Control of Air Pollution From New Motor Vehicles: Tier 2 Motor Vehicle Emissions Standards and Gasoline Sulfur Control Requirements

Federal RegisterFeb 10, 2000

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 80, 85, and 86

[AMS-FRL-6516-2]

RIN 2060-AI23

Control of Air Pollution From New Motor Vehicles: Tier 2 Motor Vehicle Emissions Standards and Gasoline Sulfur Control Requirements

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Final rule.

SUMMARY:

Today's action finalizes a major program designed to significantly reduce the emissions from new passenger cars and light trucks, including pickup trucks, vans, minivans, and sport-utility vehicles. These reductions will provide for cleaner air and greater public health protection, primarily by reducing ozone and PM pollution. The program is a comprehensive regulatory initiative that treats vehicles and fuels as a system, combining requirements for much cleaner vehicles with requirements for much lower levels of sulfur in gasoline. A list of major highlights of the program appears at the beginning of the

SUPPLEMENTARY INFORMATION

section of this

Federal Register

The program we are finalizing today will phase in a single set of tailpipe emission standards that will, for the first time, apply to all passenger cars, light trucks, and larger passenger vehicles operated on any fuel. This set of “Tier 2 standards” is feasible and the use of a single set of standards is appropriate because of the increased use of light trucks for personal transportation. The miles traveled in light trucks is increasing and the emissions from these vehicles are thus an increasing problem. This approach builds on the recent technology improvements resulting from the successful National Low-Emission Vehicles (NLEV) program.

To enable the very clean Tier 2 vehicle emission control technology to be introduced and to maintain its effectiveness, we are also requiring reduced gasoline sulfur levels nationwide. The reduction in sulfur levels will also contribute directly to cleaner air in addition to its beneficial effects on vehicle emission control systems. Refiners will generally install additional refining equipment to remove sulfur in their refining processes. Importers of gasoline will be required to import and market only gasoline meeting the sulfur standards. Today's action also introduces an averaging, banking, and trading program to provide flexibility for refiners and ease implementation of the gasoline sulfur control program.

The overall program focuses on reducing the passenger car and light truck emissions most responsible for causing ozone and particulate matter problems. Without today's action, we project that emissions of nitrogen oxides from these vehicles will represent as much as 40 percent of this ozone-forming pollutant in some cities, and almost 20 percent nationwide, by the year 2030.

Today's program will bring about major reductions in annual emissions of these pollutants and also reduce the emissions of sulfur compounds resulting from the sulfur in gasoline. For example, we project a reduction in oxides of nitrogen emissions of at least 856,000 tons per year by 2007 and 1,236,000 by 2010, the time frame when many states will have to demonstrate compliance with air quality standards. Emission reductions will continue increasing for many years, reaching at least 2,220,000 tons per year in 2020 and continuing to rise further in future years. In addition, the program will reduce the contribution of vehicles to other serious public health and environmental problems, including VOC, PM, and regional visibility problems, toxic air pollutants, acid rain, and nitrogen loading of estuaries.

Furthermore, we project that these reductions, and their resulting environmental benefits, will come at an average cost increase of less than $100 per passenger car, an average cost increase of less than $200 for light trucks, and an average cost increase of about $350 for medium-duty passenger vehicles, and an average increase of less than 2 cents per gallon of gasoline (or about $120 over the life of an average vehicle).

DATES:

This rule is effective April 10, 2000.

The incorporation by reference of certain publications contained in this rule are approved by the Director of the Federal Register as of April 10, 2000.

ADDRESSES:

Comments:

All comments and materials relevant to today's action have been placed in Public Docket No. A-97-10 at the following address: U.S. Environmental Protection Agency (EPA), Air Docket (6102), Room M-1500, 401 M Street, S.W., Washington, D.C. 20460. EPA's Air Docket makes materials related to this rulemaking available for review at the above address (on the ground floor in Waterside Mall) from 8:00 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.

FOR FURTHER INFORMATION CONTACT:

Carol Connell, U.S. EPA, National Vehicle and Fuels Emission Laboratory, 2000 Traverwood, Ann Arbor MI 48105; Telephone (734) 214-4349, FAX (734) 214-4816, E-mail connell.carol@epa.gov.

SUPPLEMENTARY INFORMATION:

Highlights of the Tier2/Gasoline Sulfur Program

For cars, and light trucks, and larger passenger vehicles, the program will—

• Starting in 2004, through a phase-in, apply for the first time the same set of emission standards covering passenger cars, light trucks, and large SUVs and passenger vehicles. These emission levels (“Tier 2 standards”) are feasible for these vehicles. The Tier 2 standards are also appropriate because of the increased use of light trucks for personal transportation—the miles traveled in light trucks is increasing and the emissions from these vehicles are thus an increasing problem.

• Introduce a new category of vehicles, “medium-duty passenger vehicles,” thus bringing larger passenger vans and SUVs into the Tier 2 program.

• During the phase-in, apply interim fleet emission average standards that match or are more stringent than current federal and California “LEV I” (Low-Emission Vehicle, Phase I) standards.

• Apply the same standards to vehicles operated on any fuel.

• Allow auto manufacturers to comply with the very stringent new standards in a flexible way while ensuring that the needed environmental benefits occur.

• Build on the recent technology improvements resulting from the successful National Low-Emission Vehicles (NLEV) program and improve the performance of these vehicles through lower sulfur gasoline.

• Set more stringent particulate matter standards.

• Set more stringent evaporative emission standards.

For commercial gasoline, the program will—

• Significantly reduce average gasoline sulfur levels nationwide as early as 2000, fully phased in in 2006. Refiners will generally add refining equipment to remove sulfur in their refining processes. Importers of gasoline will be required to import and market only gasoline meeting the sulfur limits.

• Provide for flexible implementation by refiners through an averaging, banking, and trading program.

• Encourage early introduction of cleaner fuel into the marketplace through an early sulfur credit and allotment program.

• Apply temporary gasoline sulfur standards to certain small refiners and gasoline marketed in a limited geographic area in the western U.S.

• Enable the new Tier 2 vehicles to meet the emission standards by greatly reducing the degradation of vehicle emission control performance from sulfur in gasoline. Lower sulfur gasoline also appears to be necessary for the introduction of advanced technologies that promise higher fuel economy but are very susceptible to sulfur poisoning (for example, gasoline direct injection engines).

• Reduce emissions from NLEV vehicles and other vehicles already on the road.

Regulated Entities

This action will affect you if you produce new motor vehicles, alter individual imported motor vehicles to address U.S. regulation, or convert motor vehicles to use alternative fuels. It will also affect you if you produce, distribute, or sell gasoline motor fuel.

The table below gives some examples of entities that may have to comply with the regulations. But because these are only examples, you should carefully examine these and existing regulations in 40 CFR parts 80 and 86. If you have questions, call the person listed in the

FOR FURTHER INFORMATION CONTACT

section above.

Category

NAICS codes

SIC Codes

Examples of potentially regulated entities

Industry

336111

3711

Motor Vehicle Manufacturers.

336112

336120

Industry

336311

3592

Alternative fuel vehicle converters.

336312

3714

422720

5172

454312

5984

811198

7549

541514

8742

541690

8931

Industry

811112

7533

Commercial Importers of Vehicles and Vehicle Components.

811198

7549

541514

8742

Industry

324110

2911

Petroleum Refiners.

Industry

422710

5171

Gasoline Marketers and Distributors.

422720

5172

Industry

484220

4212

Gasoline Carriers.

484230

4213

North American Industry Classification System (NAICS).

Standard Industrial Classification (SIC) system code.

Access to Rulemaking Documents Through the Internet

Today's action is available electronically on the day of publication from the Office of the Federal Register Internet Web site listed below. Electronic copies of this preamble and regulatory language as well as the Response to Comments document, the Regulatory Impact Analysis and other documents associated with today's final rule are available from the EPA 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 already incur for connecting to the Internet.

Federal Register Web Site: http://www.epa.gov/docs/fedrgstr/epa-air/ (Either select a desired date or use the Search feature.)

Office of Mobile Sources (OMS) Web Site: http://www.epa.gov/oms/ (Look in “What's New” or under the “Automobiles” topic.)

Please note that due to differences between the software used to develop the document and the software into which the document may be downloaded, changes in format, page length, etc., may occur.

Outline of This Preamble

I. Introduction

A. What Are the Basic Components of the Program?

1. Vehicle Emission Standards

2. Gasoline Sulfur Standards

B. What Is Our Statutory Authority for Today's Action?

1. Light-Duty Vehicles and Trucks

2. Gasoline Sulfur Controls

C. The Tier 2 Study and the Sulfur Staff Paper

D. Relationship of Diesel Fuel Sulfur Control to the Tier 2/Gasoline Sulfur Program

II. Tier 2 Determination

A. There Is a Substantial Need for Further Emission Reductions in Order To Attain and Maintain National Ambient Air Quality Standards

B. More Stringent Standards for Light-Duty Vehicles and Trucks Are Technologically Feasible

C. More Stringent Standards for Light-Duty Vehicles and Trucks Are Needed and Cost Effective Compared to Available Alternatives

III. Air Quality Need For and Impact of Today's Action

A. Americans Face Serious Air Quality Problems That Require Further Emission Reductions

B. Ozone

1. Background on Ozone Air Quality

2. Additional Emission Reductions Are Needed To Attain and Maintain the Ozone NAAQS.

a. Summary

b. Ozone Modeling Presented in Our Proposal and Supplemental Notice

c. Updated and Additional Ozone Modeling

d. Results and Conclusions

e. Issues and Comments Addressed

f. 8-Hour Ozone

3. Cars and Light-Duty Trucks Are a Big Part of the NO

and VOC Emissions, and Today's Action Will Reduce This Contribution Substantially

4. Ozone Reductions Expected From This Rule

C. Particulate Matter

1. Background on PM

2. Need for Additional Reductions to Attain and Maintain the PM

NAAQS

3. PM

Discussion

4. Emission Reductions and Ambient PM Reductions

D. Other Criteria Pollutants: Carbon Monoxide, Nitrogen Dioxide, Sulfur Dioxide

E. Visibility

F. Air Toxics

G. Acid Deposition

H. Eutrophication/Nitrification

I. Cleaner Cars and Light Trucks Are Critically Important to Improving Air Quality

IV. What Are the New Requirements for Vehicles and Gasoline?

A. Why Are We Proposing Vehicle and Fuel Standards Together?

1. Feasibility of Stringent Standards for Light-Duty Vehicles and Light-Duty Trucks a. Gasoline Fueled Vehicles i. LDVs and LDT1s-LDT4s ii. Medium-Duty Passenger Vehicles (MDPVs) b. Diesel Vehicles

2. Gasoline Sulfur Control Is Needed To Support the Proposed Vehicle Standards a. How Does Gasoline Sulfur Affect Vehicle Emission Performance? b. How Large Is Gasoline Sulfur's Effect on Emissions? c. Sulfur's Negative Impact on Tier 2 Catalysts d. Sulfur Has Negative Impacts on OBD Systems

B. Our Program for Vehicles

1. Overview of the Vehicle Program a. Introduction b. Corporate Average NOx Standard c. Tier 2 Exhaust Emission Standard “Bins' d. Schedules for Implementation i. Implementation Schedule for Tier 2 LDVs and LLDTs ii. Implementation Schedule for Tier 2 HLDTs e. Interim Standards i. Interim Exhaust Emission Standards for LDV/LLDTs ii Interim Exhaust Emission Standards for HLDTs iii. Interim Programs Will Provide Reductions Over Previous Standards f. Generating, Banking, and Trading NOx Credits

2. Why Are We Finalizing the Same Set of Standards for Tier 2 LDVs and LDTs?

3. Why Are We Finalizing the Same Standards for Both Gasoline and Diesel Vehicles?

4. Key Elements of the Vehicle Program a. Basic Exhaust Emission Standards and “Bin” Structure i. Why Are We Including Extra Bins? b. The Program Will Phase In the Tier 2 Vehicle Standards Over Several Years i. Primary Phase-in Schedule

ii. Alternative Phase-in Schedule

c. Manufacturers Will Meet a “Corporate Average” NO

Standard

d. Manufacturers Can Generate, Bank, and Trade NO

Credits

i. General Provisions

ii. Averaging, Banking and Trading of NO

Credits Fulfills Several Goals

iii. How Manufacturers Can Generate and Use NO

Credits

iv. Manufacturers Can Earn and Bank Credits for Early NO

Reductions

v. Tier 2 NO

Credits Will Have Unlimited Life

vi. NO

Credit Deficits Can Be Carried Forward

vii. Encouraging the Introduction of Ultra Clean Vehicles

e. Interim Standards

i. Interim Exhaust Emission Standards for LDV/LLDTs

ii. Interim Exhaust Emission Standards for HLDTs

f. Light-Duty Evaporative Emission Standards

g. Passenger Vehicles Above 8,500 Pounds GVWR

C. Our Program for Controlling Gasoline Sulfur

1. Gasoline Sulfur Standards for Refiners and Importers

a. Standards and Deadlines That Refiners/Importers Must Meet

i. What Are the Per-Gallon Caps on Gasoline Sulfur Levels in 2004 and Beyond?

ii. What Standards Must Refiners/Importers Meet on a Corporate Average Basis?

iii. What Standards Must Be Met by Individual Refineries/Importers?

b. Standards and Deadlines for Refiners/Importers Which Provide Gasoline to the Geographic Phase-in Area (GPA)

i. Justification for Our Geographic Phase-in Approach

ii. What Is the Geographic Phase-in Area and How Was It Established?

iii. Standards/Deadlines for Gasoline Sold in the Geographic Phase-in Area

iv. What Are the Per-Gallon Caps on Gasoline Sulfur Levels in the Phase-in Area?

v. How Do Refiners/Importers Account for GPA Fuel in Their Corporate Average Calculations?

vi. How Do Refiners/Importers Apply for the Geographic Phase-in Area Standards?

vii. How Will EPA Establish the GPA in Adjacent States?

c. How Does the Sulfur Averaging, Banking, and Trading Program Work?

i. Generating Allotments Prior to 2004

ii. Generating Allotments in 2004 and 2005

iii. Using Allotments in 2004 and 2005

iv. How Long Do Allotments Last?

v. Establishing Individual Refinery Sulfur Baselines for Credit Generation Purposes

vi. Generating Sulfur Credits Prior to 2004

vii. Generating Sulfur Credits in 2004 and Beyond

viii. Using Sulfur Credits

ix. How Long Do Credits Last?

x. Conversion of Allotments Into Credits

d. How are State Sulfur Programs Affected by EPA's Program?

2. Hardship Provision for Qualifying Refiners

a. Hardship Provision for Qualifying Small Refiners

i. How Are Small Refiners Defined?

ii. Standards That Small Refiners Must Meet

iii. How Do Small Refiners Apply for Small Refiner Status?

iv. How Do Small Refineries Apply for a Sulfur Baseline?

v. Volume Limitation on Use of a Small Refinery Standard

vi. Extensions Beyond 2007 for Small Refiners

vii. Can Small Refiners Participate in the ABT Program?

b. Temporary Waivers From Low Sulfur Requirements in Extreme Unforeseen Circumstances

c. Temporary Waivers Based on Extreme Hardship Circumstances

3. Streamlining of Refinery Air Pollution Permitting Process

a. Brief Summary of Proposal

b. Significant Comments Received

c. Today's Action

i. Major New Source Review

ii. Environmental Justice

D. What Are the Economic Impacts, Cost Effectiveness and Monetized Benefits of the Tier 2 Program?

1. What Are the Estimated Costs of the Vehicle Standards?

2. Estimated Costs of the Gasoline Sulfur Standards

3. What Are the Aggregate Costs of the Tier 2/Gasoline Sulfur Final Rule?

4. How Does the Cost-Effectiveness of This Program Compare to Other Programs?

a. Cost Effectiveness of this Program

b. How Does the Cost Effectiveness of This Program Compare With Other Means of Obtaining Mobile Source NO

+NMHC Reductions?

c. How Does the Cost Effectiveness of This Program Compare With Other Known Non-Mobile Source Technologies for Reducing NO

+NMHC?

