[Federal Register: October 8, 2008 (Volume 73, Number 196)]
[Rules and Regulations]
[Page 59033-59380]
[DOCID:fr08oc08-17]

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Part II

Environmental Protection Agency

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40 CFR Parts 9, 60, 80 et al.

Control of Emissions From Nonroad Spark-Ignition Engines and Equipment;
Final Rule

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 9, 60, 80, 85, 86, 89, 90, 91, 92, 94, 1027, 1033,
1039, 1042, 1045, 1048, 1051, 1054, 1060, 1065, 1068, and 1074

[EPA-HQ-OAR-2004-0008; FRL-8712-8]
RIN 2060-AM34

Control of Emissions From Nonroad Spark-Ignition Engines and
Equipment

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: We are setting emission standards for new nonroad spark-
ignition engines that will substantially reduce emissions from these
engines. The exhaust emission standards apply starting in 2010 for new
marine spark-ignition engines, including first-time EPA standards for
sterndrive and inboard engines. The exhaust emission standards 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 adopting
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, this rule will result in significantly
reduced pollutant emissions from regulated engine and equipment
sources, including estimated annual nationwide reductions of 604,000
tons of volatile organic hydrocarbon emissions, 132,200 tons of
NOX emissions, and 5,500 tons of directly-emitted
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 1,461,000 tons of
carbon monoxide emissions, with the greatest reductions in areas where
there have been problems with individual exposures. The requirements in
this rule will substantially benefit public health and welfare and the
environment. We estimate that by 2030, on an annual basis, these
emission reductions will prevent 230 PM-related premature deaths,
between 77 and 350 ozone-related premature deaths, approximately 1,700
hospitalizations and emergency room visits, 23,000 work days lost,
180,000 lost school days, 590,000 acute respiratory symptoms, and other
quantifiable benefits every year. The total annual benefits of this
rule in 2030 are estimated to be between $1.8 billion and $4.4 billion,
assuming a 3% discount rate. The total annual benefits of this rule in
2030 are estimated to be between $1.6 billion and $4.3 billion,
assuming a 7% discount rate. Estimated costs in 2030 are many times
less at approximately $190 million.

DATES: This rule is effective on December 8, 2008. The incorporation by
reference of certain publications listed in this regulation is approved
by the Director of the Federal Register as of December 8, 2008.

ADDRESSES:
    Docket: All documents in the docket are listed in the
www.regulations.gov index. Although listed in the index, some
information is not publicly available, 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 www.regulations.gov or in hard copy at the ``Control of Emissions
from Nonroad Spark-Ignition Engines, Vessels and Equipment'' Docket.
The docket is located in the EPA Headquarters Library, Room Number 3334
in the EPA West Building, located at 1301 Constitution Ave., NW.,
Washington, DC. The EPA/DC Public Reading Room hours of operation will
be 8:30 a.m. to 4:30 p.m. Eastern Standard Time (EST), Monday through
Friday, excluding holidays. The telephone number for the Public Reading
Room is<PHONE_NUMBER> and the telephone number for the Docket is (202)
566-1742.

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 regulations. Note that we are adopting
minor changes in the regulations that apply to a wide range of products
that may not be reflected in the following table (see Section VIII). If
you have questions, call the person listed in the FOR FURTHER
INFORMATION CONTACT section above:

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                                                NAICS codes   SIC codes      Examples of potentially regulated
                   Category                         \a\          \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  Manufacturers of marine vessels.
                                                                    3732
Industry......................................       811112         7533  Commercial importers of vehicles and
                                                     811198         7549   vehicle components.
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\a\ North American Industry Classification System (NAICS).
\b\ Standard Industrial Classification (SIC) system code.

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 Rule into Perspective
    E. What Requirements Are We Adopting?
    F. How Is This Document Organized?
    G. Judicial Review
II. Public Health and Welfare Effects
    A. Public Health Impacts
    B. Air Toxics
    C. Carbon Monoxide

III. Sterndrive and Inboard Marine Engines
    A. Overview
    B. Engines Covered by This Rule
    C. 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. Final Exhaust Emission Standards
    D. Changes to 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. Final 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. Final Evaporative Emission Standards
    D. Emission Credit Programs
    E. Testing Requirements
    F. Certification and Compliance Provisions
    G. Small-Business Provisions
    H. Technological Feasibility
VII. Energy, Noise, and Safety
    A. Safety
    B. Noise
    C. Energy
VIII. Requirements 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)
    H. Amendments Related to Locomotive, Marine, and Other Nonroad
Compression-Ignition Engines (40 CFR Parts 89, 92, 94, 1033, 1039,
and 1042)
IX. 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
X. Public Participation
XI. 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
    K. Congressional Review Act

I. Introduction

A. Overview

    This rule will reduce the mobile-source contribution to air
pollution in the United States. In particular, we are adopting
standards that will 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 new emission 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 rule are already regulated under existing emission
standards, except sterndrive and inboard marine engines, which are
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 2030
without this final rule these engines would account for about 33
percent (1,287,000 tons) of mobile source volatile organic hydrocarbon
compounds (VOC) emissions, 31 percent (15,605,000 tons) of mobile
source carbon monoxide (CO) emissions, 6 percent (311,300 tons) of
mobile source oxides of nitrogen (NOX) emissions, and 12
percent (44,000 tons) of mobile source particulate matter
(PM2.5) emissions. The new 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 new
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 environmental
problems associated with Marine SI engines and Small SI engines, such
as injury to vegetation and ecosystems and visibility impairment. These
effects are described in more detail later in this document.

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 set standards for nonroad spark-
ignition engines comes from section 428(b) of the 2004 Consolidated
Appropriations Act, which requires EPA to adopt 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 rule implements
Congress' mandate by adopting 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\ Public Law 108-199, Div G, Title IV, Sec.  428(b), 118 Stat.
418 (January 23, 2004).
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    We are adopting 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 adopting
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
                                     regulations        Cross  reference
       Engine categories        establishing emission    to table  I-2
                                      standards
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1. Locomotives engines........  40 CFR Part 92 and     d, l.
                                 1033.
2. Marine diesel engines......  40 CFR Part 94 and     g, i, j, l.
                                 1042.
3. Other nonroad diesel         40 CFR Parts 89 and    a, e, k.
 engines.                        1039.
4. Marine SI engines \a\......  40 CFR Part 91.......  c.
5. Recreational vehicles......  40 CFR Part 1051.....  i.
6. Small SI engines \b\.......  40 CFR Part 90.......  b, f, h.
7. Large SI engines \b\.......  40 CFR Part 1048.....  i.
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\a\ 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.
\b\ 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.

