[Federal Register: May 18, 2007 (Volume 72, Number 96)]
[Proposed Rules]
[Page 28097-28393]
[DOCID:fr18my07-17]

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Part II

Environmental Protection Agency

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40 CFR Parts 60, 63, et al.

Control of Emissions from Nonroad Spark-Ignition Engines and Equipment;
Proposed Rule

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 60, 63, 85, 89, 90, 91, 1027, 1045, 1048, 1051, 1054,
1060, 1065, 1068, and 1074

[EPA-HQ-OAR-2004-0008; FRL-8303-7]
RIN 2060-AM34

Control of Emissions from Nonroad Spark-Ignition Engines and
Equipment

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: We are proposing emission standards for new nonroad spark-
ignition engines that will substantially reduce emissions from these
engines. The proposed exhaust emission standards would apply in 2009
for new marine spark-ignition engines, including first-time EPA
standards for sterndrive and inboard engines. The proposed exhaust
emission standards would apply starting in 2011 and 2012 for different
sizes of new land-based, spark-ignition engines at or below 19
kilowatts (kW). These small engines are used primarily in lawn and
garden applications. We are also proposing evaporative emission
standards for vessels and equipment using any of these engines. In
addition, we are making other minor amendments to our regulations. We
estimate that by 2030, the proposed standards would result in
significant annual reductions of pollutant emissions from regulated
engine and equipment sources nationwide, including 631,000 tons of
volatile organic hydrocarbon emissions, 98,200 tons of NOX
emissions, and 6,300 tons of direct particulate matter
(PM2.5) emissions. These reductions correspond to
significant reductions in the formation of ground-level ozone. We also
expect to see annual reductions of 2,690,000 tons of carbon monoxide
emissions, with the greatest reductions in areas where there have been
problems with individual exposures. The requirements in this proposal
would result in substantial benefits to public health and welfare and
the environment. We estimate that by 2030, on an annual basis, these
emission reductions would prevent 450 PM-related premature deaths,
approximately 500 hospitalizations, 52,000 work days lost, and other
quantifiable benefits every year. The total estimated annual benefits
of this rule in 2030 are approximately $3.4 billion. Estimated costs in
2030 are many times less at approximately $240 million.

DATES: Comments: Comments must be received on or before August 3, 2007.
Under the Paperwork Reduction Act, comments on the information
collection provisions must be received by OMB on or before June 18,
2007.

ADDRESSES: Submit your comments, identified by Docket No. EPA-HQ-OAR-
2004-0008, by one of the following methods:
    http://www.regulations.gov: Follow the on-line instructions for submitting

comments.
    E-mail<EMAIL_ADDRESS>    Fax:<PHONE_NUMBER>.
    Mail: Environmental Protection Agency, Air Docket, Mail-code 6102T,
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/DC), EPA West, Room 3334,
1301 Constitution Ave., NW., Washington, DC, Attention Docket No. EPA-
HQ-OAR-2004-0008. Such deliveries are accepted only during the Docket's
normal hours of operation, special arrangements should be made for
deliveries of boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2004-0008. EPA's policy is that all comments received will be included
in the public docket without change and may be made available online at
http://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 http://www.regulations.gov or e-mail.

The http://www.regulations.gov Web site 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 http://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
instructions on submitting comments, go to Unit XIII of the
SUPPLEMENTARY INFORMATION section of this document.
    Docket: All documents in the docket are listed in the
http://www.regulations.gov index. Although listed in the index, some

information is not publicly available, such as 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 http://www.regulations.gov or in hard copy at the ``Control of Emissions

from Nonroad Spark-Ignition Engines, Vessels and Equipment'' Docket,
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
``Control of Emissions from Nonroad Spark-Ignition Engines, Vessels,
and Equipment'' Docket is<PHONE_NUMBER>.
    Hearing: A hearing will be held at 9:30 a.m. on Tuesday, June 5,
2007 at the Sheraton Reston Hotel. The hotel is located at 11810
Sunrise Valley Drive in Reston, Virginia; their phone number is 703-
620-9000. For more information on these hearings or to request to
speak, see Section XIII.

FOR FURTHER INFORMATION CONTACT: Carol Connell, Environmental
Protection Agency, Office of Transportation and Air Quality, Assessment
and Standards Division, 2000 Traverwood Drive, Ann Arbor, Michigan
48105; telephone number:<PHONE_NUMBER>; fax number:<PHONE_NUMBER>; e-mail
address<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:

Does This Action Apply to Me?

    This action will affect you if you produce or import new spark-
ignition engines intended for use in marine vessels or in new vessels
using such engines. This action will also affect you if you produce or
import new spark-ignition engines below 19 kilowatts used in nonroad
equipment, including agricultural and construction equipment, or
produce or import such nonroad vehicles.

    The following table gives some examples of entities that may have
to follow the regulations; however, since these are only examples, you
should carefully examine the proposed regulations. Note that we are
proposing minor changes in the regulations that apply to a wide range
of products that may not be reflected in the following table (see
Section XI). If you have questions, call the person listed in the FOR
FURTHER INFORMATION CONTACT section of this preamble:

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                                                                               Examples of potentially regulated
                Category                    NAICS codes a      SIC codes b                 entities
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Industry                                            333618              3519  Manufacturers of new engines.
Industry                                            333111              3523  Manufacturers of farm machinery
                                                                               and equipment.
Industry                                            333112              3524  Manufacturers of lawn and garden
                                                                               tractors (home).
Industry                                            336612        3731, 3732  Manufacturers of marine vessels.
Industry                                    811112, 811198        7533, 7549  Commercial importers of vehicles
                                                                               and vehicle components.
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a North American Industry Classification System (NAICS).
b Standard Industrial Classification (SIC) system code.

What Should I Consider as I Prepare My Comments for EPA?

    Submitting CBI. Do not submit this information to EPA through
http://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.
    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.

Table of Contents

I. Introduction
    A. Overview
    B. Why Is EPA Taking This Action?
    C. What Regulations Currently Apply to Nonroad Engines or
Vehicles?
    D. Putting This Proposal into Perspective
    E. What Requirements Are We Proposing?
    F. How Is This Document Organized?
II. Public Health and Welfare Effects
    A. Ozone
    B. Particulate Matter
    C. Air Toxics
    D. Carbon Monoxide
III. Sterndrive and Inboard Marine Engines
    A. Overview
    B. Engines Covered by This Rule
    C. Proposed Exhaust Emission Standards
    D. Test Procedures for Certification
    E. Additional Certification and Compliance Provisions
    F. Small-Business Provisions
    G. Technological Feasibility
IV. Outboard and Personal Watercraft Engines
    A. Overview
    B. Engines Covered by This Rule
    C. Proposed Exhaust Emission Standards
    D. Changes to Existing OB/PWC Test Procedures
    E. Additional Certification and Compliance Provisions
    F. Other Adjustments to Regulatory Provisions
    G. Small-Business Provisions
    H. Technological Feasibility
V. Small SI Engines
    A. Overview
    B. Engines Covered by This Rule
    C. Proposed Requirements
    D. Testing Provisions
    E. Certification and Compliance Provisions for Small SI Engines
and Equipment
    F. Small Business Provisions
    G. Technological Feasibility
VI. Evaporative Emissions
    A. Overview
    B. Fuel Systems Covered by This Rule
    C. Proposed Evaporative Emission Standards
    D. Emission Credit Programs
    E. Testing Requirements
    F. Certification and Compliance Provisions
    G. Small-Business Provisions
    H. Technological Feasibility
VII. General Concepts Related to Certification and Other
Requirements
    A. Scope of Application
    B. Emission Standards and Testing
    C. Demonstrating Compliance
    D. Other Concepts
VIII. General Nonroad Compliance Provisions
    A. Miscellaneous Provisions (Part 1068, subpart A)
    B. Prohibited Acts and Related Requirements (Part 1068, subpart
B)
    C. Exemptions (Part 1068, subpart C)
    D. Imports (Part 1068, subpart D)
    E. Selective Enforcement Audit (Part 1068, subpart E)
    F. Defect Reporting and Recall (Part 1068, subpart F)
    G. Hearings (Part 1068, subpart G)
IX. General Test Procedures
    A. Overview
    B. Special Provisions for Nonroad Spark-Ignition Engines
X. Energy, Noise, and Safety
    A. Safety
    B. Noise
    C. Energy
XI. Proposals Affecting Other Engine and Vehicle Categories
    A. State Preemption
    B. Certification Fees
    C. Amendments to General Compliance Provisions in 40 CFR Part
1068
    D. Amendments Related to Large SI Engines (40 CFR Part 1048)
    E. Amendments Related to Recreational Vehicles (40 CFR Part
1051)
    F. Amendments Related to Heavy-Duty Highway Engines (40 CFR Part
85)
    G. Amendments Related to Stationary Spark-Ignition Engines (40
CFR Part 60)
XII. Projected Impacts
    A. Emissions from Small Nonroad and Marine Spark-Ignition
Engines
    B. Estimated Costs
    C. Cost per Ton
    D. Air Quality Impact
    E. Benefits
    F. Economic Impact Analysis
XIII. Public Participation
XIV. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    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 and Safety Risks
    H. Executive Order 12898: Federal Actions to Address
Environmental Justice in Minority Populations and Low-Income
Populations.
    I. Executive Order 13211: Actions that Significantly Affect
Energy Supply, Distribution, or Use
    J. National Technology Transfer Advancement Act

I. Introduction

A. Overview

    Air pollution is a serious threat to the health and well-being of
millions of Americans and imposes a large burden on the U.S. economy.
Ground-level ozone is linked to potentially serious health problems,
especially respiratory effects, and environmental degradation. Carbon
monoxide emissions are also related to health problems. Over the past
quarter century, state and federal agencies have established emission
control programs that make significant progress in addressing these
concerns.
    This proposal includes steps that would reduce the mobile-source
contribution to air pollution in the United States. In particular, we
are proposing standards that would require manufacturers to
substantially reduce emissions from marine spark-ignition engines and
from nonroad spark-ignition engines below 19 kW that are generally used
in lawn and garden applications.\1\ We refer to these as Marine SI
engines and Small SI engines, respectively. The proposed standards are
a continuation of the process of establishing standards for nonroad
engines and vehicles as required by Clean Air Act section 213. All the
nonroad engines subject to this proposal are already regulated under
existing emission standards, except sterndrive and inboard marine
engines, which will be subject to EPA emission standards for the first
time.
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    \1\ Otto-cycle engines (referred to here as spark-ignition or SI
engines) typically operate on gasoline, liquefied petroleum gas, or
natural gas. Diesel-cycle engines, referred to simply as ``diesel
engines'' in this document, may also be referred to as compression-
ignition or CI engines. These engines typically operate on diesel
fuel, but other fuels may also be used.
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    Nationwide, emissions from Marine SI engines and Small SI engines
contribute significantly to mobile source air pollution. By 2020
without the proposed requirements these engines will account for about
27 percent (1,352,000 tons) of mobile source volatile organic
hydrocarbon compounds (VOC) emissions, 31 percent (16,374,000 tons) of
mobile source carbon monoxide (CO) emissions, 4 percent (202,000 tons)
of mobile source oxides of nitrogen (NOX) emissions, and 16
percent (39,000 tons) of mobile source particulate matter
(PM2.5) emissions. The proposed standards will reduce
exposure to these emissions and help avoid a range of adverse health
effects associated with ambient ozone, CO, and PM levels. In addition,
the proposed standards will help reduce acute exposure to CO, air
toxics, and PM for persons who operate or who work with or are
otherwise active in close proximity to these engines. They will also
help address other environmental problems associated with Marine SI
engines and Small SI engines, such as visibility impairment in our
national parks and other wilderness areas. These effects are described
in more detail in subsequent sections of this Preamble.