5. Does the Value of the Benefits Outweigh the Cost of the Standards?

a. What Is the Purpose of This Benefit-Cost Comparison?

b. What Was Our Overall Approach to the Benefit-Cost Analysis?

c. What Are the Significant Limitations of the Benefit-Cost Analysis?

d. How Was the Benefit-Cost Analysis Changed From Proposal?

e. How Did We Perform the Benefit-Cost Analysis?

f. What Were the Results of the Benefit-Cost Analysis?

V. Other Vehicle-Related Provisions

A. Final Tier 2 CO, HCHO and PM Standards

1. Carbon Monoxide (CO) Standards

2. Formaldehyde (HCHO) Standards

3. Use of NMHC Data To Show Compliance With NMOG Standards; Alternate Compliance With Formaldehyde Standards.

4. Particulate Matter (PM) Standards

B. Useful Life

1. Mandatory 120,000 Mile Useful Life

2. 150,000 Mile Useful Life Certification Option

C. Supplemental Federal Test Procedure (SFTP) Standards

1. Background

2. SFTP Under the NLEV Program

3. SFTP Standards for the Interim and Tier 2 LDVs and LDTs: As Proposed

4. Final SFTP Standards for Interim and Tier 2 LDVs and LDTs

5. Adding a PM Standard to the SFTP Standards

6. Future Efforts Relevant to SFTP Standards

D. LDT Test Weight

E. Test Fuels

F. Changes to Evaporative Certification Procedures to Address Impacts of Alcohol Fuels

G. Other Test Procedure Issues

H. Small Volume Manufacturers

1. Special Provisions for Independent Commercial Importers (ICIs)

2. Hardship Provision for Small Volume Manufacturers

I. Compliance Monitoring and Enforcement

1. Application of EPA's Compliance Assurance Program, CAP2000

2. Compliance Monitoring

3. Relaxed In-Use Standards for Vehicles Produced During the Phase-in Period

4. Enforcement of the Tier 2 and Interim Corporate Average NO

Standards.

J. Addressing Environmentally Beneficial Technologies Not Recognized by Test Procedures

K. Adverse Effects of System Leaks

L. The Future Development of Advanced Technology and the Role of Fuels

M. Miscellaneous Provisions

VI. Gasoline Sulfur Program Compliance and Enforcement Provisions

A. Overview

B. Requirements for Foreign Refiners and Importers

1. Requirements for Foreign Refiners With Individual Refinery Sulfur Standards or Credit Generation Baselines

2. Requirements for Truck Importers

C. What Standards and Requirements Apply Downstream?

D. Testing and Sampling Methods and Requirements

1. Test Method for Sulfur in Gasoline

2. Test Method for Sulfur in Butane

3. Quality Assurance Testing

4. Requirement to Test Every Batch of Gasoline Produced or Imported

5. Exceptions to the Every-Batch Testing Requirement

6. Sampling Methods

7. Gasoline Sample Retention Requirements

E. Federal Enforcement Provisions for California Gasoline and for Use of California Test Methods to Determine Compliance

F. Recordkeeping and Reporting Requirements

1. Product Transfer Documents

2. Recordkeeping Requirements

3. Reporting Requirements

G. Exemptions for Research, Development, and Testing

H. Liability and Penalty Provisions for Noncompliance

I. How Will Compliance With the Sulfur Standards Be Determined?

VII. Public Participation

VIII. Administrative Requirements

A. Administrative Designation and Regulatory Analysis

B. Regulatory Flexibility

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

3. Executive Order 13132 (Federalism)

E. National Technology Transfer and Advancement Act

F. Executive Order 13045: Children's Health Protection

G. Congressional Review Act

IX. Statutory Provisions and Legal Authority

I. Introduction

Since the passage of the 1990 Clean Air Act Amendments, the U.S. has made significant progress in reducing emissions from passenger cars and light trucks. The National Low-Emission Vehicle (NLEV) and Reformulated Gasoline (RFG) programs are important examples of control programs that are in place and will continue to help reduce car and light-duty truck emissions into the near future.

Nonetheless, due to increasing vehicle population and vehicle miles traveled, passenger cars and light trucks will continue to be significant contributors to air pollution inventories well into the future. In fact, the emission contribution of light trucks and sport utility vehicles now matches that of passenger cars. (This is occurring because of the combination of growth in miles traveled by light trucks and the fact that their emission standards are currently less stringent than those of passenger cars). The program we describe below builds on the NLEV and RFG Phase II programs to develop a strong new national program to protect public health and the environment well into the next century. The program, while reducing VOC and other emissions, focuses especially on NO

, because that is where the largest air quality gains can be achieved.

We have followed several overarching principles in developing this final rule:

• Design a strong national program that will assist states in every region of the country to meet their air quality objectives and that will ensure that cars and trucks continue to contribute a fair share to our nation's overall air quality solutions;

• View vehicles and fuels as an integrated system, recognizing that only by addressing both can the best overall emission performance be achieved;

• Establish a single set of emission standards that apply regardless of the fuel used and whether the vehicle is a car, a light truck, or a larger passenger vehicle;

• Provide compliance flexibilities that allow vehicle manufacturers and oil refiners to adjust to future market trends and honor consumer preferences;

• Not preclude the development of advanced low emission or fuel efficient technologies such as lean-burn engines; and

• Ensure sufficient leadtime for phase-in of the Tier 2 and gasoline sulfur program.

With these principles as background, we turn now to an overview of the vehicle and fuel aspects of the program. Sections I and II of this preamble will give you a brief overview of our program and our rationale for implementing it. Subsequent sections will expand on the air quality need, technological feasibility, economic impacts, and provide a detailed description of the specifics of the program. A public participation section reviews the process we followed in soliciting and responding to public comment. The final sections deal with several administrative requirements. You may also want to review our Final Regulatory Impact Analysis (RIA) and our Response to Comments document, both of which are found in the docket and on the Internet. They provide additional analyses and discussions of many topics raised in this preamble.

A. What Are the Basic Components of the Program?

The nation's air quality, while certainly better than in the past, will nevertheless continue to expose tens of millions of Americans to unhealthy levels of air pollution well into the future in the absence of significant new controls on emissions from motor vehicles. EPA is therefore finalizing a major, comprehensive program designed to reduce emission standards for passenger cars, light trucks, and large passenger vehicles (including sport-utility vehicles, minivans, vans, and pickup trucks) and to reduce the sulfur content of gasoline. Under the program, automakers will produce vehicles designed to have very low emissions when operated on low-sulfur gasoline, and oil refiners will provide that much cleaner gasoline nationwide. In this preamble, we refer to the comprehensive program as the “Tier 2/Gasoline Sulfur program.”

1. Vehicle Emission Standards

Today's action sets new federal emission standards (“Tier 2 standards”) for passenger cars, light trucks, and larger passenger vehicles. The program is designed to focus on reducing the emissions most responsible for the ozone and particulate matter (PM) impact from these vehicles—nitrogen oxides (NO

) and non-methane organic gases (NMOG), consisting primarily of hydrocarbons (HC) and contributing to ambient volatile organic compounds (VOC). The program will also, for the first time, apply the same set of federal standards to all passenger cars, light trucks, and medium-duty passenger vehicles. Light trucks include “light light-duty trucks” (or LLDTs), rated at less than 6000 pounds gross vehicle weight and “heavy light-duty trucks” (or HLDTs), rated at more than 6000

pounds gross vehicle weight).

“Medium-duty passenger vehicles” (or MDPVs) form a new class of vehicles introduced by this rule that includes SUVs and passenger vans rated at between 8,500 and 10,000 GVWR. The program thus ensures that essentially all vehicles designed for passenger use in the future will be very clean vehicles.

A vehicle's “Gross Vehicle Weight Rating,” or GVWR, is the curb weight of the vehicle plus its maximum recommended load of passengers and cargo.

The Tier 2 standards finalized today will reduce new vehicle NO

levels to an average of 0.07 grams per mile (g/mi). For new passenger cars and light LDTs, these standards will phase in beginning in 2004, with the standards to be fully phased in by 2007.

For heavy LDTs and MDPVs, the Tier 2 standards will be phased in beginning in 2008, with full compliance in 2009.

By comparison, the NO

standards for the National Low Emission Vehicle (NLEV) program, which will be in place nationally in 2001, range from 0.30 g/mi for passenger cars to 0.50 g/mi for medium-sized light trucks (larger light trucks are not covered). For further comparison, the standards met by today's Tier 1 vehicles range from 0.60 g/mi to 1.53 g/mi.

During the phase-in period from 2004-2007, all passenger cars and light LDTs not certified to the primary Tier 2 standards will have to meet an interim average standard of 0.30 g/mi NO

, equivalent to the current NLEV standards for LDVs and more stringent than NLEV for LDT2s (e.g., minivans).

During the period 2004-2008, heavy LDTs and MDPVs not certified to the final Tier 2 standards will phase in to an interim program with an average standard of 0.20 g/mi NO

, with those not covered by the phase-in meeting a per-vehicle standard (i.e., an emissions “cap”) of 0.6 g/mi NO

(for HLDTs) and 0.9 g/mi NO

(for MDPVs). The average standards for NO

will allow manufacturers to comply with the very stringent new standards in a flexible way, assuring that the average emissions of a company's production meet the target emission levels while allowing the manufacturer to choose from several more- and less-stringent emission categories for certification.

There are also NMOG standards associated with both the interim and Tier 2 standards. The NMOG standards vary depending on which of various individual sets of emission standards manufacturers choose to use in complying with the average NO

standard. This “bin” approach is described more fully in section IV.B. of this preamble.

We are also setting stringent particulate matter standards that will be especially important if there is substantial future growth in the sales of diesel vehicles. Before 2004, we are establishing more stringent interim PM standards for most light trucks than exist now under NLEV. With higher sales of diesel cars and light trucks, they could easily contribute between one-half and two percent of the PM10 concentration allowed by the NAAQS, with some possibility that the contribution could be as high as 5 to 40 percent in some roadside situations with heavy traffic. These increases would make attainment even more difficult for 8 counties which we already predict to need further emission reductions even without an increase in diesel sales, and would put at risk another 18 counties which are now within 10 percent of a NAAQS violation. Thus, by including a more stringent PM standard in the program finalized today, we help address environmental concerns about the potential growth in the numbers of light-duty diesels on the road—even if that growth is substantial. The new requirements also include more stringent hydrocarbon controls (exhaust NMOG and evaporative emissions standards). We will also monitor the progress of the development of advanced technologies and the role of fuels.

2. Gasoline Sulfur Standards

The other major part of today's action will significantly reduce average gasoline sulfur levels nationwide. We expect these reductions could begin to phase in as early as 2000, with full compliance for most refiners occurring by 2006. Refiners will generally install advanced refining equipment to remove sulfur during the production of gasoline. Importers of gasoline will be required to import and market only gasoline meeting the sulfur limits. Temporary, less stringent standards will apply to a few small refiners through 2007. In addition, temporary, less stringent standards will apply to a limited geographic area in the western U.S. for the 2004-2006 period.

This significant new control of gasoline sulfur content will have two important effects. The lower sulfur levels will enable the much-improved emission control technology necessary to meet the stringent vehicle standards of today's rule to operate effectively over the useful life of the new vehicles. In addition, as soon as the lower sulfur gasoline is available, all gasoline vehicles already on the road will have reduced emissions—from less degradation of their catalytic converters and from fewer sulfur compounds in the exhaust.

Today's action will encourage refiners to reduce sulfur in gasoline as early as 2000. The program requires that most refiners and importers meet a corporate average gasoline sulfur standard of 120 ppm and a cap of 300 ppm beginning in 2004. By 2006, the cap will be reduced to 80 ppm and most refineries must produce gasoline averaging no more than 30 ppm sulfur. The program builds upon the existing regulations covering gasoline composition as it relates to emissions performance. It includes provisions for trading of sulfur credits, increasing the flexibility available to refiners for complying with the new requirements. We intend for the credit program to ease compliance uncertainties by providing refiners the flexibility to phase in early controls in 2000-2003 and use credits gained in these years to delay some control until as late as 2006. As finalized today, the program will achieve the needed environmental benefits while providing substantial flexibility to refiners.

B. What Is Our Statutory Authority for Today's Action?

1. Light-Duty Vehicles and Trucks

We are setting motor vehicle emission standards under the authority of section 202 of the Clean Air Act. Sections 202(a) and (b) of the Act provide EPA with general authority to prescribe vehicle standards, subject to any specific limitations otherwise included in the Act. Sections 202(g) and (h) specify the current standards for LDVs and LDTs, which became effective beginning in model year 1994 (“Tier 1 standards”).

Section 202(i) of the Act provides specific procedures that EPA must follow to determine whether standards more stringent than Tier 1 standards for LDVs and certain LDTs

are appropriate beginning between the 2004 and 2006 model years.

Specifically, we are required to first issue a study regarding “whether or not further reductions in emissions from light-duty vehicles and light-duty trucks should be required * * *” (the “Tier 2 Study”). This study “shall examine the need for further reductions in emissions in order to attain or maintain the national ambient air quality standards.” It is also to consider: (1) The availability of technology to meet more stringent standards, taking cost, lead time, safety, and energy impacts into consideration; and (2) the need for, and cost effectiveness of, such standards, including consideration of alternative methods of attaining or maintaining the national ambient air quality standards. A certain set of “default” emission

standards for these vehicle classes is among those options for new standards that EPA is to consider.

LDTs with a loaded vehicle weight less than or equal to 3750 pounds, called LDT1s and LDT2s.

Section 202(b)(1)(C) forbids EPA from promulgating mandatory standards more stringent than Tier 1 standards until the 2004 model year.

After the study is completed and the results are reported to Congress, EPA is required to determine by rulemaking whether: (1) There is a need for further emission reductions; (2) the technology for more stringent emission standards from the affected classes is available; and (3) such standards are needed and cost-effective, taking into account alternatives. If EPA answers “yes” to these questions, then the Agency is to promulgate new, more stringent motor vehicle standards (“Tier 2 standards”).

EPA submitted its report to Congress on July 31, 1998. Today's final rule makes affirmative responses to the three questions above (see Section II below) and sets new standards that are more stringent than the default standards in the Act.

EPA is also setting standards for larger light-duty trucks and MDPVs under the general authority of Section 202(a)(1) and 202(b) and under Section 202(a)(3) of the Act, which requires that standards applicable to emissions of hydrocarbons, NO

, CO and PM from heavy-duty vehicles

reflect the greatest degree of emission reduction available for the model year to which such standards apply, giving appropriate consideration to cost, energy, and safety. We are also setting standards for formaldehyde under our authority in sections 202(a) and (l).

LDTs that have gross vehicle weight ratings above 6000 pounds are considered “heavy-duty vehicles” under the Act. See section 202(b)(3). For regulatory purposes, we refer to these LDTs as “heavy light-duty trucks” made up of LDT3s and LDT4s.

2. Gasoline Sulfur Controls

We are adopting gasoline sulfur controls pursuant to our authority under Section 211(c)(1) of the Clean Air Act.

Under Section 211(c)(1), EPA may adopt a fuel control if at least one of the following two criteria is met: (1) The emission products of the fuel cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare; or (2) the emission products of the fuel will significantly impair emissions control systems in general use or which will be in general use were the fuel control to be adopted.

We currently have regulatory requirements for conventional and reformulated gasoline adopted under Sections 211(c) and 211(k) of the Act, in addition to the “substantially similar” requirements for fuel additives of Section 211(f). These requirements have the effect of limiting sulfur levels in gasoline to some extent. See the Final RIA for more details.

