the 1-hour ozone standard, even after Tier 2 and other controls currently in place. Additional information on ozone modeling is found in the draft RIA and the technical support document for the Tier 2 rule, which is in the docket for this rulemaking. We request comment on the inventory estimates and ozone air quality modeling analysis described in this proposal. 16 Table II.B-1 excludes areas for which the Tier 2 modeling predicted exceedances in 1996 but for which the actual ozone design values in 1995-1997 and 1996-1998 were both less than 90 percent of the NAAQS. For these areas, we considered the ozone model's predictions of 2007 or 2030 exceedances to be too uncertain to play a supportive role in our rulemaking determinations. Also, 2007 ozone was not modeled for western areas. For 2030, all areas were modeled for fewer episode days which, along with a general model under-prediction bias, may result in an underestimation of 2030 exceedances. Without these factors, there could have been more western areas listed in Table II.B-1, and more areas with predicted exceedances in 2030. Table II.B-1.—Metropolitan Areas With Predicted Exceedances in 2007 or 2030 From Tier 2 Air Quality Modeling Including Emission Reductions From Tier 2 and Other Current/Committed Controls CMSA/MSAs 2007 Control case 2030 Control case 1996 Population (millions) Boston, MA CMSA X X 5.6 Chicago, IL CMSA X X 8.6 Cincinnati, OH CMSA** X 1.9 Cleveland, OH CMSA* X X 2.9 Detroit, MI CMSA* X X 5.3 Houston, TX CMSA X X 4.3 Milwaukee, WI CMSA X X 1.6 New York City, NY CMSA X X 19.9 Philadelphia, PA CMSA X X 6.0 Washington,-Baltimore, DC-VA-WV-MD CMSA X X 7.2 Atlanta, GA MSA X X 3.5 Barnstable, MA MSA X X 0.2 Baton Rouge, LA MSA X X 0.6 Benton Harbor, MI MSA X X 0.2 Biloxi, MS MSA* X X 0.3 Birmingham, AL MSA X X 0.9 Charlotte, NC MSA X X 1.3 Grand Rapids, MI MSA X X 1.0 Hartford, CT MSA X X 1.1 Houma, LA MSA X X 0.2 Huntington, WV MSA X 0.3 Indianapolis, IN MSA X 1.5 Louisville, KY MSA X X 1.0 Memphis, TN MSA X X 1.1 Nashville, TN MSA X X 1.1 New London, CT MSA X X 1.3 New Orleans, LA MSA* X X 0.3 Pensacola, FL MSA* X 0.4 Pittsburgh, PA MSA X 2.4 Providence, RI MSA X X 1.1 Richmond, VA MSA X 0.9 St. Louis, MO MSA X X 2.5 Tampa, FL MSA* X X 2.2 33 areas / 88.7 million people 32 areas/86.3 million people 28 areas/83.7 million people * These areas have registered recent (1995-1998) ozone levels within 10% of the 1-hour ozone standard. ** Based on more recent air quality monitoring data not considered in the Tier 2 analysis, and on 10-year emissions projections, we expect to redesignate Cincinnati-Hamilton to attainment soon. Ozone modeling for the Tier 2 rulemaking did not look at the effect on ozone attainment and maintenance beyond current/committed controls and the Tier 2/Gasoline Sulfur Program itself. Therefore, Table II.B-1 should be interpreted as indicating what areas are at risk of ozone violations in 2007 or 2030 without federal or state measures that may be adopted and implemented after this rulemaking is proposed. We expect many of the areas listed in Table II.B-1 to adopt additional emission reduction programs, but the Agency is unable to quantify the future reductions from additional State programs since they have not yet been adopted. In addition, Table II.B-1 reflects only the ozone predictions made in the modeling for the Tier 2 rulemaking. The Tier 2 modeling did not predict (or did not provide information regarding) 2007 or 2030 violations for a number of areas for which other available ozone modeling has shown 2007 violations, or for which the history and current degree of nonattainment indicates some risk of ozone violations in 2007 or beyond. These nine areas had a 1996 population of 30 million people. They include seven ozone nonattainment areas in California (Los Angeles, San Diego, Southeast Desert, Sacramento, Ventura County, San Joaquin Valley, and San Francisco), and two Texas areas (Beaumont-Port Arthur and Dallas). A more detailed discussion is presented in the Draft RIA. The following section will discuss the air quality prospects of these 42 areas ( i.e., the 33 shown in Table II.B-1, plus the nine additional areas identified in this paragraph). For the final rule, the Agency plans to use the same modeling system as was used in its Tier 2 air quality analysis with updated inventory estimates for 2030 and a further characterization of the inventory estimates for the interim period between 2007 and 2030 We plan to release the products of these revised analyses into the public record on a continuous basis as they are developed. Interested parties should check docket number A-99-06 periodically for updates. ii. Areas At Risk of Exceeding the 1-Hour Ozone Standard This section presents the Agency's conclusions about the risk of future nonattainment for the 42 areas identified above. These areas are listed in Table II.B-2, and are subdivided into three