[Federal Register: April 3, 2007 (Volume 72, Number 63)]
[Proposed Rules]
[Page 15937-16151]
[DOCID:fr03ap07-24]

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Part II

Environmental Protection Agency

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40 CFR Parts 92, 94, 1033, et al.

Control of Emissions of Air Pollution From Locomotive Engines and
Marine Compression-Ignition Engines Less Than 30 Liters per Cylinder;
Proposed Rule

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 92, 94, 1033, 1039, 1042, 1065 and 1068

[EPA-HQ-OAR-2003-0190; FRL-8285-5]
RIN 2006-AM06

Control of Emissions of Air Pollution From Locomotive Engines and
Marine Compression-Ignition Engines Less Than 30 Liters per Cylinder

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: Locomotives and marine diesel engines are important
contributors to our nation's air pollution today. These sources are
projected to continue to generate large amounts of particulate matter
(PM) and nitrogen oxides (NOX) emissions that contribute to
nonattainment of the National Ambient Air Quality Standards (NAAQS) for
PM2.5 and ozone across the United States. The emissions of
PM and ozone precursors from these engines are associated with serious
public health problems including premature mortality, aggravation of
respiratory and cardiovascular disease, aggravation of existing asthma,
acute respiratory symptoms, chronic bronchitis, and decreased lung
function. In addition, emissions from locomotives and marine diesel
engines are of particular concern, as diesel exhaust has been
classified by EPA as a likely human carcinogen.
    EPA is proposing a comprehensive program to dramatically reduce
emissions from locomotives and marine diesel engines. It would apply
new exhaust emission standards and idle reduction requirements to
diesel locomotives of all types--line-haul, switch, and passenger. It
would also set new exhaust emission standards for all types of marine
diesel engines below 30 liters per cylinder displacement. These include
marine propulsion engines used on vessels from recreational and small
fishing boats to super-yachts, tugs and Great Lakes freighters, and
marine auxiliary engines ranging from small gensets to large generators
on ocean-going vessels. The proposed program includes a set of near-
term emission standards for newly-built engines. These would phase in
starting in 2009. The near-term program also contains more stringent
emissions standards for existing locomotives. These would apply when
the locomotive is remanufactured and would take effect as soon as
certified remanufacture systems are available (as early as 2008), but
no later than 2010 (2013 for Tier 2 locomotives). We are requesting
comment on an alternative under consideration that would apply a
similar requirement to existing marine diesel engines when they are
remanufactured. We are also proposing long-term emissions standards for
newly-built locomotives and marine diesel engines based on the
application of high-efficiency catalytic aftertreatment technology.
These standards would phase in beginning in 2015 for locomotives and
2014 for marine diesel engines. We estimate PM reductions of 90 percent
and NOX reductions of 80 percent from engines meeting these
standards, compared to engines meeting the current standards.
    We project that by 2030, this program would reduce annual emissions
of NOX and PM by 765,000 and 28,000 tons, respectively.
These reductions are estimated to annually prevent 1,500 premature
deaths, 170,000 work days lost, and 1,000,000 minor restricted-activity
days. The estimated annual monetized health benefits of this rule in
2030 would be approximately $12 billion, assuming a 3 percent discount
rate (or $11 billion assuming a 7 percent discount rate). These
estimates would be increased substantially if we were to adopt the
remanufactured marine engine program concept. The annual cost of the
proposed program in 2030 would be significantly less, at approximately
$600 million.