                                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--Tier 1.....  56 FR 31306.............  June 17, 1994.
b. Small SI engines--Phase 1......................  60 FR 34581.............  July 3, 1995.
c. Marine SI engines--outboard and personal         61 FR 52088.............  October 4, 1996.
 watercraft.
d. Locomotives....................................  63 FR 18978.............  April 16, 1998.
e. Land-based diesel engines--Tier 1 and Tier 2     63 FR 56968.............  October 23, 1998.
 for engines < 37 kW--Tier 2 and Tier 3 for
 engines >= 37 kW.
f. Small SI engines (Nonhandheld)--Phase 2........  64 FR 15208.............  March 30, 1999.
g. Commercial marine diesel < 30 liters per         64 FR 73300.............  December 29, 1999.
 cylinder.
h. Small SI engines (Handheld)--Phase 2...........  65 FR 24268.............  April 25, 2000.
i. Recreational vehicles, Industrial spark-         67 FR 68242.............  November 8, 2002.
 ignition engines > 19 kW, and Recreational marine
 diesel.
j. Marine diesel engines >= 2.5 liters/cylinder...  68 FR 9746..............  February 28, 2003.
k. Land-based diesel engines--Tier 4..............  69 FR 38958.............  June 29, 2004.
l. Locomotives and commercial marine diesel < 30    73 FR 37096.............  June 30, 2008.
 liters per cylinder.
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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 (64 FR 15208).\4\
The Phase 2 regulations included a phase-in period that has recently
been completed. 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\ 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 handheld
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 (69 FR 1824). 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.\5\ However, we believe it is appropriate
to apply evaporative emission standards to handheld engines similar to
the standards we are adopting for the nonhandheld engines.
Manufacturers can control evaporative emissions from handheld engines
in a way that has little or no impact on exhaust emissions.
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    \5\ 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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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.
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 for the other engine categories
subject to this final rule. The Tier 2 standards also include
evaporative emission standards, new transient test procedures,
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. We 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. The
California Air Resources Board 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 do
not increase overall stringency beyond that reflected in the federal
standards. As a result, we believe it is inappropriate to adopt 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. This rule preserves this approach.
 Recreational Vehicles
    We adopted exhaust and evaporative emission standards for
recreational vehicles in our November 8, 2002 final rule (67 FR 68242).
These standards apply to all-terrain vehicles, off-highway motorcycles,
and snowmobiles.\6\ These exhaust emission standards were fully phased
in starting with the 2007 model year. The evaporative emission
standards apply starting with the 2008 model year.
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    \6\ 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 included 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. Considering these new
requirements for recreational vehicles in a 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.

All-Terrain Vehicles
    EPA's initial round of exhaust emission standards was fully
implemented starting with the 2007 model year. The regulations for all-
terrain vehicles (ATV) specify testing based on a chassis-based
transient procedure. However, we permit manufacturers on an interim
basis to optionally use a steady-state engine-based procedure. We
recently completed a change in the regulations to extend this allowance
from 2009 through 2014, after which manufacturers must certify all
their ATVs based on the chassis-based transient test procedure that
applies for off-highway motorcycles (72 FR 20730, April 26, 2007). This
change does not represent an increase in stringency, but manufacturers
will be taking time to make the transition to the different test
procedure. We expect that there will be a good potential to apply
further emission controls on these engines. However, we do not have
information at this time on possible advances in technology beyond what
is required for the current standards.
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 expect to be able to better judge
the potential for broadly applying new technology to achieve further
emission reductions from off-highway motorcycles.
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 above 50 hp and
there is still a fundamental need for time to pass to allow us to
assess the success of four-stroke engine technology in the
marketplace.\7\ This is an important aspect of the assessment we need
to conduct with regard to the Phase 3 emission standards. We believe it
is best to address this in a separate rulemaking and we have initiated
that effort to evaluate the appropriate long-term emission standards
for snowmobiles.
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    \7\ Only about 3 percent of snowmobiles are rated below 50
horsepower.
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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 recently adopted a new
round of more stringent emission standards for both locomotives and
marine diesel engines that will require widespread use of
aftertreatment technology (73 FR 37096, June 30, 2008).
    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 Rule 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.
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 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 codifying these preemption changes in this
rule.
    The California Air Resources Board (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 ARB 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 ARB 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 for identifying 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 adopted exhaust emission standards and
new evaporative emission standards for these engines, consistent with
EPA's 2007 model year standards. Their new requirements also included
an additional level of emission control for Large SI engines starting
with the 2010 model year. However, their 2010 standards do 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.
Actions in Other Countries
    While the new 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 at
or above 50 cc 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 must
require that engines placed on the market meet the requirements of the
Directive, whether or not they are already installed in machinery.
    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
----------------------------------------------------------------------------------------------------------------
Note: P = rated power in kilowatts (kW).

E. What Requirements Are We Adopting?

    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 and fuel
systems 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 in
this rulemaking. See the later sections for a full discussion of the
rule.
Marine SI Engines and Vessels
    We are adopting a more stringent level of emission standards for
outboard and personal watercraft engines starting with the 2010 model
year. The HC+NOX emission standards are the same as those
adopted by California ARB for 2008 and later model year engines. The CO
emission standard is 300 g/kW-hr for engines with maximum engine power
above 40 kW; the standard increases as a function of maximum engine
power for smaller engines. We expect manufacturers to meet these
standards with improved fueling systems and other in-cylinder controls.
We are not pursuing catalyst-based emission standards for outboard and
personal watercraft engines. As discussed below, 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 it
is not straightforward to apply the fundamental engine modifications,
fuel system upgrades, and other engine control modifications needed to
get acceptable catalyst performance. This rule 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 four-stroke
engines or 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 more
stringent controls in the future.
    We are adopting new exhaust emission standards for sterndrive and
inboard marine engines. The standards are 5.0 g/kW-hr for
HC+NOX and 75.0 g/kW-hr for CO starting with the 2010 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 will require engines to
have a diagnostic system for detecting a failure in the emission
control system. For sterndrive and inboard marine engines above 373 kW
with high-performance characteristics (generally referred to as ``SD/I
high-performance engines''), we are adopting less stringent emission
standards that reflect their limited ability to control emissions with
catalysts. The HC+NOX standard is 16 g/kW-hr in for engines
at or below 485 kW and 22 g/kW-hr for bigger engines. The CO standard
for all SD/I high-performance engines is 350 g/kW-hr. Manufacturers of
these engines must meet emission standards without generating or using
emission credits. We also include a variety of other special provisions
for these engines to reflect unique operating characteristics.
    The emission standards described above relate to engine operation
over a prescribed duty cycle for testing in the laboratory. We are also
adopting 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 (the NTE
standards do not apply to SD/I high-performance engines).
    We are adopting 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 including these new regulations for Marine SI engines in 40
CFR part 1045 rather than in the current regulations in 40 CFR part 91.
This new part allows 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.
Small SI Engines and Equipment
    We are adopting 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 maintaining 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
adopting a more stringent Phase 3 CO emission standard of 5.0 g/kW-hr.
This applies equally to all sizes of engines subject to the Small SI
standards.
    We are adopting 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 will also require control of running loss
emissions.
    We are drafting the new regulations for Small SI engines from 40
CFR part 90 rather than changing the current regulations in 40 CFR part
90. 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?