B. Why Is EPA Taking This Action?

    Clean Air Act section 213(a)(1) directs us to study emissions from
nonroad engines and vehicles to determine, among other things, whether
these emissions ``cause, or significantly contribute to, air pollution
which may reasonably be anticipated to endanger public health or
welfare.'' Section 213(a)(2) further requires us to determine whether
emissions of CO, VOC, and NOX from all nonroad engines
significantly contribute to ozone or CO concentrations in more than one
nonattainment area. If we determine that emissions from all nonroad
engines do contribute significantly to these nonattainment areas,
section 213(a)(3) then requires us to establish emission standards for
classes or categories of new nonroad engines and vehicles that cause or
contribute to such pollution. We may also set emission standards under
section 213(a)(4) regulating any other emissions from nonroad engines
that we find contribute significantly to air pollution which may
reasonably be anticipated to endanger public health or welfare.
    Specific statutory direction to propose standards for nonroad
spark-ignition engines comes from section 428(b) of the 2004
Consolidated Appropriations Act, which requires EPA to propose
regulations under the Clean Air Act ``that shall contain standards to
reduce emissions from new nonroad spark-ignition engines smaller than
50 horsepower.'' \2\ As highlighted above and more fully described in
Section II, these engines emit pollutants that contribute to ground-
level ozone and ambient CO levels. Human exposure to ozone and CO can
cause serious respiratory and cardiovascular problems. Additionally,
these emissions contribute to other serious environmental degradation.
This proposal implements Congress' mandate by proposing new
requirements for particular nonroad engines and equipment that are
regulated as part of EPA's overall nonroad emission control program.
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    \2\ Pub. L. 108-199, Div G, Title IV, Sec.  428(b), 118 Stat.
418 (January 23, 2004).
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    We are proposing this rule under the procedural authority of
section 307(d) of the Clean Air Act.

C. What Regulations Currently Apply to Nonroad Engines or Vehicles?

    EPA has been setting emission standards for nonroad engines and/or
vehicles since Congress amended the Clean Air Act in 1990 and included
section 213. These amendments have led to a series of rulemakings to
reduce the air pollution from this widely varying set of products. In
these rulemakings, we divided the broad group of nonroad engines and
vehicles into several different categories for setting application-
specific requirements. Each category involves many unique
characteristics related to the participating manufacturers, technology,
operating characteristics, sales volumes, and market dynamics.
Requirements for each category therefore take on many unique features
regarding the stringency of standards, the underlying expectations
regarding emission control technologies, the nature and extent of
testing, and the myriad details that comprise the implementation of a
compliance program.
    At the same time, the requirements and other regulatory provisions
for each engine category share many characteristics. Each rulemaking
under section 213 sets technology-based standards consistent with the
Clean Air Act and requires annual certification based on measured
emission levels from test engines or vehicles. As a result, the broader
context of EPA's nonroad emission control programs demonstrates both
strong similarities between this rulemaking and the requirements
adopted for other types of engines or vehicles and distinct differences
as we take into account the unique nature of these engines and the
companies that produce them.
    We completed the Nonroad Engine and Vehicle Emission Study to
satisfy Clean Air Act section 213(a)(1) in

November 1991.\3\ On June 17, 1994, we made an affirmative
determination under section 213(a)(2) that nonroad emissions are
significant contributors to ozone or CO in more than one nonattainment
area (56 FR 31306). Since then we have undertaken several rulemakings
to set emission standards for the various categories of nonroad
engines. Table I-1 highlights the different engine or vehicle
categories we have established and the corresponding cites for emission
standards and other regulatory requirements. Table I-2 summarizes the
series of EPA rulemakings that have set new or revised emission
standards for any of these nonroad engines or vehicles. These actions
are described in the following sections, with additional discussion to
explain why we are not proposing more stringent standards for certain
types of nonroad spark-ignition engines below 50 horsepower.
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    \3\ This study is available on EPA's web site at http://www.epa.gov/otaq/equip-ld
.

                        Table I-1.--Nonroad Engine Categories for EPA Emission Standards
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                                             CFR cite for regulationse
            Engine categories                  establishing emission          Cross reference to Table I.C-2
                                                     standards
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1. Locomotives engines...................  40 CFR Part 92..............  d
2. Marine diesel engines.................  40 CFR Part 94..............  g, i, j
3. Other nonroad diesel engines..........  40 CFR Parts 89 and 1039....  a, e, k
4. Marine SI engines \4\.................  40 CFR Part 91..............  c
5. Recreational vehicles.................  40 CFR Part 1051............  i
6. Small SI engines \5\..................  40 CFR Part 90..............  b, f, h
7. Large SI engines \4\..................  40 CFR Part 1048............  i
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                                Table I-2.--EPA's Rulemakings for Nonroad Engines
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 Nonroad engines (categories and sub-
              categories)                         Final rulemaking                           Date
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a. Land-based diesel engines >=37 kW    56 FR 31306........................  June 17, 1994.
 Tier 1.
b. Small SI engines--Phase 1..........  60 FR 34581........................  July 3, 1995.
c. Marine SI engines--outboard and      61 FR 52088........................  October 4, 1996.
 personal watercraft.
d. Locomotives........................  63 FR 18978........................  April 16, 1998.
e. Land-based diesel engines--Tier 1    63 FR 56968........................  October 23, 1998.
 and Tier 2 for engines < 37 kW--Tier 2
 and Tier 3 for engines >=37 kW.
f. Small SI engines (Nonhandheld)--     64 FR 15208........................  March 30, 1999.
 Phase 2.
g. Commercial marine diesel < 30 liters  64 FR 73300........................  December 29, 1999.
 per cylinder.
h. Small SI engines (Handheld)--Phase   65 FR 24268........................  April 25, 2000.
 2.
i. Recreational vehicles, Industrial    67 FR 68242........................  November 8, 2002.
 spark-ignition engines >19 kW, and
 Recreational marine diesel.
j. Marine diesel engines >=2.5 liters/  68 FR 9746.........................  February 28, 2003.
 cylinder.
k. Land-based diesel engines--Tier 4..  69 FR 38958........................  June 29, 2004.
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(1) Small SI Engines
    We have previously adopted emission standards for nonroad spark-
ignition engines at or below 19 kW in two phases. The first phase of
these standards introduced certification and an initial level of
emission standards for both handheld and nonhandheld engines. On March
30, 1999 we adopted a second phase of standards for nonhandheld
engines, including both Class I and Class II engines, which are almost
fully phased-in today (64 FR 15208).\6\ These standards involved
emission reductions based on improving engine calibrations to reduce
exhaust emissions and added a requirement that emission standards must
be met over the engines' entire useful life as defined in the
regulations. We believe catalyst technology has now developed to the
point that it can be applied to all nonhandheld Small SI engines to
reduce exhaust emissions. Various emission control technologies are
similarly available to address the different types of fuel evaporative
emissions we have identified.
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    \4\ The term ``Marine SI,'' used throughout this document,
refers to all spark-ignition engines used to propel marine vessels.
This includes outboard engines, personal watercraft engines, and
sterndrive/inboard engines. See Section III for additional
information.
    \5\ The terms ``Small SI'' and ``Large SI'' are used throughout
this document. All nonroad spark-ignition engines not covered by our
programs for Marine SI engines or recreational vehicles are either
Small SI engines or Large SI engines. Small SI engines include those
engines with maximum power at or below 19 kW, and Large SI engines
include engines with maximum power above 19 kW.
    \6\ Handheld engines generally include those engines for which
the operator holds or supports the equipment during operation;
nonhandheld engines are Small SI engines that are not handled
engines (see Sec.  1054.801). Class I refers to nonhandheld engines
with displacement below 225 cc; Class II refers to larger
nonhandheld engines.
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    For handheld engines, we adopted Phase 2 exhaust emission standards
in April 25, 2000 (65 FR 24268). These standards were based on the
application of catalyst technology, with the expectation that
manufacturers would have to make considerable investments to modify
their engine designs and production processes. A technology review we
completed in 2003 indicated that manufacturers were making progress
toward compliance, but that additional implementation flexibility was
needed if manufacturers were to fully comply with the regulations by
2010. This finding and a change in the rule were published in the
Federal Register on January 12, 2004 (69FR1824). At this point, we have
no information to suggest that manufacturers can uniformly apply new
technology or make design improvements to reduce exhaust emissions
below the Phase 2 levels. We therefore believe the Phase 2 standards
continue to represent the greatest degree of emission reduction
achievable for these engines.\7\ However, we believe it is appropriate
to apply evaporative emission standards to the handheld engines similar
to those we are

proposing for the nonhandheld engines. Manufacturers can control
evaporative emissions in a way that has little or no impact on exhaust
emissions.
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    \7\ Note that we refer to the handheld exhaust emission
standards in 40 CFR part 1054 as Phase 3 standards. This is intended
to maintain consistent terminology with the comparable standards in
California rather than indicating an increase in stringency.
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(2) Marine SI Engines
    On October 4, 1996 we adopted emission standards for spark-ignition
outboard and personal watercraft engines that have recently been fully
phased in (61 FR 52088). We decided not to finalize emission standards
for sterndrive or inboard marine engines at that time. Uncontrolled
emission levels from sterndrive and inboard marine engines were already
significantly lower than the outboard and personal watercraft engines.
We did, however, leave open the possibility of revisiting the need for
emission standards for sterndrive and inboard engines in the future.
See Section III for further discussion of the scope and background of
past and current rulemakings for these engines.
    We believe existing technology can be applied to all Marine SI
engines to reduce emissions of harmful pollutants, including both
exhaust and evaporative emissions. Manufacturers of outboard and
personal watercraft engines can continue the trend of producing four-
stroke engines and advanced-technology two-stroke engines to further
reduce emissions. For sterndrive/inboard engines, manufacturers can add
technologies, such as fuel injection and aftertreatment, that can
safely and substantially improve the engines' emission control
capabilities.
    (3) Large SI Engines
    We adopted emission standards for Large SI engines on November 8,
2002 (67 FR 68242). This includes Tier 1 standards for 2004 through
2006 model years and Tier 2 standards starting with 2007 model year
engines. Manufacturers are today facing a considerable challenge to
comply with the Tier 2 standards, which are already substantially more
stringent than any of the standards proposed or contemplated for the
other engine categories in this proposal. The Tier 2 standards also
include evaporative emission standards, new transient test procedures,
and additional exhaust emission standards to address off-cycle
emissions, and diagnostic requirements. Stringent standards for this
category of engines, and in particular, engines between 25 and 50
horsepower (19 to 37 kW), have been completed in the recent past, and
are currently being implemented. Because of that we do not have
information on the actual Tier 2 technology that manufacturers will use
and do not have information at this time on possible advances in
technology beyond Tier 2. We therefore believe the evidence provided in
the recently promulgated rulemaking continues to represent the best
available information regarding the appropriate level of standards for
these engines under section 213 at this time. California Air Resources
Board (ARB) has adopted an additional level of emission control for
Large SI engines starting with the 2010 model year. However, as
described in Section I.D.1, their new standards would not increase
overall stringency beyond that reflected in the federal standards. As a
result, we believe it would be inappropriate to pursue more stringent
emission standards for these engines in this rulemaking.
    Note that the Large SI standards apply to nonroad spark-ignition
engines above 19 kW. However, we adopted a special provision for engine
families where production engines have total displacement at or below
1000 cc and maximum power at or below 30 kW, allowing these engine
families to instead certify to the applicable standards for Small SI
engines.
(4) Recreational Vehicles
    We adopted exhaust and evaporative emission standards for
recreational vehicles in our November 8, 2002 final rule (67FR68242).
These standards apply to all-terrain vehicles, off-highway motorcycles,
and snowmobiles.\8\ These exhaust emission standards will be fully
phased in starting with the 2007 model year. The evaporative emission
standards apply starting with the 2008 model year.
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    \8\ Note that we treat certain high-speed off-road utility
vehicles as all-terrain vehicles (see 40 CFR part 1051).
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    Recreational vehicles will soon be subject to permeation
requirements that are very similar to the requirements proposed in this
rulemaking. We have also learned more about controlling running losses
and diffusion emissions that may eventually lead us to propose
comparable standards for recreational vehicles. We expect to revisit
these questions in the context of a rulemaking to modify the duty cycle
for all-terrain vehicles, as described below. Considering these new
requirements for recreational vehicles in this later rulemaking would
give us additional time to collect information to better understand the
feasibility, costs, and benefits of applying these requirements to
recreational vehicles.
    The following sections describe the state of technology and
regulatory requirements for the different types of recreational
vehicles.
(a) All-Terrain Vehicles
    The regulations for all-terrain vehicles (ATV) specify testing
based on a chassis-based transient procedure. However, on an interim
basis, we are permitting manufacturers the option to use a steady-state
engine-based procedure to allow manufacturers an opportunity to develop
the field operating data needed to determine if ATV operation is
dominantly steady state or transient in nature and to develop an
appropriate emission test cycle from that information. The emissions
test procedure and duty cycle are critical to getting the degree of
emission control expected from these engines. We are continuing to work
toward a resolution of this test cycle development initiative in a
separate action. The anticipated changes to the test cycle raise new
questions we will need to work through before we are prepared to change
the existing regulation and perhaps pursue new emission control
requirements. In particular, we will need to further explore the extent
to which the new duty cycle represents in-use operation and whether
engine or chassis testing is more appropriate in simulating in-use
operation for accurate emission characterization and measurements. We
believe it is appropriate to consider more stringent exhaust emission
standards for these engines after we have had the opportunity to
address the emission test cycle issue and to thus establish a long-term
testing protocols and related requirements.
(b) Off-Highway Motorcycles
    For off-highway motorcycles, manufacturers are in many cases making
a substantial transition to move away from two-stroke engines in favor
of four-stroke engines. This transition is now underway. While it may
eventually be appropriate to apply aftertreatment or other additional
emission control technologies to off-highway motorcycles, we need more
time for this transition to be completed and to assess the success of
aftertreatment technologies such as catalysts on similar applications
such as highway motorcycles. As EPA and manufacturers learn more in
implementing emission standards, we would expect to be able to better
judge the potential for broadly applying new technology to achieve
further emission reductions from off-highway motorcycles.
(c) Snowmobiles
    In our November 8, 2002 final rule we set three phases of exhaust
emission standards for snowmobiles (67 FR

