EO 12866_EPA_Response_to_Comments_Tier_3_2060-AQ86_NPRM_3_25_2013.doc
ENVIRONMENTAL PROTECTION AGENCY
40 CFR Parts 79, 80, 85, 86, 600, 1036, 1037, 1065, and 1066
[EPA - HQ - OAR - 2011 - 0135; FRL_XXXX-X]
RIN 2060-AQ86
Control of Air Pollution from Motor Vehicles: Tier 3 Motor Vehicle Emission and Fuel Standards
AGENCY: Environmental Protection Agency (EPA).
ACTION: Proposed Rule.
SUMMARY: This action would establish more stringent vehicle emissions standards and reduce the sulfur content of gasoline beginning in 2017, as part of a systems approach to addressing the impacts of motor vehicles and fuels on air quality and public health.  The proposed gasoline sulfur standard would make emission control systems more effective for both existing and new vehicles, and would enable more stringent vehicle emissions standards.  The proposed vehicle standards would reduce both tailpipe and evaporative emissions from passenger cars, light-duty trucks, medium-duty passenger vehicles, and some heavy-duty vehicles.  This would result in significant reductions in pollutants such as ozone, particulate matter, and air toxics across the country and help state and local agencies in their efforts to attain and maintain health-based National Ambient Air Quality Standards.  Motor vehicles are an important source of exposure to air pollution both regionally and near roads.  These proposed vehicle standards are intended to harmonize with California's Low Emission Vehicle program, thus creating a federal vehicle emissions program that would allow automakers to sell the same vehicles in all 50 states.  The proposed vehicle standards would be implemented over the same timeframe as the greenhouse gas/fuel efficiency standards for light-duty vehicles, as part of a comprehensive approach toward regulating emissions from motor vehicles.
DATES: EPA has announced the comment period and the public hearing dates for this proposal in a supplemental Federal Register Notice, which was published on [insert date of publication of supplemental notice in the Federal Register].  Under the Paperwork Reduction Act, comments on the information collection provisions are best assured of having full effect if the Office of Management and Budget (OMB) receives a copy of your comments on or before [insert date 30 days after publication in the federal register], thirty days after date of publication in the Federal Register.
ADDRESSES: Submit your comments, identified by Docket ID No. EPA - HQ - OAR - 2011 - 0135, by one of the following methods:
www.regulations.gov: Follow the on-line instructions for submitting comments.
Email<EMAIL_ADDRESS>Mail: Air and Radiation Docket and Information Center, Environmental Protection Agency, Mailcode: 2822T, 1200 Pennsylvania Ave., NW., Washington, DC 20460.  In addition, please mail a copy of your comments on the information collection provisions to the Office of Information and Regulatory Affairs, Office of Management and Budget (OMB), Attn: Desk Officer for EPA, 725 17th St. NW., Washington, DC 20503.
Hand Delivery: EPA Docket Center, EPA West Building, Room 3334, 1301 Constitution Ave., NW., Washington, DC 20460. Such deliveries are only accepted during the Docket's normal hours of operation, and special arrangements should be made for deliveries of boxed information.
Instructions:  Direct your comments to Docket ID No. EPA - HQ - OAR - 2011 - 0135.  EPA's policy is that all comments received will be included in the public docket without change and may be made available online at www.regulations.gov, including any personal information provided, unless the comment includes information claimed to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute.  Do not submit information that you consider to be CBI or otherwise protected through www.regulations.gov or e-mail.  The www.regulations.gov website is an "anonymous access" system, which means EPA will not know your identity or contact information unless you provide it in the body of your comment.  If you send an e-mail comment directly to EPA without going through www.regulations.gov your e-mail address will be automatically captured and included as part of the comment that is placed in the public docket and made available on the Internet.  If you submit an electronic comment, EPA recommends that you include your name and other contact information in the body of your comment and with any disk or CD-ROM you submit.  If EPA cannot read your comment due to technical difficulties and cannot contact you for clarification, EPA may not be able to consider your comment.  Electronic files should avoid the use of special characters, any form of encryption, and be free of any defects or viruses.  For additional information about EPA's public docket visit the EPA Docket Center homepage at http://www.epa.gov/epahome/dockets.htm.  For additional instructions on submitting comments, go to Section I.B of the SUPPLEMENTARY INFORMATION section of this document.
Docket: All documents in the docket are listed in the www.regulations.gov index.  Although listed in the index, some information is not publicly available, e.g., CBI or other information whose disclosure is restricted by statute.  Certain other material, such as copyrighted material, will be publicly available only in hard copy.  Publicly available docket materials are available either electronically in www.regulations.gov or in hard copy at the Air and Radiation Docket and Information Center, EPA/DC, EPA West, Room 3334, 1301 Constitution Ave., NW, Washington, DC.  The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays.  The telephone number for the Public Reading Room is<PHONE_NUMBER>, and the telephone number for the Air Docket is<PHONE_NUMBER>.
FOR FURTHER INFORMATION CONTACT: Julia MacAllister, Office of Transportation and Air Quality, Assessment and Standards Division, Environmental Protection Agency, 2000 Traverwood Drive, Ann Arbor MI 48105; Telephone number:<PHONE_NUMBER>; Fax number:<PHONE_NUMBER>; E-mail address<EMAIL_ADDRESS>SUPPLEMENTARY INFORMATION:
I.   General Information
A.  Does this Action Apply to Me?
Entities potentially affected by this proposed rule include gasoline refiners and importers, ethanol producers, gasoline additive manufacturers, transmix processors, terminals and fuel distributors, light-duty vehicle manufacturers, independent commercial importers, alternative fuel converters, and manufacturers and converters of vehicles between 8,500 and 14,000 lbs gross vehicle weight rating (GVWR).
Potentially regulated categories include:
Category
                                 NAICS[a] Code
                                  SIC[b] Code
Examples of Potentially Affected Entities
Industry
324110
2911
Petroleum refineries (including importers)
Industry
325110
2869
Butane manufacturers
Industry
325193
2869
Ethyl alcohol manufacturing
Industry
211112
1321
Natural gas liquids extraction and fractionation
Industry
325199
2869
Other basic organic chemical manufacturing
Industry
486910
4613
Natural gas liquids pipelines, refined petroleum products pipelines.
Industry
424690
5169
Chemical and allied products merchant wholesalers
Industry
325199
2869
Manufacturers of gasoline additives
Industry
424710
5171
Petroleum bulk stations and terminals.  E51-83 manufacturers.
Industry
493190
4226
Other warehousing and storage- bulk petroleum storage
Industry
336111,
336112
3711
Light-duty vehicle and light-duty truck manufacturers
Industry
811111, 811112, 811198
7538, 7533, 7534
Independent commercial importers
Industry
335312,
336312,
336322,
336399,
811198
3621, 3714, 3519, 3599, 7534
Alternative fuel converters
Industry
333618,
336120,
336211,
336312
3699, 3711, 3713, 3714
On-highway heavy-duty engine & vehicle (>8,500 lbs GVWR) manufacturers
[a] North American Industry Classification System (NAICS).
[b] Standard Industrial Classification (SIC).
	This table is not intended to be exhaustive, but rather provides a guide for readers regarding entities likely to be regulated by this proposed action.  This table lists the types of entities that EPA is now aware could potentially be regulated by this proposed action.  Other types of entities not listed in the table could also be regulated.  To determine whether your activities would be regulated by this proposed action, you should carefully examine the applicability criteria in 40 CFR parts 79, 80, 85, 86, 1065, and 1066 and the referenced regulations.  If you have any questions regarding the applicability of this proposed action to a particular entity, consult the person listed in the preceding FOR FURTHER INFORMATION CONTACT section.
B.  What Should I Consider as I Prepare My Comments for EPA?
1. Submitting CBI.
Do not submit this information to EPA through www.regulations.gov or e-mail.  Clearly mark the part or all of the information that you claim to be CBI.  For CBI information in a disk or CD ROM that you mail to EPA, mark the outside of the disk or CD ROM as CBI and then identify electronically within the disk or CD ROM the specific information that is claimed as CBI.  In addition to one complete version of the comment that includes information claimed as CBI, a copy of the comment that does not contain the information claimed as CBI must be submitted for inclusion in the public docket.  Information so marked will not be disclosed except in accordance with procedures set forth in 40 CFR part 2.
2. Tips for Preparing Your Comments.
When submitting comments, remember to:
Identify the rulemaking by docket number and other identifying information (subject heading, Federal Register date and page number).
Follow directions - The agency may ask you to respond to specific questions or organize comments by referencing a Code of Federal Regulations (CFR) part or section number.
Explain why you agree or disagree, suggest alternatives, and substitute language for your requested changes.
Describe any assumptions and provide any technical information and/or data that you used.
If you estimate potential costs or burdens, explain how you arrived at your estimate in sufficient detail to allow for it to be reproduced.
Provide specific examples to illustrate your concerns, and suggest alternatives.
Explain your views as clearly as possible, avoiding the use of profanity or personal threats.
Make sure to submit your comments by the comment period deadline identified.
C.  Did EPA Conduct a Peer Review before Issuing this Notice?
This regulatory action was supported by influential scientific information. Therefore, EPA conducted peer reviews in accordance with OMB's Final Information Quality Bulletin for Peer Review.  Specifically, EPA conducted six peer reviews in connection with data supporting the proposed Tier 3 program, including new research on the effects of fuel properties changes (including sulfur effects) on exhaust and evaporative emissions of Tier 2 vehicles.  The refinery-by-refinery cost model was also peer reviewed.  The peer review reports are located in the docket for today's action, as well as the agency's response to the peer review comments.