groups. The following discussion follows the groupings from top to bottom. A more detailed discussion is found in the Draft RIA. In general, EPA believes that the proposed new standards for heavy-duty vehicles are warranted by a sufficient risk that without these standards, some areas would experience violations of the 1-hour NAAQS at some time during the period when this rulemaking would achieve its emission reductions, despite efforts that EPA, States and localities are now making through SIPs to reach attainment and to preserve attainment by developing and implementing maintenance plans. Because ozone concentrations causing violations of the 1-hour ozone standard are well established to endanger public health and welfare, this indicates that it is appropriate for the Agency to propose setting new standards for heavy-duty vehicles. Our belief regarding the risk of future violations of the 1-hour NAAQS is based upon our consideration of predictive ozone air quality modeling and analysis we performed for U.S. metropolitan areas for the recent Tier 2 rulemaking, and the predictive ozone modeling and other information that has come to us through the SIP process, and other local air quality modeling for certain areas. We have assessed this information in light of our understanding of the factors that influence ozone concentrations, taking due consideration of current and future federal, state and local efforts to achieve and maintain the ozone standard through air quality planning and implementation. Ten metropolitan areas that fall within ozone nonattainment areas have statutorily-defined attainment dates of 2007 or 2010, or have requested attainment date extensions to 2007 (including two requests on which we have not yet proposed any action). These 10 areas are listed at the top of Table II.B-2, and are New York City, Houston, Hartford, New London, Chicago, Milwaukee, Dallas, Beaumont-Port Arthur, Los Angeles, and Southeast Desert. The Los Angeles (South Coast Air Basin) ozone attainment demonstration is fully approved, but it is based in part on reductions from new technology measures and actions that have yet to be identified. Accordingly, the State will be able to benefit from, and will need, the reductions from this proposed rule in order to meet the NO X and VOC shortfalls identified in the South Coast Air Basin's SIP. The 2007 attainment demonstration for the Southeast Desert area is also approved. However, because ozone travels from the South Coast to the Southeast Desert, attainment in the Southeast Desert may depend on progress in reducing ozone levels in the South Coast Air Basin. The process of developing adequate attainment plans has been difficult. While the efforts by EPA and the States have been more prolonged than expected, they are nearing completion. Of the remaining eight areas discussed above, two—Chicago and Milwaukee—do not have EPA-identified shortfalls in their 1998 attainment demonstrations. However, these two areas are revising their local ozone air quality modeling, which will be taken into account in the final rule. We have recently proposed to approve attainment plans for New York, Houston, Hartford and New London, and we hope to receive attainment plans and propose such approval soon for Dallas and Beaumont-Port Arthur. EPA has proposed, or expects to propose, that attainment in 2007 in each of these six areas depends upon either achieving specified additional emission reductions in the area itself, or achieving ozone reductions in an upwind nonattainment area that has such a shortfall. Those areas with shortfalls will be able to take credit for the expected reductions from the proposed rule in their attainment demonstrations, once the rule is promulgated. We expect to rely in part on these reductions in reaching our final conclusion as to whether each of the eight areas for which we have reviewed an attainment demonstration, or expect to review an attainment demonstration soon, is more likely than not to attain on its respective date, whether or not the State formally relies on these reductions as part of its strategy to fill the identified shortfall in its attainment demonstration, if any. The proposed new standards for heavy-duty vehicles would help address some of the uncertainties and risks that are inherent in predicting future air quality over a long period. Actual ozone levels may be affected by increased economic growth, unusually severe weather conditions, and unexpectedly large changes in vehicle miles traveled. For example, the emissions and air quality modeling that forms the basis for the 2007-to-2030 emissions and ozone trend described earlier used a 1.7 percent national VMT growth rate. Historical growth in national VMT for LDVs over the last 30 years has averaged 2.7 percent per year, but over the past 10 years, annual VMT growth has fluctuated from 1.2 percent to 3.5 percent. The growth rates can also vary from locality to locality. The reported annual VMT growth rate experienced in Atlanta, a fast-growing metropolitan area, was six percent from 1986-1997, or more than twice the 30-year national average, and year-to-year variations in Atlanta's reported annual VMT ranged from a 12% increase to no increase over the same period. While some factors influencing previous VMT growth rates, such as increased participation of women in the workforce, may be declining, other factors, such as widening suburbanization, more suburb-to-suburb commuting and the rise of healthier and wealthier older age drivers, may result in increased VMT growth rates. 