68242). Environmental and industry groups challenged the third phase of
these standards. The court decision upheld much of EPA's reasoning for
the standards, but vacated the NOX standard and remanded the
CO and HC standards to clarify the analysis and evidence upon which the
standards are based. See Bluewater Network, et al v. EPA, 370 F 3d 1
(D.C. Cir. 2004). A large majority of snowmobile engines are rated
below 50 hp and there is still a fundamental need for time to pass to
allow us to assess the success of 4 stroke engine technology in the
market place. This is an important of the assessment we need to conduct
with regard to 2012 and later model year emission standards. Thus we
believe is appropriate to address this in a separate rulemaking.\9\ We
expect to complete that work with sufficient lead time for
manufacturers to meet any revised Phase 3 standards that we might adopt
for the 2012 model year, consistent with the original rulemaking
requirements.
---------------------------------------------------------------------------

    \9\ Only about 3 percent of snowmobiles are rated below 50
horsepower.
---------------------------------------------------------------------------

(5) Nonroad Diesel Engines
    The 2004 Consolidated Appropriations Act providing the specific
statutory direction for this rulemaking focuses on nonroad spark-
ignition engines. Nonroad diesel engines are therefore not included
within the scope of that Congressional mandate. However, we have gone
through several rulemakings to set standards for these engines under
the broader authority of Clean Air Act section 213. In particular, we
have divided nonroad diesel engines into three groups for setting
emission standards. We adopted a series of standards for locomotives on
April 16, 1998, including requirements to certify engines to emission
standards when they are rebuilt (63 FR 18978). We also adopted emission
standards for marine diesel engines over several different rulemakings,
as described in Table I-2. These included separate actions for engines
below 37 kW, engines installed in oceangoing vessels, engines installed
in commercial vessels involved in inland and coastal waterways, and
engines installed in recreational vessels. We have recently proposed
new emission standards for both locomotive and marine diesel engines
(72 FR 15938, April 3, 2007).
    Finally, all other nonroad diesel engines are grouped together for
EPA's emission standards. We have adopted multiple tiers of
increasingly stringent standards in three separate rulemakings, as
described in Table I-2. We most recently adopted Tier 4 standards based
on the use of ultra-low sulfur diesel fuel and the application of
exhaust aftertreatment technology (69 FR 38958, June 29, 2004).

D. Putting This Proposal Into Perspective

    Most manufacturers that will be subject to this rulemaking are also
affected by regulatory developments in California and in other
countries. Each of these is described in more detail below.
(1) State Initiatives
    Clean Air Act section 209 prohibits California and other states
from setting emission standards for new motor vehicles and new motor
vehicle engines, but authorizes EPA to waive this prohibition for
California, in which case other states may adopt California's
standards. Similar preemption and waiver provisions apply for emission
standards for nonroad engines and vehicles, whether new or in-use.
However for new locomotives, new engines used in locomotives, and new
engines used in farm or construction equipment with maximum power below
130 kW, California and other states are preempted and there is no
provision for a waiver of preemption. In addition, in section 428 of
the amendment to the 2004 Consolidated Appropriations Act, Congress
further precluded other states from adopting new California standards
for nonroad spark-ignition engines below 50 horsepower. In addition,
the amendment required that we specifically address the safety
implications of any California standards for these engines before
approving a waiver of federal preemption. We are proposing to codify
these changes to preemption in this rule.
    California ARB has adopted requirements for five groups of nonroad
engines: (1) Diesel- and Otto-cycle small off-road engines rated under
19 kW; (2) spark-ignition engines used for marine propulsion; (3) land-
based nonroad recreational engines, including those used in all-terrain
vehicles, off-highway motorcycles, go-carts, and other similar
vehicles; (4) new nonroad spark-ignition engines rated over 19 kW not
used in recreational applications; and (5) new land-based nonroad
diesel engines rated over 130 kW. They have also approved a voluntary
registration and control program for existing portable equipment.
    In the 1990s California ARB adopted Tier 1 and Tier 2 standards for
Small SI engines consistent with the federal requirements. In 2003,
they moved beyond the federal program by adopting exhaust
HC+NOX emission standards of 10 g/kW-hr for Class I engines
starting in the 2007 model year and 8 g/kW-hr for Class II engines
starting in the 2008 model year. In the same rule they adopted
evaporative emission standards for nonhandheld equipment, requiring
control of fuel tank permeation, fuel line permeation, diurnal
emissions, and running losses.
    California ARB has adopted two tiers of exhaust emission standards
for outboard and personal watercraft engines beyond EPA's original
standards. The most recent standards, which apply starting in 2008,
require HC+NOX emission levels as low as 16 g/kW-hr. For
sterndrive and inboard engines, California has adopted a 5 g/kW-hr
HC+NOX emission standard for 2008 and later model year
engines, with testing underway to confirm the feasibility of standards.
California ARB's marine programs include no standards for exhaust CO
emissions or evaporative emissions.
    The California emission standards for recreational vehicles have a
different form than the comparable EPA standards but are roughly
equivalent in stringency. The California standards include no standards
for controlling evaporative emissions. Another important difference
between the two programs is California ARB's reliance on a provision
allowing noncompliant vehicles to be used in certain areas that are
less environmentally sensitive as long as they have a specified red
sticker that would identify their lack of emission controls to prevent
them from operating in other areas.
    California ARB in 1998 adopted requirements that apply to new
nonroad engines rated over 25 hp produced for California, with
standards phasing in from 2001 through 2004. Texas has adopted these
initial California ARB emission standards statewide starting in 2004.
More recently, California ARB has proposed exhaust emission standards
and new evaporative emission standards for these engines, consistent
with EPA's 2007 model year standards. Their proposal also included an
additional level of emission control for Large SI engines starting with
the 2010 model year. However, their proposed standards would not
increase overall stringency beyond that reflected in the federal
standards. Rather, they aim to achieve reductions in HC+NOX
emissions by removing the flexibility incorporated into the federal
standards allowing manufacturers to have higher HC+NOX
emissions by certifying to a more stringent CO standard.

(2) Actions in Other Countries
    While the proposed emission standards will apply only to engines
sold in the United States, we are aware that manufacturers in many
cases are selling the same products into other countries. To the extent
that we have the same emission standards as other countries,
manufacturers can contribute to reducing air emissions without being
burdened by the costs associated with meeting differing or inconsistent
regulatory requirements. The following discussion describes our
understanding of the status of emission standards in countries outside
the United States.

    Regulations for spark ignition engines in handheld and
nonhandheld equipment are included in the ``Directive 97/68/EC of
the European Parliament and of the Council of 16 December 1997 on
the approximation of the laws of the Member States relating to
measures against the emission of gaseous and particulate pollutants
from internal combustion engines to be installed in non-road mobile
machinery (OJ L 59, 27.2.1998, p. 1)'', as amended by ``Directive
2002/88/EC of the European Parliament and of the Council of 9
December 2002''. The Stage I emission standards are to be met by all
handheld and nonhandheld engines by 24 months after entry into force
of the Directive (as noted in a December 9, 2002 amendment to
Directive 97/68/EC). The Stage I emission standards are similar to
the U.S. EPA's Phase 1 emission standards for handheld and
nonhandheld engines. The Stage II emission standards are implemented
over time for the various handheld and nonhandheld engine classes
from 2005 to 2009 with handheld engines >= 50cc on August 1, 2008.
The Stage II emission standards are similar to EPA's Phase 2
emission standards for handheld and nonhandheld engines. Six months
after these dates Member States shall permit placing on the market
of engines, whether or not already installed in machinery, only if
they meet the requirements of the Directive.

    The European Commission has adopted emission standards for
recreational marine engines, including both diesel and gasoline
engines. These requirements apply to all new engines sold in member
countries and began in 2006 for four-stroke engines and in 2007 for
two-stroke engines. Table I-3 presents the European standards for
diesel and gasoline recreational marine engines. The numerical emission
standards for NOX are based on the applicable standard from
MARPOL Annex VI for marine diesel engines (See Table I-3). The European
standards are roughly equivalent to the nonroad diesel Tier 1 emission
standards for HC and CO. Emission measurements under the European
standards rely on the ISO D2 duty cycle for constant-speed engines and
the ISO E5 duty cycle for other engines.

                     Table I-3.--European Emission Standards for Recreational Marine Engines
                                                    [g/kW-hr]
----------------------------------------------------------------------------------------------------------------
                 Engine Type                           HC               NOX             CO              PM
----------------------------------------------------------------------------------------------------------------
Two-Stroke Spark-Ignition....................   30 + 100/P\0.75\            10.0     150 + 600/P  ..............
Four-Stroke Spark-Ignition...................     6 + 50/P\0.75\            15.0     150 + 600/P  ..............
Compression-Ignition.........................     1.5 + 2/P\0.5\             9.8             5.0            1.0
----------------------------------------------------------------------------------------------------------------
\*\ P = rated power in kilowatts (kW)

E. What Requirements Are We Proposing?

    EPA's emission control provisions require engine, vessel and
equipment manufacturers to design and produce their products to meet
the emission standards we adopt. To ensure that engines, vessels and
equipment meet the expected level of emission control, we also require
compliance with a variety of additional requirements, such as
certification, labeling engines, and meeting warranty requirements. The
following sections provide a brief summary of the new requirements we
are proposing in this rulemaking. See the later sections for a full
discussion of the proposal.
(1) Marine SI Engines and Vessels
    We are proposing a more stringent level of emission standards for
outboard and personal watercraft engines starting with the 2009 model
year. The proposed standards for engines above 40 kW are 16 g/kW-hr for
HC+NOX and 200 g/kW-hr for CO. For engines below 40 kW, the
standards increase gradually based on the engine's maximum power. We
expect manufacturers to meet these standards with improved fueling
systems and other in-cylinder controls. The levels of the standards are
consistent with the requirements recently adopted by California ARB
with the advantage of a simplified form of the standard for different
power ratings and with a CO emission standard. We are not pursuing
catalyst-based emission standards for outboard and personal watercraft
engines. As is discussed later in this preamble, the application of
catalyst-based standards to the marine environment creates special
technology challenges that must be addressed. Unlike the sterndrive/
inboard engines discussed in the next paragraph, outboard and personal
watercraft engines are not built from automotive engine blocks and are
not as easily amenable to the fundamental engine modifications, fuel
system upgrades, and other engine control modifications needed to get
acceptable catalyst performance. This proposal is an appropriate next
step in the evolution of technology-based standards for outboard and
personal watercraft engines as they are likely to lead to the
elimination of carbureted two-stroke engines in favor of direct-
injection two-stroke engines and to encourage the fuel system upgrades
and related engine modifications needed to achieve the required
reductions and to potentially set the stage for future considerations.
    We are proposing new exhaust emission standards for sterndrive and
inboard marine engines. The proposed standards are 5.0 g/kW-hr for
HC+NOX and 75.0 g/kW-hr for CO starting with the 2009 model
year. We expect manufacturers to meet these standards with three-way
catalysts and closed-loop fuel injection. To ensure proper functioning
of these emission control systems in use, we are proposing a
requirement that engines have a diagnostic system for detecting a
failure in the emission control system. For sterndrive and inboard
marine engines at or above 373 kW with high-performance characteristics
(generally referred to as ``SD/I high-performance engines''), we are
proposing an HC+NOX emission standard of 5.0 g/kW-hr and a
CO standard of 350 g/kW-hr. We are also proposing a variety of other
special provisions for these engines to reflect unique operating
characteristics and to make it feasible to meet emission standards
using emission credits. These standards are consistent with the
requirements recently adopted by California ARB, with some adjustment
to the provisions for SD/I high-performance engines and with a CO
emission standard.
    The emission standards described above relate to engine operation
over a