We are adopting gasoline sulfur controls based on both of these criteria. Under the first criterion, we believe that sulfur in gasoline used in Tier 1 and LEV technology vehicles contributes to ozone pollution, air toxics, and PM. Under the second criterion, we believe that gasoline sulfur in fuel will significantly impair the emissions control systems expected to be used in Tier 2 technology vehicles, as well as emissions control systems currently used in LEVs. Please refer to Section IV.C. below and to the Final Regulatory Impact Analysis (RIA) for more details of our analysis and findings. The RIA includes a more detailed discussion of EPA's authority to set gasoline sulfur standards, including a discussion of our conclusions relating to the factors required to be considered under Section 211(c).

C. The Tier 2 Study and the Sulfur Staff Paper

On July 31, 1998, EPA submitted its report to Congress containing the results of the Tier 2 study.

The study indicated that in the 2004 and later time frame, there will be a need for emission reductions to aid in meeting and maintaining the National Ambient Air Quality Standards (NAAQS) for both ozone and PM. Air quality modeling showed that in the 2007-2010 time frame, when Tier 2 standards will become fully effective, a number of areas will still be in nonattainment for ozone and PM even after the implementation of existing emission controls. The study also noted the continued existence of carbon monoxide (CO) nonattainment areas. It also found ample evidence that technologies will be available to meet more stringent Tier 2 standards. In addition, the study provided evidence that such standards could be implemented at a similar cost per ton of reduced pollutants as other programs aimed at similar air quality problems. Finally, the study identified several additional issues in need of further examination, including the relative stringency of car and light truck emission standards, the appropriateness of identical versus separate standards for gasoline and diesel vehicles, and the effects of sulfur in gasoline on catalyst efficiency. Section IV of this preamble describes the steps we have taken to follow up on the Tier 2 Study.

On April 28, 1998, EPA published a notice of availability announcing the release of a draft of the Tier 2 study and requesting comments on the draft. The final report to Congress included a summary and analysis of the comments EPA received.

In addition, on May 1, 1998, EPA released a staff paper presenting EPA's understanding of the impact of gasoline sulfur on emissions from motor vehicles and exploring what gasoline producers and automobile manufacturers could do to reduce sulfur's impact on emissions. The staff paper noted that gasoline sulfur degrades the effectiveness of catalytic converters and that high sulfur levels in commercial gasoline could affect the ability of future automobiles—especially those designed for very low emissions—to meet more stringent standards in use. It also pointed out that sulfur control will provide additional benefits by lowering emissions from the current fleet of vehicles.

D. Relationship of Diesel Fuel Sulfur Control to the Tier 2/Gasoline Sulfur Program

In the NPRM, we raised the question of what if any changes to diesel fuel may be needed to enable diesel vehicles to meet the Tier 2 standards or any future heavy-duty diesel engine standards. Specifically, we raised the question of whether diesel sulfur levels need to be controlled. Since diesel fuel controls of any kind would have an impact on the refinery as a whole, and since in some cases (including potential diesel sulfur limits) could have implications for gasoline sulfur control, we requested comment on this issue in our proposal. We also indicated that we planned to release an Advance Notice of Proposed Rulemaking to solicit more information on this subject.

We published the ANPRM on May 13, 1999 (64 FR 26142). We are in the process of considering all of the comments received in response to the ANPRM and plan to issue a Notice of Proposed Rulemaking (NPRM) in early spring of 2000. We received many comments on the subject of diesel fuel control along with the comments submitted on the proposed Tier 2/Gasoline Sulfur regulations. We have prepared brief responses to some of these comments in the Response to Comments document, and will deal fully with these comments as part of the forthcoming NPRM on diesel fuel. We are taking no action on diesel fuel as part of today's action.

II. Tier 2 Determination

Based on the statutory requirements described above and the evidence provided in the Tier 2 Study and since its release, as described elsewhere in this preamble, EPA has determined that new, more stringent emission standards are indeed needed, technologically feasible, and cost effective.

A. There Is a Substantial Need for Further Emission Reductions in Order to Attain and Maintain National Ambient Air Quality Standards

EPA finds that there is a clear air quality need for new emission standards, based on the continuing air quality problems predicted to exist in future years. As the discussion in Section III.B. illustrates, 26 metropolitan areas are each certain or highly likely to need additional reductions. These areas are distributed across most regions of the U.S., and have a combined population of over 86 million. Section III.B. also shows that an additional 12 areas each has a moderate to significant probability of needing additional reductions, representing another 25 million people. This provides ample evidence that further emission reductions are needed to meet the 1-hour ozone NAAQS.

In addition to these ozone concerns, our analysis of PM

monitoring data and PM

projections indicates that 15 PM

nonattainment counties violated the PM

NAAQS in recent years, and that 8 of them with a 1996 population of almost 8 million have a high risk of failing to attain and maintain without more emission reductions. Eighteen other counties, with a population of 23 million have a significant risk of failing or are within 10 percent of violating the PM

NAAQS. It is also important to recognize that nonattainment areas remain for other criteria pollutants (

e.g.,

CO) and that non-criteria pollution (

e.g.,

air toxics and regional haze) also contributes to environmental and health concerns.

B. More Stringent Standards for Light-Duty Vehicles and Trucks Are Technologically Feasible

We find that emission standards significantly more stringent than current Tier 1 and National Low Emission Vehicle (NLEV) levels are technologically feasible. This is true both for the LDVs and LDTs specifically covered in section 202(i) and for the medium-duty passenger vehicles also included in today's final rule. Manufacturers are currently producing NLEV vehicles that meet more stringent standards than similar Tier 1 models. Our analysis shows that mainly through improvements in engine control software and catalytic converter technology, manufacturers can build and are building durable vehicles and trucks, including heavy light-duty trucks, which have very low emission levels.

Section IV.A. below discusses our feasibility conclusions in more detail.

The Final RIA contains a more detailed analysis, and Section IV.A. below has further discussion of the technological feasibility of our standards including detailed discussions of the various technology options that we believe manufacturers may use to meet these standards.

Many current production vehicles are already certified at or near the Tier 2 standards. For year 2000 certification (although not yet complete), over 50 vehicle models have emissions at or below Tier 2 levels. In addition, we performed a demonstration program at our EPA laboratory that showed that even large vehicles, which would be expected to face the toughest challenges reaching Tier 2 emission levels, can do so with conventional technology. Others, including the Manufacturers of Emission Controls Association (MECA) and the State of California, have also performed demonstration programs, with similar results. Manufacturers have also certified LDVs and LDTs to NMOG and CO levels as much as 80 percent below Tier 1 standards. Furthermore, for passenger vehicles greater than 8500 lbs GVWR, we believe that by using technologies and control strategies similar to what will be used on lighter vehicles, manufacturers will be able to meet the Tier 2 emission standards.

Thus, we believe that, by the 2004-2009 time frame, manufacturers will be fully able to comply with the new Tier 2 emission standard levels. In addition, to facilitate manufacturers' efforts to meet these new standards, the Tier 2 regulations include a phase-in over several years and a corporate fleet average NO

standard, which will allow manufacturers to optimize the deployment of technology across their product lines with no loss of environmental benefit. Our analysis of the available technology improvements and the very low emission levels already being realized on these vehicles leads us to find that the standards adopted today are fully feasible for LDVs and LDTs.

C. More Stringent Standards for Light-Duty Vehicles and Trucks Are Needed and Cost Effective Compared to Available Alternatives

In this action, we also find that more stringent motor vehicle standards are both necessary and cost effective. As discussed above, substantial further reductions in emissions are needed to help reduce the levels of unhealthy air pollution to which millions of people are being exposed; in particular, we expect that a number of areas will not attain or maintain compliance with the National Ambient Air Quality Standards for ozone and PM

without such reductions. (We describe this further in Section III below and in the RIA.)

Furthermore, mobile sources are important contributors to the air quality problem. As we will explain more fully later in this preamble, in the year 2030, the cars and light trucks that are the subject of today's final rule are projected to contribute as much as 40 percent of the total NO

inventory in some cities, and almost 20 percent of nationwide NO

emissions. This situation would have been considerably worse without the NLEV program created by vehicle manufacturers, EPA, the Northeastern states, and others.

These emission reductions are clearly necessary to meet and maintain the 1-hour ozone NAAQS. We project that while the emission reductions of this program will lead to substantial progress in meeting and maintaining the NAAQS, many areas will still not come into attainment even with this magnitude of reductions.

We find that the Tier 2/Gasoline Sulfur program is a reasonable, cost-effective method of providing substantial progress towards attainment and maintenance of the NAAQS, costing about $2000 per ton of NO

plus hydrocarbon emissions reduced. This program will reduce annual NO

emissions by about 2.2 million tons per year in 2020 and 2.8 million tons per year in 2030 after the program is fully implemented. By way of comparison, when EPA established its 8-hour NAAQS for ozone, we identified several types of emission control programs that were reasonably cost effective. If all of the controls identified in that analysis costing less than $10,000/ton were implemented nationwide, they would produce NO

emission reductions of about 2.9 million tons per year. (That is, to achieve about the same emission reductions as the Tier 2/Gasoline Sulfur program, other alternative measures would have a significantly higher cost per ton). These emission reductions are clearly necessary to meet and maintain the one-hour ozone NAAQS. We project that while the emission reductions of this program will lead to substantial progress in meeting and maintaining the NAAQS, many areas will still not come into attainment even with this magnitude of reductions.

In addition, the magnitude of emission reductions that can be achieved by a comprehensive national Tier 2/Gasoline Sulfur program will be difficult to achieve from any other source category. Given the large contribution that light-duty mobile source emissions make to the national emissions inventory and the range of control programs ozone-affected areas

already have in place or would be expected to implement, we believe it will be very difficult, if not impossible, to meet (and maintain) the ozone NAAQS in a cost-effective manner without large emission reductions from LDVs and LDTs. We expect emissions from MDPVs to also play an increasing role.

Furthermore, we project that the Tier 2/Gasoline Sulfur program will significantly reduce direct and secondary particulate matter coming from LDVs, LDTs, and MDPVs—by about 36,000 tons per year of direct PM alone by 2030; large secondary PM reductions from significantly lower NO

and SO

emissions will add to the overall positive impact on airborne particles. These reductions will be very cost-effective compared to other measures to reduce PM pollution. Because direct PM emissions from gasoline vehicles are related the presence of sulfur in gasoline, no new emission control devices, beyond what manufacturers are expected to install to meet the NO

and NMOG standards, will be necessary to provide the reductions expected for these pollutants under the program. The standards will provide valuable insurance against increases in PM emissions from LDVs, LDTs, and MDPVs.

Finally, the Tier 2/Gasoline Sulfur program will significantly reduce CO emissions from LDVs, LDTs, and MDPVs. (See Chapter III of the RIA for an analysis of these reductions.) The technical changes needed to meet the NMOG standards will also result in CO reductions sufficient to meet the CO standards. Thus, these CO reductions will be very cost-effective since they will not require any new emission control devices beyond what manufacturers are expected to install to meet the NO

and NMOG standards.

We conclude, then, that today's final rule is a major source of ozone precursor, PM, and CO emission reductions when compared to other available options. The discussions of cost and cost effectiveness later in this preamble and in the RIA explain the derivation of cost effectiveness estimates and compares them to the cost effectiveness of other alternatives. That discussion indicates that this program will have a cost effectiveness comparable to both the Tier 1 and NLEV standards and will also be cost effective when compared to non-mobile source programs.

III. Air Quality Need For and Impact Of Today's Action

In the absence of significant new controls on emission, tens of millions of Americans would continue to be exposed to unhealthy levels of air pollution. Emissions from passenger cars and light trucks are a significant contributor to a number of air pollution problems. Today's action will significantly reduce emissions from cars and light trucks and hence will significantly reduce the health risks posed by air pollution. This section summarizes the results of the analyses we performed to arrive at our determination that continuing air quality problems are likely to exist, that these air quality problems would be in part due to emissions from cars and light trucks, and that the new standards promulgated by today's final rule will improve air quality and mitigate other environmental problems.

A. Americans Face Serious Air Quality Problems That Require Further Emission Reductions

Air quality in the United States continues to improve. Nationally, the 1997 air quality levels were the best on record for all six criteria pollutants.

In fact, the 1990s have shown a steady trend of improvement, due to reductions in emissions from most sources of air pollution, from factories to motor vehicles. Despite great progress in air quality improvement, in 1997 there were still approximately 107 million people nationwide who lived in counties with monitored air quality levels above the primary national air quality standards.

There are also people living in counties outside of the air monitoring network where violations of the NAAQS could have also occurred during the year. Moreover, unless there are reductions in overall emissions beyond those that are scheduled to be achieved by already committed controls, many of these Americans will continue to be exposed to unhealthy air.

National Air Quality and Emissions Trend Report, 1997, Air Quality Trends Analysis Group, Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, N.C., December 1998 (available on the World Wide Web at http://www/epa.gov/oar/aqtrnd97/).

U.S. Environmental Protection Agency,

Latest Findings on National Air Quality: 1997 Status and Trends.

December 1998.

Ambient ozone is formed in the lower atmosphere through a complex interaction of VOC and NO

emissions. Cars and light trucks emit a substantial fraction of these emissions. Ambient PM is emitted directly from cars and light trucks; it also forms in the atmosphere from NO

, sulfur oxides (SO

), and VOC, all of which are emitted by motor vehicles. When ozone exceeds the air quality standards, otherwise healthy people often have reduced lung function and chest pain, and hospital admissions for people with respiratory ailments like asthma increase; for longer exposures, permanent lung damage can occur. Similarly, fine particles can penetrate deep into the lungs. Results of studies suggest a likely causal role of ambient PM in contributing to reported effects, such as: premature mortality, increased hospital admissions, increased respiratory symptoms, and changes in lung tissue. When either ozone or PM air quality problems are present, those hardest hit tend to be children, the elderly, and people who already have health problems.

The health effects of high ozone and PM levels are not the only reason for concern about continuing air pollution. Ozone and PM also harm plants and damage materials. PM reduces visibility and contributes to significant visibility impairment in our national parks and monuments and in many urban areas. In addition, air pollution from motor vehicles contributes to cancer and other health risks, acidification of lakes and streams, eutrophication of coastal and inland waters, and elevated drinking water nitrate levels. These problems impose a substantial burden on public health, our economy, and our ecosystems.

In recognition of this burden, Congress has passed and subsequently amended the Clean Air Act. The Clean Air Act requires each state to have an approved State Implementation Plan (SIP) that shows how an area plans to meet its air quality obligations, including achieving and then maintaining attainment of all of the National Ambient Air Quality Standards (NAAQS), such as those for ozone and PM. The Clean Air Act also requires EPA to periodically re-evaluate the NAAQS in light of new scientific information. Our most recent re-evaluation of the ozone and PM NAAQS led us to revise both standards (62 FR 38856, July 18, 1997 and 62 FR 38652, July 18, 1997). These revised standards reflected additional information that had become available since the previous revision of the ozone and PM standards, respectively.

On May 14, 1999, a panel of the United States Court of Appeals for the District of Columbia Circuit reviewed EPA's revisions to the ozone and PM NAAQS and found, by a 2-1 vote, that sections 108 and 109 of the Clean Air Act, as interpreted by EPA, represent unconstitutional delegations of Congressional power.

American Trucking Ass'n., Inc. et al.,

Environmental Protection Agency

, 175 F.3d 1027 (D.C. Cir. 1999). Among other things the Court remanded the record

for the 8-hour ozone NAAQS and the PM

2.5

NAAQS to EPA. On October 29, 1999, EPA's petition for rehearing by the three judge panel was denied, with the exception that the panel modified its prior ruling regarding EPA's authority to implement a revised ozone NAAQS under Part D subpart 2 of Title I. EPA's petition for rehearing en banc by the full Circuit was also denied, although five of the nine judges considering the petition agreed to rehear the case.