Table of Contents
I.	Executive Summary and Overview of Proposed Program
	A.	Introduction
	B.	What Are the Basic Components of the Proposed Program?
  		1.	Proposed Standards for Light-Duty Vehicle, Light-Duty Truck, and Medium-Duty Passenger Vehicle Tailpipe Emissions
		2.	Proposed Heavy-Duty Vehicle Tailpipe Emissions Standards
		3.	Proposed Evaporative Emission Standards
		4.	Onboard Diagnostic Systems (OBD)
		5.	Emissions Test Fuel
		6.	Fuel Standards
		7.	Regulatory Streamlining and Technical Amendments
	C.	What Would the Impacts of the Proposed Standards Be?
II.	Why is EPA Making This Proposal?
	A.	Basis for Action under the Clean Air Act
		1.	Clean Air Act Section 202
		2.	Clean Air Act Section 211
	B.	Overview of Public Health Impacts of Motor Vehicles and Fuels
		1.	Ozone
		2.	Particulate Matter
		3.	Nitrogen Oxides and Sulfur Oxides
		4.	Carbon Monoxide
		5.	Mobile Source Air Toxics
		6.	Near-Roadway Pollution
		7.	Environmental Impacts of Motor Vehicles and Fuels
III.	How Would This Proposal Reduce Emissions and Air Pollution?
	A.	Effects of the Proposed Vehicle and Fuel Changes on Mobile Source Emissions
		1.	How Do Vehicles Produce the Emissions Addressed in this Proposal?
  		2. 	How Would the Proposed Changes to Gasoline Sulfur Content Affect Vehicle Emissions?
	B.	How Would Emissions Be Reduced?
		1.	NOX
		2.	VOC
		3.	CO
		4.	Direct PM2.5
		5.	Air Toxics
		6.	SO2
		7.	Greenhouse Gases
	C.	How Would Air Pollution Be Reduced?
		1.	Ozone
		2.	Particulate Matter
		3.	Nitrogen Dioxide
		4.	Air Toxics
		5.	Visibility
		6.	Nitrogen and Sulfur Deposition
		7.	Environmental Justice
IV.	Proposed Vehicle Emissions Program
	A.	Tailpipe Emission Standards for Light-Duty Vehicles, Light-Duty Trucks, and Medium-Duty Passenger Vehicles
		1.	Overview
		2.	Summary of Proposed FTP and SFTP Tailpipe Standards
		3.	Proposed FTP Standards
		4.	Proposed SFTP Standards
		5.	Feasibility of the Proposed NMOG+NOX and PM Standards
  		6.	Impact of Gasoline Sulfur Control on the Feasibility of the Proposed Vehicle Emission Standards
		7.	Other Provisions
	B.	Tailpipe Emissions Standards for Heavy-Duty Vehicles
		1.	Overview
		2.	HDV Exhaust Emissions Standards
		3.	Supplemental FTP Standards for HDVs
		4.	HDV Emissions Averaging, Banking, and Trading
		5.	Feasibility of HDV Standards
		6.	Other HDV Provisions
	C.	Evaporative Emissions Standards and Onboard Diagnostic System Requirements
		1.	Tier 3 Evaporative Emission Standards
		2.	Evaporative Emissions Program Structure and Implementation Flexibilities
		3.	Heavy-Duty Gasoline Vehicle (HDGV) Requirements
		4.	Test Procedures and Certification Test Fuel
		5.	Improvements to In-Use Performance of Fuel Vapor Control Systems
		6.	Other Initiatives
	D.	Emissions Test Fuel
		1.	Proposed Changes to Gasoline Emissions Test Fuel
		2.	Proposed Flexible Fuel Vehicle Test Fuel
		3.	Proposed Implementation Schedule
  		4.	Potential Implications on CAFE Standards, GHG Standards, and Fuel Economy Labels
  		5.	Consideration of Nonroad, Motorcycle, and Heavy-Duty Engine Emissions Test Fuel
6.  Consideration of CNG and LPG Emissions Test Fuels
	E.	Small-Business Provisions
		1.	Lead Time for Exhaust and Evaporative Emission Standards
		2.	Assigned Deterioration Factors
		3.	Reduced Testing Burden
		4.	Hardship
		5.	Applicability of Flexibilities
	F.	Compliance Provisions
		1.	Exhaust Emission Test Procedures
		2.	Reduced Test Burden
		3.	Miscellaneous Provisions
		4.	Manufacturer In-Use Verification Testing (IUVP) Requirements
V.	Proposed Fuel Program
	A.	Proposed Tier 3 Gasoline Sulfur Standards
		1.	Overview
		2.	Proposed Annual Average Sulfur Standard
		3.	Per-Gallon Sulfur Caps
	B.	Refinery Air Permitting Interactions
		1.	Background on New Source Review Programs
		2.	Background on NSR Experience Under the Tier 2 Fuel Program
		3.	Changes in the NSR Permitting Program since Tier 2 Final Rule
		4.	Assessment of Tier 3 Refinery Changes and Permitting Implications
  		5.	Proposed New Source Performance Standards and Proposed National Emission Standards for Hazardous Air Pollutants for Refineries
		6.	Possible Steps for Addressing Permitting Roadblocks
	C.	Standards for Denatured Fuel Ethanol and Other Oxygenates
	D.	Standards for Fuel Used in Flexible Fueled Vehicles
		1.	Standards for E51-83
		2.	Standards for Mid-Level Ethanol Blends (E16-50)
	E.	Proposed Program Flexibilities
		1.	Averaging, Banking, and Trading Program
		2.	Regulatory Flexibility Provisions
		3.	Provisions for Refiners Facing Hardship Situations
	F.	Compliance Provisions
		1.	Registration, Reporting, and Recordkeeping Requirements
		2.	Sampling and Testing Requirements
		3.	Small Refiner Compliance
		4.	Small Volume Refinery Compliance
		5.	Attest Engagements, Violations, and Penalties
		6.	Special Fuel Provisions and Exemptions
	G.	Statutory Authority for Proposed Tier 3 Fuel Controls
		1.	Section 211(c)(1)(A)
		2.	Section 211(c)(1)(B)
VI.	Technical Amendments and Regulatory Streamlining
	A.	Amendments to 40 CFR Part 80
		1.	Regulatory Streamlining
		2.	Subpart I Technical Amendments
		3.	Performance-Based Measurement Systems (PBMS)
		4.   Downstream Pentane Blending
	B.	Engine, Vehicle and Equipment Programs
		1.	Fuel Economy Labeling
		2.	Removing Obsolete Regulatory Text
		3.	Motorcycle Driving Schedules
		4.	Updating Reference Procedures
VII.	What are the Cost Impacts of the Proposed Rule?
	A.	Estimated Costs of the Vehicle Standards
	B.	Estimated Costs of the Fuel Program
		1.	Overview
		2.	Methodology
		3.	Summary of Costs without ABT Program
		4.	Summary of Costs with ABT Program
		5.	Other Cost Estimates
	C.	Summary of Proposed Program Costs
	D.	Cost per Ton of Emissions Reduced
VIII.	What are the Estimated Benefits of the Proposed Rule?
	A.	Overview
	B.	Quantified Human Health Impacts
	C.	Monetized Benefits
	D.	What are the Limitations of the Benefits Analysis?
   E.	Illustrative Analysis of Monetized Impacts Associated with the Proposal in 2017
IX.	Alternatives Analysis
	A.	Vehicle Emission Standards
		1.	Shorter NMOG+NOX Standard Phase-in
		2.	Longer NMOG+NOX Standards Phase-in Due to Early Credits
		3.	Shorter PM Standards Phase-in
		4.	NMOG+NOX Standards
		5.	PM Standards
	B.	Fuel Sulfur Standards
X.	Economic Impact Analysis
	A.	Introduction
	B.	Vehicle Sales Impacts
	C.	Impacts on Petroleum Refinery Sector Production
	D.	Employment Impacts
		1.	Employment Impacts in the Auto Sector
		2.	Refinery Employment Impacts
XI.	Public Participation
	A.	How Do I Submit Comments?
	B.	How Should I Submit CBI to the Agency?
	C.	Will There Be a Public Hearing?
	D.	Comment Period
	E.	What Should I Consider as I Prepare My Comments for EPA?
XII.	Statutory And Executive Order Reviews
	A.	Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: Improving Regulation and Regulatory Review
	B.	Paperwork Reduction Act
	C.	Regulatory Flexibility Act
		1.	Overview
		2.	Background
		3.	Reason for Today's Proposed Rule
		4.	Legal Basis for Agency Action
		5.	Summary of Potentially Affected Small Entities
		6.	Potential Reporting, Recordkeeping, and Compliance
		7.	Related Federal Rules
		8.	Summary of SBREFA Panel Process and Panel Outreach
	D.	Unfunded Mandates Reform Act
	E.	Executive Order 13132: Federalism
	F.	Executive Order 13175: Consultation and Coordination with Indian Tribal Governments
	G.	Executive Order 13045: Protection of Children from Environmental Health Risks and Safety Risks
	H.	Executive Order 13211: Actions Concerning Regulations That Significantly Affect Energy Supply, Distribution, or Use
	I.	National Technology Transfer and Advancement Act
	J.	Executive Order 12898:  Federal Actions to Address Environmental Justice in Minority Populations and Low-Income Populations
XIII.	Statutory Provisions And Legal Authority
Executive Summary and Overview of Proposed Program
Introduction
In this action, EPA is proposing a major program designed to reduce air pollution from passenger cars and trucks. This program includes new standards for both vehicle emissions and the sulfur content of gasoline, considering the vehicle and its fuel as an integrated system. We refer to this proposed program as the "Tier 3" vehicle and fuel standards.
This proposed rule is part of a comprehensive approach to address the impacts of motor vehicles on air quality and public health.  Over 158 million Americans are currently experiencing unhealthy levels of air pollution, which are linked with respiratory and cardiovascular problems and other adverse health impacts that lead to increased medication use, hospital admissions, emergency department visits, and premature mortality.  Motor vehicles are a particularly important source of exposure to air pollution, especially in urban areas.  By 2014 we project that in many nonattainment areas, cars and light trucks will contribute 30-45 percent of total nitrogen oxides (NOX) emissions, 20-25 percent of total volatile organic compound (VOC) emissions, and 5-10 percent of total direct particulate matter (PM2.5) emissions.  These compounds form ozone, PM, and other air pollutants, whose health and environmental effects are described in more detail in Section II.  Cars and light trucks also continue to be a significant contributor to air pollution directly near roads, with gasoline vehicles accounting for more than 50 percent of near-road concentrations of some criteria and toxic pollutants.  More than 50 million people live, work, or go to school in close proximity to high-traffic roadways, and the average American spends more than one hour traveling along roads each day.[,] Almost 90 percent of daily trips use personal vehicles.
The standards set forth in this proposed rule would significantly reduce levels of multiple air pollutants (such as ambient levels of ozone, PM, nitrogen dioxide (NO2), and mobile source air toxics (MSATs)) across the country, with immediate impacts expected due to the proposed sulfur control standards starting in 2017. These reductions would help state and local agencies in their effort to attain and maintain health-based National Ambient Air Quality Standards (NAAQS).  Few other national strategies exist that would deliver the same magnitude of multi-pollutant reductions projected to result from the proposed Tier 3 standards.  In the absence of additional controls, many areas will continue to have ambient ozone concentrations exceeding the NAAQS in the future.  See Section III.C for more details.
The Clean Air Act authorizes EPA to establish emissions standards for motor vehicles to address air pollution that may reasonably be anticipated to endanger public health or welfare (section 202). EPA also has authority to establish fuel controls to address such air pollution (section 211).  These statutory authorities are described in Section II.A.
The vehicle and gasoline sulfur standards we are proposing represent a "systems approach" to reducing vehicle-related exhaust and evaporative emissions by addressing the vehicle and fuel as a system. The systems approach enables emission reductions that are both technologically feasible and cost-effective beyond what would be possible looking at vehicle and fuel standards in isolation.  We first applied such an approach with our Tier 2 vehicle/gasoline sulfur standards (finalized in 2000).  We believe that a similar approach for the proposed Tier 3 standards would be a cost-effective way to achieve substantial additional emissions reductions.
The proposed Tier 3 standards include new light- and heavy-duty vehicle emission standards for exhaust emissions of VOC (specifically, non-methane organic gases, or NMOG), NOX, and PM, as well as evaporative emissions standards.  The proposed standards for light-duty vehicle, light-duty truck, and medium-duty passenger vehicle tailpipe emissions are an 80 percent reduction in fleet average NMOG+NOX compared to current standards, and a 70 percent reduction in per-vehicle PM standards.  The proposed Tier 3 heavy-duty vehicle tailpipe emissions standards provide reductions in both NMOG+NOX and PM that are on the order of 60 percent, compared to current standards. The proposed evaporative emissions standards represent a 50 percent reduction from current standards.
The vehicle emission standards, combined with the proposed reduction of gasoline sulfur content from the current 30 parts per million (ppm) average down to a 10-ppm average, would result in dramatic emissions reductions for NOX, VOC, direct PM2.5, carbon monoxide (CO) and air toxics.  For example, in 2030, when Tier 3 vehicles would make up the majority of the fleet as well as vehicle miles travelled, NOX and VOC emissions from on-highway vehicles would be reduced by about one quarter, and CO emissions would be reduced by about 30 percent.  Emissions of many air toxics would also be reduced by 10 to nearly 40 percent of national emissions from on-highway vehicles.  Reductions would continue beyond 2030 as more of the fleet is composed of Tier 3 vehicles.  For example, the Tier 3 program would reduce on-highway emissions of NOX and VOC nearly 40 percent by 2050, when Tier 3 vehicles would comprise almost the entire fleet.
Gasoline vehicles depend to a great degree on catalytic converters to reduce levels of pollutants in their exhaust, including NMOG and NOX, as well as PM (specifically, the volatile hydrocarbon fraction), CO, and most air toxics.  The catalytic converters become significantly less efficient when sulfur from the gasoline is deposited (adsorbed) onto the precious metals that catalyze the reactions to reduce the emissions.  The Tier 2 rulemaking required refiners to take steps to reduce sulfur levels in gasoline by approximately 90 percent, to an average of 30 ppm.  As discussed in Section IV.A.6, subsequent research provides a compelling case that even this level of sulfur not only degrades the emission performance of vehicles on the road today, but also inhibits necessary further reductions in vehicle emissions performance to reach the proposed Tier 3 standards.   Thus, the proposed Tier 3 10-ppm average sulfur standard is significant in two ways:  it enables vehicles designed to the proposed Tier 3 tailpipe exhaust standards to meet these standards in-use for the duration of their useful life, and it facilitates immediate emission reductions from all the vehicles on the road at the time the sulfur controls are implemented. Lower sulfur gasoline also facilitates the development of lower-cost technologies to improve fuel economy.  Sulfur in the fuel quickly causes the fuel economy benefits of lean-burn technologies to disappear due to its effect on NOx adsorber operation requiring more fuel to be burned.  We are not the first regulatory agency to recognize the need for lower-sulfur gasoline.  Agencies in Europe and Japan have already imposed gasoline sulfur caps of 10 ppm, and the State of California is already averaging 10 ppm sulfur with a per gallon cap of 20 ppm.  Other states are preempted by the Clean Air Act from adopting new fuel programs to meet air quality objectives.  Consequently, they could not receive the air quality benefits of lower sulfur gasoline without federal action.
This proposal is one aspect of a comprehensive national program regulating emissions from motor vehicles.  EPA's recent final rule for reducing greenhouse gas (GHG) emissions from light-duty (LD) vehicles starting with model year (MY) 2017 (referred to here as the "2017 LD GHG" standards) is another aspect of this comprehensive program.  The Tier 3 proposal addresses interactions with the 2017 LD GHG rule in a manner that aligns implementation of the two actions, to achieve significant criteria pollutant and GHG emissions reductions while providing regulatory certainty and compliance efficiency.  As vehicle manufacturers introduce new vehicle platforms for compliance with the GHG standards, they will be able to design them for compliance with the Tier 3 standards at the same time.  The proposed Tier 3 standards are also closely coordinated with California's Low Emission Vehicle (LEV III) program to create a vehicle emissions program that would allow automakers to sell the same vehicles in all 50 states.  (In December 2012 EPA approved a waiver of Clean Air Act preemption for the California Air Resources Board's (CARB's) LEV III program with compliance beginning in 2015.  Ten states have adopted the LEV III program under Section 177 of the Clean Air Act.)  We have worked closely with individual vehicle manufacturers and their trade associations, who have emphasized the importance of a harmonized national program.  Together, the Tier 3, 2017 LD GHG, and LEV III standards would maximize reductions in GHGs, criteria pollutants and air toxics from motor vehicles while streamlining programs and enabling manufacturers the flexibility to design a single vehicle for nationwide sales, thus reducing their costs of compliance.  In this way, the Tier 3 proposal responds to the May 21, 2010 Presidential Memorandum that requested that EPA develop a comprehensive approach toward regulating motor vehicles, including consideration of non-GHG emissions standards.