prescribed duty cycle for testing in the laboratory. We are also
proposing not-to-exceed (NTE) standards that establish emission limits
when engines operate under normal speed-load combinations that are not
included in the duty cycles for the other engine standards.
    We are proposing new standards to control evaporative emissions for
all Marine SI vessels. The new standards include requirements to
control fuel tank permeation, fuel line permeation, and diurnal
emissions, including provisions to ensure that refueling emissions do
not increase.
    We are proposing to place these new regulations for Marine SI
engines in 40 CFR part 1045 rather than changing the current
regulations in 40 CFR part 91. This new part will allow us to improve
the clarity of regulatory requirements and update our regulatory
compliance program to be consistent with the provisions we have
recently adopted for other nonroad programs. We are also making a
variety of changes to 40 CFR part 91 to make minor adjustments to the
current regulations and to prepare for the transition to 40 CFR part
1045.
(2) Small SI Engines and Equipment
    We are proposing HC+NOX exhaust emission standards of
10.0 g/kW-hr for Class I engines starting in the 2012 model year and
8.0 g/kW-hr for Class II engines starting in the 2011 model year. For
both classes of nonhandheld engines, we are proposing to maintain the
existing CO standard of 610 g/kW-hr. We expect manufacturers to meet
these standards by improving engine combustion and adding catalysts.
These standards are consistent with the requirements recently adopted
by California ARB.
    For spark-ignition engines used in marine generators, we are
proposing a more stringent Phase 3 CO emission standard of 5.0 g/kW-hr.
This would apply equally to all sizes of engines subject to the Small
SI standards.
    We are proposing new evaporative emission standards for both
handheld and nonhandheld engines. The new standards include
requirements to control permeation from fuel tanks and fuel lines. For
nonhandheld engines we are also proposing to require control of
diffusion emissions and running losses.
    We are proposing to place the new regulations for Small SI engines
from 40 CFR part 90 to 40 CFR part 1054. This new part will allow us to
improve the clarity of regulatory requirements and update our
regulatory compliance program to be consistent with the provisions we
have recently adopted for other nonroad programs.

F. How Is This Document Organized?

    Since this proposal covers a broad range of engines and equipment
that vary in design and use, many readers may be interested only in
certain aspects of the proposal. We have therefore attempted to
organize this preamble in a way that allows each reader to focus on the
material of particular interest. The Air Quality discussion in Section
II, however, is general in nature and applies to all the categories
covered by this proposal.
    The next several sections contain our proposal for Small SI engines
and equipment and Marine SI engines and vessels. Sections III through V
describe the proposed requirements related to exhaust emission
standards for each of the affected engine categories, including
standards, effective dates, testing information, and other specific
requirements. Section VI details the proposed requirements related to
evaporative emission requirements for all categories. Sections VII
through IX contain some general concepts that are relevant to all of
the engines, vessels and equipment covered by this proposal, such as
certification requirements and general testing procedures and
compliance provisions. Section X discusses how we took energy, noise,
and safety factors into consideration for the proposed standards.
    Section XI describes a variety of proposed provisions that affect
other categories of engines besides those that are the primary subject
of this proposal. This includes the following changes:
     We are proposing to reorganize the regulatory language
related to preemption of state standards and to clarify certain
provisions. We are also requesting comment regarding a petition to
reconsider some of the provisions including the extent to which states
may regulate the use and operation of nonroad engines and vehicles.
     We are incorporating new provisions related to
certification fees for newly regulated products covered by this
proposal. This involves some restructuring of the regulatory language.
We are also proposing various technical amendments, such as identifying
an additional payment method, that would apply broadly to our
certification programs.
     We are proposing changes to 40 CFR part 1068 to clarify
how the provisions apply with respect to evaporative emission
standards. We are also proposing various technical amendments. These
changes would apply to all types of nonroad engines that are subject to
the provisions of part 1068.
     We are proposing several technical amendments for Large SI
engines and recreational vehicles, largely to maintain consistency
across programs for different categories of engines and vehicles.
     We are proposing to amend provisions related to the
delegated-assembly exemption for heavy-duty highway engines as part of
the effort to apply these provisions to Small SI engines, as described
in Section V.E.2.
     We are proposing to apply the new standards for Small SI
engines to the comparable stationary engines.
    Section XII summarizes the projected impacts and benefits of this
proposal. Finally, Sections XIII and XIV contain information about
public participation and how we satisfy our various administrative
requirements.

II. Public Health and Welfare Effects

    The engines, vessels and equipment that would be subject to the
proposed standards generate emissions of hydrocarbons (HC), nitrogen
oxides (NOX), particulate matter (PM) and carbon monoxide
(CO) that contribute to nonattainment of the National Ambient Air
Quality Standards (NAAQS) for ozone, PM and CO. These engines, vessels
and equipment also emit hazardous air pollutants (air toxics) that are
associated with a host of adverse health effects. Emissions from these
engines, vessels and equipment also contribute to visibility impairment
and other welfare and environmental effects.
    The health and environmental effects associated with emissions from
Small SI engines and equipment and Marine SI engines and vessels are a
classic example of a negative externality (an activity that imposes
uncompensated costs on others). With a negative externality, an
activity's social cost (the cost on society imposed as a result of the
activity taking place) exceeds its private cost (the cost to those
directly engaged in the activity). In this case, as described in this
section, emissions from Small SI engines and equipment and Marine SI
engines and vessels impose public health and environmental costs on
society. The market system itself cannot correct this externality. The
end users of the equipment and vessels are often unaware of the
environmental impacts of their use for lawn care or recreation. Because
of this, consumers fail to send the market a signal to provide cleaner
equipment and vessels. In addition, producers of these engines,
equipment, and vessels are rewarded for emphasizing other aspects of
these

products (e.g., total power). To correct this market failure and reduce
the negative externality, it is necessary to give producers social cost
signals. The standards EPA is proposing will accomplish this by
mandating that Small SI engines and equipment and Marine SI engines and
vessels reduce their emissions to a technologically feasible limit. In
other words, with this proposed rule the costs of the services provided
by these engines and equipment will account for social costs more
fully.
    This section summarizes the general health and welfare effects of
these emissions. Interested readers are encouraged to refer to the
Draft RIA for more in-depth discussions.

A. Ozone

    Ground-level ozone pollution is formed by the reaction of volatile
organic compounds (VOC), of which HC are the major subset, and
NOX in the lower atmosphere in the presence of heat and
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 (including those subject to this proposed
rule), power plants, chemical plants, refineries, makers of consumer
and commercial products, industrial facilities, and smaller area
sources. The engine, vessel and equipment controls being proposed will
reduce VOCs and NOX.
    The science of ozone formation, transport, and accumulation is
complex.\10\ 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 would
occur on a single high-temperature day. Ozone also can be transported
into an area from pollution sources found hundreds of miles upwind,
resulting in elevated ozone levels even in areas with low VOC or
NOX emissions.
---------------------------------------------------------------------------

    \10\ U.S. EPA. Air Quality Criteria for Ozone and Related
Photochemical Oxidants (Final). U.S. Environmental Protection
Agency, Washington, DC, EPA/600/R-05/004aF-cF, 2006. This document
is available in Docket EPA-HQ-OAR-2004-0008.
---------------------------------------------------------------------------

    The current ozone NAAQS, established by EPA in 1997, has an 8-hour
averaging time.\11\ The 8-hour ozone NAAQS is based on well-documented
science demonstrating that more people were experiencing adverse health
effects at lower levels of exertion, over longer periods, and at lower
ozone concentrations than addressed by the previous one-hour ozone
NAAQS. The current ozone NAAQS addresses ozone exposures of concern for
the general population and populations most at risk, including children
active outdoors, outdoor workers, and individuals with pre-existing
respiratory disease, such as asthma. The 8-hour ozone NAAQS is met at
an ambient air quality monitoring site when the average of the annual
fourth-highest daily maximum 8-hour average ozone concentration over
three years is less than or equal to 0.084 parts per million (ppm).
---------------------------------------------------------------------------

    \11\ EPA's review of the ozone NAAQS is underway and a proposal
is scheduled for June 2007 with a final rule scheduled for March
2008.
---------------------------------------------------------------------------

(1) Health Effects of Ozone
    The health and welfare effects of ozone are well documented and are
assessed in the EPA's 2006 ozone Air Quality Criteria Document (ozone
AQCD) and staff paper.12 13 Ozone can irritate the
respiratory system, causing coughing, throat irritation, and/or
uncomfortable sensation in the chest. Ozone can reduce lung function
and make it more difficult to breathe deeply, and breathing may become
more rapid and shallow than normal, thereby limiting a person's
activity. Ozone can also aggravate asthma, leading to more asthma
attacks that require a doctor's attention and/or the use of additional
medication. Animal toxicologic 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. People who are more susceptible to effects
associated with exposure to ozone include children, the elderly, and
individuals with respiratory disease such as asthma. There is also
suggestive evidence that certain people may have greater genetic
susceptibility. Those with greater exposures to ozone, for instance due
to time spent outdoors (e.g., outdoor workers), are also of concern.
---------------------------------------------------------------------------

    \12\ U.S. EPA. Air Quality Criteria for Ozone and Related
Photochemical Oxidants (Final). U.S. Environmental Protection
Agency, Washington, DC, EPA/600/R-05/004aF-cF, 2006. This document
is available in Docket EPA-HQ-OAR-2004-0008.
    \13\ U.S. EPA (2007) Review of National Ambient Air Quality
Standards for Ozone, Assessment of Scientific and Technical
Information, OAQPS Staff Paper, EPA-452/R-07-003. This document is
available in Docket EPA-HQ-OAR-2004-0008.
---------------------------------------------------------------------------

    The recent ozone AQCD also examined relevant new scientific
information that has emerged in the past decade, including the impact
of ozone exposure on such health effects as changes in lung structure
and biochemistry, inflammation of the lungs, exacerbation and causation
of asthma, respiratory illness-related school absence, hospital
admissions and premature mortality. Animal toxicologic studies have
suggested potential interactions between ozone and PM with increased
responses observed to mixtures of the two pollutants compared to either
ozone or PM alone. The respiratory morbidity observed in animal studies
along with the evidence from epidemiologic studies supports 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.
    EPA typically quantifies ozone-related health impacts in its
regulatory impact analyses (RIAs) when possible. In the analysis of
past air quality regulations, ozone-related benefits have included
morbidity endpoints and welfare effects such as damage to commercial
crops. EPA has not recently included a separate and additive mortality
effect for ozone, independent of the effect associated with fine
particulate matter. For a number of reasons, including (1) Advice from
the Science Advisory Board (SAB) Health and Ecological Effects
Subcommittee (HEES) that EPA consider the plausibility and viability of
including an estimate of premature mortality associated with short-term
ozone exposure in its benefits analyses and (2) conclusions regarding
the scientific support for such relationships in EPA's 2006 Air Quality
Criteria for Ozone and Related Photochemical Oxidants (the CD), EPA is
in the process of determining how to appropriately characterize ozone-
related mortality benefits within the context of benefits analyses for
air quality regulations. As part of this process, we are seeking advice
from the National Academy of Sciences (NAS) regarding how the ozone-
mortality literature should be used to quantify the reduction in
premature mortality due to diminished exposure to ozone, the amount of
life expectancy to be added and the monetary value of this increased
life expectancy in the context of health benefits analyses associated
with regulatory assessments. In addition, the Agency has sought advice
on characterizing and communicating the uncertainty associated with
each of these aspects in health benefit analyses.
    Since the NAS effort is not expected to conclude until 2008, the
agency is currently deliberating how best to