As a result of the Court's decision, requirements on the States to implement the new 8-hour ozone standard have been suspended although the standard itself is still in force and the science behind it has generally not been contradicted. The court also did not question EPA's findings regarding the health effects of PM

and PM

2.5

. However, due to the uncertainty regarding the status of the new NAAQS, we will rely on the preexisting NAAQS in determining air quality need under section 202(i) of the Act.

Carbon monoxide (CO) can cause serious health effects for those who suffer from cardiovascular disease, such as angina pectoris. There has been considerable progress in attaining the longstanding NAAQS for carbon monoxide, largely through more stringent standards for CO from motor vehicles. This progress has been made despite large increases in travel by vehicle. In 1997, there were about 9 million people living in three counties with CO concentrations above the level of the CO NAAQS. In the recent past, this figure has fluctuated up and down. At the present time there are 15 counties classified as serious CO nonattainment areas, all with a recent history of NAAQS violations. At this time, prospects for these areas attaining by the serious CO area attainment deadline of December 31, 2000 are uncertain. While violations of the NAAQS have not occurred recently in most of the other 33 counties still classified as nonattainment, even these must demonstrate that they will remain safely below the NAAQS for ten years despite expected growth in vehicle travel and other sources of CO emissions before they can be reclassified to attainment. Because of the large role of motor vehicles in causing high ambient CO concentrations, where there is reason to be concerned about CO attainment and maintenance, local areas look to national emission standards for most of the solution.

As discussed below, EPA has also finalized regulations that regions and states implement plans for protecting and improving visibility in the 156 mandatory Federal Class I areas as defined in Section 162(a) of the Clean Air Act. These areas are primarily national parks and wilderness areas.

To accomplish the goal of full attainment in all areas according to the schedules for the various NAAQS, and to achieve the goals of the visibility program, the federal government must assist the states by reducing emissions from sources that are not as practical to control at the state level as at the federal level. Vehicles and fuels move freely among the states, and they are produced by national or global scale industries. Most individual states are not in a position to regulate these industries effectively and efficiently. The Clean Air Act therefore gives EPA primary authority to regulate emissions from the various types of highway vehicles and their fuels. Our actions to reduce emissions from these and other national sources are a crucial and essential complement to actions by states to reduce emissions from more localized sources.

If we were not to adopt new standards to reduce emissions from cars and light trucks, emissions from these vehicles would remain a large portion of the emissions burden that causes elevated ozone and continued nonattainment with the ozone NAAQS, which in turn would affect tens of millions of Americans. Because the contribution of cars and light trucks to both local emissions and transported pollution would be so great, and the expected emission reduction shortfall in many areas is so large, further reductions from cars and light trucks will be an important element of many attainment strategies, especially for ozone in the 2007 to 2010 time frame. The contribution of these vehicles to PM exposure and PM nonattainment would also remain significant, and would increase considerably if diesel engines are used in more cars or light trucks. Furthermore, without new standards, steady annual increases in fleet size and miles of travel would outstrip the benefits of current emission controls, and would cause ozone-forming emissions from cars and trucks to grow each year starting about 2013.

The standards being promulgated by today's actions will reduce emissions of ozone precursors and PM precursors from cars and light trucks greatly. However, even with this decrease, many areas will likely still find it necessary to obtain additional reductions from other sources in order to fully attain the ozone and PM NAAQS. Their task will be easier and the economic impact on their industries and citizens will be lighter as a result of the standards promulgated by today's actions. Following implementation of the Regional Ozone Transport Rule, states will have already adopted emission reduction requirements for nearly all large sources of VOC and NO

for which cost-effective control technologies are known. Those that remain in nonattainment therefore will have to consider their remaining alternatives. Many of the state and local programs states may consider as alternatives are very costly, and the emissions impact from each additional emissions source subjected to new emissions controls would be considerably smaller than the emissions impact of the standards being promulgated today. Therefore, the emission reductions from these standards for gasoline, cars, and light trucks will ease the need for states to find first-time reductions from the mostly smaller sources that have not yet been controlled, including area sources that are closely connected with individual and small business activities. The emission reductions from the standards being promulgated today will also reduce the need for states to seek even deeper reductions from large and small sources already subject to emission controls.

We project that today's actions will also have important benefits for carbon monoxide, regional visibility, acid rain, and coastal water quality.

For these and other reasons discussed in this document, we have determined that significant emission reductions will still be needed by the middle of the next decade and beyond to achieve and maintain further improvements in air quality in many, geographically dispersed areas. We also believe that a significant portion of these emission reductions will be obtained by reducing emissions from cars and light trucks as a result of today's actions. We believe that such reductions are necessary (since cars and light trucks are such large contributors to current and projected ozone problems) and reasonable (since these reductions can be achieved at a reasonable cost compared to other alternative reductions).

The remainder of this section describes the health and environmental problems that today's actions will help mitigate and the expected health and environmental benefits of these actions. Ozone is discussed first, followed by PM, other criteria pollutants, visibility, air toxics, and other environmental impacts. The emission inventories and air quality analyses are explained more fully in the Regulatory Impact Analysis for today's actions.

B. Ozone

1. Background on Ozone Air Quality

Ground-level ozone is the main harmful ingredient in smog.

Ozone is produced by complex chemical reactions when its precursors, VOC and NO

, react in the presence of sunlight.

Total column ozone, a large percentage of which occurs in the stratosphere and a smaller percentage of which occurs in the troposphere, helps to provide a protective layer against ultraviolet radiation.

Short-term (1-3 hours) and prolonged (6-8 hours) exposures to ambient ozone at levels common in many cities have been linked to a number of health effects of concerns. For example, increased hospital admissions and emergency room visits for respiratory causes have been associated with ambient ozone exposures at such levels. Repeated exposures to ozone can make people more susceptible to respiratory infection, result in lung inflammation, and aggravate pre-existing respiratory diseases such as asthma. Other health effects attributed to ozone exposures include significant decreases in lung function and increased respiratory symptoms such as chest pain and cough. These effects generally occur while individuals are engaged in moderate or heavy exertion.

Children active outdoors during the summer when ozone levels are at their highest are most at risk of experiencing such effects. Other at-risk groups include adults who are active outdoors (

e.g.,

outdoor workers), and individuals with pre-existing respiratory disease such as asthma and chronic obstructive lung disease. In addition, longer-term exposures to moderate levels of ozone present the possibility of irreversible changes in the lungs which could lead to premature aging of the lungs and/or chronic respiratory illnesses.

Ozone also affects vegetation and ecosystems, leading to reductions in agricultural and commercial forest yields, reduced growth and survivability of tree seedlings, and increased plant susceptibility to disease, pests, and other environmental stresses (

e.g.,

harsh weather). In long-lived species, these effects may become evident only after several years or even decades, thus having the potential for long-term effects on forest ecosystems. Ground-level ozone damage to the foliage of trees and other plants also can decrease the aesthetic value of ornamental species as well as the natural beauty of our national parks and recreation areas.

Many areas which were classified as nonattainment when classifications were made under the 1990 Clean Air Act Amendments have not experienced violations more recently. However, 50 metropolitan areas had ozone design values above the NAAQS in either or both of the 1995-1997 and the 1996-1998 monitoring periods. In many urban areas, the downward trend in ozone that prevailed earlier has become less strong or stopped in the last few years, even when adjustments are made for meteorological conditions. We believe that one factor that has worked against ozone improvement in the last few years has been the growing use of light trucks with higher emissions than the cars used formerly. The predictions of future ozone concentrations used in developing today's action take account of this growing use of light trucks.

2. Additional Emission Reductions Are Needed To Attain and Maintain the Ozone NAAQS

a. Summary

We have determined that additional emission reductions are needed to attain and maintain the 1-hour ozone NAAQS. This overall conclusion is based on our prediction that 26 metropolitan areas are each certain or highly likely to need additional reductions, and that an additional 12 areas each have a moderate to significant probability of needing them.

To determine whether additional reductions are needed in order to attain and maintain the ozone NAAQS, we used ozone modeling to predict what areas would not attain the NAAQS in the future. We accounted for the emission reductions that have already been achieved, those that will be achieved in the future by actions already underway, and increases in emissions expected from increased use of sources of pollution.

In our May 13, 1999 proposal, we presented information from photochemical modeling we performed to predict what areas would meet the ozone NAAQS in 2007. The year 2007 falls after the expected date of most emission reductions which states are required to achieve or have otherwise committed to achieve, and near the attainment deadline for many ozone nonattainment areas. We presented additional information from the same photochemical modeling work in two supplemental notices, on June 30, 1999 (to better explain the basis for our proposal in light of the Court's ruling on the 8-hour ozone NAAQS), and October 25, 1999 (to explain the implications for our Tier 2/Gasoline Sulfur proposal from our more recent proposal, which we expect to make final shortly, to re-instate the 1-hour ozone NAAQS in many areas). In Response to Comments on these Federal Register notices, we made revisions to our own ozone modeling. We also obtained ozone modeling results from a number of state air planning agencies and from members of the automobile manufacturing industry. We have considered all of this information as part of our determination that the regulations promulgated in this rule are needed and appropriate.

Based on the available ozone modeling and other information, we project that there are 26 metropolitan areas which will be unable to attain and maintain the NAAQS, in the absence of additional reductions. These areas had a combined population of over 86 million in 1996, and are distributed across most regions of the U.S. We have concluded that each is certain or very likely to require additional reductions to attain the NAAQS. Taken together and considering their number, size, and geographic distribution, these areas establish the case that additional reductions are needed in order to attain and maintain the 1-hour standard.

In addition, our analysis suggests there will be other areas that will have problems attaining and maintaining compliance with the one-hour ozone standard in the future. There are 12 additional metropolitan areas with a total 1996 population of over 25 million people in this category. EPA's ozone modeling for 2007 predicts exceedances for each of these areas. However, for six of them local recent monitoring information is not indicating nonattainment. Given how close to nonattainment these areas are, EPA believes it is likely that at least a significant subset of this group of areas will face compliance problems by 2007 or beyond if additional actions to lower air emissions are not taken. This belief is based on historical experience with areas that will undergo economic and population growth over time and that are in larger regions that are also experiencing growth. The other six areas in this group are nonattainment now, and local modeling shows them reaching attainment by 2005 or 2007. Modeling uncertainties and growth beyond the attainment date make it likely that at least some of these areas will also face compliance problems if additional actions to lower air emissions are not taken. This situation further supports our determination that additional reductions in mobile source emissions are needed for attainment and maintenance.

We would like to emphasize that the advantages of the Tier 2/Gasoline Sulfur program will be enjoyed by the whole country. There are important advantages for approximately 30 more metropolitan

areas, with close to 30 million people residing in them, whose ozone levels are now within 10 percent of violating the 1-hour NAAQS.

Most of these areas have been in nonattainment in the past. We believe the emission reductions from the Tier 2/Gasoline Sulfur program are an important component of an overall EPA-state approach to enable these areas to continue to maintain clean air given expected growth. EPA believes that the long term ability of the states to continue to meet the NAAQS is extremely important. In the future, EPA will be considering additional approaches for assisting in maintenance of the NAAQS. Also, we believe that the Tier 2/Gasoline Sulfur program has important benefits for other nonattainment areas which our modeling and local modeling show to be on a path to come into attainment in the next eight years. For these areas, the extra emission reductions from the program will take some of the uncertainty out of their plan to attain the standard and give them a head start on developing their plan to stay in attainment.

As measured by ozone design value.

In every area of the country, the new standards will give transportation planning bodies and industrial development leaders more options within the area's overall emissions constraints. This will allow local and state officials to better accommodate local needs and growth opportunities. With these new standards for vehicles and gasoline, unusually adverse weather or strong local economic growth will be less likely to cause ozone levels high enough to trigger the planning requirements of the Clean Air Act. In addition, by reducing emissions and ozone levels across the nation as a whole, there will be less transport of ozone between areas, reducing the amount of ozone entering downwind areas. This will give the downwind areas a better opportunity to maintain and attain the NAAQS through local efforts.

All of our determinations presented here about the need for the Tier 2/Gasoline Sulfur program take into account the prior NO

reductions we expect from the Regional Ozone Transport Rule. This rule is now in litigation. If the outcome of that litigation reduces the NO

reductions that will be achieved, the need for the Tier 2/Gasoline Sulfur program will be even greater.

b. Ozone Modeling Presented in Our Proposal and Supplemental Notices

The ozone modeling we presented in our proposal and the two supplemental notices was originally conducted as part of our development of the Regional Ozone Transport Rule. The “revised budget” emission control scenario we modeled for the Regional Ozone Transport Rule contained the right set of existing and committed emission controls for it to serve as the starting point for making our determination on the need for additional emission reductions. We added a new “control case” to represent the effects of our proposed vehicle and gasoline standards.

This ozone modeling provided predictions of ozone concentrations in 2007 across the eastern U.S., under certain meteorological conditions. Predictions of attainment or nonattainment are based on these predicted ozone concentrations. Two approaches to making attainment predictions have been used or advocated in the past: a rollback approach and an exceedance approach. In the NPRM of May 13, 1999, we presented predictions of attainment and nonattainment using a rollback approach. For the 1-hour standard, we reported that 8 metropolitan areas and two rural counties were predicted to be in nonattainment in 2007 under the rollback method. In the first supplemental notice of June 30, 1999 we presented a prediction that 17 areas would be nonattainment based on the exceedance method, and invited comment on all aspects of the modeling and its interpretation. Our second and last notice on October 27, 1999, presented predictions of violations using the exceedance method for additional areas which we had previously excluded because the 1-hour standard did not apply to them. This was in anticipation of the reinstatement of the 1-hour standard to these areas, which we proposed on October 25, 1999 and expect to complete very soon. 64 FR 57524. We also announced that we were conducting another round of modeling, described below. See the Response to Comments document for more discussion of the rollback and exceedance approaches.

c. Updated and Additional Ozone Modeling

We have updated and expanded our ozone modeling. We updated the ozone modeling so that it is now based on estimates of vehicle emissions that reflect the most recent data and our best understanding of several aspects of emissions estimation.

We also changed most of the episodes for which we modeled ozone concentrations, with all of our final episode days coming from a single calendar year. By selecting days from within a single year, we responded to a comment that the original episode periods might together contain an atypically high number of days favorable to ozone formation for some parts of the country. The new episodes are also better at representing conditions that lead to high ozone in areas along the Gulf Coast, whose ozone-forming conditions were not well represented in the episodes used for the original modeling.

While the use of these emissions estimates was new to our baseline ozone modeling in the latest ozone modeling, they were not new to this rulemaking, having already been used in calculations of cost-effectiveness in the draft RIA. We therefore were able to consider public comments on these estimates prior to using them in the latest ozone modeling

While we considered these improvements necessary and appropriate in light of comments and other information available to us, the actual results of the two rounds of modeling with regard to the need for additional reductions have turned out to be similar. The latest round of modeling provided us ozone predictions for 2007 and 2030 in the eastern U.S., and for 2030 in the western U.S. There are some differences in specific results, where and when the two models can be directly compared. However, the same conclusion would be reached from either, namely that there is a broad set of areas with predicted ozone concentrations in 2007 above 0.124 ppm, in the baseline scenario without additional emission reductions.