17 Activity by other source types also varies due to economic factors. Actual future VMT and other economic growth in specific areas may vary from the best predictions that have been used in each attainment demonstration. Over a number of years, differences in annual growth can cause substantial differences in total emissions. These uncertainties, and others, dictate that a prudent course for the Agency is to protect public health by increasing our confidence that the necessary reductions will be in place. This proposed rulemaking would provide significant and needed reductions to those areas at risk of violating the 1-hour ozone standard during the time period when this rule would take effect. 17 See Tier 2 Response to Comments document for a longer decision. The reductions from this proposal would begin in 2007 and would continue to grow over time as the existing heavy-duty fleet is replaced by newer vehicles meeting the proposed emission standards. Even assuming attainment is achieved, areas that wish a redesignation to attainment may rely on further reductions generated by this rulemaking to support their 10-year maintenance plan. Even if an area does not choose to seek redesignation, the continuing reductions from this proposed rulemaking would help ensure maintenance with the 1-hour standard after attainment is reached. Thus, a total of six metropolitan areas need additional measures to meet the shortfalls in the applicable attainment demonstrations, or are subject to ozone transport from an upwind area that has an identified shortfall. In addition, two areas are expected to need additional emission reductions to demonstrate attainment in future SIPs. EPA believes that the States responsible may need, among other reductions, the level of reductions provided by this rule in order to fill the shortfalls. We expect to rely in part on these reductions in reaching our final conclusion as to whether each of the eight areas for which we have reviewed an attainment demonstration is more likely than not to attain on its respective date, whether or not the State formally relies on these reductions as part of its strategy to fill the identified shortfall in its attainment demonstration. As to all ten areas, even if all shortfalls were filled by the States, there is some risk that at least some of the areas will not attain the standards by their attainment dates of 2007, or 2010 for Los Angeles. In that event, the reductions associated with this proposed program, which increase substantially after 2007, would help assure that any residual failures to attain are remedied. Finally, there is also some risk that the areas will be unable to maintain attainment after 2007. Considered collectively, there is a significant risk that some areas would not be in attainment throughout the period when the proposed rule would reduce heavy-duty vehicle emissions. The next group of 26 areas have required attainment dates prior to 2007, or have no attainment date but are subject to a general obligation to have a SIP that provides for attainment and maintenance. EPA and the States are pursuing the established statutory processes for attaining and maintaining the ozone standard where it presently applies. EPA has also proposed to re-apply the ozone standard to the remaining areas. The Agency believes that there is a significant risk that future air quality in a number of these areas would exceed the ozone standard at some time in the 2007 and later period. This belief is based on three factors: (1) Recent exceedances in 1995-1997 or 1996-1998, (2) predicted exceedances in 2007 or 2030 after accounting for reductions from Tier 2 and other local or regional controls currently in place or required, and (3) our assessment of the magnitude of recent violations, the variability of meteorological conditions, transport from areas with later attainment dates, and other variables inherent in predicting future attainment such as the potential for some areas to experience unexpectedly high economic growth rates, growth in vehicle miles traveled, varying population growth from area to area, and differences in vehicle choice. Only a subset of these areas have yet adopted specific control measures that have allowed the Agency to fully approve an attainment plan. For some of these areas, we have proposed a finding, based on all the available evidence, that the area will attain on its attainment date. In one case, we have proposed that an area will maintain over the required 10-year time period. However, in many cases, these proposals depend on the State adopting additional emission reduction measures. The draft RIA provides more information on our recent proposals on attainment demonstrations and maintenance plans. 