As part of the systems approach to this program, we are considering the future fuels on which vehicles will be operating.  In particular, the renewable fuels mandate that was revised by the Energy Independence and Security Act (EISA) and is being implemented through the Renewable Fuel Standards program (RFS2) will result in significant amounts of ethanol-blended gasoline in the implementation timeframe of the proposed Tier 3 program.  We are proposing to update the specifications of the certification test fuel with which vehicles demonstrate compliance with emissions standards, in order to better reflect the ethanol content and other properties of gasoline that will be in use.
This section provides an overview of the vehicle- and fuel-related standards we are proposing as well as the impacts of the proposed standards.  The public health issues and statutory requirements that have prompted this proposal are described in Section II, and our discussion of how the proposal would reduce emissions and air pollution is presented in Section III.  Details of proposed standards and how they would be implemented can be found in Sections IV through VI.  Sections VII through X contain our discussion of the proposed standards' technological feasibility and cost, benefits, alternatives and economic impacts.
What Are the Basic Components of the Proposed Program?
In the more than 10 years since EPA finalized the Tier 2 Vehicle Program, manufacturers of light-duty vehicles have continued to develop a wide range of improved technologies capable of reducing key exhaust emissions, especially VOC, NOX, and PM.  The California LEV II program has been instrumental in the continuous technology improvements by requiring year after year reductions in the fleet average hydrocarbon levels, in addition to requiring the introduction of advanced exhaust and evaporative emission controls in partial zero emission vehicles (PZEVs).  This progress in vehicle technology has made it possible for manufacturers to achieve emission reductions well beyond the requirements of the Tier 2 program if gasoline sulfur levels are lowered further.
As a result, we are proposing new standards for exhaust emissions of NMOG, NOX, and PM, as well as evaporative emissions standards.  These standards would phase in beginning with MY 2017.  The proposed Tier 3 standards are very similar in structure to those in the existing Tier 2 program.  As with the Tier 2 program, the proposed standards would apply to all light-duty vehicles (LDVs, or passenger cars), light-duty trucks (LDT1s, LDT2s, LDT3s, and LDT4s) and Medium-Duty Passenger Vehicles (or MDPVs).  We are also proposing separate but closely related standards for heavy-duty vehicles up to 14,000 lbs Gross Vehicle Weight Rating (GVWR).  These vehicles were not included in Tier 2 but were made subject to new standards in a final rule that covered the broad heavy-duty sector (66 FR 5002, January 18, 2001).  We have concluded that the proposed vehicle emissions standards, in conjunction with the reductions in fuel sulfur also proposed in this action, are feasible across the fleet in the proposed time frame.
In the discussions of the various elements of our proposed program for light- and heavy-duty vehicles throughout this preamble, we describe how the provisions would be consistent with the California Air Resources Board (CARB) LEV III program.  Auto manufacturers have stressed to us the importance of their being able to design and produce a single fleet of vehicles in all 50 states that would comply with requirements under the Tier 3 program and the LEV III program, as well as greenhouse gas/Corporate Average Fuel Economy (CAFE) requirements in the same timeframe.  Consistency among the federal and California programs means that special versions of vehicles with different emission control hardware and calibrations would not be necessary for different geographic areas.  This would allow manufacturers to avoid the additional costs of parallel design, development, calibration, and manufacturing.  Consistency among programs would also eliminate the need to supply aftermarket parts for repair of multiple versions of a vehicle.  To that end, we worked closely with CARB and with the vehicle manufacturers, both with individual companies and with their trade associations, to align the two programs in most respects.
We have also designed the proposed Tier 3 program to be implemented in the same timeframe as the federal and California GHG emissions and fuel economy standards for model years 2017-2025.  We expect that in response to these programs, manufacturers will be developing entirely new powertrains for most of their vehicles.  Because the Tier 3 standards would phase in over the same timeframe, manufacturers would be in a position to simultaneously respond to all of these requirements.
      Proposed Tailpipe Standards for Light-Duty Vehicle, Light-Duty Truck, and Medium-Duty Passenger Vehicle Tailpipe Emissions
We are proposing a comprehensive program that would include new fleet-average standards for the sum of NMOG and NOX tailpipe emissions (presented as NMOG+NOX) and for PM.  These proposed standards, when applied in conjunction with reduced gasoline sulfur content, would result in very significant improvements in vehicle emissions from the levels of the Tier 2 program.  For these pollutants, we are proposing standards as measured on test procedures that represent a range of vehicle operation, including the Federal Test Procedure (or FTP, simulating typical driving) and the Supplemental Federal Test Procedure (or SFTP, a composite test simulating higher temperatures, higher speeds, and quicker accelerations).  In addition to the standards, we are also proposing to extend the regulatory useful life period during which the standards apply and to make test fuel more representative of expected real-world fuel (see Section I.B.5 below).
As discussed in Section IV.A.6., the impact of gasoline sulfur poisoning on exhaust catalyst performance provides a compelling argument, particularly for larger vehicles and trucks, that these vehicle standards would be achievable only with a reduction of gasoline sulfur content from the current 30-ppm average down to a 10-ppm average.  Sulfur is a well-known catalyst poison.  The nature of sulfur's interactions with active catalytic materials is complex and varies with catalyst composition, exhaust gas composition and exhaust temperature.  Thus, even if a manufacturer were able to certify a new vehicle to the proposed new stringent standards, the manufacturer's ability to maintain the emission performance of that vehicle in-use is greatly jeopardized if the vehicle is being operated on gasoline sulfur levels greater than 10 ppm.  Vehicle manufacturers, both individually and through their trade associations, have emphasized that reduced gasoline sulfur would be required to meet the proposed standards.[,]  Due to the variation in actual vehicle operation, any amount of gasoline sulfur will deteriorate catalyst efficiency.  However, we believe that a 10-ppm average sulfur level is sufficiently low to enable compliance with these proposed Tier 3 vehicle standards, and as described below and in Section V, reducing sulfur levels further would cause sulfur control costs to quickly escalate.
The proposed FTP and SFTP NMOG+NOX standards would be fleet-average standards, meaning that a manufacturer would calculate the average emissions of the vehicles it sells in each model year and compare that average to the applicable standard for that model year.  The manufacturer would certify each of its vehicles to a per-vehicle "bin" standard (see Section IV.A.2) and sales-weight these values to calculate its fleet-average NMOG+NOX emissions for each model year.  The proposed fleet average standards for NMOG+NOX evaluated over the FTP are summarized in Table I-1.  The standards for light-duty vehicles would begin in MY 2017 at a level representing a 46 percent reduction from the current Tier 2 requirements.  (For vehicles over 6000 lbs GVWR, the standards would apply beginning in MY 2018).  As shown, these proposed fleet-average standards would decline during the first several years of the program, becoming increasingly stringent until ultimately reaching an 81 percent reduction when the transition is complete.  The proposed FTP NMOG+NOX program includes two separate sets of declining fleet-average standards, with LDVs and small light trucks (LDT1s) in one grouping and heavier light trucks (LDT2s, LDT3s, LDT4s) and MDPVs in a second grouping, that would converge at 30 milligram per mile (mg/mi) in MY 2025 and later.
Manufacturers could also earn credits for fleet average NMOG+NOX levels below the applicable standard in any model year.  Credits that were previously banked or obtained from other manufacturers could be used, or credits could be transferred to other manufacturers (see Section IV.A.7.a).  Unused credits would expire after 5 model years.  Manufacturers would also be allowed to carry deficits in their credit balance for up to 3 model years.
Table I-1 Proposed LDV, LDT, and MDPV Fleet Average NMOG+NOX FTP Standards (mg/mi)

                                  Model Year

                                    2017[a]
                                     2018
                                     2019
                                     2020
                                     2021
                                     2022
                                     2023
                                     2024
                                2025 and later
                                  LDV/LDT1[b]
                                      86
                                      79
                                      72
                                      65
                                      58
                                      51
                                      44
                                      37
                                      30
                              LDT2,3,4 and MDPV
                                      101
                                      92
                                      83
                                      74
                                      65
                                      56
                                      47
                                      38
                                      30
a For vehicles above 6000 lbs GVWR, the fleet average standards would apply beginning in MY 2018.
b These proposed standards would apply for a 150,000 mile useful life.  Manufacturers could choose to certify all of their LDVs and LDT1s to a useful life of 120,000 miles.  If any of these families are certified to the shorter useful life, a proportionally lower numerical fleet-average standard would apply, calculated by multiplying the respective 150,000 mile standard by 0.85 and rounding to the nearest mg. See Section IV.A.7.b.
Similarly, the proposed NMOG+NOX standards measured over the SFTP would be fleet-average standards, declining from MY 2017 until MY 2025, as shown in Table I-2.  In this case, the same standards would apply to both lighter and heavier vehicles.  In MY 2025, the SFTP NMOG+NOX standard would reach its final fleet average level of 50 mg/mi.
Table I-2 Proposed LDV, LDT, and MDPV Fleet Average NMOG+NOX SFTP Standards (mg/mi)

                                  Model Year

                                    2017[a]
                                     2018
                                     2019
                                     2020
                                     2021
                                     2022
                                     2023
                                     2024
                                2025 and later
                                  NMOG + NOX
                                      103
                                      97
                                      90
                                      83
                                      77
                                      70
                                      63
                                      57
                                      50
a For vehicles above 6000 lbs GVWR, the fleet average standards would apply beginning in MY 2018.
We are also proposing PM standards as part of this Tier 3 program, both on the FTP and US06 cycles (US06 is a component of the SFTP test).  Research has demonstrated that the level of PM from gasoline light-duty vehicles is more significant than previously thought.  Although many vehicles today are performing at or near the levels of the proposed standards, the data indicate that improvements, especially in high-load fuel control and in the durability of engine components, are possible.
Under typical driving, as simulated by the FTP, the PM emissions of most current-technology gasoline vehicles are fairly low at certification and in use, well below the Tier 2 PM standards.  At the same time we see considerable variation in PM emissions among vehicles of various makes, models, and designs.  As a result, we are proposing a new FTP PM standard that is set to ensure that all new vehicles perform at the level already being achieved by well-designed Tier 2 emission control technologies. The proposed PM standards would apply to each vehicle separately (i.e., not as a fleet average).  Also, in contrast to the declining NMOG+NOX standards, the proposed PM standard on the FTP for certification testing is 3 mg/mi for all vehicles and for all model years.  As for the NMOG+NOX standards, for vehicles over 6000 lbs GVWR, the FTP PM standard would apply beginning in MY 2018.  Manufacturers could phase in their vehicle models as a percent of U.S. sales through MY 2022.  Most vehicles are already performing at this stringent PM level, and the primary intent of the proposed standard is to bring all light-duty vehicles to the typical level of PM performance being demonstrated by the current light-duty fleet.
The proposed program also includes a separate in-use FTP PM standard of 6 mg/mi for the testing of in-use vehicles that would apply during the percent phase-in period only.  This in-use standard would address the uncertainties that accompany the introduction of new technologies, and then expire.  Table I-3 presents the FTP certification and in-use PM standards and the phase-in percentages.  The proposed standards represent a significant numerical reduction from the Tier 2 PM emission standards of 10 mg/mi for light-duty vehicles.
Table I-3  Phase-In for Proposed FTP PM Standards

                                    2017[a]
                                     2018
                                     2019
                                     2020
                                     2021
                                2022 and later
Phase-In
(percent of U.S. sales)
                                      20
                                      20
                                      40
                                      70
                                      100
                                      100
Certification Standard (mg/mi)
                                       3
                                       3
                                       3
                                       3
                                       3
                                       3
In-Use Standard (mg/mi)
                                       6
                                       6
                                       6
                                       6
                                       6
                                       3
[a] For vehicles above 6000 lbs GVWR, the proposed FTP PM standards would apply beginning in MY 2018.
Finally, the proposed Tier 3 program includes certification PM standards evaluated over the SFTP (specifically the US06 component of the SFTP procedure) at a level of 10 mg/mi for lighter vehicles and 20 mg/mi for heavier vehicles.  PM levels over the SFTP are typically higher than the PM emitted over the FTP due to the increased load on the vehicle.  Test data show that most current light-duty vehicles are already performing in the range of the proposed standard.  As in the case of the FTP PM standards, the intent of the proposed standard is to bring the emission performance of all vehicles to that already being demonstrated by many vehicles in the current light-duty fleet.
As with the FTP PM standard, we propose separate in-use US06 PM standards during the percent phase-in only, of 15 and 25 mg/mi for vehicles up to and above 6,000 lbs (lbs) GVWR, respectively.  The US06 PM standards would also phase in on the same schedule as the FTP PM standards, reaching 100 percent of each company's U.S. sales by MY 2022.
Proposed Heavy-Duty Vehicle Tailpipe Emissions Standards
As discussed in detail in Section IV.B, we are proposing Tier 3 exhaust emissions standards for complete heavy-duty vehicles (HDVs) between 8,501 and 14,000 lb GVWR.  Vehicles in this GVWR range are often referred to as Class 2b (8,501-10,000 lb) and Class 3 (10,001-14,000 lb) vehicles, and are typically full-size pickup trucks and work vans.  Most are built by companies with even larger light-duty truck markets, and as such they frequently share major design characteristics and potential emissions control technologies with their LDT counterparts.  However, in contrast to the largely gasoline-fueled LDT fleet, roughly half of the HD pickup and van fleet in the U.S. is diesel-fueled, which is a consideration in setting emissions standards, as diesel engine emissions and control strategies differ from those of gasoline engines.