We have compared and supplemented our own ozone modeling with other modeling studies, either submitted to us as comments to this rulemaking, as state implementation plan (SIP) revisions, or brought to our attention through our consultations with states on SIP revisions that are in development. The ozone modeling in the SIP revisions has the advantage of using emission inventories that are more specific to the area being modeled, and of using meteorological conditions selected specifically for each area. Also, the SIP revisions included other evidence and analysis, such as analysis of air quality and emissions trends, observation based models that make use of data on concentrations of ozone precursors, alternative rollback analyses, and information on the responsiveness of the air quality model. For some areas, we decided that the predictions of attainment or nonattainment from our

modeling were less reliable than conclusions that could be drawn from this additional evidence and analysis. For example, in some areas our episodes did not capture the meteorological conditions that have caused high ozone, while local modeling did so.

d. Results and Conclusions

As discussed in detail below, it is clear that the NO

and VOC reductions to be achieved through the Tier 2/Gasoline Sulfur program are needed to attain and maintain compliance with the 1 hour ozone NAAQS. Although the general pattern observed in our modeling indicates improvements in the near term, growth in overall emissions will lead to worsening of air quality over the long term.

Based on our ozone modeling, we have analyzed ozone predictions for 52 metropolitan areas for 1996, 2007, and 2030. In addition, we reviewed ozone attainment modeling and other evidence covering 15 of these areas, from SIP submittals or from modeling underway to support SIP revisions. This local modeling addressed only the current or requested attainment date in each area. We then made attainment and nonattainment predictions from this information.

The general pattern we observed with the baseline scenario, i.e., without new emission reductions, is a broad reduction between 1996 and 2007 in the geographic extent of ozone concentrations above the NAAQS, and in the frequency and severity of exceedances. This is consistent with the national emissions inventory trend between these two years. At the same time, we also found that peak ozone concentrations and the frequency of exceedances in 2030 were generally somewhat higher than in 2007 for most areas analyzed. This too is consistent with our analysis of emission inventory trends, which shows that the total NO

inventory from all sources will decline from 2007 to about 2015 and then begin to increase due to growth in the activity of emission sources. In 2030, our analysis predicts that NO

emissions from all sources will be about one percent higher than in 2007. While we did not model ozone concentrations for years between 2007 and 2030, we expect that they would track the national emissions trend by showing a period of improvement after 2007 and then deterioration, although individual areas will vary due to local source mix and growth rates.

EPA's modeling presumed that cars and light trucks will continue to meet the emission levels of the National Low Emissions Vehicle (NLEV) program after model year 2003, even though the program will end in model year 2003 or shortly thereafter. Had our modeling not included such levels in its inventory assumptions, trends for ozone concentrations would have shown earlier increases in ozone concentrations.

Within this general pattern of ozone attainment changes between 1996 and 2030, we have determined that 26 metropolitan areas are certain or highly likely to need additional reductions to attain and maintain the 1-hour ozone NAAQS. These 26 areas are those that have current violations of the 1-hour ozone NAAQS and are predicted by the best ozone modeling we have available to still be in violation without a new federal vehicle program in 2007.

Based on the general trends described above, without further emissions reductions many of these areas may also have violations continuously throughout the period from 2007 to 2030, while others may briefly attain and then return to nonattainment on or before 2030. These 26 metropolitan areas are listed in Table III.B-1, along with their 1996 population which totals over 86 million. The sizes of these areas and their geographical distribution strongly support an overall need for additional reductions in order to attain and maintain under section 202(i). Because ozone concentration patterns causing violations of the 1-hour NAAQS are well established to endanger public health or welfare, this determination also supports our actions today under the general authority of sections 202(a)(1), 202(a)(3), and 202(b).

The date of the predicted violation was 2007 for most areas, 2010 in the case of Los Angeles, CA, and 2030 in the case of Portland-Salem, OR.

As indicated above, in reaching this conclusion about these 26 areas, we examined local ozone modeling in SIP submittals. These local analyses are considered to be more extensive than our own modeling for estimating whether there would be NAAQS nonattainment without further emission reductions, when interpreted by a weight of evidence method which meets our guidance for such modeling. One of the areas which submitted a SIP revision was a special case. We have recently proposed to approve the 1-hour ozone attainment demonstration for the nonattainment area of Washington, D.C. (but not Baltimore). We have nevertheless included this area on the list of 26 that are certain or highly likely to require further reductions to attain and maintain, because its SIP attainment demonstration assumed emission reductions from vehicles meeting the National Low Emissions Vehicle (NLEV) standards.

However, by its own terms, the NLEV standards would not extend beyond the 2003 model year if we did not promulgate Tier 2 vehicle standards at least as stringent as the NLEV standards. See 40 CFR 86.1701-99(c). Thus, the emission reductions relied upon from 2004 and later model year NLEV vehicles are themselves “further reductions” for the purposes of CAA section 202(i).

The local modeling indicating attainment with these reductions is therefore strong evidence that further reductions are needed past 2003, beyond those provided by the Tier 1 program. Based on this, and on the fact that our own ozone modeling showed the Washington, DC area to violate the NAAQS in 2007 even with full NLEV emission reductions, we have concluded that it should be included with areas that do require further reductions to attain and maintain the 1-hour ozone NAAQS.

With regard to eventual final action on the 1-hour attainment demonstration for Washington, DC, the issue of the continuation of the NLEV standards is mooted by the promulgation of the Tier 2/Gasoline Sulfur program. A portion of the emission reductions from this program will replace the post-2003 model year NLEV reductions assumed in the SIP.

The 1-hour ozone NAAQS presently does not apply in 12 of the 26 areas listed in Table III.B-1, but we have proposed to re-instate it and expect to complete that action shortly. These areas are indicated in the table. Our decision to include these areas on this list is based on the contingency that we will re-instate the 1-hour standard in these areas. However, even if we considered only the 14 areas where the 1-hour standard applies as of the signature date of this notice, we have concluded that our determination would be the same.

Table III.B-1.—Twenty-Six Metropolitan Areas Which Are Certain or Highly Likely To Require Additional Emission Reductions in Order To Attain and Maintain the 1-Hour Ozone NAAQS

Metropolitan area

1996

Population

(millions)

Atlanta, GA MSA

3.5

Barnstable-Yarmouth, MA MSA

0.2

Baton Rouge, LA MSA

0.6

Beaumont-Port Arthur, TX MSA

0.4

Birmingham, AL MSA

0.9

Boston-Worcester-Lawrence, MA-NH-ME-CT CMSA

5.6

Charlotte-Gastonia-Rock Hill, NC-SC MSA

1.3

Cincinnati-Hamilton, OH-KY-IN CMSA

1.9

Dallas-Fort Worth, TX CMSA

4.6

Houma, LA MSA

0.2

Houston-Galveston-Brazoria, TX CMSA

4.3

Huntington-Ashland, WV-KY-OH MSA

0.3

Indianapolis, IN MSA

1.5

Los Angeles-Riverside-San Bernardino CA CMSA

15.5

Louisville, KY-IN MSA

1.0

Macon, GA MSA

0.3

Memphis, TN-AR-MS MSA

1.1

Nashville, TN MSA

1.1

New York-Northern New Jersey-Long Island, NY-NJ-CT-PA CMSA

19.9

Philadelphia-Wilmington-Atlantic City, PA-NJ-DE-MD CMSA

6.0

Pittsburgh, PA MSA

2.4

Portland-Salem, OR-WA CMSA

2.1

Providence-Fall River-Warwick, RI-MA MSA

1.1

Richmond-Petersburg, VA MSA

0.9

St. Louis, MO-IL MSA

2.5

Washington-Baltimore, DC-MD-VA-WV CMSA

7.2

Total Population

86.3

Notes:

The 1-hour ozone NAAQS does not currently apply, but we have proposed and expect to re-instate it shortly.

There are 12 additional metropolitan areas, with another 25.3 million people in 1996, for which the available ozone modeling suggests significant risk of failing to attain and maintain the 1-hour ozone NAAQS without additional emission reductions. Table III.B-2 lists the areas we put in this second category. Our own ozone modeling predicted these 12 areas to need further reductions to avoid violations in 2007. For six of these areas, recent air quality monitoring data indicate violation, but we have reviewed local ozone modeling and other evidence indicating attainment in 2007.

Based on this evidence, we have kept these areas separate from the previous set of 26 areas which we consider certain or highly likely to need additional reductions. However, we still consider there to be a significant risk of failure to attain and maintain in these six areas because this local modeling has inherent uncertainties, as all ozone modeling does. Moreover, the local modeling did not examine the period after initial attainment.

The SIP revisions for Chicago and Milwaukee demonstrated that these two areas as well as Benton Harbor and Grand Rapids areas in Michigan (which are maintenance areas but have experienced ozone NAAQS violations recently) would not experience NAAQS violations in 2007, with a strategy that relied only on Tier 1 vehicle emission standards. We have also recently proposed to approve the 1-hour attainment demonstration for Greater Connecticut, covering the Hartford and New London areas, which assumed full NLEV emission reductions. However, Connecticut is committed in its SIP to adopt California vehicle standards if NLEV does end with the 2003 model year if a more stringent federal program is not promulgated. The California standards are more stringent than NLEV. The case of one additional area whose attainment demonstration we recently proposed to approve, Western Massachusetts (Springfield), should be explained here to avoid possible confusion. Our own ozone modeling predicted that Springfield would attain the NAAQS in 2007. Massachusetts has adopted the California vehicle emission standards, so there is no issue of the continuation of the NLEV standards.

For the other six of the 12 areas, the air quality monitoring data shows current attainment but with less than a 10 percent margin below the NAAQS. This suggests these areas may remain without violations for some time, but we believe there is still a moderate risk of future violation of the NAAQS because meteorological conditions may be more severe in the future.

It is highly likely that at least some of these 12 areas will violate the NAAQS without additional reductions, and it is a distinct possibility that many of them will do so. We consider the situation in these areas to support our determination that, overall, additional reductions are needed for attainment and maintenance. However, we reiterate that our predictions for the 26 areas listed in Table III.B-1, and even our predictions for only the 14 of those 26 for which the 1-hour standard now applies, are a sufficient basis for our determination of an overall need for additional reductions and for our actions today.

Table III.B-2.—Twelve Metropolitan Areas With Moderate to Significant Risk of Failing To Attain and Maintain the 1-Hour Ozone NAAQS Without Additional Emission Reductions

Metropolitan area

1996

Population

(millions)

Benton Harbor, MI MSA

0.2

Biloxi-Gulfport-Pascagoula, MS MSA

0.3

Chicago-Gary-Kenosha, IL-IN-WI CMSA

8.6

Cleveland-Akron, OH CMSA

2.9

Detroit-Ann Arbor-Flint, MI CMSA

5.3

Grand Rapids-Muskegon-Holland, MI MSA

1.0

Hartford, CT MSA

1.1

Milwaukee-Racine, WI CMSA

1.6

New London-Norwich, CT-RI MSA

1.3

New Orleans, LA MSA

0.3

Pensacola, FL MSA

0.4

Tampa, FL MSA

2.2

Total Population

25.3

Notes:

The 1-hour ozone NAAQS does not currently apply, but we have proposed and expect to re-instate it shortly.

e. Issues and Comments Addressed

We received detailed comments from the automobile industry related to ozone modeling and the need for additional emission reductions in order to attain and maintain. These were of three types.

Accuracy of modeling ozone concentrations.—

The automobile industry commenters pointed out that in the modeling presented with our proposal, the ozone model and exceedance predicted violations of the NAAQS in 1995 in areas where monitoring data indicated no violations. They cited these cases as examples of model inaccuracy. We have made improvements to our emissions estimates, our episodes, and other aspects of the modeling system. These changes have improved the accuracy of the predicted ozone concentrations. Also, as stated above, our list of 26 areas that support our finding that additional reductions are needed does not include any areas where recent monitoring data shows no violations. The final RIA addresses issues of model accuracy in more depth.

As explained in the final RIA, our very latest estimates of car and light truck emissions without the benefits of our new standards are actually somewhat higher than the estimates used in the final round of ozone modeling, because the most recent data indicate even more serious adverse emissions effects from sulfur in

gasoline. Thus, we think our predictions of ozone nonattainment using emission estimates prepared before this most recent data on sulfur was considered, may be conservative. This topic is discussed in more detail in section III.B.3.

Prediction of attainment/nonattainment.

—For most areas, we predicted 2007 or 2030 attainment or nonattainment based on the exceedance method. The exceedance method predicts an area to be in attainment only if there are no predicted exceedances of the NAAQS during any episode day. However, for the areas for which we have received 1-hour attainment demonstrations in SIP revisions, our predictions were based on a larger and more robust set of data. When a state's modeling shows an exceedance that would otherwise indicate nonattainment, we allow the state to submit a variety of other evidence and analysis, such as locality specific meteorological conditions, analysis of air quality and emissions trends, observational based models that make use of data on concentrations of ozone precursors, a rollback analysis, and information on the responsiveness of the air quality model. We then make a weight-of-evidence determination of attainment or nonattainment based on consideration of all this local evidence. We did this in forming the set of 26 areas we consider certain or highly likely to need additional reductions to attain or maintain, in some cases concluding that attainment was demonstrated and in others that it was not.

The auto industry commenters recommended the use of rollback as the single method for making attainment and nonattainment predictions from predicted ozone concentrations. They stated that the rollback method would be more consistent than the exceedance method with the NAAQS's allowance of three exceedances in a three year period. They also believed that the rollback method would compensate for what they considered to be model over predictions of ozone concentrations. We believe that the rollback method is not appropriate for use as the sole, or even a primary, test of 1-hour ozone attainment or nonattainment. A rollback analysis may overlook violations that occur away from ozone monitors, and it may inappropriately project the effect of a recent period of favorable weather into the prediction of future attainment. In determining the attainment and maintenance prospects of numerous areas, as here, it is not possible to assemble and consider the full set of local evidence that should accompany any consideration of a rollback analysis. In such a situation, we believe that the exceedance method is the appropriate choice. A fuller explanation of our reasons for considering the exceedance method more appropriate than rollback is given in our Response to Comments document.

We have not completely excluded the rollback approach from the determinations in this rulemaking. We have considered it for those areas for which we had enough information to allow us to consider it in its proper context, i.e., for those areas covered by recent 1-hour SIP submissions. Of these areas, we concluded that some will not attain without additional reductions and some will.

While we disagree with the use of the rollback method, we have conducted a hypothetical analysis of 2007 attainment in all areas based only on our own ozone modeling, applying the rollback method recommended by the commenters. We calculated in this analysis that 15 metropolitan areas and three other counties with nearly 56 million in population in 1996 would violate the NAAQS in 2007. Moreover, these 15 metro areas are geographically spread out

. We believe that this result using the rollback method does not fully capture the likely nonattainment that would exist in 2007 in the absence of additional emission reductions. However, even if we were to consider the use of rollback valid, we consider this set of areas to also be an adequate basis for making the same determinations we have made based on the more appropriate exceedance-based analysis. The details of our hypothetical analysis using the rollback method are given in the final RIA and the technical support document for our ozone modeling analyses.

We did not include the Los Angeles-Riverside-San Bernardino area in this analysis, since it was not covered by our 2007 modeling, but we do believe it is rightly part of the basis for a determination on the need for additional reductions.

Ozone modeling and predictions.

—Members of the automobile manufacturing industry submitted two modeling studies: (1) a repetition of our first round of modeling of the 37-state eastern U.S. domain but with their recommendations regarding estimates of motor vehicle emissions in 2007 and with the rollback method used to predict 2007 nonattainment, and (2) finer grid modeling for three smaller domains, also with their recommended estimates of emissions and with nonattainment predicted using a rollback method. Both modeling efforts showed less widespread nonattainment than we have determined and described here. Taken together, these studies predicted 2007 violations by the rollback method in or downwind of New York City, Chicago, Milwaukee, western Michigan, Baton-Rouge, and Houston.