characterize ozone-related mortality benefits in its rulemaking
analyses in the interim. We do not quantify an ozone mortality benefit
for the analysis of the proposed emission standards. So that we do not
provide an incomplete picture of all of the benefits associated with
reductions in emissions of ozone precursors, we have chosen not to
include an estimate of total ozone benefits in the proposed RIA. By
omitting ozone benefits in this proposal, we acknowledge that this
analysis underestimates the benefits associated with the proposed
standards. For more information regarding the quantified benefits
included in this analysis, please refer to Chapter 8 of the Draft RIA.
(2) Plant and Ecosystem Effects of Ozone
    Ozone contributes to many environmental effects, with impacts to
plants and ecosystems being of most concern. Ozone can produce both
acute and chronic injury in sensitive species depending on the
concentration level and the duration of the exposure. Ozone effects
also tend to accumulate over the growing season of the plant, so that
even lower concentrations experienced for a longer duration have the
potential to create chronic stress on vegetation. Ozone damage to
plants includes visible injury to leaves and a reduction in food
production through impaired photosynthesis, both of which can lead to
reduced crop yields, forestry production, and use of sensitive
ornamentals in landscaping. In addition, the reduced food production in
plants and subsequent reduced root growth and storage below ground, can
result in other, more subtle plant and ecosystems impacts. These
include increased susceptibility of plants to insect attack, disease,
harsh weather, interspecies competition and overall decreased plant
vigor. The adverse effects of ozone on forest and other natural
vegetation can potentially lead to species shifts and loss from the
affected ecosystems, resulting in a loss or reduction in associated
ecosystem goods and services. Lastly, visible ozone injury to leaves
can result in a loss of aesthetic value in areas of special scenic
significance like national parks and wilderness areas. The 2006 ozone
AQCD presents more detailed information on ozone effects on vegetation
and ecosystems.
(3) Current and Projected 8-Hour Ozone Levels
    Currently, ozone concentrations exceeding the level of the 8-hour
ozone NAAQS occur over wide geographic areas, including most of the
nation's major population centers.\14\ As of October, 2006 there are
approximately 157 million people living in 116 areas designated as not
in attainment with the 8-hour ozone NAAQS. There are 461 full or
partial counties that make up the 116 8-hour ozone nonattainment areas.
These numbers do not include the people living in areas where there is
a potential risk of failing to maintain or achieve the 8-hour ozone
NAAQS in the future.
---------------------------------------------------------------------------

    \14\ A map of the 8-hour ozone nonattainment areas is included
in the RIA for this proposed rule.
---------------------------------------------------------------------------

    EPA has already adopted many emission control programs that are
expected to reduce ambient ozone levels. These control programs include
the Clean Air Interstate Rule (70 FR 25162, May 12, 2005), as well as
many mobile source rules, some of which are described in Section I of
this preamble. As a result of these programs, the number of areas that
fail to meet the 8-hour ozone NAAQS in the future is expected to
decrease.
    Based on the recent ozone modeling performed for the CAIR analysis,
barring additional local ozone precursor controls, we estimate 37
eastern counties (where 24 million people are projected to live) will
exceed the 8-hour ozone NAAQS in 2010.15 16 An additional
148 eastern counties (where 61 million people are projected to live)
are expected to be within 10 percent of the 8-hour ozone NAAQS in 2010.
---------------------------------------------------------------------------

    \15\ Technical Support Document for the Final Clean Air
Interstate Rule Air Quality Modeling. This document is available in
Docket EPA-HQ-OAR-2004-0008, Document  EPA-HQ-OAR-2004-
0008-0484.
    \16\ We expect many of the 8-hour ozone nonattainment areas to
adopt additional emission reduction programs but we are unable to
quantify or rely upon future reductions from additional state and
local programs that have not yet been adopted.
---------------------------------------------------------------------------

    States with 8-hour ozone nonattainment areas will be required to
take action to bring those areas into compliance in the future. Based
on the final rule designating and classifying 8-hour ozone
nonattainment areas (69 FR 23951, April 30, 2004), most 8-hour ozone
nonattainment areas will be required to attain the 8-hour ozone NAAQS
in the 2007 to 2014 time frame and then be required to maintain the 8-
hour ozone NAAQS thereafter.\17\ Emissions of ozone precursors from the
engines, vessels and equipment subject to the proposed standards
contribute to ozone in many, if not all, of these areas. Therefore, the
expected HC and NOX reductions from the standards proposed
in this action will be useful to states in attaining or maintaining the
8-hour ozone NAAQS.
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    \17\ The Los Angeles South Coast Air Basin 8-hour ozone
nonattainment area will have until June 15, 2021 to reach
attainment.
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    EPA's review of the ozone NAAQS is currently underway and a
proposed decision in this review is scheduled for June 2007 with a
final rule scheduled for March 2008. If the ozone NAAQS is revised then
new nonattainment areas could be designated. While EPA is not relying
on it for purposes of justifying this rule, the emission reductions
from this rulemaking would also be helpful to states if there is an
ozone NAAQS revision.
(4) Air Quality Modeling for Ozone
    To model the ozone air quality benefits of this rule we used the
Comprehensive Air Quality Model with Extension (CAMx). CAMx simulates
the numerous physical and chemical processes involved in the formation,
transport, and destruction of ozone. This model is commonly used in
developing attainment demonstration State Implementation Plans (SIPs)
as well as estimating the ozone reductions expected to occur from a
reduction in emitted pollutants. Meteorological data are developed by a
separate program, the Regional Atmospheric Modeling System (RAMS), and
input into CAMx. The simulation periods modeled by CAMx include several
multi-day periods when ambient measurements were representative of
ozone episodes over the eastern United States: June 12-24, July 5-15
and August 7-21, 1995. The modeling domain we used includes the 37
eastern states modeled in the Clean Air Interstate Rule (CAIR). More
detailed information is included in the Air Quality Modeling Technical
Support Document (TSD), which is located in the docket for this rule.
    Note that the emission control scenarios used in the air quality
and benefits modeling are slightly different than the emission control
program in this proposal reflecting further refinement of the
regulatory program since we performed the air quality modeling for this
proposal. Additional detail on the difference between the modeled and
proposed inventories is included in Section 3.6 of the Draft RIA.
(5) Results of the Air Quality Modeling for Ozone
    According to air quality modeling performed for this proposal, the
proposed controls for emissions from the engines, vessels and equipment
subject to the proposed standards are expected to provide nationwide
improvements in ozone levels. On a population-weighted basis, the
average modeled future-year 8-hour ozone design values would decrease
by 0.7

ppb in 2020 and 0.8 ppb in 2030.\18\ Within areas predicted to have
design values greater than 85 ppb the average decrease would be
somewhat higher: 0.8 ppb in 2020 and 1.0 ppb in 2030.
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    \18\ A design value is the monitored reading used by EPA to
determine an area's air quality status; e.g., for ozone, the fourth
highest reading measured over the most recent three years is the
design value. (http://www.epa.gov/OCEPAterms/dterms.html).

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B. Particulate Matter

    Particulate matter (PM) represents a broad class of chemically and
physically diverse substances. It can be principally characterized as
discrete particles that exist in the condensed (liquid or solid) phase
spanning several orders of magnitude in size. PM is further described
by breaking it down into size fractions. PM10 refers to
particles generally less than or equal to 10 micrometers ([mu]m) in
diameter. PM2.5 refers to fine particles, those particles
generally less than or equal to 2.5 [mu]m in diameter. Inhalable (or
``thoracic'' ) coarse particles refer to those particles generally
greater than 2.5 [mu]m but less than or equal to 10 [mu]m in diameter.
Ultrafine PM refers to particles with diameters generally less than 100
nanometers (0.1 [mu]m). Larger particles (>10 [mu]m) tend to be removed
by the respiratory clearance mechanisms, whereas smaller particles are
deposited deeper in the lungs.
    Fine particles are produced primarily by combustion processes and
by transformations of gaseous emissions (e.g., SOx,
NOX and VOCs) 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 pollutants including sulfates, nitrates,
organic compounds, elemental carbon and metal compounds. These
particles can remain in the atmosphere for days to weeks and travel
through the atmosphere hundreds to thousands of kilometers.
    EPA's final rule to amend the PM NAAQS addressed revisions to the
primary and secondary NAAQS for PM to provide increased protection of
public health and welfare, respectively (71 FR 61144, October 17,
2006). The primary PM2.5 NAAQS include a short-term (24-
hour) and a long-term (annual) standard. The level of the 24-hour
PM2.5 NAAQS has been revised from 65[mu]g/m 3 to
35[mu]g/m 3 to provide increased protection against health
effects associated with short-term exposures to fine particles. The
current form of the 24-hour PM2.5 standard was retained
(e.g., based on the 98th percentile concentration averaged over three
years). The level of the annual PM2.5 NAAQS was retained at
15[mu]g/m 3, continuing protection against health effects
associated with long-term exposures. The current form of the annual
PM2.5 standard was retained as an annual arithmetic mean
averaged over three years, however, the following two aspects of the
spatial averaging criteria were narrowed: (1) The annual mean
concentration at each site shall be within 10 percent of the spatially
averaged annual mean, and (2) the daily values for each monitoring site
pair shall yield a correlation coefficient of at least 0.9 for each
calendar quarter. With regard to the primary PM10 standards,
the 24-hour PM10 NAAQS was retained at a level of 150[mu]g/m
3 not to be exceeded more than once per year on average over
a three-year period. Given that the available evidence does not suggest
an association between long-term exposure to coarse particles at
current ambient levels and health effects, EPA has revoked the annual
PM10 standard.
    With regard to the secondary PM standards, EPA has revised these
standards to be identical in all respects to the revised primary
standards. Specifically, EPA has revised the current 24-hour
PM2.5 secondary standard by making it identical to the
revised 24-hour PM2.5 primary standard, retained the annual
PM2.5 and 24-hour PM10 secondary standards, and
revoked the annual PM10 secondary standards. This suite of
secondary PM standards is intended to provide protection against PM-
related public welfare effects, including visibility impairment,
effects on vegetation and ecosystems, and material damage and soiling.
(1) 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
the 2004 EPA Particulate Matter Air Quality Criteria Document (PM AQCD)
as well as the 2005 PM Staff Paper.19 20 Further discussion
of health effects associated with PM can also be found in the Draft
RIA.
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    \19\ U.S. EPA (2004) Air Quality Criteria for Particulate Matter
(Oct 2004), Volume I Document No. EPA600/P-99/002aF and Volume II
Document No. EPA600/P-99/002bF. This document is available in Docket
EPA-HQ-OAR-2004-0008. This document is available electronically at:
http://cfpub2.epa.gov/ncea/cfm/recordisplay.cfm?deid=87903.