    Many readers may be interested only in certain aspects of the rule
since it covers a broad range of engines and equipment that vary in
design and use. We have therefore attempted to organize this
information 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 subject
to the rule.
    The next several sections describe the provisions that apply for
Small SI engines and equipment and Marine SI engines and vessels.
Sections III through V describe the new 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 new requirements related
to evaporative emissions for all categories. Section VII discusses how
we took energy, noise, and safety factors into consideration for the
new standards.
    Section VIII describes a variety of provisions that affect other
categories of engines besides those that are the primary subject of
this rule. This includes the following changes:
     We are reorganizing the regulatory language related to
preemption of state standards and to clarify certain provisions.
     We are incorporating new provisions related to
certification fees for newly regulated products covered by this rule.
This involves some restructuring of the regulatory language. We are
also adopting various technical amendments, such as identifying an
additional payment method, that apply broadly to our certification
programs.
     We are modifying 40 CFR part 1068 to clarify when engines
are subject to standards. This includes several new provisions to
address special cases for partially complete engines.
     We are also modifying part 1068 to clarify how the
provisions apply with respect to evaporative emission standards and we
are adopting various technical amendments. These changes apply to all
types of nonroad engines that are subject to the provisions of part
1068.
     We are adopting several technical amendments for other
categories of nonroad engines and vehicles, largely to maintain
consistency across programs for different categories of engines and
vehicles.
     We are amending provisions related to delegated assembly.
The new approach is to adopt a universal set of requirements in Sec.
1068.261 that applies uniformly to heavy-duty highway engines and
nonroad engines.
     We are clarifying that the new exhaust and evaporative
emission standards for Small SI engines also apply to the comparable
stationary engines.

    Section IX summarizes the projected impacts and benefits of this
rule. Finally, Sections X and XI summarize the primary public comments
received and describe how we satisfy our various administrative
requirements.

G. Judicial Review

    Under section 307(b)(1) of the Clean Air Act (CAA), judicial review
of these final rules is available only by filing a petition for review
in the U.S. Court of Appeals for the District of Columbia Circuit by
December 8, 2008. Under section 307(b)(2) of the CAA, the requirements
established by these final rules may not be challenged separately in
any civil or criminal proceedings brought by EPA to enforce these
requirements.
    Section 307(d)(7)(B) of the CAA further provides that ``[o]nly an
objection to a rule or procedure which was raised with reasonable
specificity during the period for public comment (including any public
hearing) may be raised during judicial review.'' This section also
provides a mechanism for us to convene a proceeding for
reconsideration, ``[i]f the person raising an objection can demonstrate
to the EPA that it was impracticable to raise such objection within
[the period for public comment] or if the grounds for such objection
arose after the period for public comment (but within the time
specified for judicial review) and if such objection is of central
relevance to the outcome of the rule.'' Any person seeking to make such
a demonstration to us should submit a Petition for Reconsideration to
the Office of the Administrator, U.S. EPA, Room 3000, Ariel Rios
Building, 1200 Pennsylvania Ave., NW., Washington, DC 20460, with a
copy to both the person(s) listed in the preceding FOR FURTHER
INFORMATION CONTACT section and the Associate General Counsel for the
Air and Radiation Law Office, Office of General Counsel (Mail Code
2344A), U.S. EPA, 1200 Pennsylvania Ave., NW., Washington, DC 20460.

II. Public Health and Welfare Effects

    The engines and fuel systems subject to this rule 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 and fuel systems also emit hazardous air pollutants
(air toxics) that are associated with a host of adverse health effects.
Emissions from these engines and fuel systems also contribute to
visibility impairment and other welfare and environmental effects.
    This section summarizes the general health and welfare effects of
these emissions. Interested readers are encouraged to refer to the
Final RIA for more in-depth discussions.

A. Public Health Impacts

Ozone
    The Small SI engine and Marine SI engine standards finalized in
this action will result in reductions of volatile organic compounds
(VOC), of which HC are a subset, and NOX emissions. VOC and NOX
contribute to the formation of ground-level ozone pollution or smog.
People in many areas across the U.S. continue to be exposed to
unhealthy levels of ambient ozone.
Background
    Ground-level ozone pollution is typically formed by the reaction of
VOC 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, power plants, chemical plants, refineries,
makers of consumer and commercial products, industrial facilities, and
smaller area sources.
    The science of ozone formation, transport, and accumulation is
complex.\8\ Ground-level ozone is produced and destroyed in a cyclical
set of chemical reactions, many of which are sensitive to temperature
and sunlight. When ambient temperatures and sunlight levels remain high
for several days and the air is relatively stagnant, ozone and its
precursors can build up and result in more ozone than typically occurs
on a single high-temperature day. Ozone can be transported hundreds of
miles downwind of precursor emissions, resulting in elevated ozone
levels even in areas with low local VOC or NOX emissions.
---------------------------------------------------------------------------

    \8\ U.S. EPA Air Quality Criteria for Ozone and Related
Photochemical Oxidants (Final). U.S. Environmental Protection
Agency, Washington, D.C., EPA 600/R-05/004aF-cF, 2006. This document
is available in Docket EPA-HQ-OAR-2003-0190. This document may be
accessed electronically at: http://www.epa.gov/ttn/naaqs/standards/
ozone/s_o3_cr_cd.html.
---------------------------------------------------------------------------

    EPA has recently amended the ozone NAAQS (73 FR 16436, March 27,
2008). The final ozone NAAQS rule addresses revisions to the primary
and secondary NAAQS for ozone to provide increased protection of public
health and welfare, respectively. With regard to the primary standard
for ozone, EPA has revised the level of the 8-hour standard to 0.075
parts per million (ppm), expressed to three decimal places. With regard
to the secondary standard for ozone, EPA has revised the current 8-hour
standard by making it identical to the revised primary standard.
Health Effects of Ozone
    The health and welfare effects of ozone are well documented and are
assessed in EPA's 2006 ozone Air Quality Criteria Document (ozone AQCD)
and EPA Staff Paper.9, 10 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; breathing may also 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
medical attention and/or the use of additional medication. In addition,
there is suggestive evidence of a contribution of ozone to
cardiovascular-related morbidity and highly suggestive evidence that
short-term ozone exposure directly or indirectly contributes to non-
accidental and cardiopulmonary-related mortality, but additional
research is needed to clarify the underlying mechanisms causing these
effects. In a recent report on the estimation of ozone-related
premature mortality published by the National Research Council (NRC), a
panel of experts and reviewers concluded that short-term exposure to
ambient ozone is likely to contribute to premature deaths and that
ozone-related mortality should be included in estimates of the health
benefits of reducing ozone exposure.\11\ Animal toxicological evidence
indicates that with repeated exposure, ozone can inflame and damage the
lining of the lungs, which may lead to permanent changes in lung tissue
and irreversible reductions in lung function. People who are more
susceptible to effects

associated with exposure to ozone can include children, the elderly,
and individuals with respiratory disease such as asthma. Those with
greater exposures to ozone, for instance due to time spent outdoors
(e.g., children and outdoor workers), are also of particular concern.
---------------------------------------------------------------------------