The main difference between the automobile industry's ozone modeling and ours is in the emission estimates. We have reviewed the emissions estimates used in the industry studies. We concluded that the industry's emissions estimates employ inappropriate analytical steps in the calculation. Among the problems are that the adjustments for the benefits of inspection and maintenance programs were not consistent with the base estimate of in-use emissions, and the sales trend towards light trucks and SUVs was not properly captured. Also, as stated, we disagree with the use of the rollback approach as the sole test of attainment. As a consequence, we conclude that the industry's ozone modeling is not an appropriate basis for making predictions of future attainment or nonattainment. The final RIA explains in detail how we have addressed these and other emissions modeling issues in a manner which is more technically consistent and correct,

and how we have considered the results from rollback analyses but only as part of broad weight-of-evidence determinations for areas for which this was possible at this time. Our point-by-point review is given in our Response to Comments document.

As explained in the final RIA, our very lastest estimates of car and light truck emissions without the benefits of our new standards are actually somewhat higher than the estimates used in the final round of ozone modeling, because more recent data indicate even more serious adverse emissions effects from sulfur in gasoline. Thus, we think our predictions of ozone nonattainment may be conservative.

The material on ozone modeling submitted by the commenters, having been prepared by the rollback method, was difficult to re-interpret according to our preferred exceedance method. However, it appears that if this modeling were interpreted by the exceedance method, it would indicate 2007 nonattainment in Baltimore and Washington, D.C. in addition to New York City, Chicago, Milwaukee, western Michigan, Baton-Rouge, and Houston. Overall, we conclude that the material submitted by the automobile industry does not contradict the facts we have used to make our determinations or the actions we are taking today.

f. 8-Hour Ozone

The predictions of ozone concentrations from the ozone modeling

can be used to make predictions of attainment or nonattainment with the 8-hour ozone NAAQS. In our draft RIA, we estimated that 28 metropolitan areas and 4 rural counties with a combined population of 80 million people would violate the 8-hour ozone NAAQS in 2007 without additional emission reductions. Commenters noted differences between exact rollback procedure we had used in this projection and the steps specified in recent draft guidance we have issued on 8-hour ozone modeling. We agree with the commenters that the steps specified in our guidance are the correct ones to use. However, since we are not basing our promulgation of the Tier 2/Gasoline Sulfur Program on the 8-hour ozone NAAQS, we have not made any new predictions of 8-hour ozone nonattainment areas in 2007. Based on our findings in previous analyses of this sort, however, we believe that in the absence of the Tier 2/Gasoline Sulfur program there would be 8-hour nonattainment areas that are not also areas which we have concluded are certain or highly likely to violate the 1-hour NAAQS. If we considered it appropriate to proceed with implementation of the 8-hour standard, these areas would support our determination on the need for emission reductions, and the appropriateness and necessity of the vehicle and gasoline standards we are establishing.

3. Cars and Light-duty Trucks Are a Big Part of the NO

and VOC Emissions, and Today's Action Will Reduce This Contribution Substantially

Emissions of VOCs and NO

come from a variety of sources, both natural and man-made. Natural sources, including emissions that have been traced to vegetation, account for a substantial portion of total VOC emissions in rural areas. The remainder of this section focuses on the contribution of motor vehicles to emissions from human sources. Man-made VOCs are released as byproducts of incomplete combustion as well as evaporation of solvents and fuels. For gasoline-fueled cars and light trucks, approximately half of the VOC emissions come from the vehicle exhaust and half come from the evaporation of gasoline from the fuel system. NO

emissions are dominated by man-made sources, most notably high-temperature combustion processes such as those occurring in automobiles and power plants. Emissions from cars and light trucks are currently, and will remain, a major part of nationwide VOC and NO

emissions. In 1996, cars and light trucks comprised 25 percent of the VOC emissions and 21 percent of the NO

emissions from human sources in the U.S.

The contribution in metropolitan areas was generally larger.

Emission Trend Report, 1997.

We have made significant improvements in the analysis used to estimate the emission inventory impacts of this action, including improving the emission factor modeling, using more detailed local modeling input, and using a more conservative (lower) estimate of VMT growth. These changes are detailed in the Regulatory Impact Analysis for this rule. The following discussion is based on this improved analysis.

In addition to the improvements which are incorporated in this analysis, we also made further improvements in the emission factor modeling after analyzing comments which we did not have time to incorporate into the detailed inventory analysis described here. The most notable change is related to data which indicates that NO

and NMOG emissions are even more sensitive to gasoline sulfur than previously thought. This change and others are described in detail in the Response to Comments. Our early analysis of these changes indicates that incorporating them into this analysis would provide further support for this action because these changes result in both increases in the baseline emissions without Tier 2 and in the reductions that would result from Tier 2. For example, in the detailed inventory analysis we report below, we project nationwide Tier 2/Gasoline Sulfur control NO

reductions from cars and light trucks of 856,471 tons per year in 2007. Using the version of the emission factor model that incorporates these additional changes increases the estimated Tier 2 reductions to approximately 1.0 million tons per year in 2007 (estimated baseline emissions without Tier 2 increase from 3.1 million tons per year in 2007 to approximately 3.7 million tons per year using the version of the emission factor model that incorporates these additional changes). Therefore, the estimates of the inventory reductions given here (and used as the basis for the ozone air quality analysis) are clearly conservative.

Motor vehicle emission controls have led to significant improvements in emissions released to the air (the “emission inventory”) and will continue to do so in the near term

. In the current analysis, we continue to find that total emissions from the car and light truck fleet would continue to decline for a period, even if we were not establishing the Tier 2/Gasoline Sulfur program. This decline would result from the introduction of cleaner reformulated gasoline in 2000, the introduction of National Low Emission Vehicles (NLEVs) and vehicles complying with the Enhanced Evaporative Test Procedure and Supplemental Federal Test Procedures, and the continuing removal of older, higher-emitting vehicles from the in-use vehicle fleet. On a per mile basis, VOC and NO

emissions from cars and light trucks combined would have continued to decline well beyond 2015, reflecting the continuing effect of fleet turnover under existing emission control programs. However, projected increases in vehicle miles traveled (VMT) will cause total emissions from these vehicles to increase. With this increase in travel and without additional controls, we project that combined NO

and VOC emissions for cars and light trucks without the Tier 2/Gasoline Sulfur program would increase starting in 2013 and 2016, respectively, so that by 2030 they would return to levels above or nearly the same as they will be in 2000. In cities experiencing rapid growth, such as Charlotte, North Carolina, the near-term trend towards lower emissions tends to reverse sooner.

With additional improvements in the modeling done in Response to Comments, we now estimate that without the Tier 2/Gasoline Sulfur program, there will be a constant increase in these emission over time.

The auto manufacturer and northeastern state commitments to the NLEV program are scheduled to end in 2004 without further EPA action on Tier 2 standards, although continued voluntary compliance by automobile manufacturers and the affected states is a possibility. Our analysis of emission trends and the emission benefits expected from today's action assumes for the base scenario a continuation of the NLEV program past 2004. If the NLEV program does not continue beyond 2004, the reductions resulting from Tier 2 would be larger than what is shown here. It also includes all other control measures assumed to be implemented in local areas, such as reformulated gasoline in all required and opt-in areas and enhanced I/M where required.

Also, if the NLEV program ends in model year 2004 or shortly thereafter, as scheduled, this trend would reverse more quickly in all areas.

Figure III-1 illustrates this expected trend in car and light truck NO

emissions in the absence of today's action. The figure also allows the contribution of cars to be distinguished from that of light trucks. The figure clearly shows the impact of steady growth in light truck sales and travel on overall light-duty NO

emissions; the decrease in overall light-duty emission levels is due solely to reductions in LDV emissions. In 2000, we project that

trucks will produce about 50 percent of combined car and light truck NO

emissions. We project that truck emissions would actually increase after 2000, and over the next 30 years, trucks would grow to dominate light-duty NO

emissions. By 2010, we project trucks would make up two-thirds of light-duty NO

emissions; by 2020, nearly three-quarters of all light-duty NO

emissions would be produced by trucks.

BILLING CODE 6560-50-P

ER10FE00.000

BILLING CODE 6560-50-C

Today's action will significantly decrease NO

and VOC emissions from cars and light trucks, and will delay the date by which NO

and VOC emissions will begin to increase due to continued VMT growth. With Tier 2/Gasoline Sulfur control, light-duty vehicle NO

and VOC emissions are projected to continue their downward trend past 2020. Table III.B-3 shows the annual tons of NO

that we project will be reduced by today's action.

These projections include the benefits of low sulfur fuel and the introduction of Tier 2 car and light truck standards.

Today's action for both vehicles and fuels will apply in 49 states and the U.S. territories, excluding only California. There will also be emissions reductions in California from vehicles that relocate or visit from other states. However, much of the emissions inventory analysis for this action was made for a 47-state region which excludes California, Alasks, and Hawaii. The latter two states were not included in the scope of ozone, PM and economic benefits modeling.

Table III.B-3.—

Emissions From Cars and Light Trucks as Percent of Total Emissions, and Reductions Due to Tier 2/Gasoline Sulfur Control (tons per year)

Year

Light-duty tons— without tier 2

Light-duty percent of total without tier 2

Light-duty tons reduced by tier 2

b, c

2007

3,095,698

856,471

2010

2,962,093

1,235,882

2015

2,968,707

1,816,767

2020

3,160,155

2,220,210

2030

3,704,747

2,795,551

Notes:

Estimates exclude California, Alaska, and Hawaii, although reductions will occur in all three.

Does not include emission reductions from heavy-duty gasoline vehicles.

These numbers represent a conservative estimate of the benefits of the Tier 2/Sulfur program. Based on the updated emission factor model developed in response to comments, the program will result in significantly larger benefits. For example, our new model projects NO

reductions of 1,100,000 tons in 2007.

The lower sulfur levels in today's action will produce large emission reductions on pre-Tier 2 vehicles as soon as low-sulfur gasoline is introduced, in addition to enabling Tier 2 vehicles to achieve lower emission levels. Among the pre-Tier 2 vehicles, the largest per vehicle emission reductions from lower sulfur in gasoline will be achieved from vehicles which automobile manufacturers will have sold under the voluntary National Low Emission Vehicle program. These vehicles are capable of substantially lower emissions when operated on low sulfur fuel. Older technology vehicles experience a smaller but significant effect.

In 2007, when all gasoline will meet the new sulfur limit and when large numbers of 2004 and newer vehicles meeting these standards will be in use, the combined NO

emission reduction from vehicles and fuels will be over 850,000 tons per year. After 2007, emissions will be reduced further as the fleet turns over to Tier 2 vehicles operating on low sulfur fuel. By 2020, NO

emissions will be reduced by 70% from the levels that would occur without today's action. This reduction equals the NO

emissions from over 164 million pre-Tier 2 cars and light trucks. This reduction represents a 12 percent reduction in NO

emissions from all manmade sources.

VOC emissions will also be reduced by today's action, with reductions increasing as the fleet turns over. We estimate that the reductions as a percent of emissions from cars and light trucks will be 7 percent in 2007 and grow to 17 percent in 2020.

As discussed earlier, in California, smaller but still substantial reductions in both NO

and VOC will be achieved because vehicles visiting and relocating to California will be designed to meet these standards. Also, vehicles from California visiting other states will not be exposed to high sulfur fuel. California Air Resources Board staff have estimated that Tier 2/Sulfur will reduce NO

emissions in the South Coast Air Quality Management District by approximately 4 tons per day in 2007.

CARB staff plan to incorporate these reductions in their revised attainment plan for this district, which includes most of the Los Angeles-Long Beach region.

California Air Resources Board, Executive Order G-99-037, May 20, 1999, Attachment A, 6-7, 10. These NO

reductions represent a small fraction of the emission reductions needed in the South Coast to attain the NAAQS.

These estimates of emission reductions reflect a mixture of urban, suburban, and rural areas. However, cars and light trucks generally make up a larger fraction of the emission inventory for urban and suburban areas, where human population and personal vehicle travel is more concentrated than emissions from other sources such as heavy-duty highway vehicles, power plants, and industrial boilers. We have estimated emission inventories for three cities using the same methods as were used to project the nationwide inventories, and we present the results for 2007 below in Table III.B-4.

These results confirm that light-duty vehicles make up a greater share of the NO

emission inventories in urban areas than they do in the nationwide inventory. While these vehicles' share of national NO

emissions in 2007 is about 16 percent, it is estimated to be about 34 percent in the Atlanta area. There is also a range in VOC contributions, with Atlanta again being the area with the largest car and light truck contribution at 17 percent. In metropolitan areas with high car and light truck contributions, today's action will represent a larger step towards attainment since it will have a larger effect on total emissions.

Table III.B-4—

Proportion of the Total Urban Area NO

and VOC Inventory in 2007 Attributable to Light-Duty Vehicles

Region

(percent)

VOC

(percent)

Nationwide

New York urban area

Atlanta urban area

Charlotte urban area

Notes:

The estimates reflect continuation of NLEV beyond 2004.

Another useful perspective from which to view the magnitude of the emission reductions from today's proposal is in terms of the additional emission reductions from all human sources that areas will need to attain the 1-hour ozone standard. For this analysis, we reviewed our proposals for action on the 1-hour attainment demonstrations submitted by the states. With these proposals, EPA identified estimates of additional emission reductions (measures in addition to those submitted by the state in their plans) necessary for attainment for some

of the areas. These estimates of additional emission reductions are documented in the individual

Federal Register

Notices. Using these estimates and the estimates of Tier 2 reductions developed for today's action, we have determined what portion of these additional emission reductions would be accounted for by today's action. These estimates are reported in Table III.B-5, which shows the contribution of Tier 2/Sulfur NO

reductions to the additional emission reduction necessary for attainment for three metropolitan areas. For example, for the New York nonattainment area, 89% of the additional NO

emission reductions needed for attainment are provided for with today's action. This leaves 11% of the additional NO

emission reductions to be addressed by the State through other local sources.

EPA and the States already have significant efforts underway to lower ozone precursor emissions through national regulations and State Implementation Plans. Table III.B-5 shows the contribution of Tier 2 to the substantial State-led efforts to provide attainment with the ozone NAAQS. Since the Tier 2 program has evolved in the past year after much of the States' efforts were completed, many of the States were unable to estimate the benefits of Tier 2 in their areas. EPA's proposal actions on these SIPs for the ozone NAAQS addresses the need for Tier 2 in many areas. More specifically, Tier 2 is being used to help States identify additional measures, in addition to those in their plans, necessary for attainment.

These estimates are subject to change as the states review and comment on our proposed action on the SIPs. These figures show that today's proposal would make a very substantial contribution to these cities' attainment programs, but that there will still be a need for additional reductions from other sources. The emission reductions from today's proposal would clearly not exceed the reductions needed from an air quality perspective for these areas.

Table III.B-5.—Contribution of Tier 2/Sulfur NO

Reductions to Ozone Attainment Efforts of Selected Nonattainment Areas

Nonattainment area (attainment date)

Percent of additional NO

reductions necessary for attainment

From tier 2

Needed after tier 2

Baltimore (2005)

100

New York (2007)

Philadelphia (2005)

4. Ozone Reductions Expected From This Rule

The large reductions in emissions of ozone precursors from today's standards will be very beneficial to federal and state efforts to lower ozone levels and bring about attainment with the current one-hour ozone standard. The air quality modeling for the final rule shows that improvements in ozone levels are expected to occur throughout the country because of the Tier 2/Gasoline Sulfur program.

EPA found that the program significantly lowers model-predicted exceedances of the ozone standard. In 2007 the number of exceedances in CMSA/MSAs is forecasted to decline by nearly one-tenth and in 2030, when full turnover of the vehicle fleet has occurred, the program lowers such exceedances by almost one-third. In these same areas, the total amount of ozone above the NAAQS is forecasted to decline by about 15 percent in 2007 and by more than one-third in 2030. In the vast majority of areas, the air quality modeling predicts that the program will lower peak summer ozone concentrations for both 2007 and 2030. The reduction in daily maximum ozone is nearly 2 ppb on average in 2007 and over 5 ppb on average in 2030. These reductions contribute to EPA's assessment that the program will provide the large set of public health and environmental benefits summarized in Section IV.D of the Preamble. The forecasted impacts of the program on ozone in 2007 and 2030 are further described in the Tier 2 Air Quality Modeling Technical Support Document.