    \20\ U.S. EPA (2005) Review of the National Ambient Air Quality
Standard for Particulate Matter: Policy Assessment of Scientific and
Technical Information, OAQPS Staff Paper. EPA-452/R-05-005. This
document is available electronically at http://www.epa.gov/ttn/naaqs/standards/pm/s_pm_cr_sp.html
 and in Docket EPA-HQ-OAR-2004-

0008.
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    Health effects associated with short-term exposures (e.g. hours to
days) in ambient PM2.5 include premature mortality,
increased hospital admissions, heart and lung diseases, increased
cough, adverse lower-respiratory symptoms, decrements in lung function
and changes in heart rate rhythm and other cardiac effects. Studies
examining populations exposed to different levels of air pollution over
a number of years, including the Harvard Six Cities Study and the
American Cancer Society Study, show associations between long-term
exposure to ambient PM2.5 and both total and
cardiorespiratory mortality. In addition, the reanalysis of the
American Cancer Society Study shows an association between fine
particle and sulfate concentrations and lung cancer mortality. The
engines, vessels and equipment covered in this proposal contribute to
both acute and chronic PM2.5 exposures. Additional
information on acute exposures is available in Section 2.5 of the Draft
RIA.
    Recently, several studies have highlighted the adverse effects of
PM specifically from mobile sources.21 22 Studies have also
focused on health effects due to PM exposures on or near roadways.\23\
Although these studies include all air pollution sources, including
both spark-ignition (gasoline) and diesel powered vehicles, they
indicate that exposure to PM emissions near roadways, thus dominated by
mobile sources, are associated with health effects. The proposed
controls may help to reduce exposures, and specifically exposures near
the source, to mobile source related PM2.5.
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    \21\ Laden, F.; Neas, L.M.; Dockery, D.W.; Schwartz, J. (2000)
Association of Fine Particulate Matter from Different Sources with
Daily Mortality in Six U.S. Cities. Environmental Health
Perspectives 108: 941-947.
    \22\ Janssen, N.A.H.; Schwartz, J.; Zanobetti, A.; Suh, H.H.
(2002) Air Conditioning and Source-Specific Particles as Modifiers
of the Effect of PM10 on Hospital Admissions for Heart
and Lung Disease. Environmental Health Perspectives 110: 43-49.
    \23\ Riediker, M.; Cascio, W.E.; Griggs, T.R..; Herbst, M.C.;
Bromberg, P.A.; Neas, L.; Williams, R.W.; Devlin, R.B. (2003)
Particulate Matter Exposures in Cars is Associated with
Cardiovascular Effects in Healthy Young Men. Am. J. Respir. Crit.
Care Med. 169: 934-940.
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(2) Visibility
    Visibility can be defined as the degree to which the atmosphere is
transparent to visible light.\24\ Visibility impairment

manifests in two principal ways: as local visibility impairment and as
regional haze.\25\ Local visibility impairment may take the form of a
localized plume, a band or layer of discoloration appearing well above
the terrain as a result from complex local meteorological conditions.
Alternatively, local visibility impairment may manifest as an urban
haze, sometimes referred to as a ``brown cloud.'' This urban haze is
largely caused by emissions from multiple sources in the urban areas
and is not typically attributable to only one nearby source or to long-
range transport. The second type of visibility impairment, regional
haze, usually results from multiple pollution sources spread over a
large geographic region. Regional haze can impair visibility over large
regions and across states.
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    \24\ National Research Council, 1993. Protecting Visibility in
National Parks and Wilderness Areas. National Academy of Sciences
Committee on Haze in National Parks and Wilderness Areas. National
Academy Press, Washington, DC. This document is available in Docket
EPA-HQ-OAR-2004-0008. This book can be viewed on the National
Academy Press Website at http://www.nap.edu/books/0309048443/html/.

    \25\ See discussion in U.S. EPA , National Ambient Air Quality
Standards for Particulate Matter; Proposed Rule; January 17, 2006,
Vol71 p 2676. This information is available electronically at http://epa.gov/fedrgstr/EPA-AIR/2006/January/Day-17/a177.pdf
.

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    Visibility is important because it has direct significance to
people's enjoyment of daily activities in all parts of the country.
Individuals value good visibility for the well-being it provides them
directly, where they live and work, and in places where they enjoy
recreational opportunities. Visibility is also highly valued in
significant natural areas such as national parks and wilderness areas,
and special emphasis is given to protecting visibility in these areas.
For more information on visibility see the 2004 PM AQCD as well as the
2005 PM Staff Paper.26 27
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    \26\ U.S. EPA (2004) Air Quality Criteria for Particulate Matter
(Oct 2004), Volume I Document No. EPA600/P-99/002aF and Volume II
Document No. EPA600/P-99/002bF. This document is available in Docket
EPA-HQ-OAR-2004-0008.
    \27\ U.S. EPA (2005) Review of the National Ambient Air Quality
Standard for Particulate Matter: Policy Assessment of Scientific and
Technical Information, OAQPS Staff Paper. EPA-452/R-05-005. This
document is available in Docket EPA-HQ-OAR-2004-0008.
---------------------------------------------------------------------------

    Fine particles are the major cause of reduced visibility in parts
of the United States. To address the welfare effects of PM on
visibility, EPA set secondary PM2.5 standards that would act
in conjunction with the establishment of a regional haze program. In
setting this secondary standard, EPA concluded that PM2.5
causes adverse effects on visibility in various locations, depending on
PM concentrations and factors such as chemical composition and average
relative humidity. The secondary (welfare-based) PM2.5 NAAQS
was established as equal to the suite of primary (health-based) NAAQS.
Furthermore, section 169 of the Act provides additional authorities to
remedy existing visibility impairment and prevent future visibility
impairment in the 156 national parks, forests and wilderness areas
categorized as mandatory class I Federal areas (62 FR 38680-81, July
18, 1997).\28\ In July 1999 the regional haze rule (64 FR 35714) was
put in place to protect the visibility in mandatory class I federal
areas. Visibility can be said to be impaired in both PM2.5
nonattainment areas and mandatory class I federal areas.
---------------------------------------------------------------------------

    \28\ These areas are defined in section 162 of the Act as those
national parks exceeding 6,000 acres, wilderness areas and memorial
parks exceeding 5,000 acres, and all international parks which were
in existence on August 7, 1977.
---------------------------------------------------------------------------

(a) Current Visibility Impairment
    Recently designated PM2.5 nonattainment areas indicate
that, as of October 2006, almost 90 million people live in
nonattainment areas for the 1997 PM2.5 NAAQS. Thus, at least
these populations would likely be experiencing visibility impairment,
as well as many thousands of individuals who travel to these areas. In
addition, while visibility trends have improved in mandatory Class I
federal areas, the most recent data show that these areas continue to
suffer from visibility impairment. In summary, visibility impairment is
experienced throughout the U.S., in multi-state regions, urban areas,
and remote mandatory class I federal areas.29 30 The
mandatory class I federal areas are listed in Chapter 2 of the RIA for
this action. The areas that have design values above the 1997
PM2.5 NAAQS are also listed in Chapter 2 of the RIA for this
action.
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    \29\ US EPA, Air Quality Designations and Classifications for
the Fine Particles (PM2.5) National Ambient Air Quality
Standards, December 17, 2004. (70 FR 943, Jan 5. 2005) This document
is also available on the web at: http://www.epa.gov/pmdesignations/.

    \30\ US EPA. Regional Haze Regulations, July 1, 1999. (64 FR
35714, July 1, 1999).
---------------------------------------------------------------------------

(b) Future Visibility Impairment
    Recent modeling for the CAIR was used to project visibility
conditions in mandatory class I federal areas across the country in
2015. The results for the mandatory class I federal areas suggest that
these areas are predicted to continue to have annual average deciview
levels above background in the future.\31\ Modeling done for the PM
NAAQS projected PM2.5 levels in 2015. These projections
include all sources of PM2.5, including the engines, vessels
and equipment covered in this rule, and suggest that PM2.5
levels above the NAAQS will persist into the future.
---------------------------------------------------------------------------

    \31\ The deciview metric describes perceived visual changes in a
linear fashion over its entire range, analogous to the decibel scale
for sound. A deciview of 0 represents pristine conditions. The
higher the deciview value, the worse the visibility, and an
improvement in visibility is a decrease in deciview value.
---------------------------------------------------------------------------

    The engines, vessels and equipment that would be subject to these
proposed standards contribute to visibility concerns in these areas
through both their primary PM emissions and their VOC and
NOX emissions, which contribute to the formation of
secondary PM2.5. Reductions in these direct and secondary PM
emissions will help to improve visibility across the nation, including
mandatory class I federal areas.
(3) Atmospheric Deposition
    Wet and dry deposition of ambient particulate matter delivers a
complex mixture of metals (e.g., mercury, zinc, lead, nickel, aluminum,
cadmium), organic compounds (e.g., POM, dioxins, furans) and inorganic
compounds (e.g., nitrate, sulfate) to terrestrial and aquatic
ecosystems. The chemical form of the compounds deposited is impacted by
a variety of factors including ambient conditions (e.g., temperature,
humidity, oxidant levels) and the sources of the material. Chemical and
physical transformations of the particulate compounds occur in the
atmosphere as well as the media onto which they deposit. These
transformations in turn influence the fate, bioavailability and
potential toxicity of these compounds. Atmospheric deposition has been
identified as a key component of the environmental and human health
hazard posed by several pollutants including mercury, dioxin and
PCBs.\32\
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    \32\ U.S. EPA (2000) Deposition of Air Pollutants to the Great
Waters: Third Report to Congress. Office of Air Quality Planning and
Standards. EPA-453/R-00-0005.
---------------------------------------------------------------------------

    Adverse impacts on water quality can occur when atmospheric
contaminants deposit to the water surface or when material deposited on
the land enters a waterbody through runoff. Potential impacts of
atmospheric deposition to waterbodies include those related to both
nutrient and toxic inputs. Adverse effects to human health and welfare
can occur from the addition of excess particulate nitrate nutrient
enrichment, which contributes to toxic algae blooms and zones of
depleted oxygen, which can lead to fish kills, frequently in coastal
waters. Particles contaminated with heavy metals or other toxins may
lead to the ingestion of contaminated fish, ingestion of contaminated
water, damage to the marine ecology, and limited recreational uses.
Several

studies have been conducted in U.S. coastal waters and in the Great
Lakes Region in which the role of ambient PM deposition and runoff is
investigated.33 34 35 36 37
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    \33\ U.S. EPA (2004) National Coastal Condition Report II.
Office of Research and Development/ Office of Water. EPA-620/R-03/
002.
    \34\ Gao, Y., E.D. Nelson, M.P. Field, et al. 2002.
Characterization of atmospheric trace elements on PM2.5
particulate matter over the New York-New Jersey harbor estuary.
Atmos. Environ. 36: 1077-1086.
    \35\ Kim, G., N. Hussain, J.R. Scudlark, and T.M. Church. 2000.
Factors influencing the atmospheric depositional fluxes of stable
Pb, 210Pb, and 7Be into Chesapeake Bay. J. Atmos. Chem. 36: 65-79.
    \36\ Lu, R., R.P. Turco, K. Stolzenbach, et al. 2003. Dry
deposition of airborne trace metals on the Los Angeles Basin and
adjacent coastal waters. J. Geophys. Res. 108(D2, 4074): AAC 11-1 to
11-24.
    \37\ Marvin, C.H., M.N. Charlton, E.J. Reiner, et al. 2002.
Surficial sediment contamination in Lakes Erie and Ontario: A
comparative analysis. J. Great Lakes Res. 28(3): 437-450.
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    Adverse impacts on soil chemistry and plant life have been observed
for areas heavily impacted by atmospheric deposition of nutrients,
metals and acid species, resulting in species shifts, loss of
biodiversity, forest decline and damage to forest productivity.
Potential impacts also include adverse effects to human health through
ingestion of contaminated vegetation or livestock (as in the case for
dioxin deposition), reduction in crop yield, and limited use of land
due to contamination.
(4) Current and Projected PM2.5 Levels
    In 2005 EPA designated 39 nonattainment areas for the 1997
PM2.5 NAAQS based on air quality design values (using 2001-
2003 or 2002-2004 measurements) and a number of other factors (70 FR
943, January 5, 2005).\38\ These areas are comprised of 208 full or
partial counties with a total population exceeding 88 million. As
mentioned in Section II.B.2, the 1997 PM2.5 NAAQS was
recently revised and the 2006 PM2.5 NAAQS became effective
on December 18, 2006. Table II-1 presents the number of counties in
areas currently designated as nonattainment for the 1997
PM2.5 NAAQS as well as the number of additional counties
that have monitored data that is violating the 2006 PM2.5
NAAQS. Nonattainment areas will be designated with respect to the new
2006 PM2.5 NAAQS in early 2010.
---------------------------------------------------------------------------

    \38\ The full details involved in calculating a PM2.5
design value are given in Appendix N of 40 CFR part 50.

  Table II-1.--Fine Particle Standards: Current Nonattainment Areas and
                        Other Violating Counties
------------------------------------------------------------------------
 Nonattainment areas/other violating      Number of
              counties                    counties       Population \1\
------------------------------------------------------------------------
1997 PM2.5 Standards: 39 areas                     208        88,394,000
 currently designated...............
2006 PM2.5 Standards: counties with                 49        18,198,676
 violating monitors \2\.............
                                     -----------------------------------
    Total...........................               257      106,592,676
------------------------------------------------------------------------
\1\ Population numbers are from 2000 census data.
\2\ This table provides an estimate of the counties violating the 2006
  PM2.5 NAAQS based on 2003-05 air quality data. The areas designated as
  nonattainment for the 2006 PM2.5 NAAQS will be based on 3 years of air
  quality data from later years. Also, the county numbers in the summary
  table include only the counties with monitors violating the 2006 PM2.5
  NAAQS. The monitored county violations may be an underestimate of the
  number of counties and populations that will eventually be included in
  areas with multiple counties designated nonattainment.