    \9\ 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-2003-0190. This document may be
accessed electronically at: http://www.epa.gov/ttn/naaqs/standards/
ozone/s_o3_cr_cd.html.
    \10\ U.S. EPA (2007) Review of the National Ambient Air Quality
Standards for Ozone, Policy Assessment of Scientific and Technical
Information. OAQPS Staff Paper.EPA-452/R-07-003. This document is
available in Docket EPA-HQ-OAR-2003-0190. This document is available
electronically at: http:www.epa.gov/ttn/naaqs/standards/ozone/s_
o3_cr_sp.html.
    \11\ National Research Council (NRC), 2008. Estimating Mortality
Risk Reduction and Economic Benefits from Controlling Ozone Air
Pollution. The National Academies Press: Washington, DC.
---------------------------------------------------------------------------

    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 toxicological 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.
Plant and Ecosystem Effects of Ozone
    Elevated ozone levels contribute to 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 low 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 final 2006
Criteria Document presents more detailed information on ozone effects
on vegetation and ecosystems.
Current and Projected Ozone Levels
    Ozone concentrations exceeding the level of the 1997 8-hour ozone
NAAQS occur over wide geographic areas, including most of the nation's
major population centers.\12\ As of March 12, 2008, there were
approximately 140 million people living in 72 areas (which include all
or part of 337 counties) designated as not in attainment with the 1997
8-hour ozone NAAQS.\13\ These numbers do not include the people living
in areas where there is a future risk of failing to maintain or attain
the 8-hour ozone NAAQS. The 1997 ozone NAAQS was recently revised and
the 2008 ozone NAAQS was final on March 12, 2008. Table II-1 presents
the number of counties in areas currently designated as nonattainment
for the 1997 ozone NAAQS as well as the number of additional counties
that have design values greater than the 2008 ozone NAAQS.
---------------------------------------------------------------------------

    \12\ A listing of the 8-hour ozone nonattainment areas is
included in the RIA for this rule.
    \13\ Population numbers are from 2000 census data.

   Table II-1--Counties With Design Values Greater Than the 2008 Ozone
                NAAQS Based on 2004-2006 Air Quality Data
------------------------------------------------------------------------
                                          Number of
                                          Counties       Population \a\
------------------------------------------------------------------------
 1997 Ozone Standard: Counties                     337       139,633,458
 within the 72 areas currently
 designated as nonattainment........
2008 Ozone Standard: Additional                     74        15,984,135
 counties that would not meet the
 2008 NAAQS \b\.....................
                                     -----------------------------------
    Total...........................               411       155,617,593
------------------------------------------------------------------------
Notes:
\a\ Population numbers are from 2000 census data.
\b\ Attainment designations for 2008 ozone NAAQS have not yet been made.
  Nonattainment for the 2008 Ozone NAAQS will be based on three years of
  air quality data from later years. Also, the county numbers in the
  table include only the counties with monitors violating the 2008 Ozone
  NAAQS. The numbers in this table may be an underestimate of the number
  of counties and populations that will eventually be included in areas
  with multiple counties designated nonattainment.

    States with 8-hour ozone nonattainment areas are 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 1997 ozone NAAQS in the 2007 to 2013
time frame and then maintain the NAAQS thereafter.\14\ Many of these
nonattainment areas will need to adopt additional emission reduction
programs and the VOC and NOX reductions from this final action are
particularly important for these states. The attainment dates
associated with the potential new 2008 ozone nonattainment areas are
likely to be in the 2013 to 2021 timeframe, depending on the severity
of the problem.
---------------------------------------------------------------------------

    \14\ The Los Angeles South Coast Air Basin 8-hour ozone
nonattainment area will have to attain before June 15, 2021.
---------------------------------------------------------------------------

    EPA has already adopted many emission control programs that are
expected to reduce ambient ozone levels. Some of these control programs
are described in Section I.C.1. As a result of existing programs, the
number of areas that fail to meet the ozone NAAQS in the future is
expected to decrease. Based on the air quality modeling performed for
this rule, which does not include any additional local controls, we
estimate eight counties (where 22 million people are projected to live)
will exceed the 1997 8-hour

ozone NAAQS in 2020.\15\ An additional 37 counties (where 27 million
people are projected to live) are expected to be within 10 percent of
violating the 1997 8-hour ozone NAAQS in 2020.
---------------------------------------------------------------------------

    \15\ 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.
---------------------------------------------------------------------------

    Results from the air quality modeling conducted for this final rule
indicate that the Small SI and Marine SI engine emission reductions in
2020 and 2030 will improve both the average and population-weighted
average ozone concentrations for the U.S. In addition, the air quality
modeling shows that on average this final rule will help bring counties
closer to ozone attainment as well as assist counties whose ozone
concentrations are within ten percent below the standard. For example,
on a population-weighted basis, the average modeled future-year 8-hour
ozone design values will decrease by 0.57 ppb in 2020 and 0.76 ppb in
2030.\16\ The air quality modeling methodology and the projected
reductions are discussed in more detail in Chapter 2 of the RIA.
---------------------------------------------------------------------------

    \16\ Ozone design values are reported in parts per million (ppm)
as specified in 40 CFR Part 50. Due to the scale of the design value
changes in this action, results have been presented in parts per
billion (ppb) format.
---------------------------------------------------------------------------

Particulate Matter
    The Small SI engine and Marine SI engine standards detailed in this
action will result in reductions in emissions of VOCs and NOX which
contribute to the formation of secondary PM2.5. In addition,
the standards finalized today will reduce primary (directly emitted)
PM2.5 emissions.
Background
    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 (m) in aerodynamic diameter.
PM2.5 refers to fine particles, generally less than or equal
to 2.5 in aerodynamic 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 aerodynamic diameter. Ultrafine PM
refers to particles less than 100 nanometers (0.1 [mu]m) in aerodynamic
diameter. Larger particles tend to be removed by the respiratory
clearance mechanisms (e.g. coughing), 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 VOC) in the
atmosphere. The chemical and physical properties of PM2.5 may vary
greatly with time, region, meteorology, and source category. Thus,
PM2.5 may include a complex mixture of different pollutants including
sulfates, nitrates, organic compounds, elemental carbon and metal
compounds. These particles can remain in the atmosphere for days to
weeks and travel hundreds to thousands of kilometers.
    The primary PM2.5 NAAQS includes a short-term (24-hour) and a long-
term (annual) standard. The 1997 PM2.5 NAAQS established by EPA set the
24-hour standard at a level of 65[mu]g/m\3\ based on the 98th
percentile concentration averaged over three years. The annual standard
specifies an expected annual arithmetic mean not to exceed 15[mu]g/m\3\
averaged over three years.
    In 2006, EPA amended the NAAQS for PM2.5 (71 FR 61144, October 17,
2006). The final rule addressed revisions to the primary and secondary
NAAQS for PM to provide increased protection of public health and
welfare, respectively. The level of the 24-hour PM2.5 NAAQS was revised
from 65[mu]g/m\3\ to 35 [mu]g/m\3\ and the level of the annual PM2.5
NAAQS was retained at 15[mu]g/m\3\. With regard to the secondary
standards for PM2.5, EPA has revised these standards to be identical in
all respects to the revised primary standards.
Health Effects of PM2.5
    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), and the 2005 PM Staff Paper.17 18 Further discussion
of health effects associated with PM can also be found in the RIA for
this rule.
---------------------------------------------------------------------------