EPA assessment of air quality changes for 2007 and 2030 focused on 37 states in the East because these states cover most of the areas with 1-hour nonattainment problems.

During the public comment period on the proposed rule, EPA received several comments that expressed concern about potential increases in ozone that might occur as a result of this rule. As indicated above, the air quality modeling results indicate an overall reduction in ozone levels in 2007 and 2030 during the various episodes modeled. In addition to ozone reductions, a few areas had predicted ozone increases in portions of the area during parts of the episodes modeled. In most of these cases, we observed a net reduction in ozone levels in these areas due to the program. In the very small number of exceptions to this, the Agency did find benefit from reduction of peak ozone levels. Based upon a careful examination of this issue, including EPA's modeling results as well as consideration of the modeling and analyses submitted by commenters, it is clear that the significant ozone reductions from this rule outweigh the limited ozone increases that may occur. Additional details on this issue are provided in the Response to Comments document and in the Tier 2 Air Quality Modeling Technical Support Document.

Taken together, EPA believes these results indicate that it will be much easier for States to develop State Implementation Plans which will attain and maintain compliance with the one-hour ozone standard. EPA will work with States conducting more detailed local modeling of their specific ozone situation, to ensure that their SIPs will provide attainment. Notably, there are also other upcoming federal measures to lower ozone precursors that will aid these efforts. If the State modeling of local programs shows a need, the Agency will work with states to plan further actions to produce attainment with the NAAQS in order to protect the public's health and the environment. Further details on EPA's modeling results can be found in the Agency's Response to Comments and technical support documents.

C. Particulate Matter

The need to control the contribution of cars and light trucks to ambient concentrations of particulate matter (PM) is the basis for our adoption of the new PM emission standards for vehicles. PM is also a supplemental consideration in our promulgation of

the vehicle emission standards for NO

and VOC, and for the limits on sulfur in gasoline, because SOx, NO

, and VOC are PM precursors.

For cars and for light trucks under 3750 pounds loaded vehicle weight, we are establishing new emission standards under the provisions of CAA section 202(i), which ties our action to the need for additional emission reductions in order to attain and maintain the NAAQS. The NAAQS relevant to the PM emission standards is the PM

NAAQS. The PM

NAAQS also provides additional but not essential support to our promulgation of the NO

and VOC standards, since these standards are fully supportable on the basis of the 1-hour ozone NAAQS.

For the vehicles not subject to CAA 202(i), and for the gasoline sulfur limits, our actions are tied to determinations regarding public health and welfare risks more broadly, under CAA sections 202(a), 202(b), and 211(c). The role of NO

, VOC, and PM emissions in contributing to atmospheric concentrations of PM

is an important element of the risk that these emissions pose to public health and welfare.

PM also poses risks to public health not fully reflected in the PM

NAAQS. Though EPA has not relied on the adverse health impacts of fine PM to promulgate this rule, it is well established that such impacts exist. A summary of these effects is given in the next section. In addition, based on the available science, EPA's Office of Research and Development has recently submitted to a committee of our Science Advisory Board a draft assessment document which contains a proposed conclusion that diesel exhaust is a likely human cancer hazard and is a potential cause of other nonmalignant respiratory effects. The scientific advisory committee has met to discuss this document, and we are awaiting written review comments from the committee. We expect to submit a further revision of the document to the advisory committee before we make the document final.

1. Background on PM

Particulate matter (PM) represents a broad class of chemically and physically diverse substances that exist as discrete particles (liquid droplets or solids) over a wide range of sizes. The NAAQS that regulates PM addresses only PM with a diameter less than or equal to 10 microns, or PM

. The coarse fraction of PM

consists of those particles which have a diameter in the range between 2.5 and 10 microns, and the fine fraction consists of those particles which have a diameter less than or equal to 2.5 microns, or PM

2.5

. These particles and droplets are produced as a direct result of human activity and natural processes, and they are also formed as secondary particles from the atmospheric transformation of emissions of SO

, NO

, ammonia, and VOCs.

Natural sources of particles in the coarse fraction of PM

include windblown dust, salt from dried sea spray, fires, biogenic emanation (

e.g.,

pollen from plants, fungal spores), and volcanoes. Fugitive dust and crustal material (geogenic materials) comprise approximately 80% of the coarse fraction of the PM

inventory as estimated by methods in use today.

Manmade sources of these coarser particles arise predominantly from combustion of fossil fuel by large and small industrial sources (including power generating plants, manufacturing plants, quarries, and kilns), wind erosion from crop land, roads, and construction, dust from industrial and agricultural grinding and handling operations, metals processing, and burning of firewood and solid waste. Coarse-fraction PM

remains suspended in the atmosphere a relatively short period of time.

U.S. EPA (1998) National Air Pollutant Emission Trends Update, 1970-1997. EPA-454/E-98-007. There is evidence from ambient studies that emissions of these materials may be overestimated and/or that once emitted they have less of an influence on monitored PM concentrations (of both PM

and PM

2.5

) than this inventory share would suggest.

Most of the emission sources listed for coarse particles also have a substantial fine particle fraction. Their share of the PM

2.5

inventory is somewhat smaller, however, because of the role of other sources that give rise primarily to PM

2.5

. The other sources of PM

2.5

include carbon-based particles emitted directly from gasoline and diesel internal combustion engines, sulfate-based particles formed from SO

and ammonia, nitrate-based particles formed from NO

and ammonia, and carbonaceous particles formed through transformation of VOC emissions. PM

2.5

particles from fugitive dust and crustal sources comprise substantially less than their share of coarse PM emissions, approximately one-half of the directly emitted PM

2.5

inventory as estimated by methods in use today. The presence and magnitude of crustal PM

2.5

in the ambient air is much lower even than suggested by this smaller inventory share, due to the additional presence of secondary PM from non-crustal sources and the removal of a large portion of crustal emissions close to their source. This near-source removal results from crustal PM's lack of inherent thermal buoyancy, low release height, and interaction with surrounding vegetation (which acts to filter out some of these particles).

Secondary PM is dominated by sulfate particles in the eastern U.S. and parts of the western U.S., with nitrate particles and carbonaceous particles dominant in some western areas. Mobile sources can reasonably be estimated to contribute to ambient secondary nitrate and sulfate PM in proportion to their contribution to total NO

and SO

emissions.

The sources, ambient concentration, and chemical and physical properties of PM

vary greatly with time, region, meteorology, and source category. A first step in developing a plan to attain the PM

NAAQS is to disaggregate ambient PM

into the basic categories of sulfate, nitrate, carbonaceous, and crustal PM, and then determine the major contributors to each category based on knowledge of local and upwind emission sources. Following this approach, SIP strategies to reduce ambient PM concentrations have generally focused on controlling fugitive dust from natural soil and soil disturbed by human activity, paving dirt roads and controlling soil on paved roads, reducing emissions from residential wood combustion, and controlling major stationary sources of PM

where applicable. The control programs to reduce stationary, area, and mobile source emissions of sulfur dioxide, oxides of nitrogen, and volatile organic compounds in order to achieve attainment with the sulfur dioxide and ozone NAAQS also have contributed to reductions in the fine fraction of PM

concentrations. In addition, the EPA standards for PM emissions from highway and nonroad engines are contributing to reducing PM

concentrations. As a result of all these efforts, in the last ten years, there has been a downward trend in PM

concentrations, with a leveling off in the later years.

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 in contributing to a series of health effects. The key health effects categories associated with 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), changes in lung function and increased respiratory symptoms, changes to lung tissues and structure, and altered respiratory defense

mechanisms. PM also causes damage to materials and soiling. It is a major cause of substantial visibility impairment in many parts of the U.S.

Motor vehicle particle emissions and the particles formed by the transformation of motor vehicle gaseous emissions tend to be in the fine particle range. Fine particles are a special health concern because they easily reach the deepest recesses of the lungs. Scientific studies have linked fine particles (alone or in combination with other air pollutants), with a series of significant health problems, including premature death; respiratory related hospital admissions and emergency room visits; 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.

These effects are discussed further in EPA's “Staff Paper” and “Air Quality Criteria Document” for particulate matter.

U.S. EPA, 1996, Air Quality Criteria for Particulate Matter, EPA/600/P-95/001aF. Review of the National Ambient Air Quality Standards for Particulate Matter: Policy Assessment of Scientific and Technical Information, OAQPS Staff Paper, EPA-452 R-96-013, July 1996.

EPA first established primary (health-based) and secondary (welfare-based) National Ambient Air Quality Standards for PM

in 1987. The annual and 24-hour primary PM

standards were set at 50 μg/m

, and 150 μg/m

, respectively.

In July 1997, the primary standards were revised to add two new PM

2.5

standards. At the same time, we changed the statistical form of the primary PM

standard and set all the secondary standards to be the same as the primary.

The annual average PM10 NAAQS is based on a three-year average, and the 24-hour NAAQS is based on expected exceedances over a three-year period.

On May 14, 1999, a panel of the U.S. Court of Appeals for the District of Columbia Circuit reviewed EPA's revisions to the ozone and PM NAAQS and found, by a 2-1 vote, that sections 108 and 109 of the Clean Air Act, as interpreted by EPA, represent unconstitutional delegations of Congressional power.

American Trucking Ass'ns, Inc., et al.,

Environmental Protection Agency

, 175 F.3d 1027 (D.C. Cir. 1999). Among other things the Court remanded the record for the 8-hour ozone NAAQS and the PM

2.5

NAAQS to EPA. On October 29, 1999, EPA's petition for rehearing by the three judge panel was denied, with an exception regarding the revised ozone NAAQS. EPA's petition for rehearing en banc by the full Circuit was also denied, although five of the nine judges considering the petition agreed to rehear the case.

The pre-existing PM

NAAQS remains in effect (except for one area—Boise, ID—where prior to the court's decision we had determined it no longer to apply). We believe that given the uncertain status of the new PM

2.5

NAAQS, it is most appropriate to rely primarily on the pre-existing PM

NAAQS in establishing the Tier 2/Gasoline Sulfur program's vehicle emission standards and limits on sulfur in gasoline. However, because we believe, and the Court did not dispute, that there are very substantial public health risks from PM

2.5

and substantial health and economic benefits from reducing PM

2.5

concentrations, we have conducted analyses of the PM

2.5

changes likely to occur from the Tier 2/Gasoline Sulfur program. These analyses are summarized in the section of this preamble dealing with the economic benefits of the new standards, section IV.D.5, and corresponding sections of the final RIA.

There is additional concern regarding the health effects of PM from diesel vehicles, apart from the health effects which were considered in setting the NAAQS for PM

and PM

2.5

. Diesel PM contains small quantities of chemical species that are known carcinogens, and diesel PM as a whole has been implicated in occupational epidemiology studies. EPA's Office of Research and Development has considered these studies, and has recently submitted to a committee of our Science Advisory Board a draft conclusion that diesel exhaust is a “highly likely” human cancer hazard.

Because we are awaiting a formal response from our advisory committee before revising and finalizing our assessment document, we are not relying on the conclusions in this document as formal support for our action today. More information about this aspect of PM air quality is given in section III.F of this preamble.

Health Assessment Document for Diesel Emissions, SAB Review Draft EPA/600/8-90/057D. November 1999. The document is available electronically at http://www.epa.gov/ncea/diesel.htm.

2. Need for Additional Reductions to Attain and Maintain the PM

NAAQS

The most recent PM

monitoring data indicates that 15 designated PM

nonattainment counties, with a population of almost 9 million in 1996, violated the PM

NAAQS in the period 1996-1998. The areas that are violating do so because of exceedances of the 24-hour PM

NAAQS. No areas had monitored violations of the annual standard in this period. Table III.C-1 lists the 15 counties. The table also indicates the classification for each area and the status of our review of the State Implementation Plan.

Table III.C-1.—

Fifteen PM

Nonattainment Areas Violating the PM

NAAQS in

1996-1998

Area

Classification

SIP approved?

1996

Population

(millions)

Clark Co., NV

Serious

0.93

El Paso, TX

Moderate

Yes

0.67

Gila, AZ

Moderate

0.05

Imperial Co., CA

Moderate

0.14

Inyo Co., CA

Moderate

0.02

Kern Co., CA

Serious

0.62

Mono Co., CA

Moderate

0.01

Kings Co., CA

Serious

0.11

Maricopa Co., AZ

Serious

2.61

Power Co., ID

Moderate

0.01

Riverside Co., CA

Serious

1.41

San Bernardino Co., CA

Serious

1.59

Santa Cruz Co., AZ

Moderate

0.04

Tulare Co., CA

Serious

0.35

Walla Walla Co., WA

Moderate

Yes

0.05

Total Population

8.61

Although we do not believe that we are limited to considering only designated nonattainment areas in implementing CAA section 202(i), we have focused on the designated areas in the case of PM

. An official designation of PM

nonattainment indicates the existence of a confirmed PM

problem that is more than a result of a one-time monitoring upset or a results of PM

exceedances attributable to natural events. In addition to these designated nonattainment areas, there are 15 unclassified counties in 12 geographically spread out states, with a 1996 population of over 4 million, for which the state has reported PM

monitoring data for this period indicating a PM

NAAQS violation. We have not yet excluded the possibility that a one-time monitoring upset or a natural event(s) is responsible for the monitored violations in 1996-1998 in the 15 unclassified counties. We adopted a policy in 1996 that allows areas whose PM

exceedances are attributable to natural events to remain unclassified if the state is taking all reasonable measures to safeguard public health regardless of the source of PM

emissions. Areas that remain unclassified areas are not required to submit attainment plans, but we work with each of these areas to understand the nature of the PM

problem and to determine what best can be done to reduce it. The Tier 2/Gasoline Sulfur program will reduce PM

concentrations in these 15 unclassified counties, because all have car and light truck travel that contributes to PM

and precursor emissions loadings. This reduction will assist these areas in reducing their PM

nonattainment problem, if a problem is confirmed upon closer examination of each local situation. Boise, ID, had also been classified as a PM

nonattainment area at one time and was monitored to have a PM

NAAQS violation in 1996-1998. However, the pre-existing PM

NAAQS does not presently apply in Boise, ID, because in the period between our revision of the old PM

NAAQS and the Court's decision to vacate the revised PM

NAAQS, we determined that Boise was in attainment with the old PM

NAAQS and that it therefore no longer applied in that area.

Because the types and sources of PM

are complex and vary from area to area, the best projections of future PM

concentrations are the local emission inventory and air quality modeling analyses that states have developed or are still in the process of developing for their PM

attainment plans. We do employ a modeling approach, known as the source-receptor matrix approach, for relating emission reductions to PM

reductions on a national scale. This approach is one of our established air quality models for purposes of quantifying the health and welfare related economic benefits of PM reductions from major regulatory actions. One application of this modeling approach was for the Regulatory Impact Analysis for the establishment of the new PM NAAQS

. This model is also the basis for the estimates of PM

(and PM

2.5

) concentrations reductions we have used to estimate the economic benefits of the Tier 2/Gasoline Sulfur program in 2030. Its use for this purpose is described in the final RIA. In both applications, we modeled an emissions scenario corresponding to controls currently in place or committed to by states. As such, this scenario is an appropriate baseline for determining if further reductions in emissions are needed in order to attain and maintain the PM

NAAQS.

Regulatory Impact Analyses for the Particulate Matter and Ozone National Ambient Air Quality Standards and Proposed Regional Haze Rule, Innovative Strategies and Economics Group, Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park, N.C., July 16, 1997.