DATES: Comments must be received on or before July 2, 2007. Under the
Paperwork Reduction Act, comments on the information collection
provisions must be received by OMB on or before May 3, 2007.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2003-0190, by one of the following methods:
     http://www.regulations.gov: Follow the on-line instructions for

submitting comments.
     Fax:<PHONE_NUMBER>
     Mail: Air Docket, Environmental Protection Agency,
Mailcode: 6102T, 1200 Pennsylvania Ave., NW., Washington, DC 20460. In
addition, please mail a copy of your comments on the information
collection provisions to the Office of Information and Regulatory
Affairs, Office of Management and Budget (OMB), Attn: Desk Officer for
EPA, 725 17th St., NW., Washington, DC 20503.
     Hand Delivery: EPA Docket Center, (EPA/DC) EPA West, Room
3334, 1301 Constitution Ave., NW, Washington DC, 20004. Such deliveries
are only accepted during the Docket's normal hours of operation, and
special arrangements should be made for deliveries of boxed
information.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2003-0190. EPA's policy is that all comments received will be included
in the public docket without change and may be made available online at
http://www.regulations.gov, including any personal information

provided, unless the comment includes information claimed to be
Confidential Business Information (CBI) or other information whose
disclosure is restricted by statute. Do not submit information that you
consider to be CBI or otherwise protected through http://www.regulations.gov or e-mail. The http://www.regulations.gov Web site

is an ``anonymous access'' system, which means EPA will not know your
identity or contact information unless you provide it in the body of
your comment. If you send an e-mail comment directly to EPA without
going through http://www.regulations.gov your e-mail address will be

automatically captured and included as part of the comment that is
placed in the public docket and made available on the Internet. If you
submit an electronic comment, EPA recommends that you include your name
and other contact information in the body of your comment and with any
disk or CD-ROM you submit. If EPA cannot read your comment due to
technical difficulties and cannot contact you for clarification, EPA
may not be able to consider your comment. Electronic files should avoid
the use of special characters, any form of encryption, and be free of
any defects or viruses. For additional information about EPA's public
docket visit the EPA Docket Center homepage at http://www.epa.gov/epahome/dockets.htm.
 For additional instructions on submitting

comments, go to section I.A. of the SUPPLEMENTARY INFORMATION section
of this document, and also go to section VIII.A. of the Public
Participation section of this document.
    Docket: All documents in the docket are listed in the http://www.regulations.gov
 index. Although listed in the index, some

information is not publicly available, e.g., CBI or other information
whose disclosure is restricted by statute. Certain other material, such
as copyrighted material, will be publicly available only in hard copy.
Publicly available docket materials are available either electronically
in http://www.regulations.gov or in hard copy at the EPA-EQ-OAR-2003-

0190 Docket, EPA/DC, EPA West, Room 3334, 1301 Constitution Ave., NW.,
Washington,

DC. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday
through Friday, excluding legal holidays. The telephone number for the
Public Reading Room is<PHONE_NUMBER>, and the telephone number for the
EPA-EQ-OAR-2003-0190 is<PHONE_NUMBER>.
    Hearing: Two hearings will be held, at 10 a.m. on Tuesday, May 8,
2007 in Seattle, WA, and at 10 a.m. on Thursday, May 10, 2007 in
Chicago, IL. For more information on these hearings or to request to
speak, see section VIII.C. ``WILL THERE BE A PUBLIC HEARING.''

FOR FURTHER INFORMATION CONTACT: John Mueller, U.S. EPA, Office of
Transportation and Air Quality, Assessment and Standards Division
(ASD), Environmental Protection Agency, 2000 Traverwood Drive, Ann
Arbor, MI 48105; telephone number:<PHONE_NUMBER>; fax number: (734)
214-4816; e-mail address<EMAIL_ADDRESS>or Assessment and
Standards Division Hotline; telephone number:<PHONE_NUMBER>.

SUPPLEMENTARY INFORMATION:

General Information

[diams] Does This Action Apply to Me?

[diams] Locomotive
    Entities potentially regulated by this action are those which
manufacture, remanufacture and/or import locomotives and/or locomotive
engines; and those which own and operate locomotives. Regulated
categories and entities include:

------------------------------------------------------------------------
                                                        Examples of
           Category               NAICS Code \1\    potentially affected
                                                          entities
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Industry......................  333618, 336510...  Manufacturers,
                                                    remanufacturers and
                                                    importers of
                                                    locomotives and
                                                    locomotive engines.
Industry......................  482110, 482111,    Railroad owners and
                                 482112.            operators.
Industry......................  488210...........  Engine repair and
                                                    maintenance.
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\1\ North American Industry Classification System (NAICS).