    \17\ 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-2003-0190.
    \18\ 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-2003-0190.
---------------------------------------------------------------------------

    Health effects associated with short-term exposures (hours to days)
to ambient PM 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 cardiovascular and respiratory mortality.\19\ In
addition, a reanalysis of the American Cancer Society Study shows an
association between fine particle and sulfate concentrations and lung
cancer mortality.\20\
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    \19\ Dockery, DW; Pope, CA III: Xu, X; et al. 1993. An
association between air pollution and mortality in six U.S. cities.
N Engl J Med 329:1753-1759.
    \20\ Pope, C. A., III; Burnett, R. T.; Thun, M. J.; Calle, E.
E.; Krewski, D.; Ito, K.; Thurston, G. D. (2002) Lung cancer,
cardiopulmonary mortality, and long-term exposure to fine
particulate air pollution. J. Am. Med. Assoc. 287:1132-1141.
---------------------------------------------------------------------------

    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 controls
finalized in this action 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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Visibility

    Visibility can be defined as the degree to which the atmosphere is
transparent to visible light. Airborne particles degrade visibility by
scattering and absorbing light. 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 final 2004 PM AQCD as well as the 2005 PM Staff
Paper.24 25
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    \24\ 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-2003-0190.
    \25\ 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-2003-0190.
---------------------------------------------------------------------------

    EPA is pursuing a two-part strategy to address visibility. First,
to address the welfare effects of PM on visibility, EPA has set
secondary PM2.5 standards which act in conjunction with the
establishment of a regional haze program. In setting this secondary
standard, EPA has 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.
Second, section 169 of the Clean Air Act provides additional authority
to address 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).\26\ 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.
---------------------------------------------------------------------------

    \26\ 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.
---------------------------------------------------------------------------

Current Visibility Impairment

    As of March 12, 2008, over 88 million people live in nonattainment
areas for the 1997 PM2.5 NAAQS.\27\ These populations, as well as large
numbers of individuals who travel to these areas, are likely to
experience visibility impairment. 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.\28\ 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
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    \27\ Population numbers are from 2000 census data.
    \28\ U.S. EPA (2002) Latest Findings on National Air Quality--
2002 Status and Trends. EPA 454/K-03-001.
    \29\ U.S. 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\ U.S. EPA. Regional Haze Regulations, July 1, 1999. (64 FR
35714, July 1, 1999).
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Future Visibility Impairment
    Air quality modeling conducted for this final rule was used to
project visibility conditions in 133 mandatory class I federal areas
across the U.S. in 2020 and 2030. The results indicate that
improvements in visibility will occur in the future, although all areas
will continue to have annual average deciview levels above background
in 2020 and 2030. Chapter 2 of the RIA contains more detail on the
visibility portion of the air quality modeling.
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.\31\
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    \31\ 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. This document is available in Docket
EPA-HQ-OAR-2003-0190.
---------------------------------------------------------------------------

    Adverse impacts on water quality can occur when atmospheric
contaminants deposit to the water surface or when material deposited on
the land enters a water body through runoff. Potential impacts of
atmospheric deposition to water bodies 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.32 33 34 35 36
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    \32\ U.S. EPA (2004) National Coastal Condition Report II.
Office of Research and Development/ Office of Water. EPA-620/R-03/
002. This document is available in Docket EPA-HQ-OAR-2003-0190.
    \33\ 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.
    \34\ 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.
    \35\ 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.
    \36\ 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.
Materials Damage and Soiling
    The deposition of airborne particles can reduce the aesthetic
appeal of buildings and culturally important articles through soiling,
and can contribute directly (or in conjunction with other pollutants)
to structural damage by means of corrosion or erosion.\37\ Particles
affect materials principally by promoting and accelerating the
corrosion of metals, by degrading paints, and by deteriorating building
materials such as concrete and limestone. Particles contribute to these
effects because of their electrolytic, hygroscopic, and acidic
properties, and their ability to adsorb corrosive gases (principally
sulfur dioxide). The rate of metal corrosion depends on a number of
factors, including the deposition rate and nature of the pollutant; the
influence of the metal protective

corrosion film; the amount of moisture present; variability in the
electrochemical reactions; the presence and concentration of other
surface electrolytes; and the orientation of the metal surface.
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    \37\ U.S EPA (2005) Review of the National Ambient Air Quality
Standards for Particulate Matter: Policy Assessment of Scientific
and Technical Information, OAQPS Staff Paper. This document is
available in Docket EPA-HQ-OAR-2003-0190.
---------------------------------------------------------------------------

Current and Projected PM2.5 Levels
    PM2.5 concentrations exceeding the level of the
PM2.5 NAAQS occur in many parts of the country.\38\ In 2005
EPA designated 39 nonattainment areas for the 1997 PM2.5
NAAQS (70 FR 943, January 5, 2005). These areas are comprised of 208
full or partial counties with a total population exceeding 88 million.
The 1997 PM2.5 NAAQS was revised and the 2006
PM2.5 NAAQS became effective on December 18, 2006. Table II-
2 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 design values greater than the 2006
PM2.5 NAAQS.
---------------------------------------------------------------------------

    \38\ A listing of the PM2.5 nonattainment areas is
included in the RIA for this rule.

   Table II-2--Counties With Design Values Greater Than the 2006 PM2.5
                NAAQS Based on 2003-2005 Air Quality Data
------------------------------------------------------------------------
 Nonattainment areas/other violating      Number of
              counties                    counties        Population a
------------------------------------------------------------------------
1997 PM2.5 Standards: Counties                     208        88,394,000
 within the 39 areas currently
 designated as nonattainment........
2006 PM2.5 Standards: Additional                    49        18,198,676
 counties that would not meet the
 2006 NAAQS b.......................
                                     -----------------------------------
    Total...........................               257       106,595,676
------------------------------------------------------------------------
Notes:
a Population numbers are from 2000 census data.
b Attainment designations for 2006 PM2.5 NAAQS have not yet been made.
  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 table
  includes only the counties with monitors violating the 2006 PM2.5
  NAAQS. The numbers in this table may be an underestimate of the number
  of counties and populations that will eventually be included in areas
  with multiple counties designated nonattainment.