In the RIA for the establishment of the PM NAAQS, we projected that in 2010 there will be 45 counties not in attainment with the original PM

NAAQS . We cited these modeling results in our proposal for the Tier 2/Gasoline Sulfur program and in our first supplemental notice. After reviewing public comments on our presentation of these modeling results, we have concluded that while the source-receptor matrix approach is a suitable model for estimating PM concentration reductions for economic benefits estimation, it is not a tool we can use with high confidence for predicting that individual areas that are now in attainment will become nonattainment in the future. However, we believe the source-receptor matrix approach is appropriate for, and is a suitable tool for, determining that a current designated nonattainment area has a high risk of remaining in PM

nonattainment at a future date. Therefore, we have cross-matched the results for 2030 from our final RIA for Tier 2 and the list of current PM

nonattainment areas with monitored violations in 1996 to 1998 shown in Table III.C-1.

Based on this, we conclude that the 8 areas shown in Table III.C-2 have a high risk of failing to attain and maintain without further emission reductions. These areas have a population of nearly 8 million. Included in the group are the counties that are part of the Los Angeles, Phoenix, and Las Vegas metropolitan areas, where traffic from cars and light trucks is substantial. California areas will benefit from the Tier 2/Gasoline Sulfur program because of travel within California by vehicles originally sold outside the state, and by reduced poisoning of catalysts from fuel purchased outside of California.

We used the more recent modeling for 2030 rather than the earlier modeling for 2010, because the modeling the 2030 incorporates more recent estimates of emissions inventories. Our emission estimates in our final RIA indicate that PM

emissions under the basline scenario increase steadily between 1996 and 2030, for 47 states combined and for four specific cities, suggesting that areas in nonattainment in both 1996-1998 and 2030 will be in nonatainment in the intermediate years as well assuming no further emission reductions. A factor tending to make Table III.C-2 shorter is that we have not relied on the source-receptor matrix model's prediction of 24-hour nonattainment, as those predictions on an individual areas basis are less reliable than the predictions of annual average nonattainment.

Table III.C-

2.—

Eight Areas With a High Risk of Failing To Attain and Maintain the PM

NAAQS Without Further Reductions in Emissions

Area

1996

population

(millions)

Clark Co., NV

0.93

Imperial Co., CA

0.14

Kern Co., CA

0.62

Kings Co., CA

0.11

Maricopa Co., AZ

2.61

Riverside Co., CA

1.41

San Bernardino Co., CA

1.59

Tulare Co., CA

0.35

Total population

7.76

Table III.C-2 is limited to designated PM

nonattainment areas which both had monitored violations of the PM

NAAQs in 1996-1998 and are predicted to be in nonattainment in 2030 in our PM

air quality modeling. This gives us high confidence that these areas require further emission reductions to attain and maintain, but does not fully

consider the possibility that there are other areas which are now meeting the PM

NAAQS which have at least a significant probability of requiring further reductions to continue to maintain it. Our air quality modeling predicted 2030 violations of the annual average PM

NAAQS in five additional counties that in either 1997 or 1998 had single-year annual average monitored PM

levels of at least 90 percent of the NAAQS, but did not exceed the formal definition of the NAAQS over the three-year period ending in 1998

. These areas are shown in Table III.C-3. They have a combined population of almost 17 million, and a broad geographic spread. Unlike the situation for ozone, for which precursor emissions are generally declining over the next 10 years or so before beginning to increase, we estimate that emissions of PM

will rise steadily unless new controls are implemented. The small margin of attainment which these areas currently enjoy will likely erode; the PM air quality modeling suggests that it will be reversed. We therefore consider these areas to each individually have a significant risk of failing to maintain the NAAQS without further emission reductions. There is a substantial risk that at least some of them would fail to maintain without further emission reductions. The emission reductions from the Tier 2/Gasoline Sulfur program will help to keep them in attainment.

In fact, in two of these areas, New York Co., NY and Harris Co., TX, the average PM

level in 1998 was above the 50 μg/m

value of the NAAQS. These two areas are not included in the Table III.C-2 list of areas with a high risk of failing to attain and maintain because lower PM

levels in 1996 and 1997 caused their three-year average PM

level to be lower than the NAAQS. Official nonattainment determinations for the annual PM

NAAQS are made based on the average of 12 quarterly PM

averages.

Table III.C-3.—Five Areas With a Significant Risk of Failing to Attain and Maintain the PM

NAAQS Without Further Reductions in Emissions

Area

1996

population

(millions)

New York Co., NY

1.33

Cuyahoga Co., OH

1.39

Harris, Co., TX

3.10

San Diego Co., CA

2.67

Los Angeles Co., CA

8.11

Total population

16.6

Taken together and considering their number, size, and geographic distribution, these 13 areas are sufficient to establish the case that additional reductions are needed in order to attain and maintain the PM

NAAQS. This determination provides additional support for the NOx and VOC standards and for the limits on gasoline sulfur, which are also fully supported on ozone attainment and health effects considerations. The sulfate particulate, sulfur dioxide, NO

, and VOC emission reductions from the Tier 2/Gasoline Sulfur program will help the 8 areas in Table III.C-2 and the 5 areas in Table III.C.-3 to attain and maintain the PM

NAAQS. The new PM standards for gasoline and diesel vehicles are also supported by this PM

determination.

We are also establishing the new PM emissions standard today to avoid the possibility that PM

concentrations in these and other areas do get even worse due to an increase in sales of diesel vehicles, which could create a need for further reductions which would be larger and would affect more areas of the country. At the present time, virtually all cars and light trucks being sold are gasoline fueled. The ambient PM

air quality data for 1996 to 1998 reflects that current situation, and this data was an important factor in what areas are listed in Tables III.C-2 and III.C-3. Also, the predictions of future PM

air quality, used to develop the Tables III.C-2 and III.C-3 lists of areas with high or significant risk of being unable to attain and maintain, are based on an assumption that this will continue to be true. However, we are concerned over the possibility that diesels will become more prevalent in the car and light-duty truck fleet, since automotive companies have announced their desire to increase their sales of diesel cars and light trucks. Because current diesel vehicles emit higher levels of PM

than gasoline vehicles, a larger number of diesel vehicles could dramatically increase levels of exhaust PM

, especially if more stringent PM emissions standards are not in place. The new PM emissions standards will ensure that an increase in the sales of diesel cars and light trucks will not increase PM emissions from cars and light trucks so substantially as to endanger PM

attainment and maintenance on a more widespread basis. Given this potential, it is appropriate to establish the new PM emissions standards now on the basis of the increase in sales of diesel vehicles being a reasonable possibility without such standards. Establishing the new PM emissions standards now avoids the public health impact and industry disruption that could result if we waited until an increase in sales of diesels with high PM emissions had already occurred.

In order to assess the potential impact of increased diesel sales penetration on PM emissions, we analyzed the increase in PM

emissions from cars and trucks under a scenario in which the use of diesel engines in cars and light trucks increases. We used projections developed by A.D. Little, Inc. as part of a study conducted for the American Petroleum Institute. The “Most Likely” case projected by A.D. Little forecasts that diesel engines” share of the light truck market will grow to 24 percent by the 2015 model year. Diesel engines' share of the car market would grow somewhat more slowly, reaching 9 percent by 2015. The A.D. Little forecasts did not address the period after 2015; we have assumed that diesel sales stabilize at the level reached in 2015, with the fraction of in-use vehicles with diesel engines continuing to increase through turnover. We believe these projections are more realistic than the scenario of even higher sales of diesels described in the notice for the proposed Tier 2/Gasoline Sulfur program, though the A.D. Little forecasts still show much higher percentages of diesel vehicles in the light-duty fleet than have ever existed historically in the U.S.

The A.D. Little scenario of increased diesels, and even more so the scenario described in our proposal, would result in dramatic increases in direct PM

emissions from cars and light trucks, if there were no change in these vehicles' PM standards. The increase in diesel exhaust PM

emissions would more than overcome the reduction in direct PM

attributable to the sulfur reduction in gasoline. With no change in the existing PM standards for cars and light trucks, our analysis of this scenario shows that direct PM

emissions in 2020 would be approximately 98,000 tons per year, which is nearly two times the 50,000 tons projected if diesel sales do not increase. The portion of ambient PM

concentrations attributable to cars and light trucks would climb steadily. The final RIA presents alternative estimates of the amount by which future PM

concentrations could increase due to such an emissions increase, based on extrapolations from several studies' estimates of the contribution that heavy-duty diesel vehicles have made to recent or PM

concentrations. The increase is estimated to range from 0.6 to 20 μg/m3.

The added PM

emissions from cars and trucks due to an increase in diesel sales without action to reduce PM

from new diesel vehicles would exacerbate the PM

nonattainment problems of the areas listed in Tables

III.C-2 and III.C-3, for which our air quality modeling predicted future nonattainment even without an increase in diesel sales. Moreover, it might cause PM

nonattainment in additional areas. In addition to the counties already listed in Tables III.C-2 and III.C-3, there are other areas for which 1997 and 1998 data indicate that maintenance of the PM

NAAQS is at risk if diesel sales of cars and light truck increase. Table III.C-4 lists additional counties for which either 1997 or 1998 monitoring data, or both, indicated a second-high PM

concentration for the single year within 10 percent of the PM

24-hour NAAQS or an annual average PM

concentration within 10 percent of the annual average PM

NAAQS. Only counties which are part of metropolitan statistical areas are listed in Table III.C-4, in order to focus on those in which traffic densities are high. Considering both the annual and 24-hour NAAQS, there were 13 areas within 10 percent of the standard. Increases in PM

emissions from more diesel vehicles would put these areas in greater risk of violating the PM

NAAQS, especially if growth in other sources is high or meteorological conditions are more adverse than in the 1996 to 1998 period.

Table III.C-4.—Thirteen Metropolitan Statistical Area Counties With 1997 and/or 1998 Ambient PM

Concentrations Within 10 Percent of the Annual or 24-Hour the PM

NAAQS

1996

population

(millions)

Areas within 10 percent of the annual

NAAQS:

Lexington Co., SC

0.20

Union Co., TN

0.02

Washoe Co., NV

0.30

Madison Co., IL

0.26

Dona Ana Co., NM

0.16

El Paso Co., TX

0.68

Ellis Co., TX

0.97

Fresno Co., CA

0.74

Philadelphia Co., PA

1.47

Areas within 10 percent of the 24-hour

NAAQS:

Lexington Co., SC

0.20

El Paso Co., TX

0.68

Union Co., TN

0.02

Mobile Co., AL

0.40

Dona Ana Co., NM

0.16

Lake Co., IN

0.48

Philadelphia Co., PA

1.47

Pennington Co., SD

0.09

Ventura Co., CA

0.71

Total Population of all 13 areas

6.48

Notes:

These areas are listed based on their second high 24-hour concentration and annual average concentration in 1997, 1998, or both. Official nonattainment determinations are made based on three years of data, and on estimates of expected exceedances of the 24-hour standard.

Fortunately, the standards included in today's actions will result in a steady decrease in total direct PM

from cars and light trucks even if this increase in the use of diesel engines in these vehicles were to occur. If the A.D. Little “Most Likely” scenario for increased diesel engines in light trucks were to occur, today's actions would reduce diesel PM

from cars and light trucks by over 75 percent in 2020. Stated differently, by 2030 today's actions would reduce 98,000 tons of the potential increase in PM

emissions from passenger cars and light trucks. The result would be less direct PM

than is emitted today, because the increase in diesel PM

would be more than offset by the reduction in PM

emissions from gasoline vehicles resulting from lower gasoline sulfur levels.

We are establishing tighter PM standards for cars and light trucks to help avoid the adverse impact of greater diesel PM emissions on PM

attainment and public health and welfare if diesel sales increased in the future without the protection of the tighter standards. Because diesel vehicles will essentially be performing the same functions as the gasoline vehicles they will replace, it is appropriate for the new PM standards to also apply equally to gasoline and diesel vehicles. We expect that gasoline vehicles will need little or no redesign to meet the new PM standards when free of defects and properly operating. However, the new vehicle and gasoline sulfur standards may achieve some reduction in real world PM emissions from gasoline vehicles by encouraging more durable designs and by ensuring that these vehicles are operated on lower-sulfur fuel. The new standards for PM will also prevent any changes in gasoline engine design which would increase PM emissions. These changes would otherwise be possible because the current PM standard is so much higher than the current performance on the gasoline vehicles.

3. PM

2.5

Discussion

We are not basing our promulgation of the Tier 2 vehicle standards on a finding on the need for additional emission reductions in order to attain and maintain the NAAQS for PM

2.5

. We are providing this information to explain that this program will result in substantial benefit in reduction of PM

2.5

concentrations, to an even broader set of geographic areas than will benefit in terms of PM

attainment.

The annual and 24-hour PM

2.5

NAAQS set in 1997 are numerically much lower than the corresponding PM

standards: 15 versus 50 μg/m

for the annual average standards and 65 versus 150 μg/m

for the 24-hour average standards. While geographically broad PM

2.5

monitoring is just now reaching the end of the first of three years of operation needed to determine compliance, our best analysis from the more limited PM

2.5

conducted in some areas indicates that many areas that are in compliance with the PM

standards will be found to be in violation of the annual average PM

2.5

standard. Violations of the 24-hour PM

2.5

standard appear to be infrequent.

Therefore, if we considered it appropriate to proceed with implementing the PM

2.5

NAAQS, we are confident that there would be a larger set of areas for which we would determine that further reductions in emissions are needed in order to attain and maintain the NAAQS.

Moreover, gasoline and diesel cars and light trucks have a more important contributing role for ambient PM

2.5

concentrations, and other emission sources that play a major role in ambient PM

concentrations will be relatively less important. Cars and light trucks contribute essentially the same absolute amount to ambient concentrations of PM

and of PM

2.5

. However, most other sources contribute much more to PM

than to PM

2.5

, so the relative contribution from cars and light trucks is larger. In addition, the absolute contribution from cars and light trucks is larger in relationship to the numerically lower PM

2.5

standard, making them more important to attainment and maintenance. This is also true for the potential contribution that more diesel cars and light trucks would make to ambient PM

2.5

concentrations.

4. Emission Reductions and Ambient PM Reductions

The NO

and VOC emission reductions from the Tier 2/Gasoline Sulfur program are presented in the ozone section above. The SO

and PM reductions are presented in our final RIA, and are essentially unchanged from those presented in our proposal, except for the revision of the diesel sales scenario discussed above.

Because virtually all of the PM reduction from the Tier 2/Gasoline

Sulfur program is in the fine fraction of PM

, our estimates of the PM

2.5

and PM

reductions are essentially the same. Estimates of the ambient PM reductions in 2030 in different parts of the nation, after full phase in of the vehicle standards, are presented in the final RIA. The reductions in ambient PM are largest in the parts of the country with more vehicle travel, i.e, larger in the east than in the west and larger in urban areas than in rural areas. In the eastern half of the nation, the reductions in annual average PM concentrations range from 0.2 to over 1.2 micrograms per cubic meter.

D. Other Criteria Pollutants: Carbon Monoxide, Nitrogen Dioxide, Sulfur Dioxide

The standards being promulgated today will help reduce levels of three other pollutants for which NAAQSs have been established: carbon monoxide (CO), nitrogen dioxide (NO

), and sulfur dioxide (SO

). As of 1998, every area in the United States has been designated to be in attainment with the NO

NAAQS. As of 1997, one area (Buchanan County, Missouri) did not meet the primary SO

short-term standard, due to emissions from the local power plant. There are currently 20 designated CO nonattainment areas, with a combined population of 33 million. There are also 24 designated maintenance areas with a combined population of 22 million. However, the broad trends indicate that ambient levels of CO are declining. In 1997, 6 of 537 monitoring sites reported ambient CO levels in excess of the CO NAAQS.

The reductions in SO

precursor emissions from today's actions are essentially equal to the SO

reductions described in Section III.B. and III.C., respectively. The impact of today's actions on NO

emissions depends on the specific emission control technologies used to meet the Tier 2 vehicl

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