The key elements of the proposed Tier 3 program for HDVs would parallel those proposed for passenger cars and LDTs, with adjustments in standards levels, emissions test requirements, and implementation schedules, appropriate to this sector.  These key elements include a combined NMOG+NOX declining fleet average standard, new stringent PM standards phasing in on a separate schedule, adoption of a 15 percent ethanol by volume (E15) certification test fuel for gasoline-fueled vehicles, extension of the regulatory useful life to 150,000 miles or 15 years (whichever occurs first), and a new requirement to meet standards over an SFTP that would address real-world driving modes not well-represented by the FTP cycle alone.
We are proposing the separate Class 2b and Class 3 fleet average NMOG+NOX standards shown in Table I-4.  The proposed standards would become more stringent in successive model years from 2018 to 2022, with voluntary standards made available in 2016 and 2017, all of which would be set at levels that match those of California's LEV III program for these classes of vehicles.  Each covered HDV sold by a manufacturer in each model year would contribute to this fleet average based on the mg/mi NMOG+NOX level of the emission level ("bin") declared for it by the manufacturer.  Manufacturers could also earn credits for fleet average NMOG+NOX levels below the standard in any model year.  Tier 3 credits that were previously banked, obtained from other manufacturers, or transferred across the Class 2b/Class 3 categories could be used to help demonstrate compliance.  Unused credits would expire after 5 model years.  Manufacturers would also be allowed to carry deficits in their credit balance for up to 3 model years.
Table I-4 Proposed HDV Fleet Average NMOG+NOX Standards (mg/mi)

                                   Voluntary
                               Required Program
                                  Model Year
                                     2016
                                     2017
                                     2018
                                     2019
                                     2020
                                     2021
                                2022 and later
                                   Class 2b
                                      333
                                      310
                                      278
                                      253
                                      228
                                      203
                                      178
                                    Class 3
                                      548
                                      508
                                      451
                                      400
                                      349
                                      298
                                      247

We are proposing PM standards of 8 mg/mi and 10 mg/mi for Class 2b and Class 3 HDVs, respectively, phasing in as an increasing percentage of a manufacturer's sales per year.  We are proposing the same phase-in schedule as proposed for the light-duty sector during model years 2018-2019-2020-2021: 20-40-70-100 percent, respectively, and a more flexible but equivalent alternative PM phase-in is also being proposed.  Tier 3 HDVs would also be subject to more stringent CO and formaldehyde exhaust emissions standards.
Finally, we are proposing first-ever SFTP standards for HDVs to ensure a robust overall control program that precludes high off-FTP cycle emissions by having vehicle designers consider them in their choice of compliance strategies.  As for light-duty vehicles, we are proposing that SFTP compliance be based on a weighted composite of measured emissions from testing over the FTP cycle, the SC03 cycle, and an aggressive driving cycle, with the latter tailored to various HDV sub-categories: the US06 cycle for most HDVs, the highway portion of the US06 cycle for low power-to-weight Class 2b HDVs, and the LA-92 (or "Unified") cycle for Class 3 HDVs.  The proposed SFTP standards are the same as those adopted for California LEV III vehicles, and would apply to NMOG+NOX, PM, and CO emissions.
Overall, we expect the Tier 3 program we are proposing for HDVs to result in substantial reductions in harmful emissions from this large fleet of work trucks and vans.  The final Tier 3 standards levels for NMOG+NOX and PM are on the order of 60 percent lower than the current stringent standards that took full effect in the 2009 model year.
Proposed Evaporative Emission Standards
Gasoline vapor emissions from vehicle fuel systems occur when a vehicle is in operation, when it is parked, and when it is being refueled.  These evaporative emissions, which occur on a daily basis from gasoline-powered vehicles, are primarily functions of temperature, fuel vapor pressure, and activity.  EPA first instituted evaporative emission standards in the early 1970s to address emissions when vehicles are parked after being driven.  These are commonly referred to as hot soak plus diurnal emissions.  Over the subsequent years the test procedures have been modified and improved and the standards have become more numerically stringent.  We have addressed emissions which arose from new fuel system designs by putting in place new requirements such as running loss emission standards and test procedure provisions to address permeation emissions.  Subsequently standards were put in place to control refueling emissions from all classes of gasoline-powered motor vehicles up to 10,000 lbs GVWR.  Even though evaporative and refueling emission control systems have been in place for most of these vehicles for many years, they still contribute about 30-40 percent of the summer on-highway mobile source hydrocarbon inventory.  These fuel vapor emissions are ozone and PM precursors, and also contain air toxics such as benzene.
To control evaporative emissions, EPA is proposing more stringent standards that would require covered vehicles to have essentially zero fuel vapor emissions in use. These include more stringent evaporative emissions standards, new test procedures, and a new fuel/evaporative system leak emission standard.  The program also includes refueling emission standards for a portion of heavy-duty gasoline vehicles (HDGVs) over 10,000 lbs GVWR.  EPA is proposing phase-in flexibilities as well as credit and allowance programs.  The proposed standards, harmonized with California's "zero evap" standards, are designed to essentially allow for a use of common technology in vehicle models sold throughout the U.S.  The level of the standard remains above zero to account for nonfuel background emissions from the vehicle hardware itself.
Requirements to meet the Tier 3 evaporative emission regulations would phase-in over a six model year period. We are proposing two options for the 2017 model year, but after that the sales percentage requirements are 60 percent for MYs 2018 and 2019, 80 percent for model years 2020 and 2021, and 100 percent for model years 2022 and later. In Table I-5 we present the proposed evaporative diurnal plus hot soak emission standards by vehicle class.  The standards are approximately a 50 percent reduction from the existing standards.  To enhance flexibility and reduce costs, EPA is proposing a program that would allow manufacturers to generate allowances through early certifications (basically before the 2017 model year) and to demonstrate compliance using averaging concepts.  Manufacturers may comply on average within each of the four vehicle categories, but not across these categories.  EPA is not proposing any changes to the existing light-duty running loss or refueling emission standards, with the exception of the certification test fuel requirement discussed in Section I.B.5 below.
Table I-5 Proposed Evaporative Emission Standards (g/test)
                                 Vehicle Class
                       Highest Diurnal + Hot Soak Level
                   (over both 2-day and 3-day diurnal tests)
                                   LDV, LDT1
                                     0.300
                                     LDT2
                                     0.400
                               LDT3, LDT4, MDPV
                                     0.500
                                     HDGVs
                                     0.600
EPA is proposing a new testing requirement referred to as the bleed emission test procedure to help ensure fuel vapor emissions are eliminated.  Under this proposal, manufacturers would be required to measure diurnal emissions over the 2-day diurnal test procedure from just the fuel tank and the evaporative emission canister and comply with a 0.020 gram per test (g/test) standard for all LDVs, LDTs, and MDPVs, without averaging.  The corresponding canister bleed test standard for HDGVs would be 0.030 g/test.  The proposed Tier 3 evaporative emission standards would be phased in over a period of six model years between MY 2017 and MY 2022, with the leak test phasing in beginning in 2018.
 Data from in-use evaporative emissions testing indicates that vapor leaks from vehicle fuel/evaporative systems are found in the fleet and that even very small leaks have the potential to make relatively significant contributions to the mobile source VOC inventory. To help address this issue, we are also proposing to add a new emission standard and test procedure to control vapor leaks from vehicle fuel and vapor control systems.  The standard would prohibit leaks with a cumulative equivalent diameter of 0.02 inches or greater.  We are proposing to add this simple and inexpensive test and emission standard to help ensure vehicles maintain zero fuel vapor emissions over their full useful life.  New LDV, LDT, MDPV, and HDGV equal to or less than 14.000 lbs GVWR meeting the proposed Tier 3 evaporative emission regulations would also be required to meet the leak emission standard beginning in the 2018 model year.  The requirement to meet the leak emission standard would phase-in on the same percentage of sales schedule as the proposed Tier 3 evaporative emission standard.  Manufacturers would comply with the leak emission standard during certification and in use.  EPA is not proposing that the leak emission standard apply to HDGVs above 14,000 lbs GVWR.
EPA is also proposing new refueling emission control requirements for all HDGVs equal to or less than 14,000 lbs GVWR (i.e., Class 2b/3 HDGVs), starting in the 2018 model year.  EPA is proposing to include these vehicles as part of the same basic implementation scheme used for LDVs and LDTs.  The current refueling emission control requirements apply to complete Class 2b HDGVs, and EPA is proposing to extend those requirements to Class 3 HDGVs as well, since the fuel and evaporative control systems on these vehicles are very similar to those on their slightly lighter-weight Class 2b counterparts.
Onboard Diagnostic Systems (OBD)
EPA and CARB both have OBD regulations applicable to the vehicle classes covered by the proposed Tier 3 emission standards.  In the past the requirements have been very similar, so most manufacturers have met CARB OBD requirements and, as permitted in our regulations, EPA has generally accepted compliance with CARB's OBD requirements as satisfying EPA's OBD requirements.  Over the past several years CARB has upgraded its requirements to help improve the effectiveness of OBD in ensuring good in-use exhaust and evaporative system emissions performance.  We have reviewed these provisions and agree with CARB that these revisions will help to improve in-use emissions performance, while at the same time harmonizing with the CARB program.  Toward that end, we are proposing to adopt and incorporate by reference the current CARB OBD regulations effective for the 2017 MY.  We are also proposing two specific additions to enhance the implementation of the leak emission standard.  EPA would retain the provision that certifying with CARB's program would permit manufacturers to seek a separate EPA certificate on that basis.
Emissions Test Fuel
In-use gasoline has changed considerably since EPA's test fuel specifications were first set and last revised.  Gasoline sulfur and benzene have been reduced and, perhaps most importantly, gasoline containing 10 percent ethanol by volume (E10) has replaced clear gasoline (E0) across the country.  This has had second-order effects on other gasoline properties.  In-use fuel is projected to continue to change with the implementation of the RFS2 program (e.g., the potential expansion of the number of retailers that offer gasoline containing 15 percent ethanol by volume (E15)) as well as today's proposed Tier 3 gasoline sulfur program.
As a result, we are proposing to update our federal emissions test fuel to better match today's in-use gasoline and also to be forward-looking with respect to future ethanol and sulfur content.  The new test fuel specifications would apply to new vehicle certification, assembly line, and in-use testing.  EPA is also proposing changes consistent with CARB's LEV III emissions test fuel specifications.  Key changes include:
Moving away from "Indolene" (E0) to an E15 test fuel ;
Lowering octane to match regular-grade gasoline (except for premium-required vehicles);
Adjusting distillation temperatures, aromatics, and olefins to better match today's in-use fuel and to be consistent with anticipated E15 composition; and
Lowering the existing sulfur specification and setting a benzene specification to be consistent with proposed Tier 3 gasoline sulfur requirements and recent MSAT2 gasoline benzene requirements.
The proposed E15 emissions test fuel specifications are detailed in Section IV.D.1 as well as §1065.710 of the proposed regulations.  For more information on how we arrived at the proposed fuel parameters and ASTM test methods, refer to Chapter 3 of the draft Regulatory Impact Analysis (RIA).
In addition to proposing a new E15 emissions test fuel, we are also proposing for the first time detailed specifications for the E85 emissions test fuel used for flexible fuel vehicle (FFV) certification, as discussed in Section IV.D.2.  This is intended to avoid uncertainty and confusion in the certification of FFVs designed to operate on ethanol levels up to 83 percent.  Furthermore, we are proposing to allow vehicle manufacturers to request approval for an alternative certification fuel such as a high-octane 30 percent ethanol by volume (E30) blend for vehicles they might design or optimize for use on such a fuel.  This could help manufacturers that wish to raise compression ratios to improve vehicle efficiency, as a step toward complying with the 2017 and later light-duty greenhouse gas and CAFE standards (2017 LD GHG).  This in turn could help provide a market incentive to increase ethanol use beyond E10 by overcoming the disincentive of lower fuel economy associated with increasing ethanol concentrations in fuel, and enhance the environmental performance of ethanol as a transportation fuel by using it to enable more fuel efficient engines.
In addition to seeking comment on all aspects of the proposed new emission test fuel requirements, we also seek comment on whether there are other aspects of today's proposed standards that, if modified, might provide an incentive for, or remove obstacles to, the development of highly efficient vehicles optimized for use on higher level ethanol blends.