    Areas designated as not attaining the 1997 PM2.5 NAAQS
will need to attain the 1997 standards in the 2010 to 2015 time frame,
and then maintain them thereafter. The attainment dates associated with
the potential new 2006 PM2.5 nonattainment areas are likely
to be in the 2014 to 2019 timeframe. The emission standards finalized
in this action become effective as early as 2009 making the inventory
reductions from this rulemaking useful to states in attaining or
maintaining the PM2.5 NAAQS.
    EPA has already adopted many emission control programs that are
expected to reduce ambient PM2.5 levels and which will
assist in reducing the number of areas that fail to achieve the
PM2.5 NAAQS. Even so, our air quality modeling for this
final rule projects that in 2020, with all current controls but
excluding the reductions achieved through this rule, up to 11 counties
with a population of over 24 million may not attain the current annual
PM2.5 standard of 15 [mu]g/m3. These numbers do
not account for additional areas that have air quality measurements
within 10 percent of the annual PM2.5 standard. These areas,
although not violating the standards, will also benefit from the
additional reductions from this rule ensuring long term maintenance of
the PM2.5 NAAQS.
    Air quality modeling performed for this final rule shows the
emissions reductions will improve both the average and population-
weighted average PM2.5 concentrations for the U.S. On a
population-weighted basis, the average modeled future-year annual
PM2.5 design value (DV) for all counties is expected to
decrease by 0.02 [mu]g/m3 in 2020 and 2030. There are areas
with larger decreases in their future-year annual PM2.5 DV,
for instance the Chicago region will experience a 0.08 [mu] g/m\3\
reduction by 2030. The air quality modeling methodology and the
projected reductions are discussed in more detail in Chapter 2 of the
RIA.

B. Air Toxics

    Small SI and Marine SI emissions also contribute to ambient levels
of air toxics known or suspected as human or animal carcinogens, or
that have noncancer health effects. These air toxics 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 cancer risk or
noncancer hazard 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 and
noncancer risk from breathing outdoor air toxics. In addition, human
exposure to toxics from spark-ignition engines also occurs as a result
of operating these engines and from intrusion of emissions in
residential garages into attached indoor spaces.39 40 The
emission reductions from Small SI and Marine SI engines that are
finalized in this rulemaking will help reduce exposure to these harmful
substances.
---------------------------------------------------------------------------

    \39\ Baldauf, R.; Fortune, C.; Weinstein, J.; Wheeler, M.;
Blanchard, B. (2006) Air contaminant exposures during the operation
of lawn and garden equipment. J Expos Sci Environ Epidmeiol 16: 362-
370.
    \40\ Isbell, M.; Ricker, J.; Gordian, M.E.; Duff, L.K. (1999)
Use of biomarkers in an indoor air study: lack of correlation
between aromatic VOCs with respective urinary biomarkers. Sci Total
Environ 241: 151-159.
---------------------------------------------------------------------------

    Benzene: The EPA's IRIS database lists benzene as a known human
carcinogen (causing leukemia) by all routes of exposure, and concludes
that exposure is associated with additional health effects, including
genetic changes in both humans and animals and increased proliferation
of bone marrow cells in mice.41 42 43 EPA states in its IRIS
database that data indicate a causal relationship between benzene
exposure and acute lymphocytic leukemia and suggest a relationship
between benzene exposure and chronic non-lymphocytic

leukemia and chronic lymphocytic leukemia. The International Agency for
Research on Carcinogens (IARC) has determined that benzene is a human
carcinogen and the U.S. Department of Health and Human Services (DHHS)
has characterized benzene as a known human carcinogen.44 45
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    \41\ 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.
    \42\ International Agency for Research on Cancer (IARC). 1982.
Monographs on the evaluation of carcinogenic risk of chemicals to
humans, Volume 29, Some industrial chemicals and dyestuffs, World
Health Organization, Lyon, France, p. 345-389.
    \43\ 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.
    \44\ International Agency for Research on Cancer (IARC). 1987.
Monographs on the evaluation of carcinogenic risk of chemicals to
humans, Volume 29, Supplement 7, Some industrial chemicals and
dyestuffs, World Health Organization, Lyon, France.
    \45\ U.S. Department of Health and Human Services National
Toxicology Program 11th Report on Carcinogens available at: http://
ntp.niehs.nih.gov/go/16183.
---------------------------------------------------------------------------

    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.
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    \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\ U.S. EPA (2002) Toxicological Review of Benzene (Noncancer
Effects). Environmental Protection Agency, Integrated Risk
Information System (IRIS), Research and Development, National Center
for Environmental Assessment, Washington DC. This material is
available electronically at 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 IARC has determined that
1,3-butadiene is a human carcinogen and the U.S. DHHS has characterized
1,3-butadiene as a known human carcinogen.56 57 There are
numerous studies consistently demonstrating that 1,3-butadiene is
metabolized into genotoxic metabolites by experimental animals and
humans. The specific mechanisms of 1,3-butadiene-induced carcinogenesis
are unknown; however, the scientific evidence strongly suggests that
the carcinogenic effects are mediated by genotoxic metabolites. Animal
data suggest that females may be more sensitive than males for cancer
effects associated with 1,3-butadiene exposure; there are insufficient
data in humans from which to draw conclusions about sensitive
subpopulations. 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.\58\
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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. This document is available electronically at http://
www.epa.gov/iris/supdocs/buta-sup.pdf.
    \55\ U.S. EPA (2002) Full IRIS Summary for 1,3-butadiene (CASRN
106-99-0). Environmental Protection Agency, Integrated Risk
Information System (IRIS), Research and Development, National Center
for Environmental Assessment, Washington, DC http://www.epa.gov/
iris/subst/0139.htm.
    \56\ International Agency for Research on Cancer (IARC) (1999)
Monographs on the evaluation of carcinogenic risk of chemicals to
humans, Volume 71, Re-evaluation of some organic chemicals,
hydrazine and hydrogen peroxide and Volume 97 (in preparation),
World Health Organization, Lyon, France.
    \57\ U.S. Department of Health and Human Services (2005)
National Toxicology Program 11th Report on Carcinogens available at:
ntp.niehs.nih.gov/index.cfm?objectid=32BA9724-F1F6-975E-
7FCE50709CB4C932.
    \58\ 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.\59\ EPA is currently reviewing recently
published epidemiological data. For instance, 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.60 61 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.\62\ Extended follow-up of a cohort of
British chemical workers did not find evidence of an increase in
nasopharyngeal or lymphohematopoietic cancers, but a continuing
statistically significant excess in lung cancers was reported.\63\
Recently, the IARC re-classified formaldehyde as a human carcinogen
(Group 1).\64\
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    \59\ 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.
    \60\ 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.
    \61\ 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.
    \62\ Pinkerton, L. E. 2004. Mortality among a cohort of garment
workers exposed to formaldehyde: an update. Occup. Environ. Med. 61:
193-200.
    \63\ Coggon, D, EC Harris, J Poole, KT Palmer. 2003. Extended
follow-up of a cohort of British chemical workers exposed to
formaldehyde. J National Cancer Inst. 95:1608-1615.
    \64\ International Agency for Research on Cancer (IARC). 2006.
Formaldehyde, 2-Butoxyethanol and 1-tert-Butoxypropan-2-ol. Volume
88. (in preparation), World Health Organization, Lyon, France.
---------------------------------------------------------------------------