18 Until the SIPs for these areas are actually submitted, reviewed and approved, there is some risk that these areas will not adopt fully approvable SIPs. Furthermore, some of these areas are not under a current requirement to obtain EPA approval for an attainment plan. The mechanisms to get to attainment in areas without a requirement to submit an attainment demonstration are less automatic, and more uncertain. Even with suitable plans, implementation success is uncertain, and therefore there is some risk that 2007 attainment, or maintenance thereafter, would not happen. 18 We have recently proposed favorable action, in some cases with a condition that more emission reductions be obtained, on attainment demonstrations in these areas with attainment dates prior to 2007: Philadelphia, Washington-Baltimore, Atlanta, and St. Louis. We expect to give final approval soon to a maintenance plan and redesignation to attainment for Cincinnati. Finally, there are six additional metropolitan areas, with another 11.4 million people in 1996, for which the available ozone modeling and other evidence is less clear regarding the need for additional reductions. These areas include Biloxi-Gulfport-Pascagoula, MS, Cleveland-Akron, OH, Detroit-Ann Arbor-Flint, MI, New Orleans, LA, Pensacola, FL, and Tampa, FL. Our own ozone modeling predicted these six areas to need further reductions to avoid exceedances in 2007 or 2030. The recent air quality monitoring data for these six areas shows ozone levels with less than a 10 percent margin below the NAAQS. This suggests that ozone concentrations in these areas may remain below the NAAQS for some time, but we believe there is still a risk of that future ozone levels will be above the NAAQS because meteorological conditions may be more severe in the future. In sum, without these reductions, there is a significant risk that an appreciable number of the 42 areas, with a population of 123 million people in 1996, will violate the 1-hour ozone standard during the time period when these proposed standards will apply to heavy-duty vehicles. The 42 areas consist of the 27 areas with predicted exceedances in 2007 or 2030 under Tier 2 air quality modeling and recent violations of the 1-hour ozone standard, plus seven California areas (South Coast Air Basin, San Diego, Ventura County, Southeast Desert, San Francisco, San Joaquin Valley, Sacramento), two Texas areas (Dallas and Beaumont-Port Arthur), and six areas that have recent ozone concentrations within 10% of exceeding the standard and predicted exceedances. Additional information about these areas is provided in the draft RIA. iii. Conclusion We have reviewed the air quality situation of three broad groups of areas: (1) Those areas with recent violations of the ozone standard and attainment dates in 2007 or 2010, (2) those areas with recent violations and attainment dates (if any) prior to 2007, and (3) those areas with recent ozone concentrations within 10% of a violation of the 1-hour ozone standard, with predicted exceedances, and without proposed or approved SIP attainment demonstrations. In general, the evidence summarized in this section, and presented in more detail in the draft RIA, supports the Agency's belief that emissions of NO X and VOC from heavy-duty vehicles in 2007 and later will contribute to a national ozone air pollution problem that warrants regulatory attention under section 202(a)(3) of the Act. Table II.B-2 Metropolitan area/State Proposed reinstatement of ozone standard 1996 population (in millions) Areas with 2007/2010 Attainment Dates (Established or Requested): New York City, NY-NJ-CT 19.9 Houston, TX 4.3 Hartford, CT 1.1 New London, CT 1.3 Chicago, IL-IN 8.6 Milwaukee, WI 1.6 Dallas, TX 4.6 Beaumont-Port Arthur, TX 0.4 Los Angeles, CA 15.5 Southeast Desert, CA 0.4 Subtotal of 10 areas 57.7 Areas with Pre-2007 Attainment Dates or No Specific Attainment Date, with a Recent History of Nonattainment:** Atlanta, GA 3.5 Philadelphia-Wilmington-Atlantic City, PA-NJ-DE-MD 6.0 Sacramento, CA 1.5 San Joaquin Valley, CA *possible future reclassification and change of attainment date to 2005 2.7 Ventura County, CA 0.7 Washington-Baltimore, DC-MD-VA-WV 7.2 Charlotte-Gastonia, NC X 1.3 Grand Rapids, MI X 1.0 Huntington-Ashland, WV-KY X 0.3 Indianapolis, IN X 1.5 Memphis, TN X 1.1 Nashville, TN X 1.1 Barnstable-Yarmouth, MA X 0.2 Boston-Worcester-Lawrence, MA X 5.6 Houma, LA X 0.2 Providence-Fall