Fuel Standards
 Under the Tier 3 fuel program, we are proposing that gasoline and any ethanol-gasoline blend contain no more than 10 ppm sulfur on an annual average basis by January 1, 2017.  Similar to the Tier 2 gasoline program, the proposed Tier 3 program would apply to gasoline in the U.S. and the U.S. territories of Puerto Rico and the Virgin Islands, excluding California.  The proposed program would result in gasoline that contains, on average, two-thirds less sulfur than it does today.  In addition, following discussions with numerous refiners and other segments of the fuel market (e.g., pipelines, terminals, marketers, ethanol industry representatives, transmix processors, additive manufacturers), we are proposing a Tier 3 fuel program that contains considerable flexibility to ease both initial and long-term implementation of the program.  We are proposing an averaging, banking, and trading (ABT) program that would allow refiners and importers to spread out their investments through an early credit program and rely on ongoing nationwide averaging to meet the 10-ppm sulfur standard.  We are also proposing a three-year delay for small refiners and "small volume refineries" processing less than or equal to 75,000 barrels of crude oil per day.  As a result of the early credit program, even considering the proposed ABT program and flexibilities offered to small refiners and small volume refineries, we anticipate considerable reductions in gasoline sulfur levels prior to 2017, with final refinery control to the 10-ppm average occurring by January 1, 2020.  For more on the proposed gasoline sulfur program flexibilities, refer to Section V.D.
Under today's Tier 3 gasoline sulfur program, we are proposing to either maintain the current 80-ppm refinery gate and 95-ppm downstream per-gallon caps or lower them to 50 and 65 ppm, respectively.  We also evaluated and are seeking comment on the potential of lowering the per-gallon caps to as low as 20 and 25 ppm.  There are advantages and disadvantages with each of the various sulfur cap options (explained in more detail in Section V.A.3), but under all scenarios, the stringency of the 10-ppm annual average standard would result in reduced gasoline sulfur levels nationwide.  A summary of the proposed Tier 3 sulfur standards is provided in Table I-6.
Table I-6 Proposed Tier 3 Gasoline Sulfur Standards
Proposed Tier 3 Gasoline Sulfur Standards
Cap Option 1
Cap Option 2

Limit
Effective
Limit
Effective
Refinery annual average standard
10 ppm
January 1, 2017[a]
10 ppm
January 1, 2017[a]
Refinery gate per-gallon cap
80 ppm
Already
50 ppm
January 1, 2020
Downstream per-gallon cap
95 ppm
Already
65 ppm
March 1, 2020
a Effective January 1, 2020 for eligible small refiners and small volume refineries.

We are proposing that manufacturers of gasoline additives that are used downstream of the refinery at less than 1 volume percent must limit the sulfur contribution to the finished gasoline from the use of their additive to less than 3 ppm when the additive is used at the maximum recommended treatment rate.
The proposed vehicle emissions standards are fuel neutral (i.e. they are applicable regardless of the type of fuel that the vehicle is designed to use).  The sulfur content of highway diesel fuel is already required to meet a 15ppm sulfur cap.  Thus, no further action is needed to enable diesel fuel vehicles to meet the proposed emissions standards.   There currently are no sulfur standards for the fuel used in compressed natural gas (CNG) and liquid propane gas (LPG) vehicles.  We request comment on whether it is necessary for EPA to establish sulfur standards for CNG and LPG, and whether a 15 ppm sulfur cap similar to that established for highway diesel fuel would be appropriate.  Comment is also requested on whether and how to address the sulfur contribution from odorants and other additives used in CNG and LPG.
As the number of flex-fuel vehicles (FFVs) in the in-use fleet increases, it is now becoming increasingly important that all fuels used in FFVs, not just gasoline, meet fuel quality standards.  A lack of clarity regarding the standards that apply to fuels used in FFVs could act to impede the further expansion of ethanol blended fuels with concentrations greater than 15 volume percent, which is important to satisfying the requirements of the RFS2 program.  For these reasons, we believe it is important that our gasoline quality standards for not only sulfur, but also benzene, RVP, detergency, and chemical composition (i.e., contains only carbon, hydrogen, oxygen, nitrogen, and sulfur) apply to any fuel used in an FFV.  At the same time, it is not necessarily clear how we should implement such standards within the context of our existing regulations as these fuels tend to be produced downstream of the petroleum refinery.  For this reason we are seeking comment on both the need to extend our gasoline standards to all gasoline-ethanol blends, as well as the appropriate regulatory mechanisms for doing so.
Regulatory Streamlining and Technical Amendments
We are proposing and requesting comment in this action on a number of items to help streamline the in-use fuels regulations at 40 CFR part 80.  The majority of items involve clarifying vague or inconsistent language, removal or updating of outdated provisions, and decrease in frequency and/or volume of reporting burden where data are no longer needed or are redundant with other EPA fuels programs.  In general, we believe that these changes would reduce burden on industry and allow us to achieve the standards and resulting environmental benefits as early as possible with no expected loss in environmental control.  In some cases, these regulatory streamlining items are non-substantive amendments that correct minor errors or inconsistencies in the regulations.
The regulatory streamlining items that we are proposing for the in-use fuels regulations are changes that we believe are straightforward and should be made quickly.  In addition, there are a number of items that we believe need further consideration and discussion on which we are seeking comment.
The proposal also includes a variety of technical amendments to certification-related requirements for engine and vehicle emission standards.  We are proposing to revise the fuel economy labeling requirements to correspond to the new Tier 3 standards.  We are also proposing to remove obsolete regulatory text and make several minor corrections and clarifications.
Please refer to Section VI for a complete discussion of technical amendments and regulatory streamlining provisions and issues.
What Would the Impacts of the Proposed Standards Be?
The proposed Tier 3 vehicle and fuel standards together would reduce dramatically emissions of NOX, VOC, PM2.5, and air toxics.  The gasoline sulfur standards, which would take effect in 2017, would provide large immediate reductions in emissions from existing gasoline vehicles and engines.  NOX emissions would be reduced by about 284,000 tons, or about 8 percent of emissions from on-highway vehicles, in 2017 alone.  The emission reductions would increase over time as newer vehicles become a larger percentage of the fleet.  In 2030, when 80 percent of the light-duty fleet (and 90 percent of the vehicle miles travelled) consists of Tier 3 vehicles, we expect the NOX and VOC emissions to be reduced by about 525,000 tons and 226,000 tons, respectively, or one quarter of emissions from on-highway vehicles compared to their 2030 levels without the Tier 3 program.  Emissions of CO would decrease by almost 6 million tons, or 30 percent of emissions from on-highway vehicles.  Emissions of many air toxics would also be reduced, including benzene, 1,3-butadiene, acetaldehyde, formaldehyde, acrolein and ethanol, with reductions ranging from 10 to nearly 40 percent of national emissions from on-highway vehicles. We expect these reductions to continue beyond 2030 as more of the fleet continues to turn over to Tier 3 vehicles; for example, by 2050, when nearly all of the fleet would have turned over to Tier 3 standards, we estimate the Tier 3 program would reduce on-highway emissions of NOX and VOC nearly 40 percent from the level of emissions projected without Tier 3 controls.
These reductions in emissions of NOX, VOC, PM2.5 and air toxics from the proposed Tier 3 standards are projected to lead to significant decreases in ambient concentrations of ozone, PM2.5 and air toxics by 2030, and would immediately reduce ozone in 2017 when the proposed sulfur controls take effect.  Specifically, the proposed Tier 3 standards would significantly decrease ozone concentrations across the country, with a population-weighted annual average decrease of 0.47 ppb in 2017 and 1.55 ppb in 2030 from projected population-weighted average levels of 71.3 ppb in 2017 and 66.7 ppb in 2030. The magnitude of reductions is significant enough to bring ozone levels in five counties from above the standard to below the standard, even without any additional controls.  Few other national strategies exist that would deliver the reductions needed for states to meet the current ozone standards. The proposed Tier 3 standards would decrease annual ambient PM2.5 concentrations across the country in nonattainment and highly-populated urban areas, with a population-weighted annual average decrease of 0.06 ug/m[3] by 2030 from projected population-weighted average levels of 9.3 ug/m3 in 2017 and 9.5 ug/m3 in 2030.  Decreases in ambient concentrations of air toxics are also projected with the proposed standards, including notable nationwide reductions in benzene concentrations.  Additional information on the emission and air quality impacts of the proposed Tier 3 program is presented in Sections III.B and C.
Exposure to ambient concentrations of ozone, PM2.5, and air toxics is linked to adverse human health impacts such as premature deaths as well as other important public health and environmental effects (see Section II.B).  The proposed Tier 3 standards would reduce these adverse impacts and yield significant benefits, including those we can monetize and those we are unable to quantify.  We estimate that by 2030, the annual emission reductions of the Tier 3 standards would annually prevent between 670 and 1,700 PM-related premature deaths, between 160 and 710 ozone-related premature deaths, 81,000 work days lost, and approximately 1.4 million minor restricted-activity days.  The estimated annual monetized health benefits of the proposed Tier 3 standards in 2030 (2010$) would be between $8.0 and $23 billion, assuming a 3-percent discount rate (or between $7.4 billion and $21 billion assuming a 7-percent discount rate).   The proposed fuel standards are projected to cost on average less than one cent per gallon of gasoline, and the proposed light-duty vehicle standards would have an average cost that increases in proportion to the increase in stringency from $50 per vehicle in 2017 to $134 per vehicle when the standards are fully phased in 2025.  The annual cost of the overall program in 2030 would be approximately $3.4 billion.  The 2030 benefits could outweigh the costs by a factor of 7.
The benefits in Table I-7 include all of the human health impacts we are able to quantify and monetize at this time.  However, the full complement of human health and welfare effects associated with PM, ozone and air toxics remain unquantified because of current limitations in methods and/or available data.  As a result, the health benefits quantified in this section are likely underestimates of the total benefits attributable to the proposed standards.  See Sections VII and VIII for detailed descriptions of the costs and benefits of this proposal.
Table I-7 Summary of Annual Benefts and Costs Associated with the Proposed Tier 3 Program (Billions, 2010$)[a]
Description
2030
Vehicle Program Costs
Fuels Program Costs
Total Estimated Costsb
$2.1
$1.3
$3.4
Total Estimated Health Benefitsc,d,e,f,g
     3 percent discount rate
     7 percent discount rate

$8.0 - $23
$7.4 - $21
Annual Net Benefits (Total Benefits  -  Total Costs)
     3 percent discount rate
     7 percent discount rate

$4.6 - $20
$4.0 - $18
Notes:a All estimates represent annual benefits and costs anticipated for the year 2030. Totals are rounded to two significant digits and may not sum due to rounding.
[b]  The calculation of annual costs does not require amortization of costs over time. Therefore, the estimates of annual cost do not include a discount rate or rate of return assumption (see Section VII of the preamble for more information on vehicle and fuel costs).  The program costs include the costs associated with the Tier 3 vehicle and fuel standards in all states except California.
c The benefits presented in this table have been adjusted to remove benefits of the Tier 3 program in California.
d Total includes ozone and PM2.5 benefits.  Range was developed by adding the estimate from the Bell et al., 2004 ozone premature mortality function to PM2.5-related premature mortality derived from the American Cancer Society cohort study (Pope et al., 2002) for the low estimate and ozone premature mortality derived from the Levy et al., 2005 study to PM2.5-related premature mortality derived from the Six-Cities (Laden et al., 2006) study for the high estimate.
[e] Annual benefits analysis results reflect the use of a 3 percent and 7 percent discount rate in the valuation of premature mortality and nonfatal myocardial infarctions, consistent with EPA and OMB guidelines for preparing economic analyses.
[f] Valuation of premature mortality based on long-term PM exposure assumes discounting over the SAB recommended 20-year segmented lag structure described in the Regulatory Impact Analysis for the 2006 PM National Ambient Air Quality Standards (September, 2006).
g Not all possible benefits are quantified and monetized in this analysis; the total monetized benefits presented here may therefore be underestimated.  Potential benefit categories that have not been quantified and monetized, due to current limitations in methods and/or data availability, are listed in Table VIII-2. For example, we have not quantified a number of known or suspected health and welfare effects linked with reductions in ozone and PM (e.g., reductions in heart rate variability, reduced material damage to structures and cultural monuments, and reduced eutrophication in coastal areas).  We are also unable to quantify health and welfare benefits associated with reductions in air toxics.
Why Is EPA Making This Proposal?
The Clean Air Act authorizes EPA to establish emissions standards for motor vehicles to address air pollution that may reasonably be anticipated to endanger public health or welfare. EPA also has authority to establish fuel controls to address such air pollution.  These statutory requirements are described in Section II.A.
Emissions from motor vehicles and their fuels contribute to ambient levels of ozone, PM, NO2, sulfur dioxide (SO2) and CO, which are all pollutants for which EPA has established health-based NAAQS. These pollutants are linked with respiratory and/or cardiovascular problems and other adverse health impacts leading to increased medication use, hospital admissions, emergency department visits, and premature mortality.  Over 158 million people currently live in areas designated nonattainment for one or more of the current NAAQS.
Motor vehicles also emit air toxics, and the majority of Americans continue to be exposed to ambient concentrations of air toxics at levels which have the potential to cause adverse health effects, including cancer, immune system damage, and neurological, reproductive, developmental, respiratory, and other health problems. A more detailed discussion of the health and environmental effects of these pollutants is included in Section II.B.
Cars and light trucks also continue to be a significant contributor to air pollution directly near roads, with gasoline vehicles accounting for more than 50 percent of near-road concentrations of some criteria and toxic pollutants.  More than 50 million people live, work, or go to school in close proximity to high-traffic roadways, and the average American spends more than one hour traveling each day, with nearly 90 percent of daily trips occurring by personal vehicle.[,][,]  Exposure to traffic-related pollutants has been linked with adverse health impacts such as respiratory problems (particularly in asthmatic children) and cardiovascular problems.