    This table is not intended to be exhaustive, but rather provides a
guide for readers regarding entities likely to be regulated by this
action. This table lists the types of entities that EPA is now aware
could potentially be regulated by this action. Other types of entities
not listed in the table could also be regulated. To determine whether
your company is regulated by this action, you should carefully examine
the applicability criteria in 40 CFR sections 92.1, 92.801, 92.901,
92.1001, 1065.1, 1068.1, 85.1601, 89.1, and the proposed regulations.
If you have questions, consult the person listed in the preceding FOR
FURTHER INFORMATION CONTACT section.
[diams] Marine
    This proposed action would affect companies and persons that
manufacture, sell, or import into the United States new marine
compression-ignition engines, companies and persons that rebuild or
maintain these engines, companies and persons that make vessels that
use such engines, and the owners/operators of such vessels. Affected
categories and entities include:

------------------------------------------------------------------------
                                                        Examples of
           Category               NAICS Code \1\    potentially affected
                                                          entities
------------------------------------------------------------------------
Industry......................  333618...........  Manufacturers of new
                                                    marine diesel
                                                    engines.
Industry......................  33661 and 346611.  Ship and boat
                                                    building; ship
                                                    building and
                                                    repairing.
Industry......................  811310...........  Engine repair,
                                                    remanufacture, and
                                                    maintenance.
Industry......................  483..............  Water transportation,
                                                    freight and
                                                    passenger.
Industry......................  336612...........  Boat building
                                                    (watercraft not
                                                    built in shipyards
                                                    and typically of the
                                                    type suitable or
                                                    intended for
                                                    personal use).
------------------------------------------------------------------------
\1\ North American Industry Classification System (NAICS).

    This table is not intended to be exhaustive, but rather provides a
guide for readers regarding entities likely to be regulated by this
action. This table lists the types of entities that EPA is now aware
could potentially be regulated by this action. Other types of entities
not listed in the table could also be regulated. To determine whether
your company is regulated by this action, you should carefully examine
the applicability criteria in 40 CFR 94.1, 1065.1, 1068.1, and the
proposed regulations. If you have questions, consult the person listed
in the preceding FOR FURTHER INFORMATION CONTACT section.

[diams] Additional Information About This Rulemaking

[diams] Locomotive
    The current emission standards for locomotive engines were adopted
by EPA in 1998 (see 63 FR 18978, April 16, 1998). This notice of
proposed rulemaking relies in part on information that was obtained for
that rule, which can be found in Public Docket A-94-31. That docket is
incorporated by reference into the docket for this action, OAR-2003-
0190.
[diams] Marine
    The current emission standards for new commercial marine diesel
engines were adopted in 1999 and 2003 (see 64 FR 73300, December 29,
1999 and 66 FR 9746, February 28, 2003). The current emission standards
for new recreational marine diesel engines were adopted in 2002 (see 67
FR 68241, November 8, 2002). The current emission standards for marine
diesel engines below 37 kW (50 hp) were adopted in 1998 (see 63 FR
56967, October 23, 1998). This notice of proposed rulemaking relies in
part on information that was obtained for those rules, which can be
found in Public Dockets A-96-40, A-97-50, A-98-01, A-2000-01, and A-
2001-11. Those dockets are incorporated by reference into the docket
for this action, OAR-2003-0190.
[diams] Other Dockets
    This notice of proposed rulemaking relies in part on information
that was obtained for our recent highway diesel and nonroad diesel
rulemakings, which can be found in Public Dockets A-99-06 and A-2001-28
(see also OAR 2003-