River-Warwick, RI-MA X 1.1 Richmond-Petersburg, VA X 1.0 Benton Harbor, MI X 0.2 Baton Rouge, LA 0.6 Birmingham, AL 0.9 Cincinnati-Hamilton, OH-KY-IN* 1.9 Louisville, KY-IN 0.3 Pittsburgh, PA MSA 2.4 San Diego, CA 2.8 San Francisco Bay Area, CA 6.2 St. Louis, MO-IL 2.5 Subtotal of 26 areas 53.8 Areas with Pre-2007 Attainment Dates and Recent Concentrations within 10% of an Exceedance, But With No Recent History of Nonattainment: Biloxi-Gulfport-Pascagoula, MS MSA X 0.3 Cleveland-Akron, OH CMSA X 2.9 Detroit-Ann Arbor-Flint, MI CMSA X 5.3 New Orleans, LA MSA X 0.3 Pensacola, FL MSA X 0.4 Tampa, FL MSA X 2.2 Subtotal of 6 areas 11.4 Total 1996 Population of All Areas at Risk of Exceeding the Ozone Standard in 2007 or Thereafter: 42 Areas—total population 122.9 *Based on more recent air quality monitoring data not considered in the Tier 2 analysis, and on 10-year emissions projections, we expect to redesignate Cincinnati-Hamilton to attainment soon. **The list includes certain areas that are currently not violating the 1-hour NAAQS. c. Public Health and Welfare Concerns From Prolonged and Repeated Exposures to Ozone A large body of scientific literature regarding health and welfare effects of ozone has associated health effects with certain patterns of ozone exposures that do not include any hourly ozone concentration above the 0.12 parts per million (ppm) level of the 1-hour NAAQS. The science indicates that there are health effects attributable to prolonged and repeated exposures to lower ozone concentrations. Studies of 6 to 8 hour exposures showed health effects from prolonged and repeated exposures at moderate levels of exertion to ozone concentrations as low as 0.08 ppm. Prolonged and repeated ozone concentrations at these levels are common in areas throughout the country, and are found in areas that are exceeding, and areas that are not exceeding, the 1-hour ozone standard. For example, in 1998, almost 62 million people lived in areas with 2 or more days with concentrations of 0.09 ppm or higher, excluding areas currently violating the 1-hour NAAQS. Since prolonged exposures at moderate levels of ozone are more widespread than exceedances of the 1-hour ozone standard, and given the continuing nature of the 1-hour ozone problem described above, adverse health effects from this type of ozone exposure can reasonably be anticipated to occur in the future in the absence of this rule. Adverse welfare effects can also be anticipated, primarily from damage to vegetation. See the draft RIA for further details. Studies of acute health effects have shown transient pulmonary function responses, transient respiratory symptoms, effects on exercise performance, increased airway responsiveness, increased susceptibility to respiratory infection, increased hospital and emergency room visits, and transient pulmonary respiratory inflammation. Such acute health effects have been observed following prolonged exposures at moderate levels of exertion at concentrations of ozone well below the current standard of 0.12 ppm. The effects are more pronounced at concentrations above 0.09 ppm, affecting more subjects or having a greater effect on a given subject in terms of functional changes or symptoms. A more detailed discussion may be found in the Draft RIA. With regard to chronic health effects, the collective data have many ambiguities, but provide suggestive evidence of chronic effects in humans. There is a biologically plausible basis for considering the possibility that repeated inflammation associated with exposure to ozone over a lifetime, as can occur with prolonged exposure to moderate ozone levels below peak levels, may result in sufficient damage to respiratory tissue that individuals later in life may experience a reduced quality of life, although such relationships remain highly uncertain. We believe that the evidence in the Draft RIA regarding the occurrence of adverse health effects due to prolonged and repeated exposure to ozone concentrations in the range discussed above, and regarding the populations that are expected to receive exposures at these levels, supports a conclusion that emissions of NO X , and VOC from heavy-duty vehicles in 2007 and later will be contributing to a national air pollution problem that warrants regulatory attention under section 202(a)(3) of the Act. Ozone has many welfare effects, with damage to plants being of most concern. Plant damage affects crop yields, forestry production, and ornamentals. The adverse effect of ozone on forests and other natural vegetation can in turn cause damage to associated ecosystems, with additional resulting economic losses. Ozone concentrations of 0.10 ppm can be phytotoxic to a large number of plant species, and can produce acute injury and reduced crop yield and biomass production. Ozone concentrations at or below 0.10 ppm have the potential over a longer duration of creating chronic stress