    Based on modeling performed for the PM NAAQS analysis, we estimate
that 52 counties (where 53 million people are projected to live) will
exceed the 2006 PM2.5 standard in 2015.\39\ In addition, 54
counties (where 27 million people are projected to live) are expected
to be within 10 percent of the 2006 PM2.5 NAAQS in 2015.
---------------------------------------------------------------------------

    \39\ US EPA (2006). Regulatory Impact Analysis for the 2006
NAAQS for Particle Pollution. This document is available in Docket
EPA-HQ-OAR-2004-0008.
---------------------------------------------------------------------------

    Areas designated as not attaining the 1997 PM2.5 NAAQS
will need to attain these standards in the 2010 to 2015 time frame, and
then be required to maintain the NAAQS thereafter. The attainment dates
associated with the potential new 2006 PM2.5 nonattainment
areas would likely be in the 2015 to 2020 timeframe. The emission
standards being proposed in this action would become effective as early
as 2009 making the expected HC, NOX and PM inventory
reductions from this rulemaking useful to states in attaining or
maintaining the PM2.5 NAAQS.
(5) Current PM10 Levels
    As of October 2006 approximately 28.5 million people live in 46
designated PM10 nonattainment areas, which include all or
part of 46 counties. These population numbers do not include the people
living in areas where there is a potential risk of failing to maintain
or achieve the PM10 NAAQS in the future. The expected PM, HC
and NOX inventory reductions from these proposed standards
would be useful to states in maintaining the PM10 NAAQS.

C. Air Toxics

    Emissions from the engines, vessels and equipment subject to the
proposed standards contribute to ambient levels of gaseous air toxics
known or suspected as human or animal carcinogens, or that have non-
cancer health effects. These compounds include benzene, 1,3-butadiene,
formaldehyde, acetaldehyde, acrolein, polycyclic organic matter (POM),
and naphthalene. All of these compounds, except acetaldehyde, were
identified as national or regional risk drivers in the 1999 National-
Scale Air Toxics Assessment (NATA) and have significant inventory
contributions from mobile sources. That is, for a significant portion
of the population, these compounds pose a significant portion of the
total cancer risk from breathing outdoor air toxics. The reductions in
the emissions from these engines, vessels and equipment would help
reduce exposure to these harmful substances.
    Air toxics can cause a variety of cancer and noncancer health
effects. A number of the mobile source air toxic pollutants described
in this section are known or likely to pose a cancer hazard in humans.
Many of these compounds also cause adverse noncancer health effects
resulting from chronic,\40\ subchronic,\41\ or acute \42\ inhalation
exposures. These include neurological, cardiovascular, liver, kidney,
and respiratory effects as well as effects on the immune and
reproductive systems.
---------------------------------------------------------------------------

    \40\ Chronic exposure is defined in the glossary of the
Integrated Risk Information (IRIS) database (http://www.epa.gov/iris
) as repeated exposure by the oral, dermal, or inhalation route

for more than approximately 10% of the life span in humans (more
than approximately 90 days to 2 years in typically used laboratory
animal species).
    \41\ Defined in the IRIS database as exposure to a substance
spanning approximately 10 of the lifetime of an organism.
    \42\ Defined in the IRIS database as exposure by the oral,
dermal, or inhalation route for 24 hours or less.

---------------------------------------------------------------------------

    Benzene. The EPA's Integrated Risk Information (IRIS) database
lists benzene as a known human carcinogen (causing leukemia) by all
routes of exposure, and 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.43 44 45 EPA states in its IRIS database that data
indicate a causal relationship between benzene exposure and acute
lymphocytic leukemia and suggests a relationship between benzene
exposure and chronic non-lymphocytic leukemia and chronic lymphocytic
leukemia. 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.46 47 The most
sensitive noncancer effect observed in humans, based on current data,
is the depression of the absolute lymphocyte count in
blood.48 49 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.50 51 52 53 EPA's IRIS program has not
yet evaluated these new data.
---------------------------------------------------------------------------

    \43\ U.S. EPA (2000). Integrated Risk Information System File
for Benzene. This material is available electronically at http://www.epa.gov/iris/subst/0276.htm
.

    \44\ International Agency for Research on Cancer, IARC
monographs on the evaluation of carcinogenic risk of chemicals to
humans, Volume 29, Some industrial chemicals and dyestuffs,
International Agency for Research on Cancer, World Health
Organization, Lyon, France, p. 345-389, 1982.
    \45\ Irons, R.D.; Stillman, W.S.; Colagiovanni, D.B.; Henry,
V.A. (1992) Synergistic action of the benzene metabolite
hydroquinone on myelopoietic stimulating activity of granulocyte/
macrophage colony-stimulating factor in vitro, Proc. Natl. Acad.
Sci. 89:3691-3695.
    \46\ Aksoy, M. (1989). Hematotoxicity and carcinogenicity of
benzene. Environ. Health Perspect. 82: 193-197.
    \47\ Goldstein, B.D. (1988). Benzene toxicity. Occupational
medicine. State of the Art Reviews. 3: 541-554.
    \48\ Rothman, N., G.L. Li, M. Dosemeci, W.E. Bechtold, G.E.
Marti, Y.Z. Wang, M. Linet, L.Q. Xi, W. Lu, M.T. Smith, N. Titenko-
Holland, L.P. Zhang, W. Blot, S.N. Yin, and R.B. Hayes (1996)
Hematotoxicity among Chinese workers heavily exposed to benzene. Am.
J. Ind. Med. 29: 236-246.
    \49\ EPA 2005 ``Full IRIS Summary for Benzene (CASRN 71-43-2)''
Environmental Protection Agency, Integrated Risk Information System
(IRIS), Office of Health and Environmental Assessment, Environmental
Criteria and Assessment Office, Cincinnati, OH http://www.epa.gov/iris/subst/0276.htm
.

    \50\ Qu, O.; Shore, R.; Li, G.; Jin, X.; Chen, C.L.; Cohen, B.;
Melikian, A.; Eastmond, D.; Rappaport, S.; Li, H.; Rupa, D.;
Suramaya, R.; Songnian, W.; Huifant, Y.; Meng, M.; Winnik, M.; Kwok,
E.; Li, Y.; Mu, R.; Xu, B.; Zhang, X.; Li, K. (2003). HEI Report
115, Validation & Evaluation of Biomarkers in Workers Exposed to
Benzene in China.
    \51\ Qu, Q., R. Shore, G. Li, X. Jin, L.C. Chen, B. Cohen, et
al. (2002). Hematological changes among Chinese workers with a broad
range of benzene exposures. Am. J. Industr. Med. 42: 275-285.
    \52\ Lan, Qing, Zhang, L., Li, G., Vermeulen, R., et al. (2004).
Hematotoxically in Workers Exposed to Low Levels of Benzene. Science
306: 1774-1776.
    \53\ Turtletaub, K.W. and Mani, C. (2003). Benzene metabolism in
rodents at doses relevant to human exposure from Urban Air. Research
Reports Health Effect Inst. Report No.113.
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    1,3-Butadiene. EPA has characterized 1,3-butadiene as carcinogenic
to humans by inhalation.54 55 The specific mechanisms of
1,3-butadiene-induced carcinogenesis are unknown. However, it is
virtually certain that the carcinogenic effects are mediated by
genotoxic metabolites of 1,3-butadiene. Animal data suggest that
females may be more sensitive than males for cancer effects, but there
are insufficient data in humans from which to draw conclusions about
sensitive subpopulations. 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.\56\
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    \54\ U.S. EPA. (2002). Health Assessment of 1,3-Butadiene.
Office of Research and Development, National Center for
Environmental Assessment, Washington Office, Washington, DC. Report
No. EPA600-P-98-001F.
    \55\ U.S. EPA (1998). A Science Advisory Board Report: Review of
the Health Risk Assessment of 1,3-Butadiene. EPA-SAB-EHC-98.
    \56\ Bevan, C.; Stadler, J.C.; Elliot, G.S.; et al. (1996)
Subchronic toxicity of 4-vinylcyclohexene in rats and mice by
inhalation. Fundam. Appl. Toxicol. 32:1-10.
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    Formaldehyde. Since 1987, EPA has classified formaldehyde as a
probable human carcinogen based on evidence in humans and in rats,
mice, hamsters, and monkeys.\57\ EPA is currently reviewing recently
published epidemiological data. For instance, recently released
research conducted by the National Cancer Institute (NCI) found an
increased risk of nasopharyngeal cancer and lymphohematopoietic
malignancies such as leukemia among workers exposed to
formaldehyde.58 59 NCI is currently performing an update of
these studies. A recent National Institute of Occupational Safety and
Health (NIOSH) study of garment workers also found increased risk of
death due to leukemia among workers exposed to formaldehyde.\60\ Based
on the developments of the last decade the working group of the
International Agency for Research on Cancer (IARC) concluded in 2004
that formaldehyde is carcinogenic to humans (Group 1), a higher
classification than previous IARC evaluations, on the basis of
sufficient evidence in humans and sufficient evidence in experimental
animals.
---------------------------------------------------------------------------

    \57\ U.S. EPA (1987). Assessment of Health Risks to Garment
Workers and Certain Home Residents from Exposure to Formaldehyde,
Office of Pesticides and Toxic Substances, April 1987.
    \58\ Hauptmann, M.; Lubin, J.H.; Stewart, P.A.; Hayes, R.B.;
Blair, A. 2003. Mortality from lymphohematopoetic malignancies among
workers in formaldehyde industries. Journal of the National Cancer
Institute 95: 1615-1623.
    \59\ Hauptmann, M.; Lubin, J.H.; Stewart, P.A.; Hayes, R.B.;
Blair, A. 2004. Mortality from solid cancers among workers in
formaldehyde industries. American Journal of Epidemiology 159: 1117-
1130.
    \60\ Pinkerton, L.E. 2004. Mortality among a cohort of garment
workers exposed to formaldehyde: an update. Occup. Environ. Med. 61:
193-200.
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    Formaldehyde exposure also causes a range of noncancer health
effects, including irritation of the eyes (tearing of the eyes and
increased blinking) and mucous membranes.
    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.\61\
The primary acute effect of exposure to acetaldehyde vapors is
irritation of the eyes, skin, and respiratory tract.\62\ The agency is
currently conducting a reassessment of the health hazards from
inhalation exposure to acetaldehyde.
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    \61\ U.S. EPA (1988). Integrated Risk Information System File of
Acetaldehyde. This material is available electronically at http://www.epa.gov/iris/subst/0290.htm
.

    \62\ U.S. EPA (1988). Integrated Risk Information System File of
Acetaldehyde. This material is available electronically at http://www.epa.gov/iris/subst/0290.htm
.

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    Acrolein. Acrolein is intensely irritating to humans when inhaled,
with acute exposure resulting in upper respiratory tract irritation and
congestion. EPA determined in 2003 using the 1999 draft cancer
guidelines 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.\63\
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    \63\ U.S. EPA. 2003. Integrated Risk Information System File of
Acrolein. Research and Development, National Center for
Environmental Assessment, Washington, DC. This material is available
electronically at http://www.epa.gov/iris/subst/0364.htm.

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    Polycyclic Organic Matter (POM). POM is generally defined as a
large class of organic compounds with multiple benzene rings and a
boiling point greater than 100 degrees Celsius. One of these compounds,
naphthalene, is discussed separately below. Polycyclic aromatic
hydrocarbons (PAH) are a class of POM that contain only hydrogen and
carbon atoms. A number of PAHs are known or suspected carcinogens.