    Formaldehyde exposure also causes a range of noncancer health
effects, including irritation of the eyes (burning and watering of the
eyes), nose and throat. Effects from repeated exposure in humans
include respiratory tract irritation, chronic bronchitis and nasal
epithelial lesions such as metaplasia and loss of cilia. Animal studies
suggest that formaldehyde may also cause airway inflammation--including
eosinophil infiltration into the airways. There are several studies
that suggest that formaldehyde may increase the risk of asthma--
particularly in the young.65 66
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    \65\ Agency for Toxic Substances and Disease Registry (ATSDR).
1999. Toxicological profile for Formaldehyde. Atlanta, GA: U.S.
Department of Health and Human Services, Public Health Service.
http://www.atsdr.cdc.gov/toxprofiles/tp111.html
    \66\ WHO (2002) Concise International Chemical Assessment
Document 40: Formaldehyde. Published under the joint sponsorship of
the United Nations Environment Programme, the International Labour
Organization, and the World Health Organization, and produced within
the framework of the Inter-Organization Programme for the Sound
Management of Chemicals. Geneva.
---------------------------------------------------------------------------

    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.67 Acetaldehyde is

reasonably anticipated to be a human carcinogen by the U.S. DHHS in the
11th Report on Carcinogens and is classified as possibly carcinogenic
to humans (Group 2B) by the IARC.68 69 EPA is currently
conducting a reassessment of cancer risk from inhalation exposure to
acetaldehyde.
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    \67\ U.S. EPA. 191. Integrated Risk Information System File of
Acetaldehyde. Research and Development, National Center for
Environmental Assessment, Washington, DC. This material is available
electronically at http://www.epa.gov/iris/subst/0290.htm.
    \68\ U.S. Department of Health and Human Services National
Toxicology Program 11th Report on Carcinogens available at:
ntp.niehs.nih.gov/index.cfm?objectid=32BA9724-F1F6-975E-
7FCE50709CB4C932.
    \69\ International Agency for Research on Cancer (IARC). 1999.
Re-evaluation of some organic chemicals, hydrazine, and hydrogen
peroxide. IARC Monographs on the Evaluation of Carcinogenic Risk of
Chemical to Humans, Vol 71. Lyon, France.
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    The primary noncancer effects of exposure to acetaldehyde vapors
include irritation of the eyes, skin, and respiratory tract.\70\ In
short-term (4 week) rat studies, degeneration of olfactory epithelium
was observed at various concentration levels of acetaldehyde
exposure.71 72 Data from these studies were used by EPA to
develop an inhalation reference concentration. Some asthmatics have
been shown to be a sensitive subpopulation to decrements in functional
expiratory volume (FEV1 test) and bronchoconstriction upon acetaldehyde
inhalation.\73\ The agency is currently conducting a reassessment of
the health hazards from inhalation exposure to acetaldehyde.
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    \70\ U.S. EPA. 1991. Integrated Risk Information System File of
Acetaldehyde. This material is available electronically at http://
www.epa.gov/iris/subst/0290.htm.
    \71\ Appleman, L. M., R. A. Woutersen, V. J. Feron, R. N.
Hooftman, and W. R. F. Notten. 1986. Effects of the variable versus
fixed exposure levels on the toxicity of acetaldehyde in rats. J.
Appl. Toxicol. 6: 331-336.
    \72\ Appleman, L.M., R.A. Woutersen, and V.J. Feron. 1982.
Inhalation toxicity of acetaldehyde in rats. I. Acute and subacute
studies. Toxicology. 23: 293-297.
    \73\ Myou, S.; Fujimura, M.; Nishi K.; Ohka, T.; and Matsuda, T.
1993. Aerosolized acetaldehyde induces histamine-mediated
bronchoconstriction in asthmatics. Am. Rev. Respir.Dis.148(4 Pt 1):
940-3.
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    Acrolein: EPA determined in 2003 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.\74\ The IARC determined in 1995 that
acrolein was not classifiable as to its carcinogenicity in humans.\75\
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    \74\ 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
at http://www.epa.gov/iris/subst/0364.htm.
    \75\ International Agency for Research on Cancer (IARC). 1995.
Monographs on the evaluation of carcinogenic risk of chemicals to
humans, Volume 63, Dry cleaning, some chlorinated solvents and other
industrial chemicals, World Health Organization, Lyon, France.
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    Acrolein is extremely acrid and irritating to humans when inhaled,
with acute exposure resulting in upper respiratory tract irritation,
mucus hypersecretion and congestion. Levels considerably lower than 1
ppm (2.3 mg/m3) elicit subjective complaints of eye and
nasal irritation and a decrease in the respiratory
rate.76 77 Lesions to the lungs and upper respiratory tract
of rats, rabbits, and hamsters have been observed after subchronic
exposure to acrolein. Based on animal data, individuals with
compromised respiratory function (e.g., emphysema, asthma) are expected
to be at increased risk of developing adverse responses to strong
respiratory irritants such as acrolein. This was demonstrated in mice
with allergic airway-disease by comparison to non-diseased mice in a
study of the acute respiratory irritant effects of acrolein.\78\
---------------------------------------------------------------------------

    \76\ Weber-Tschopp, A; Fischer, T; Gierer, R; et al. (1977)
Experimentelle reizwirkungen von Acrolein auf den Menschen. Int Arch
Occup Environ Hlth 40(2):117-130. In German.
    \77\ Sim, VM; Pattle, RE. (1957) Effect of possible smog
irritants on human subjects. J Am Med Assoc 165(15):1908-1913.
    \78\ Morris JB, Symanowicz PT, Olsen JE, et al. 2003. Immediate
sensory nerve-mediated respiratory responses to irritants in healthy
and allergic airway-diseased mice. J Appl Physiol 94(4):1563-1571.
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    EPA is currently in the process of conducting an assessment of
acute exposure effects for acrolein. The intense irritancy of this
carbonyl has been demonstrated during controlled tests in human
subjects, who suffer intolerable eye and nasal mucosal sensory
reactions within minutes of exposure.\79\
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    \79\ Sim VM, Pattle RE. Effect of possible smog irritants on
human subjects JAMA165: 1980-2010, 1957.
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    Polycyclic Organic Matter (POM): POM is generally defined as a
large class of organic compounds which have multiple benzene rings and
a boiling point greater than 100 degrees Celsius. Many of the compounds
included in the class of compounds known as POM are classified by EPA
as probable human carcinogens based on animal data. One of these
compounds, naphthalene, is discussed separately below. Polycyclic
aromatic hydrocarbons (PAHs) are a subset 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
(a subclass of POM) 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.80 81 EPA has not yet evaluated these recent
studies.
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    \80\ 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.
    \81\ 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. Naphthalene emissions have been measured in larger
quantities in both gasoline and diesel exhaust compared with
evaporative emissions from mobile sources, indicating it is primarily a
product of combustion. EPA recently released an external review draft
of a reassessment of the inhalation carcinogenicity of naphthalene
based on a number of recent animal carcinogenicity studies.\82\ The
draft reassessment recently completed external peer review.\83\ Based
on external peer review comments received to date, additional analyses
are being undertaken. This external review draft does not represent
official agency opinion and was released solely for the purposes of
external peer review and public comment. Once EPA evaluates public and
peer reviewer comments, the document will be revised. The National
Toxicology Program listed naphthalene as ``reasonably anticipated to be
a human carcinogen'' in 2004 on the basis of bioassays reporting clear
evidence of carcinogenicity in rats and some evidence of
carcinogenicity in mice.\84\ 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.\85\
Naphthalene