In the absence of additional controls such as Tier 3 standards, many areas will continue to have ambient ozone and PM2.5 concentrations exceeding the NAAQS in the future.  States and local areas are required to adopt control measures to attain the NAAQS and, once attained, to demonstrate that control measures are in place sufficient to maintain the NAAQS for ten years (and eight years later, a similar demonstration is required for another ten-year period).  The proposed Tier 3 standards would be a critical part of areas' strategies to attain and maintain the standards.  Maintaining the standards has been challenging in the past, particularly for areas where high population growth rates lead to significant annual increases in vehicle trips and vehicle miles traveled.  Our air quality modeling for this proposal, which is described in more detail in Section III.C,  projects that in 2017 a significant number of counties outside CA will be within 10 percent of the 2008 ozone NAAQS, in the absence of additional controls.  These counties in particular would benefit from the proposed Tier 3 standards as they work to ensure long-term maintenance of the NAAQS.
Section III provides more detail on how this proposal would reduce motor vehicle emissions and ambient levels of pollution.  The proposed rule would meaningfully reduce ozone concentrations as early as 2017 (the first year of the program), and even more significantly in 2030.  The reductions are of significant enough magnitude to bring ozone levels in some counties from above the standard to below the standard, even without any additional controls.  We also project that the Tier 3 standards would reduce ambient PM2.5 concentrations.
Without this proposal to reduce nationwide motor vehicle emissions, areas would have to adopt other measures to reduce emissions from other sources under their state or local authority.  Few other measures exist for providing multi-pollutant reductions of the same magnitude and cost-effectiveness as those expected from the proposed Tier 3 standards.    Furthermore, states outside California do not have the authority to lower the sulfur in gasoline, which is needed to immediately reduce emissions from the existing fleet and also enable new vehicles to meet the proposed Tier 3 emissions standards throughout their useful life.
The reductions in ambient ozone and PM2.5 that would result from the proposed Tier 3 standards would provide significant health benefits.  By 2030, the standards would annually prevent between 670 and 1,700 PM-related premature deaths, between 160 and 710 ozone-related premature deaths, 81,000 work days lost, and approximately 1.4 million minor restricted-activity days (see Section VIII for more details).  This proposal would also reduce air toxics; for example, we project that in 2030, the proposal would decrease ambient benzene concentrations by 10-25 percent in some urban areas.  Furthermore, the proposed Tier 3 standards would reduce traffic-associated pollution near major roads.    EPA is proposing Tier 3 vehicle and fuel standards as part of a comprehensive nationwide program for regulating all types of air pollution from motor vehicles.  EPA recently finalized standards to reduce GHG emissions from light-duty vehicles, starting with model year 2017.  The Tier 3 standards in this proposal, which address non-GHGs, would be implemented on the same timeframe, thus allowing manufacturers to optimize their vehicle redesigns over both sets of standards.  Furthermore, the Tier 3 vehicle and fuel standards are also closely aligned with California's LEV III program, in such a way that manufacturers could design a single vehicle for nationwide sales.  This reduces the cost of compliance for auto manufacturers.
This Tier 3 proposal responds to the President's request in his May 2010 memorandum for EPA to review the adequacy of its existing non-GHG standards for new motor vehicles and fuels, and to promulgate new standards, if necessary, as part of a comprehensive approach to regulating motor vehicles.  Based on our review, we have concluded that improved vehicle technology, combined with lower sulfur gasoline, make it feasible and cost-effective to reduce emissions well below the current Tier 2 levels.  These emission reductions are necessary to reduce air pollution that is (and projected to continue to be) at levels that endanger public health and welfare.
Basis for Action under the Clean Air Act
Clean Air Act Section 202
We are proposing to set motor vehicle emission standards under the authority of section 202 of the Clean Air Act.  Section 202(a) provides EPA with general authority to prescribe vehicle standards, subject to any specific limitations elsewhere 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 under section 202(a)(3), which requires that standards applicable to emissions of hydrocarbons, NOX, 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. In addition, section 202(k) provides EPA with authority to issue and revise regulations applicable to evaporative emissions of hydrocarbons from all gasoline-fueled motor vehicles during: (1) operation, and (2) over 2 or more days of nonuse; under ozone-prone summertime conditions. Regulations under section 202(k) shall take effect as expeditiously as possible and shall require the greatest degree of emission reduction achievable by means reasonably expected to be available for production during any model year to which the regulations apply, giving appropriate consideration to fuel volatility, and to cost, energy, and safety factors associated with the application of the appropriate technology.  Further, section 206 and in particular section 206(d) of the Clean Air Act authorizes EPA to establish methods and procedures for testing whether a motor vehicle or motor vehicle engine conforms with section 202 requirements.
Clean Air Act Section 211
We are proposing to adopt gasoline sulfur controls pursuant to our authority under section 211(c)(1) of the CAA. This section allows EPA to establish 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 impair to a significant degree the performance of any emissions control device or system which is either in general use or which the Administrator finds has been developed to a point where in a reasonable time it will be in general use were the fuel control to be adopted. We are proposing gasoline sulfur controls based on both of these criteria. Under the first criterion, we believe that gasoline with current levels of sulfur contributes to ambient levels of air pollution that endanger public health and welfare, as described in Section II.B.  Under the second criterion, we believe that gasoline sulfur impairs the emissions control systems of vehicles, as discussed in Section III.A.2.
Overview of Public Health Impacts of Motor Vehicles and Fuels
Motor vehicles emit pollutants that contribute to ambient levels of ozone, PM, NO2, SO2, CO, and air toxics.  Motor vehicles are significant contributors to emissions of VOC and NOX, which contribute to the formation of both ozone and PM2.5.  Approximately 159 million people currently live in counties designated nonattainment for one or more of the NAAQS, and this figure does not include the people living in areas with a risk of exceeding the NAAQS in the future.  The majority of Americans continue to be exposed to ambient concentrations of air toxics at levels which have the potential to cause adverse health effects.  In addition, populations who live, work, or attend school near major roads experience elevated exposure concentrations to a wide range of air pollutants.
EPA has already adopted many emission control programs that are expected to reduce ambient pollution levels.  As a result of these programs, the number of areas that continue to violate the ozone and PM2.5 NAAQS or have high levels of air toxics is expected to continue to decrease.  However, the baseline air quality modeling completed for this proposed rule predicts that without additional controls there will continue to be a need for reductions in ozone, PM2.5 and air toxics concentrations in the future.  Section III.C of this preamble presents the air quality modeling results for this proposed rule.
Ozone
Background
Ground-level ozone pollution is typically formed through reactions involving VOC and NOX in the lower atmosphere in the presence of sunlight.  These pollutants, often referred to as ozone precursors, are emitted by many types of pollution sources, such as highway and nonroad motor vehicles and engines, power plants, chemical plants, refineries, makers of consumer and commercial products, industrial facilities, and smaller area sources.
The science of ozone formation, transport, and accumulation is complex.   Ground-level ozone is produced and destroyed in a cyclical set of chemical reactions, many of which are sensitive to temperature and sunlight.  When ambient temperatures and sunlight levels remain high for several days and the air is relatively stagnant, ozone and its precursors can build up and result in more ozone than typically occurs on a single high-temperature day.  Ozone and its precursors can be transported hundreds of miles downwind from precursor emissions, resulting in elevated ozone levels even in areas with low local VOC or NOX emissions.
Health Effects of Ozone
The health and welfare effects of ozone are well documented and are assessed in EPA's 2006 Air Quality Criteria Document and 2007 Staff Paper.[,]  People who are more susceptible to effects associated with exposure to ozone can include children, the elderly, and individuals with respiratory disease such as asthma.  Those with greater exposures to ozone, for instance due to time spent outdoors (e.g., children and outdoor workers), are of particular concern.  Ozone can irritate the respiratory system, causing coughing, throat irritation, and breathing discomfort.  Ozone can reduce lung function and cause pulmonary inflammation in healthy individuals.  Ozone can also aggravate asthma, leading to more asthma attacks that require medical attention and/or the use of additional medication.  Thus, ambient ozone may cause both healthy and asthmatic individuals to limit their outdoor activities.  In addition, there is suggestive evidence of a contribution of ozone to cardiovascular-related morbidity and highly suggestive evidence that short-term ozone exposure directly or indirectly contributes to non-accidental and cardiopulmonary-related mortality, but additional research is needed to clarify the underlying mechanisms causing these effects.  In a report on the estimation of ozone-related premature mortality published by the National Research Council (NRC), a panel of experts and reviewers concluded that short-term exposure to ambient ozone is likely to contribute to premature deaths and that ozone-related mortality should be included in estimates of the health benefits of reducing ozone exposure.  Animal toxicological evidence indicates that with repeated exposure, ozone can inflame and damage the lining of the lungs, which may lead to permanent changes in lung tissue and irreversible reductions in lung function.  The respiratory effects observed in controlled human exposure studies and animal studies are coherent with the evidence from epidemiologic studies supporting a causal relationship between acute ambient ozone exposures and increased respiratory-related emergency room visits and hospitalizations in the warm season.  In addition, there is suggestive evidence of a contribution of ozone to cardiovascular-related morbidity and non-accidental and cardiopulmonary mortality.
Current and Projected Ozone Levels
Concentrations that exceed the level of the ozone NAAQS occur in many parts of the country, including many major population centers.  In addition, our modeling without the proposed Tier 3 controls projects that in the future we will continue to have many areas that will have ambient ozone concentrations above the level of the NAAQS (see Section III.C.1).  States will need to meet the standard in the 2015-2032 timeframe.  The emission reductions and significant ambient ozone improvements from this proposed rule, which would take effect starting in 2017, would be helpful to states as they work to attain and maintain the ozone NAAQS.
The primary and secondary NAAQS for ozone are 8-hour standards with a level of 0.075 ppm.  The most recent revision to the ozone standards was in 2008; the previous 8-hour ozone standards, set in 1997, had a level of 0.08 ppm.  In 2004, the U.S. EPA designated nonattainment areas for the 1997 8-hour ozone NAAQS.[,]  As of December 14, 2012, there were 41 ozone nonattainment areas for the 1997 ozone NAAQS composed of 221 full or partial counties with a total population of over 118 million.  Nonattainment designations for the 2008 ozone standard were finalized on April 30, 2012 and May 31, 2012.  These designations include 46 areas, composed of 227 full or partial counties, with a population of over 123 million.  As of December 14, 2012, over 138 million people are living in ozone nonattainment areas.
States with ozone nonattainment areas are required to take action to bring those areas into attainment.  The attainment date assigned to an ozone nonattainment area is based on the area's classification.  Most ozone nonattainment areas are required to attain the 1997 8-hour ozone NAAQS in the 2007 to 2013 time frame and then to maintain it thereafter.  The attainment dates for areas designated nonattainment for the 2008 8-hour ozone NAAQS are in the 2015 to 2032 timeframe, depending on the severity of the problem in each area.  In addition, EPA is working to complete the current review of the ozone NAAQS by mid-2014.  If EPA revises the ozone standards in 2014 pursuant to that review, the attainment dates associated with areas designated nonattainment for that NAAQS would likely be in the 2019 to 2036 timeframe, depending on the severity of the problem in each area.
EPA has already adopted many emission control programs that are expected to reduce ambient ozone levels.  As a result of these and other federal, state and local programs, 8-hour ozone levels are expected to improve in the future.  However, even with the implementation of all current state and federal regulations, there are projected to be counties violating the ozone NAAQS well into the future.  Thus additional federal control programs, such as Tier 3, can assist areas with attainment dates in 2017 and beyond in attaining the NAAQS as expeditiously as practicable and may relieve areas with already stringent local regulations from some of the burden associated with adopting additional local controls.
Particulate Matter
Background
Particulate matter is a highly complex mixture of solid particles and liquid droplets distributed among numerous atmospheric gases which interact with solid and liquid phases. Particles range in size from those smaller than 1 nanometer (10[-9] meter) to over 100 micrometer (um, or 10[-6] meter) in diameter (for reference, a typical strand of human hair is 70 um in diameter and a grain of salt is about 100 um). Atmospheric particles can be grouped into several classes according to their aerodynamic and physical sizes, including ultrafine particles (<0.1 um), accumulation mode or `fine' particles (< 1 to 3 um), and coarse particles (>1 to 3 um). For regulatory purposes, fine particles are measured as PM2.5 and inhalable or thoracic coarse particles are measured as PM10-2.5, corresponding to their size (diameter) range in micrometers and referring to total particle mass under 2.5 and between 2.5 and 10 micrometers, respectively. The EPA currently has standards that measure PM2.5 and PM10.
Particles span many sizes and shapes and consist of hundreds of different chemicals. Particles are emitted directly from sources and are also formed through atmospheric chemical reactions; the former are often referred to as "primary" particles, and the latter as "secondary" particles. Particle pollution also varies by time of year and location and is affected by several weather-related factors, such as temperature, clouds, humidity, and wind. A further layer of complexity comes from particles' ability to shift between solid/liquid and gaseous phases, which is influenced by concentration and meteorology, especially temperature.