on vegetation that can result in reduced plant growth and yield, shifts in competitive advantages in mixed populations, decreased vigor, and injury from other environmental stresses. The forestry, crop and other environmental damage from ozone in times and places where the 1-hour NAAQS is attained adds support to the Agency's belief that there will be air pollution in 2007 and thereafter that warrants regulatory attention under section 202(a)(3) of the Act. 2. Particulate Matter a. Health and Welfare Effects i. Particulate Matter Generally Particulate matter (PM) represents a broad class of chemically and physically diverse substances. It can be principally characterized as discrete particles that exist in the condensed (liquid or solid) phase spanning several orders of magnitude in size. All particles equal to and less than 10 microns are called PM 10 . Fine particles can be generally defined as those particles with an aerodynamic diameter of 2.5 microns or less (also known as PM 2.5 ), and coarse fraction particles are those particles with an aerodynamic diameter greater than 2.5 microns, but equal to or less than a nominal 10 microns. The health and environmental effects of PM are strongly related to the size of the particles. The emission sources, formation processes, chemical composition, atmospheric residence times, transport distances and other parameters of fine and coarse particles are distinct. Fine particles are directly emitted from combustion sources and are formed secondarily from gaseous precursors such as sulfur dioxide, nitrogen oxides, or organic compounds. Fine particles are generally composed of sulfate, nitrate, chloride and ammonium compounds; organic and elemental carbon; and metals. Combustion of coal, oil, diesel, gasoline, and wood, as well as high temperature process sources such as smelters and steel mills, produce emissions that contribute to fine particle formation. In contrast, coarse particles are typically mechanically generated by crushing or grinding and are often dominated by resuspended dusts and crustal material from paved or unpaved roads or from construction, farming, and mining activities. Fine particles can remain in the atmosphere for days to weeks and travel through the atmosphere hundreds to thousands of kilometers, while coarse particles deposit to the earth within minutes to hours and within tens of kilometers from the emission source. Particulate matter, like ozone, has been linked to a range of serious respiratory health problems. Scientific studies suggest a likely causal role of ambient particulate matter (which is attributable to a number of sources including diesel) in contributing to a series of health effects. The key health effects categories associated with ambient particulate matter include premature mortality, aggravation of respiratory and cardiovascular disease (as indicated by increased hospital admissions and emergency room visits, school absences, work loss days, and restricted activity days), aggravated asthma, acute respiratory symptoms, including aggravated coughing and difficult or painful breathing, chronic bronchitis, and decreased lung function that can be experienced as shortness of breath. For additional information on health effects, see the draft RIA. Both fine and coarse particles can accumulate in the respiratory system. Exposure to fine particles is most closely associated with such health effects as premature mortality or hospital admissions for cardiopulmonary disease. PM also causes damage to materials and soiling. It is a major cause of substantial visibility impairment in many parts of the U.S. Diesel particles are a component of both coarse and fine PM, but fall mostly in the fine range. Noncancer health effects associated with exposure to diesel PM overlap with some health effects reported for ambient PM including respiratory symptoms (cough, labored breathing, chest tightness, wheezing), and chronic respiratory disease (cough, phlegm, chronic bronchitis and some evidence for decreases in pulmonary function). ii. Special Considerations for Diesel PM Primary diesel particles mainly consist of carbonaceous material, ash (trace metals), and sulfuric acid. Many of these particles exist in the atmosphere as a carbon core with a coating of organic carbon compounds, sulfuric acid and ash, sulfuric acid aerosols, or sulfate particles associated with organic carbon. Most diesel particles are in the fine and ultrafine size range. Diesel PM contains small quantities of numerous mutagenic and carcinogenic compounds. While representing a very small portion (less than one percent) of the national emissions of metals, and a small portion of diesel particulate matter (one to five percent), we note that several trace metals of toxicological significance are also emitted by diesel engines in small amounts including chromium, manganese, mercury and nickel. In addition, small amounts