also causes a number of chronic non-cancer effects in animals,
including abnormal cell changes and growth in respiratory and nasal
tissues.\86\
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    \82\ 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.
    \83\ Oak Ridge Institute for Science and Education (2004)
External Peer Review for the IRIS Reassessment of the Inhalation
Carcinogenicity of Naphthalene. August 2004. http://cfpub.epa.gov/
ncea/cfm/recordisplay.cfm?deid=84403.
    \84\ National Toxicology Program (NTP). (2004). 11th Report on
Carcinogens. Public Health Service, U.S. Department of Health and
Human Services, Research Triangle Park, NC. Available from: http://
ntp-server.niehs.nih.gov.
    \85\ International Agency for Research on Cancer (IARC) (2002)
Monographs on the Evaluation of the Carcinogenic Risk of Chemicals
for Humans. Vol. 82. Lyon, France.
    \86\ 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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    The standards finalized in this action will reduce air toxics
emitted from these engines, vessels and equipment. These emissions
reductions will help to mitigate some of the adverse health effects
associated with their operation.

C. 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 previously 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 are adopting a finding, based on the
information in this section and in Chapters 2 and 3 of the Final 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.\87\ Additional
information on CO related health effects can be found in the Carbon
Monoxide Air Quality Criteria Document (CO AQCD).\88\
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    \87\ 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.
    \88\ 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
Final 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.\89\ 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.\90\ 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.\91\
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    \89\ 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.
    \90\ 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.
    \91\ 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.
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    As of March 12, 2008, there were approximately 850,000 people
living in 4 areas (which include 5 counties) designated as
nonattainment for CO.\92\ The CO nonattainment areas are presented in
the Final RIA.
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    \92\ Population numbers are from 2000 census data.
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    EPA's NONROAD model indicates that Marine SI emissions 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-3.

       Table II-3--CO Emissions From Marine SI Engines and Vessels in Classified CO Nonattainment Areas a
----------------------------------------------------------------------------------------------------------------
                                                                                CO (short tons
                  Area                              County                     Category              in 2005)
----------------------------------------------------------------------------------------------------------------
Las Vegas, NV...........................  Clark.....................  Marine SI.................           3,016
Reno, NV................................  Washoe....................  Marine SI.................           3,494
El Paso, TX.............................  El Paso...................  Marine SI.................              37
----------------------------------------------------------------------------------------------------------------
Source: U.S. EPA, NONROAD 2005 model.
\a\ This table does not include Salem, OR which is an unclassified CO nonattainment area.

    Based on the national inventory numbers in Chapter 3 of the Final
RIA and the local inventory numbers described in this section, we 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 will undermine the broader goal of achieving the greatest degree
of emission control from the full set of Marine SI engines.
    We believe this 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, while an emission control program for SD/I
engines will increase the price of these engines, we no longer think
this will result in a market shift to higher-emitting outboard engines.
The economic impact analysis performed for this final rule, summarized
in Section XII, suggests that the prices will increase less than 1
percent and sales will be impacted by less than 2 percent. It is also
possible that SD/I engine manufacturers may promote higher fuel
efficiency and other performance advantages of compliant engines which
would allow them to promote these engines as having a greater value and
justifying these small expected 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 adopting 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 new 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 the new
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.
    We are adopting the regulatory requirements for marine spark-
ignition engines in 40 CFR part 1045. These requirements are similar to
the regulations that have been in place for outboard and personal
watercraft engines for several years, but include updated certification
procedures, as described in Section IV.A. Engines and vessels subject
to part 1045 are also subject to the general compliance provisions in
40 CFR part 1068. These include prohibited acts and penalties,
exemptions and importation provisions, selective enforcement audits,
defect reporting and recall, and hearing procedures. See Section VIII
of the preamble to the proposed rule for further discussion of these
general compliance provisions.

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 revised 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 definitions for sterndrive and inboard engines at 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 amending the above definitions for determining which exhaust
emission standards apply to spark-ignition marine engines in 2010. The
new definition establishes a single term to include sterndrive and
inboard engines together as a single engine category. The new
definition for sterndrive/inboard also is drafted to include all
engines not otherwise classified as outboard or personal watercraft
engines.
    The new definition has several noteworthy impacts. First, it
removes a requirement that only four-stroke engines can qualify as
sterndrive/inboard engines. We believe limiting the definition to
include only four-stroke engines is unnecessarily restrictive and could
create an incentive to use two-stroke (or rotary) engines to avoid
catalyst-based standards. Second, it removes limitations caused by
reference to propellers. The definition should not refer specifically
to propellers, because there are other propulsion drives on marine
vessels, such as jet drives, that could be used with SD/I engines.
Third, as explained in the section on the OB/PWC definitions, the new
definitions treat engines installed in open-bay vessels (e.g. jet
boats) and in vessels over 4 meters long as SD/I engines. Finally, the
definition in part 91 does not clearly specify how to treat specialty
vessels such as airboats or hovercraft that use engines similar to
those in conventional SD/I applications. The

definition of personal watercraft grants EPA the discretion to classify
engines as SD/I engines if the engine is comparable in technology and
emissions to an inboard or sterndrive engine. EPA has used this
discretion to classify airboats as SD/I engines. See 40 CFR 91.3 for
the existing definitions of the marine engine classes. We continue to
believe these engines share fundamental characteristics with
traditional SD/I engines and should therefore be treated the same way.
However, we believe the definitions should address these applications
expressly to make clear which standards apply. We are adopting the
following definition:
     Sterndrive/inboard engine means a spark-ignition engine
that is used to propel a vessel, but is not an outboard engine or a
personal watercraft engine. A sterndrive/inboard engine may be either a
conventional sterndrive/inboard engine or a high-performance engine.
Engines on propeller-driven vessels, jet boats, air boats, and
hovercraft are all sterndrive/inboard engines.
    SD/I high-performance engines are generally characterized by high-