Fine particles are produced primarily by combustion processes and by transformations of gaseous emissions (e.g., sulfur oxides (SOX), nitrogen oxides (NOX), and volatile organic compounds (VOC)) in the atmosphere.  The chemical and physical properties of PM2.5 may vary greatly with time, region, meteorology, and source category.  Thus, PM2.5 may include a complex mixture of different components including sulfates, nitrates, organic compounds, elemental carbon and metal compounds.  These particles can remain in the atmosphere for days to weeks and travel hundreds to thousands of kilometers.
Health Effects of PM
Scientific studies show ambient PM is associated with a series of adverse health effects.  These health effects are discussed in detail in EPA's Integrated Science Assessment (ISA) for Particulate Matter.  Further discussion of health effects associated with PM can also be found in the draft RIA.  The ISA summarizes health effects evidence associated with both short-term and long-term exposures to PM2.5, PM10-2.5, and ultrafine particles.
The ISA concludes that health effects associated with short-term exposures (hours to days) to ambient PM2.5 include mortality, cardiovascular effects, such as altered vasomotor function and myocardial ischemia, and hospital admissions and emergency department visits for ischemic heart disease and congestive heart failure, and respiratory effects, such as exacerbation of asthma symptoms in children and hospital admissions and emergency department visits for chronic obstructive pulmonary disease and respiratory infections.  The ISA notes that long-term exposure (months to years) to PM2.5 is associated with the development/progression of cardiovascular disease, premature mortality, and respiratory effects, including reduced lung function growth in children, increased respiratory symptoms, and asthma development.  The ISA concludes that the currently available scientific evidence from epidemiologic, controlled human exposure, and toxicological studies supports a causal association between short- and long-term exposures to PM2.5 and cardiovascular effects and premature mortality.  Furthermore, the ISA concludes that the collective evidence supports likely causal associations between short- and long-term PM2.5 exposures and respiratory effects.  The ISA also concludes that the scientific evidence is suggestive of a causal association for reproductive and developmental effects including respiratory-related infant mortality, and cancer, mutagenicity, and genotoxicity and long-term exposure to PM2.5.
For PM10-2.5, the ISA concludes that the current evidence is suggestive of a causal relationship between short-term exposures and premature mortality, cardiovascular effects, and respiratory effects.  Data are inadequate to draw conclusions regarding the health effects associated with long-term exposure to PM10-2.5.
For ultrafine particles, the ISA concludes that there is suggestive evidence of a causal relationship between short-term exposures and cardiovascular effects, such as changes in heart rhythm and blood vessel function.  It also concludes that there is suggestive evidence of association between short-term exposure to ultrafine particles and respiratory effects. Data are inadequate to draw conclusions regarding the health effects associated with long-term exposure to ultrafine particles.
Current and Projected PM2.5 Levels
There are many areas of the country that are currently in nonattainment for the annual and 24-hour PM2.5 NAAQS.  Our modeling without the proposed Tier 3 controls projects that in the future we will continue to have many areas that will have ambient PM2.5 concentrations above the level of the NAAQS (see Section III.C.2).  States will need to meet the 24-hour standard in the 2015-2019 timeframe and the annual standard in the 2021-2025 timeframe.  The emission reductions and improvements in ambient PM2.5 from this proposed rule, which would take effect starting in 2017, would be helpful to states as they work to attain and maintain the PM2.5 NAAQS.
There are two NAAQS for PM2.5: an annual standard (12 micrograms per cubic meter (μg/m3)) and a 24-hour standard (35 μg/m3).  The most recent revisions to these standards were in 1997, 2006 and in December 2012.  The December 2012 rule revised the level of the annual PM2.5 standard from 15 μg/m3 to 12 μg/m3.
In 2005 EPA designated nonattainment areas for the 1997 PM2.5 NAAQS.  As of December 14, 2012, over 91 million people lived in the 35 areas that are designated as nonattainment for the 1997 PM2.5 NAAQS.  These PM2.5 nonattainment areas are comprised of 191 full or partial counties.  On October 8, 2009, the EPA issued final nonattainment area designations for the 2006 24-hour PM2.5 NAAQS.  These designations include 32 areas composed of 121 full or partial counties with a population of over 70 million.  In total, there are 50 PM2.5 nonattainment areas with a population of over 105 million people.
States with PM2.5 nonattainment areas will be required to take action to bring those areas into attainment in the future.  Most 1997 PM2.5 nonattainment areas are required to attain the 1997 PM2.5 NAAQS in the 2010 to 2015 time frame and then required to maintain the 1997 PM2.5 NAAQS thereafter.  The 2006 24-hour PM2.5 nonattainment areas will be required to attain the 2006 24-hour PM2.5 NAAQS in the 2014 to 2019 time frame and then be required to maintain the 2006 24-hour PM2.5 NAAQS thereafter.  The 2012 PM2.5 nonattainment areas will likely be required to attain the 2012 PM2.5 NAAQS in the 2020 to 2025 time frame, depending on the severity of an area's fine particle pollution problems and the availability of pollution controls.  The standards proposed here begin taking effect in 2017.
EPA has already adopted many mobile source emission control programs that are expected to reduce ambient PM levels.  As a result of these and other federal, state and local programs, the number of areas that fail to meet the PM2.5 NAAQS in the future is expected to decrease.  However, even with the implementation of all current state and federal regulations, there are projected to be counties violating the PM2.5 NAAQS well into the future.  Thus additional federal control programs, such as Tier 3, can assist areas with attainment dates in 2017 and beyond in attaining the NAAQS as expeditiously as practicable and may relieve areas with already stringent local regulations from some of the burden associated with adopting additional local controls.
Nitrogen Oxides and Sulfur Oxides
Background
Nitrogen dioxide (NO2) is a member of the NOX family of gases.  Most NO2 is formed in the air through the oxidation of nitric oxide (NO) emitted when fuel is burned at a high temperature.  Sulfur dioxide (SO2), a member of the sulfur oxide (SOX) family of gases, is formed from burning fuels containing sulfur (e.g., coal or oil derived), extracting gasoline from oil, or extracting metals from ore.
SO2 and NO2 and their gas phase oxidation products can dissolve in water droplets and further oxidize to form sulfuric and nitric acid which react with ammonia to form sulfates and nitrates, both of which are important components of ambient PM.  The health effects of ambient PM are discussed in Section II.B.2.b of this preamble.  NOX and VOC are the two major precursors of ozone.  The health effects of ozone are covered in Section II.B.2.1.b.
Health Effects of NO2
Information on the health effects of NO2 can be found in the EPA Integrated Science Assessment (ISA) for Nitrogen Oxides.  The EPA has concluded that the findings of epidemiologic, controlled human exposure, and animal toxicological studies provide evidence that is sufficient to infer a likely causal relationship between respiratory effects and short-term NO2 exposure.  The ISA concludes that the strongest evidence for such a relationship comes from epidemiologic studies of respiratory effects including symptoms, emergency department visits, and hospital admissions.  Based on both short- and long-term studies, the ISA concludes that associations of NO2 with respiratory health effects are stronger among a number of groups; these include individuals with preexisting pulmonary conditions (e.g., asthma or COPD), children and older adults.  The ISA also draws two broad conclusions regarding airway responsiveness following NO2 exposure.  First, the ISA concludes that NO2 exposure may enhance the sensitivity to allergen-induced decrements in lung function and increase the allergen-induced airway inflammatory response following 30-minute exposures of asthmatics to NO2 concentrations as low as 0.26 ppm.  Second, exposure to NO2 has been found to enhance the inherent responsiveness of the airway to subsequent nonspecific challenges in controlled human exposure studies of asthmatic subjects.  Small but significant increases in non-specific airway hyperresponsiveness were reported following 1-hour exposures of asthmatics to 0.1 ppm NO2.  Enhanced airway responsiveness could have important clinical implications for asthmatics since transient increases in airway responsiveness following NO2 exposure have the potential to increase symptoms and worsen asthma control.  Together, the epidemiologic and experimental data sets form a plausible, consistent, and coherent description of a relationship between NO2 exposures and an array of adverse health effects that range from the onset of respiratory symptoms to hospital admission.
Although the weight of evidence supporting a causal relationship is somewhat less certain than that associated with respiratory morbidity, NO2 has also been linked to other health endpoints.  These include all-cause (nonaccidental) mortality, hospital admissions or emergency department visits for cardiovascular disease, and decrements in lung function growth associated with chronic exposure.
Health Effects of SO2
Information on the health effects of SO2 can be found in the EPA Integrated Science Assessment for Sulfur Oxides.  SO2 has long been known to cause adverse respiratory health effects, particularly among individuals with asthma.  Other potentially sensitive groups include children and the elderly. During periods of elevated ventilation, asthmatics may experience symptomatic bronchoconstriction within minutes of exposure.  Following an extensive evaluation of health evidence from epidemiologic and laboratory studies, the EPA has concluded that there is a causal relationship between respiratory health effects and short-term exposure to SO2.  Separately, based on an evaluation of the epidemiologic evidence of associations between short-term exposure to SO2 and mortality, the EPA has concluded that the overall evidence is suggestive of a causal relationship between short-term exposure to SO2 and mortality.
Current Levels of NO2
Between 2003 and 2005, national mean concentrations of NO2 were about 15 parts per billion (ppb) for averaging periods ranging from a day to a year.  There are two NAAQS for NO2: an annual standard (53 ppb) and a 1-hour standard (100 ppb).  The primary NAAQS for NO2 was revised in January 2010.  EPA completed area designations in January 2012 and there are currently no nonattainment areas.  The designations were based on the existing community-wide monitoring network.  Once the expanded network of NO2 monitors is fully deployed and three years of air quality data have been collected, EPA intends to redesignate areas, as appropriate, based on the air quality data from the new monitoring network.[,]
Carbon Monoxide
Carbon monoxide (CO) is a colorless, odorless gas emitted from combustion processes.  Nationally and, particularly in urban areas, the majority of CO emissions to ambient air come from mobile sources.
Health Effects of Carbon Monoxide
Information on the health effects of CO can be found in the EPA Integrated Science Assessment (ISA) for Carbon Monoxide.  The ISA concludes that ambient concentrations of CO are associated with a number of adverse health effects.  This section provides a summary of the health effects associated with exposure to ambient concentrations of CO.
Human clinical studies of subjects with coronary artery disease show a decrease in the time to onset of exercise-induced angina (chest pain) and electrocardiogram changes following CO exposure.  In addition, epidemiologic studies show associations between short-term CO exposure and cardiovascular morbidity, particularly increased emergency room visits and hospital admissions for coronary heart disease (including ischemic heart disease, myocardial infarction, and angina).  Some epidemiologic evidence is also available for increased hospital admissions and emergency room visits for congestive heart failure and cardiovascular disease as a whole.  The ISA concludes that a causal relationship is likely to exist between short-term exposures to CO and cardiovascular morbidity.  It also concludes that available data are inadequate to conclude that a causal relationship exists between long-term exposures to CO and cardiovascular morbidity.
Animal studies show various neurological effects with in-utero CO exposure.  Controlled human exposure studies report inconsistent neural and behavioral effects following low-level CO exposures.  The ISA concludes the evidence is suggestive of a causal relationship with both short- and long-term exposure to CO and central nervous system effects.
A number of epidemiologic and animal toxicological studies cited in the ISA have evaluated associations between CO exposure and birth outcomes such as preterm birth or cardiac birth defects.  The epidemiologic studies provide limited evidence of a CO-induced effect on preterm births and birth defects, with weak evidence for a decrease in birth weight.  Animal toxicological studies have found associations between perinatal CO exposure and decrements in birth weight, as well as other developmental outcomes.  The ISA concludes these studies are suggestive of a causal relationship between long-term exposures to CO and developmental effects and birth outcomes.
Epidemiologic studies provide evidence of effects on respiratory morbidity such as changes in pulmonary function, respiratory symptoms, and hospital admissions associated with ambient CO concentrations.  A limited number of epidemiologic studies considered copollutants such as ozone, SO2, and PM in two-pollutant models and found that CO risk estimates were generally robust, although this limited evidence makes it difficult to disentangle effects attributed to CO itself from those of the larger complex air pollution mixture.  Controlled human exposure studies have not extensively evaluated the effect of CO on respiratory morbidity.  Animal studies at levels of 50-100 ppm CO show preliminary evidence of altered pulmonary vascular remodeling and oxidative injury.  The ISA concludes that the evidence is suggestive of a causal relationship between short-term CO exposure and respiratory morbidity, and inadequate to conclude that a causal relationship exists between long-term exposure and respiratory morbidity.
Finally, the ISA concludes that the epidemiologic evidence is suggestive of a causal relationship between short-term exposures to CO and mortality.  Epidemiologic studies provide evidence of an association between short-term exposure to CO and mortality, but limited evidence is available to evaluate cause-specific mortality outcomes associated with CO exposure.  In addition, the attenuation of CO risk estimates which was often observed in copollutant models contributes to the uncertainty as to whether CO is acting alone or as an indicator for other combustion-related pollutants. The ISA also concludes that there is not likely to be a causal relationship between relevant long-term exposures to CO and mortality.