    Recent 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 at age three.64 65
EPA has not yet evaluated these recent studies.
---------------------------------------------------------------------------

    \64\ Perera, F.P.; Rauh, V.; Tsai, W-Y.; et al. (2002) Effect of
transplacental exposure to environmental pollutants on birth
outcomes in a multiethnic population. Environ Health Perspect. 111:
201-205.
    \65\ Perera, F.P.; Rauh, V.; Whyatt, R.M.; Tsai, W.Y.; Tang, D.;
Diaz, D.; Hoepner, L.; Barr, D.; Tu, Y.H.; Camann, D.; Kinney, P.
(2006) Effect of prenatal exposure to airborne polycyclic aromatic
hydrocarbons on neurodevelopment in the first 3 years of life among
inner-city children. Environ Health Perspect 114: 1287-1292.
---------------------------------------------------------------------------

    Naphthalene. Naphthalene is found in small quantities in gasoline
and diesel fuels but is primarily a product of combustion. EPA recently
released an external review draft of a reassessment of the inhalation
carcinogenicity of naphthalene.\66\ The draft reassessment recently
completed external peer review.\67\ Based on external peer review
comments, additional analyses are being considered. 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.\68\ Naphthalene also causes a number of chronic
non-cancer effects in animals, including abnormal cell changes and
growth in respiratory and nasal tissues.\69\
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    \66\ U.S. EPA. 2004. Toxicological Review of Naphthalene
(Reassessment of the Inhalation Cancer Risk), Environmental
Protection Agency, Integrated Risk Information System, Research and
Development, National Center for Environmental Assessment,
Washington, DC. This material is available electronically at http://www.epa.gov/iris/subst/0436.htm
.

    \67\ Oak Ridge Institute for Science and Education. (2004).
External Peer Review for the IRIS Reassessment of the Inhalation
Carcinogenicity of Naphthalene. August 2004. http://cfpub2.epa.gov/ncea/cfm/recordisplay.cfm?deid=86019
.

    \68\ International Agency for Research on Cancer (IARC). (2002).
Monographs on the Evaluation of the Carcinogenic Risk of Chemicals
for Humans. Vol. 82. Lyon, France.
    \69\ U.S. EPA. 1998. Toxicological Review of Naphthalene,
Environmental Protection Agency, Integrated Risk Information System,
Research and Development, National Center for Environmental
Assessment, Washington, DC. This material is available
electronically at http://www.epa.gov/iris/subst/0436.htm.

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    In addition to reducing VOC, NOX, CO and
PM2.5 emissions from these engines, vessels and equipment,
the standards proposed in this document would also reduce air toxics
emitted from these engines, vessels and equipment, thereby helping to
mitigate some of the adverse health effects associated with operation
of these engines, vessels and equipment.

D. Carbon Monoxide

    Carbon monoxide (CO) is a colorless, odorless gas produced through
the incomplete combustion of carbon-based fuels. The current primary
NAAQS for CO are 35 ppm for the 1-hour average and nine ppm for the 8-
hour average. These values are not to be exceeded more than once per
year.
    We have already found that emissions from nonroad engines
contribute significantly to CO concentrations in more than one
nonattainment area (59 FR 31306, June 17, 1994). We have also
previously found that emissions from Small SI engines contribute to CO
concentrations in more than one nonattainment area. We propose to find
here, based on the information in this section of the preamble and
Chapters 2 and 3 of the Draft RIA, that emissions from Marine SI
engines and vessels likewise contribute to CO concentrations in more
than one CO nonattainment area.
    Carbon monoxide enters the bloodstream through the lungs, forming
carboxyhemoglobin and reducing the delivery of oxygen to the body's
organs and tissues. The health threat from CO is most serious for those
who suffer from cardiovascular disease, particularly those with angina
or peripheral vascular disease. Healthy individuals also are affected,
but only at higher CO levels. Exposure to elevated CO levels is
associated with impairment of visual perception, work capacity, manual
dexterity, learning ability and performance of complex tasks. Carbon
monoxide also contributes to ozone nonattainment since carbon monoxide
reacts photochemically in the atmosphere to form ozone.\70\ Additional
information on CO related health effects can be found in the Carbon
Monoxide Air Quality Criteria Document (CO AQCD).\71\
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    \70\ U.S. EPA (2000). Air Quality Criteria for Carbon Monoxide,
EPA/600/P-99/001F. This document is available in Docket EPA-HQ-OAR-
2004-0008.
    \71\ U.S. EPA (2000). Air Quality Criteria for Carbon Monoxide,
EPA/600/P-99/001F. This document is available in Docket EPA-HQ-OAR-
2004-0008.
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    In addition to health effects from chronic exposure to ambient CO
levels, acute exposures to higher levels are also a problem, see the
Draft RIA for additional information. In recent years a substantial
number of CO poisonings and deaths have occurred on and around
recreational boats across the nation.\72\ The actual number of deaths
attributable to CO poisoning while boating is difficult to estimate
because CO-related deaths in the water may be labeled as drowning. An
interagency team consisting of the National Park Service, the U.S.
Department of the Interior, and the National Institute for Occupational
Safety and Health maintains a record of published CO-related fatal and
nonfatal poisonings.\73\ Between 1984 and 2004, 113 CO-related deaths
and 458 non-fatal CO poisonings have been identified based on hospital
records, press accounts and other information. Deaths have been
attributed to exhaust from both onboard generators and propulsion
engines. Houseboats, cabin cruisers, and ski boats are the most common
types of boats associated with CO poisoning cases. These incidents have
prompted other federal agencies, including the United States Coast
Guard and National Park Service, to issue advisory statements and other
interventions to boaters to avoid excessive CO exposure.\74\
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    \72\ Mott, J.S.; Wolfe, M.I.; Alverson, C.J.; Macdonald, S.C.;
Bailey, C.R.; Ball, L.B.; Moorman, J.E.; Somers, J.H.; Mannino,
D.M.; Redd, S.C. (2002) National Vehicle Emissions Policies and
Practices and Declining US Carbon Monoxide-Related Mortality. JAMA
288:988-995.
    \73\ National Park Service; Department of the Interior; National
Institute for Occupational Safety and Health. (2004) Boat-related
carbon monoxide poisonings. This document is available
electronically at http://safetynet.smis.doi.gov/thelistbystate10-19-04.pdf
 and in docket EPA-HQ-OAR-2004-0008.

    \74\ U.S Department of the Interior. (2004) Carbon monoxide
dangers from generators and propulsion engines. On-board boats--
compilation of materials. This document is available online at
http://safetynet.smis.doi.gov/COhouseboats.htm and in docket EPA-HQ-

OAR-2004-0008.
---------------------------------------------------------------------------

    As of October 2006, there were approximately 15 million people
living in 6 areas (which include 10 counties) designated as
nonattainment for CO. The CO nonattainment areas are presented in the
Draft RIA.
    EPA previously determined that emissions from nonroad engines and
equipment contribute significantly to ozone and CO concentrations in
more than one nonattainment area (59 FR 31306, June 17, 1994). EPA also
determined that the categories of small land-based SI engines cause or
contribute to ambient ozone and CO in more than one nonattainment area
(65 FR 76790, Dec. 7, 2000). With regard to Marine SI engines and
vessels, our NONROAD model indicates that these engines are present in
each of the CO nonattainment areas and thus contribute to CO
concentrations in those nonattainment areas. The CO contribution from
Marine SI engines in classified CO nonattainment areas is presented in
Table II-2.

        Table II-2.--CO Emissions from Marine SI Engines and Vessels in Classified CO Nonattainment Areas
----------------------------------------------------------------------------------------------------------------
                                                                                CO (short tons
                  Area                             County                     Category              in 2005)
----------------------------------------------------------------------------------------------------------------
Missoula, MT...........................  Missoula..................  Marine SI................                94
Las Vegas, NV..........................  Clark.....................  Marine SI................             3,016
Reno, NV...............................  Washoe....................  Marine SI................             3,494
El Paso, TX............................  El Paso...................  Marine SI................                37
South Coast Air Basin..................  Los Angeles...............  Marine SI................             4,615
                                         Riverside.................  Marine SI................             1,852
                                         Orange....................  Marine SI................             5,360
                                         San Bernardino............  Marine SI................            2,507
----------------------------------------------------------------------------------------------------------------
Source: U.S. EPA, NONROAD 2005 model.

    Based on the national inventory numbers in Chapter 3 of the Draft
RIA and the local inventory numbers described in this section of the
preamble, we propose to find that emissions of CO from Marine SI
engines and vessels contribute to CO concentrations in more than one CO
nonattainment area.

III. Sterndrive and Inboard Marine Engines

A. Overview

    This section applies to sterndrive and inboard marine (SD/I)
engines. Sterndrive and inboard engines are spark-ignition engines
typically derived from automotive engine blocks for which a
manufacturer will take steps to ``marinize'' the engine for use in
marine applications. This marinization process includes choosing and
optimizing the fuel management system, configuring a marine cooling
system, adding intake and exhaust manifolds, and adding accessory
drives and units. These engines typically have water-jacketed exhaust
systems to keep surface temperatures low. Ambient surface water
(seawater or freshwater) is generally added to the exhaust gases before
the mixture is expelled under water.
    As described in Section I, the initial rulemaking to set standards
for Marine SI engines did not include final emission standards for SD/I
engines. In that rulemaking, we finalized the finding under Clean Air
Act section 213(a)(3) that all Marine SI engines cause or contribute to
ozone concentrations in two or more ozone nonattainment areas in the
United States. However, because uncontrolled SD/I engines appeared to
be a low-emission alternative to outboard and personal watercraft
engines in the marketplace, even after the emission standards for these
engines were fully phased in, we decided to set emission standards only
for outboard and personal watercraft engines. At that time, outboard
and personal watercraft engines were almost all two-stroke engines with
much higher emission rates compared to the SD/I engines, which were all
four-stroke engines. We pointed out in that initial rulemaking that we
wanted to avoid imposing costs on SD/I engines that could cause a
market shift to increased use of the higher-emitting outboard engines,
which would undermine the broader goal of achieving the greatest degree
of emission control from the full set of Marine SI engines.
    We believe now is an appropriate time to set standards for SD/I
engines, for several reasons. First, the available technology for SD/I
engines has developed significantly, so we are now able to anticipate
substantial emission reductions. With the simultaneous developments in
technology for outboard and personal watercraft engines, we can set
standards that achieve substantial emission reductions from all Marine
SI engines. Second, now that California has adopted standards for SD/I
engines, the cost impact of setting new standards for manufacturers
serving the California market is generally limited to the hardware
costs of adding emission control technology; these manufacturers will
be undergoing a complete redesign effort for these engines to meet the
California standards. Third, we believe SD/I engines meeting the
proposed standards will in many cases have performance advantages over
pre-control engines, which will allow manufacturers of SD/I engines to
promote their engines as having a greater value to justify any price
increases. As a result, we believe we can achieve the maximum emission
reductions from Marine SI engines by setting standards for SD/I engines
based on the use of catalyst technology at the same time that we adopt
more stringent standards for outboard and personal watercraft engines.
    As described in Section II, we are proposing to make the finding
under Clean Air Act section 213(a)(3) that Marine SI engines cause or
contribute to CO concentrations in two or more nonattainment areas of
the United States. We believe the proposed CO standards will also
reduce the exposure of individual boaters and bystanders to potentially
dangerous CO levels.
    We believe catalyst technology is available for achieving these
proposed standards. Catalysts have been used for decades in automotive
applications to reduce emissions, and catalyst manufacturers have
continued to develop and improve this technology. Design issues for
using catalysts in marine applications are primarily centered on
packaging catalysts in the water-jacketed, wet exhaust systems seen on
most SD/I engines. Section III.G discusses recent development work that
has shown success in packaging catalysts in SD/I applications. In
addition, there are ongoing efforts in evaluating catalyst technology
in SD/I engines being sponsored by the marine industry, U.S. Coast
Guard, and California ARB.

B. Engines Covered by This Rule

(1) Definition of Sterndrive and Inboard Engines
    For the purpose of this regulation, SD/I engines encompass all
spark-ignition marine propulsion engines that are not outboard or
personal watercraft engines. A discussion of the proposed new
definitions for outboard and personal watercraft engines is in Section
IV.B. We consider all the following to be SD/I engines: inboard,
sterndrive (also known as inboard/outboard), airboat engines, and jet
boat engines.
    The existing definitions for sterndrive and inboard engines from 40
CFR part 91 are presented below:
     Sterndrive engine means a four stroke Marine SI engine
that is designed such that the drive unit is external to the hull of
the marine vessel, while the engine is internal to the hull of the
marine vessel.
     Inboard engine means a four stroke Marine SI engine that
is designed such that the propeller shaft penetrates the

hull of the marine vessel while the engine and the remainder of the
drive unit is internal to the hull of the marine vessel.
    We are proposing to amend the above definitions for determining
which exhaust emission standards apply to spark-ignition marine engines
in 2009. The new proposed definition would be a single term to include
sterndrive and inboard engines together as a single engine category.