of dioxins have been measured in diesel exhaust, some of which may partition into the particle phase, though the impact of these emissions on human health is not clear. Because the chemical composition of diesel PM includes these hazardous air pollutants, or air toxics, diesel PM emissions are of concern to the agency beyond their contribution to general ambient PM. Moreover, as discussed in detail in the draft RIA, there have been health studies specific to diesel PM emissions which indicate potential hazards to human health that appear to be specific to this emissions source. For chronic exposure, these hazards included respiratory system toxicity and carcinogenicity. Acute exposure also causes transient effects (a wide range of physiological symptoms stemming from irritation and inflammation mostly in the respiratory system) in humans though they are highly variable depending on individual human susceptibility. b. Potential Cancer Effects of Diesel Exhaust The EPA draft Health Assessment Document for Diesel Emissions (draft Assessment) is currently being revised based on comments received from the Clean Air Scientific Advisory Committee (CASAC) of EPA's Science Advisory Board. 19 The current EPA position is that diesel exhaust is a likely human lung carcinogen and that this cancer hazard exists for occupational and environmental levels of exposure. 20 19 U.S. EPA (1999) Health Assessment Document for Diesel Emissions: SAB Review Draft. EPA/600/8-90/057D Office of Research and Development, Washington, DC. The document is available electronically at www.epa.gov/ncea/diesel.htm. 20 The EPA designation of diesel exhaust as a likely human carcinogen is subject to further comment by CASAC in 2000. The designation of diesel exhaust as a likely human carcinogen under the 1996 Proposed Guidelines for Carcinogen Risk Assessment is very similar to the current 1986 Guidelines for Carcinogen Risk Assessment that designate diesel exhaust as a probable carcinogen (B-1 carcinogen). The new guidelines, once finalized, will incorporate a narrative approach to assist the risk manager in the interpretation of the carcinogen's mode of action, the weight of evidence, and any risk related exposure-response or protective exposure recommendations. In evaluating the available research for the draft Assessment, EPA found that individual epidemiological studies numbering about 30 show increased lung cancer risks associated with diesel emissions within the study populations of 20 to 89 percent depending on the study. Analytical results of pooling the positive study results show that on average the risks were increased by 33 to 47 percent. Questions remain about the influence of other factors (e.g., effect of smoking), the quality of the individual epidemiology studies, exposure levels, and consequently the precise magnitude of the increased risk of lung cancer. From a weight of the evidence perspective, EPA believes that the epidemiology evidence, as well as supporting data from certain animal and mode of action studies, support the Agency's proposed conclusion that exposure to diesel exhaust is likely to pose a human health hazard at occupational exposure levels, as well as to the general public exposed to typically lower environmental levels of diesel exhaust. Risk assessments on epidemiological studies in the peer-reviewed literature which have attempted to assess the lifetime risk of lung cancer in workers occupationally exposed to diesel exhaust suggests that lung cancer risk may range from 10 −4 to 10 − . 21 22 23 The Agency recognizes the significant uncertainties in these studies, and has not used these estimates to assess the possible cancer unit risk associated with ambient exposure to diesel exhaust. 21 California Environmental Protection Agency, Office of Health Hazard Assessment (CAL-EPA, OEHHA) (1998) Proposed Identification of Diesel Exhaust as a Toxic Air Contaminant. Appendix III Part B Health Risk Assessment for Diesel Exhaust. April 22, 1998. 22 Steenland, K., Deddens, J., Stayner, L. (1998) Diesel Exhaust and Lung Cancer in the Trucking Industry: Exposure-Response Analyses and Risk Assessment. Am. J Indus. Medicine 34:220-228. 23 Harris, J.E. (1983) Diesel emissions and Lung Cancer. Risk Anal. 3:83-100. While available evidence supports EPA's conclusion that diesel exhaust is a likely human lung carcinogen, and thus is likely to pose a cancer hazard to humans, the absence of quantitative estimates of the lung cancer unit risk for diesel exhaust limits our ability to quantify with confidence the actual magnitude of the cancer risk. In the draft 1999 Assessment, EPA acknowledged these limitations and provided a discussion of the possible cancer risk consistent with general occupational epidemiological findings of increased lung cancer risk and relative exposure ranges in the occupational and environmental settings. 