Mobile Source Air Toxics
Light-duty vehicle emissions contribute to ambient levels of air toxics known or suspected as human or animal carcinogens, or that have noncancer health effects.  The population experiences an elevated risk of cancer and other noncancer health effects from exposure to the class of pollutants known collectively as "air toxics."  These compounds include, but are not limited to, benzene, 1,3-butadiene, formaldehyde, acetaldehyde, acrolein, polycyclic organic matter, and naphthalene.  These compounds were identified as national or regional risk drivers or contributors in the 2005 National-scale Air Toxics Assessment and have significant inventory contributions from mobile sources.
Health Effects of Air Toxics
Benzene
The EPA's IRIS database lists benzene as a known human carcinogen (causing leukemia) by all routes of exposure, and concludes that exposure is associated with additional health effects, including genetic changes in both humans and animals and increased proliferation of bone marrow cells in mice.,,  EPA states in its IRIS database that data indicate a causal relationship between benzene exposure and acute lymphocytic leukemia and suggest a relationship between benzene exposure and chronic non-lymphocytic leukemia and chronic lymphocytic leukemia.  EPA's IRIS documentation for benzene also lists a range of 2.2 x 10-6 to 7.8 x 10-6 as the unit risk estimate (URE) for benzene.,  The International Agency for Research on Carcinogens (IARC) has determined that benzene is a human carcinogen and the U.S. Department of Health and Human Services (DHHS) has characterized benzene as a known human carcinogen.,
A number of adverse noncancer health effects including blood disorders, such as preleukemia and aplastic anemia, have also been associated with long-term exposure to benzene.,  The most sensitive noncancer effect observed in humans, based on current data, is the depression of the absolute lymphocyte count in blood.[,]  EPA's inhalation reference concentration (RfC) for benzene is 30 ug/m[3].  The RfC is based on suppressed absolute lymphocyte counts seen in humans under occupational exposure conditions.  In addition, recent work, including studies sponsored by the Health Effects Institute (HEI), provides evidence that biochemical responses are occurring at lower levels of benzene exposure than previously known.,,,  EPA's IRIS program has not yet evaluated these new data.  EPA does not currently have an acute reference concentration for benzene.  The Agency for Toxic Substances and Disease Registry (ATSDR) Minimal Risk Level (MRL) for acute exposure to benzene is 29 ug/m[3] for 1-14 days exposure.[,]
Formaldehyde
In 1991, EPA concluded that formaldehyde is a carcinogen based on nasal tumors in animal bioassays. An Inhalation Unit Risk for cancer and a Reference Dose for oral noncancer effects were developed by the Agency and posted on the Integrated Risk Information System (IRIS) database.  Since that time, the National Toxicology Program (NTP) and International Agency for Research on Cancer (IARC) have concluded that formaldehyde is a known human carcinogen.[,][,]
The conclusions by IARC and NTP reflect the results of epidemiologic research published since 1991 in combination with previous animal, human and mechanistic evidence.  Research conducted by the National Cancer Institute reported an increased risk of nasopharyngeal cancer and specific lymphohematopoietic malignancies among workers exposed to formaldehyde.,,  A National Institute of Occupational Safety and Health study of garment workers also reported increased risk of death due to leukemia among workers exposed to formaldehyde.  Extended follow-up of a cohort of British chemical workers did not report evidence of an increase in nasopharyngeal or lymphohematopoietic cancers, but a continuing statistically significant excess in lung cancers was reported.  Finally, a study of embalmers reported formaldehyde exposures to be associated with an increased risk of myeloid leukemia but not brain cancer.
	Health effects of formaldehyde in addition to cancer were reviewed by the Agency for Toxics Substances and Disease Registry in 1999 and supplemented in 2010, and by the World Health Organization.  These organizations reviewed the literature concerning effects on the eyes and respiratory system, the primary point of contact for inhaled formaldehyde, including sensory irritation of eyes and respiratory tract, pulmonary function, nasal histopathology, and immune system effects.  In addition, research on reproductive and developmental effects and neurological effects were discussed.
	EPA released a draft Toxicological Review of Formaldehyde  -  Inhalation Assessment through the IRIS program for peer review by the National Research Council (NRC) and public comment in June 2010.  The draft assessment reviewed more recent research from animal and human studies on cancer and other health effects.  The NRC released their review report in April 2011.  The EPA is currently revising the draft assessment in response to this review.
Acetaldehyde
Acetaldehyde is classified in EPA's IRIS database as a probable human carcinogen, based on nasal tumors in rats, and is considered toxic by the inhalation, oral, and intravenous routes.  The URE in IRIS for acetaldehyde is 2.2 x 10[-6] per ug/m[3].  Acetaldehyde is reasonably anticipated to be a human carcinogen by the U.S. DHHS in the 12[th] Report on Carcinogens and is classified as possibly carcinogenic to humans (Group 2B) by the IARC.[,]  EPA is currently conducting a reassessment of cancer risk from inhalation exposure to acetaldehyde.
The primary noncancer effects of exposure to acetaldehyde vapors include irritation of the eyes, skin, and respiratory tract.  In short-term (4 week) rat studies, degeneration of olfactory epithelium was observed at various concentration levels of acetaldehyde exposure.[,]  Data from these studies were used by EPA to develop an inhalation reference concentration of 9 ug/m[3].  Some asthmatics have been shown to be a sensitive subpopulation to decrements in functional expiratory volume (FEV1 test) and bronchoconstriction upon acetaldehyde inhalation.  The agency is currently conducting a reassessment of the health hazards from inhalation exposure to acetaldehyde.
Acrolein
EPA most recently evaluated the toxicological and health effects literature related to acrolein in 2003 and concluded that the human carcinogenic potential of acrolein could not be determined because the available data were inadequate.  No information was available on the carcinogenic effects of acrolein in humans and the animal data provided inadequate evidence of carcinogenicity.  The IARC determined in 1995 that acrolein was not classifiable as to its carcinogenicity in humans.
Lesions to the lungs and upper respiratory tract of rats, rabbits, and hamsters have been observed after subchronic exposure to acrolein.  The Agency has developed an RfC for acrolein of 0.02 ug/m3 and an RfD of 0.5 ug/kg-day.  EPA is considering updating the acrolein assessment with data that have become available since the 2003 assessment was completed.
Acrolein is extremely acrid and irritating to humans when inhaled, with acute exposure resulting in upper respiratory tract irritation, mucus hypersecretion and congestion.  The intense irritancy of this carbonyl has been demonstrated during controlled tests in human subjects, who suffer intolerable eye and nasal mucosal sensory reactions within minutes of exposure.  These data and additional studies regarding acute effects of human exposure to acrolein are summarized in EPA's 2003 IRIS Human Health Assessment for acrolein.  Studies in humans indicate that levels as low as 0.09 ppm (0.21 mg/m[3]) for five minutes may elicit subjective complaints of eye irritation with increasing concentrations leading to more extensive eye, nose and respiratory symptoms.  Acute exposures in animal studies report bronchial hyper-responsiveness.  Based on animal data (more pronounced respiratory irritancy in mice with allergic airway disease in comparison to non-diseased mice) and demonstration of similar effects in humans (e.g., reduction in respiratory rate), individuals with compromised respiratory function (e.g., emphysema, asthma) are expected to be at increased risk of developing adverse responses to strong respiratory irritants such as acrolein.  EPA does not currently have an acute reference concentration for acrolein.  The available health effect reference values for acrolein have been summarized by EPA and include an ATSDR MRL for acute exposure to acrolein of 7 ug/m[3] for 1-14 days exposure; and Reference Exposure Level (REL) values from the California Office of Environmental Health Hazard Assessment (OEHHA) for one-hour and 8-hour exposures of 2.5 ug/m[3] and 0.7 ug/m[3], respectively.
1,3-Butadiene
EPA has characterized 1,3-butadiene as carcinogenic to humans by inhalation.,  The IARC has determined that 1,3-butadiene is a human carcinogen and the U.S. DHHS has characterized 1,3-butadiene as a known human carcinogen.,,  There are numerous studies consistently demonstrating that 1,3-butadiene is metabolized into genotoxic metabolites by experimental animals and humans.  The specific mechanisms of 1,3-butadiene-induced carcinogenesis are unknown; however, the scientific evidence strongly suggests that the carcinogenic effects are mediated by genotoxic metabolites.  Animal data suggest that females may be more sensitive than males for cancer effects associated with 1,3-butadiene exposure; there are insufficient data in humans from which to draw conclusions about sensitive subpopulations.  The URE for 1,3-butadiene is 3 x 10[-5] per ug/m[3].  1,3-butadiene also causes a variety of reproductive and developmental effects in mice; no human data on these effects are available.  The most sensitive effect was ovarian atrophy observed in a lifetime bioassay of female mice.  Based on this critical effect and the benchmark concentration methodology, an RfC for chronic health effects was calculated at 0.9 ppb (approximately 2 ug/m[3]).
Ethanol
EPA is planning to develop an assessment of the health effects of exposure to ethanol, a compound which is not currently listed on EPA's IRIS database.  Extensive health effects data are available for ingestion of ethanol, while data on inhalation exposure effects are sparse.  In developing the assessment, EPA is evaluating pharmacokinetic models as a means of extrapolating across species (animal to human) and across exposure routes (oral to inhalation) to better characterize the health hazards and dose-response relationships for low levels of ethanol exposure in the environment.

Polycyclic Organic Matter
The term polycyclic organic matter (POM) defines a broad class of compounds that includes the polycyclic aromatic hydrocarbon compounds (PAHs).  One of these compounds, naphthalene, is discussed separately below.  POM compounds are formed primarily from combustion and are present in the atmosphere in gas and particulate form.  Cancer is the major concern from exposure to POM.  Epidemiologic studies have reported an increase in lung cancer in humans exposed to diesel exhaust, coke oven emissions, roofing tar emissions, and cigarette smoke; all of these mixtures contain POM compounds.[,]  Animal studies have reported respiratory tract tumors from inhalation exposure to benzo[a]pyrene and alimentary tract and liver tumors from oral exposure to benzo[a]pyrene.  In 1997 EPA classified seven PAHs (benzo[a]pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, dibenz[a,h]anthracene, and indeno[1,2,3-cd]pyrene) as Group B2, probable human carcinogens.  Since that time, studies have found that maternal exposures to PAHs in a population of pregnant women were associated with several adverse birth outcomes, including low birth weight and reduced length at birth, as well as impaired cognitive development in preschool children (3 years of age).[,] These and similar studies are being evaluated as a part of the ongoing IRIS assessment of health effects associated with exposure to benzo[a]pyrene.
PAN
PAN (peroxy acetyl nitrate) has not been evaluated by EPA's IRIS program.  Information regarding the potential carcinogenicity of PAN is limited.  As noted in the EPA air quality criteria document for ozone and related photochemical oxidants, cytogenetic studies indicate that PAN is not a potent mutagen, clastogen (a compound that can cause breaks in chromosomes), or DNA-damaging agent in mammalian cells either in vivo or in vitro. Some studies suggest that PAN may be a weak bacterial mutagen at concentrations much higher than exist in present urban atmospheres.
Effects of ground-level smog causing intense eye irritation have been attributed to photochemical oxidants, including PAN.  Animal toxicological information on the inhalation effects of the non-ozone oxidants has been limited to a few studies on PAN.  Acute exposure to levels of PAN can cause changes in lung morphology, behavioral modifications, weight loss, and susceptibility to pulmonary infections.  Human exposure studies indicate minor pulmonary function effects at high PAN concentrations, but large inter-individual variability precludes definitive conclusions.
Naphthalene
Naphthalene is found in small quantities in gasoline and diesel fuels.  Naphthalene emissions have been measured in larger quantities in both gasoline and diesel exhaust compared with evaporative emissions from mobile sources, indicating it is primarily a product of combustion.  Acute (short-term) exposure of humans to naphthalene by inhalation, ingestion, or dermal contact is associated with hemolytic anemia and damage to the liver and the nervous system.  Chronic (long term) exposure of workers and rodents to naphthalene has been reported to cause cataracts and retinal damage.  EPA released an external review draft of a reassessment of the inhalation carcinogenicity of naphthalene based on a number of recent animal carcinogenicity studies.  The draft reassessment completed external peer review.  Based on external peer review comments received, a revised draft assessment that considers all routes of exposure, as well as cancer and noncancer effects, is under development.  The external review draft does not represent official agency opinion and was released solely for the purposes of external peer review and public comment.  The National Toxicology Program listed naphthalene as "reasonably anticipated to be a human carcinogen" in 2004 on the basis of bioassays reporting clear evidence of carcinogenicity in rats and some evidence of carcinogenicity in mice.  California EPA has released a new risk assessment for naphthalene, and the IARC has reevaluated naphthalene and re-classified it as Group 2B: possibly carcinogenic to humans.
Naphthalene also causes a number of chronic non-cancer effects in animals, including abnormal cell changes and growth in respiratory and nasal tissues.  The current EPA IRIS assessment includes noncancer data on hyperplasia and metaplasia in nasal tissue that form the basis of the inhalation RfC of 3 ug/m[3].  The ATSDR MRL for acute exposure to naphthalene is 0.6 mg/kg/day.
Other Air Toxics
In addition to the compounds described above, other compounds in gaseous hydrocarbon and PM emissions from light-duty vehicles would be affected by this proposal.  Mobile source air toxic compounds that would potentially be impacted include ethylbenzene, propionaldehyde, toluene, and xylene.  Information regarding the health effects of these compounds can be found in EPA's IRIS database.
Current Levels of Air Toxics