24 The Agency believes that the techniques that were used in the draft Assessment to qualitatively gauge the potential for and possible magnitude of risk are reasonable. The details of this approach are provided in the draft RIA. 24 See Chapter 8.3 and 9.6 of the draft Health Assessment for Diesel Exhaust. U.S. 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 the absence of a quantitative unit cancer risk to assess environmental risk, EPA has considered the relevant epidemiological studies and principles for their assessment, the risk from occupational exposure as assessed by others, and relative exposure margins between occupational and ambient environmental levels of diesel exhaust exposure. Based on this epidemiological and other information, there is the potential that upper bounds on environmental cancer risks from diesel exhaust may exceed 10 −6 and could be as high as 10 −3 . 25 While uncertainty exists in estimating risk, the likely hazard to humans together with the potential for significant environmental risks leads the Agency to believe that diesel exhaust emissions should be reduced in order to protect the public's health. We believe that this is a prudent measure in light of the designation of diesel exhaust as a likely human carcinogen, the exposure of almost the entire population to diesel exhaust, the significant and consistent finding of an increase in lung cancer risk in workers exposed to diesel exhaust, and the potential overlap and/or small difference between some occupational and environmental exposures. 25 As used in this proposal, environmental risk is defined as the risk (i.e. a mathematical probability) that lung cancer would be observed in the population after a lifetime exposure to diesel exhaust. Exposure levels may be occupational lifetime or environmental lifetime exposures. A population risk in the magnitude of 10 −6 translates as the probability of lung cancer being evidenced in one person in one million over a lifetime exposure. As discussed in section I.C.6, “Actions in California”, the Office of Environmental Health Hazard Assessment (OEHHA, California EPA) has identified diesel PM as a toxic air contaminant. 26 California is in the process of determining the need for, and appropriate degree of control measures for diesel PM. Apart from the EPA draft Assessment and California EPA's actions, several other agencies and governing bodies have designated diesel exhaust or diesel PM as a “potential” or “probable” human carcinogen. 27 28 29 The International Agency for Research on Cancer (IARC) considers diesel exhaust a “probable” human carcinogen and the National Institutes for Occupational Safety and Health have classified diesel exhaust a “potential occupational carcinogen.” Thus, the concern for the health hazard resulting from diesel exhaust exposures is widespread. 26 Office of Environmental Health Hazard Assessment (1998) Health risk assessment for diesel exhaust, April 1998. California Environmental Protection Agency, Sacramento, CA. 27 National Institute for Occupational Safety and Health (NIOSH) (1988) Carcinogenic effects of exposure to diesel exhaust. NIOSH Current Intelligence Bulletin 50. DHHS, Publication No. 88-116. Centers for Disease Control, Atlanta, GA. 28 International Agency for Research on Cancer (1989) Diesel and gasoline engine exhausts and some nitroarenes, Vol. 46. Monographs on the evaluation of carcinogenic risks to humans. World Heath Organization, International Agency for Research on Cancer, Lyon, France. 29 World Health Organization (1996) Diesel fuel and exhaust emissions: International program on chemical safety. World Health Organization, Geneva, Switzerland. c. Noncancer Effects of Diesel Exhaust The noncancer effects of diesel exhaust emissions are also of concern to the Agency. EPA believes that chronic diesel exhaust exposure, at sufficient exposure levels, increases the hazard and risk of an adverse consequence (including respiratory tract irritation/inflammation and changes in lung function). The draft 1999 Assessment discussed an existing inhalation reference concentration (RfC) for chronic effects that EPA intends to revise in the next draft Assessment in response to CASAC comments. The revised RfC will be reviewed by CASAC at a future meeting. An RfC provides an estimate of the continuous human inhalation exposure (including sensitive subgroups) that is likely to be without an appreciable risk of deleterious noncancer effects during a lifetime. d. Attainment and Maintenance of the PM 10 NAAQS Under the CAA, we are to regulate HD emissions if they contribute to air pollution that can reasonably be anticipated to endanger public health and welfare. We have already addressed the question of what concentration patterns of PM endanger public health, in setting the NAAQS for PM 10 in 1987. The PM NAAQS were rev [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%3A00-12952. Public record. Not legal advice.