0012).\1\ \2\ Those dockets are incorporated by reference
into the docket for this action, OAR-2003-0190.
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    \1 2\ Control of Air Pollution From New Motor Vehicles: Heavy-
Duty Engine and Vehicle Standards and Highway Diesel Fuel Sulfur
Control Requirements, 66 FR 5002 (January 18, 2001); Control of
Emissions of Air Pollution From Nonroad Diesel Engines and Fuel, 69
FR 38958 (June 29, 2004).
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Outline of This Preamble

I. Overview
    A. What Is EPA Proposing?
    B. Why Is EPA Making This Proposal?
II. Air Quality and Health Impacts
    A. Overview
    B. Public Health Impacts
    C. Other Environmental Effects
    D. Other Criteria Pollutants Affected by This NPRM
    E. Emissions From Locomotive and Marine Diesel Engines
III. Emission Standards
    A. What Locomotives and Marine Engines Are Covered?
    B. Existing EPA Standards
    C. What Standards Are We Proposing?
    D. Are the Proposed Standards Feasible?
    E. What Are EPA's Plans for Diesel Marine Engines on Large
Ocean-Going Vessels?
IV. Certification and Compliance Program
    A. Issues Common to Locomotives and Marine
    B. Compliance Issues Specific to Locomotives
    C. Compliance Issues Specific to Marine Engines
V. Costs and Economic Impacts
    A. Engineering Costs
    B. Cost Effectiveness
    C. EIA
VI. Benefits
    A. Overview
    B. Quantified Human Health and Environmental Effects of the
Proposed Standards
    C. Monetized Benefits
    D. What Are the Significant Limitations of the Benefit-Cost
Analysis?
    E. Benefit-Cost Analysis
VII. Alternative Program Options
    A. Summary of Alternatives
    B. Summary of Results
VIII. Public Participation
    A. How Do I Submit Comments?
    B. How Should I Submit CBI to the Agency?
    C. Will There Be a Public Hearing?
    D. Comment Period
    E. What Should I Consider as I Prepare My Comments for EPA?
IX. 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 13211: Actions That Significantly Affect
Energy Supply, Distribution, or Use
    I. National Technology Transfer Advancement Act
X. Statutory Provisions and Legal Authority

I. Overview

    This proposal is an important step in EPA's ongoing National Clean
Diesel Campaign (NCDC). In recent years, we have adopted major new
programs designed to reduce emissions from highway and nonroad diesel
engines.\3\ When fully implemented, these new programs would largely
eliminate emissions of harmful pollutants from these sources. This
Notice of Proposed Rulemaking (NPRM) sets out the next step in this
ambitious effort by addressing two additional diesel sectors that are
major sources of air pollution nationwide: locomotive engines and
marine diesel engines below 30 liters per cylinder displacement.\4\
This addresses all types of diesel locomotives-- line-haul, switch, and
passenger rail, and all types of marine diesel engines below 30 liters
per cylinder displacement (hereafter collectively called ``marine
diesel engines.''). These include marine propulsion engines used on
vessels from recreational and small fishing boats to super-yachts, tugs
and Great Lakes freighters, and marine auxiliary engines ranging from
small gensets to large generators on ocean-going vessels.\5\
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    \3\ See 65 FR 6698 (February 10, 2000), 66 FR 5001 (January 18,
2001), and 69 FR 38958 (June 29, 2004) for the final rules regarding
the light-duty Tier 2, clean highway diesel (2007 highway diesel)
and clean nonroad diesel (nonroad Tier 4) programs, respectively.
EPA has also recently promulgated a clean stationary diesel engine
rule containing standards similar to those in the nonroad Tier 4
rule. See 71 FR 39153. See also http://www.epa.gov/diesel/ for

information on all EPA programs that are part of the NCDC.
    \4\ In this NPRM, ``marine diesel engine'' refers to
compression-ignition marine engines below 30 liters per cylinder
displacement unless otherwise indicated. Engines at or above 30
liters per cylinder are being addressed in separate EPA actions,
including a planned rulemaking, participation on the U.S. delegation
to the International Maritime Organization's standard-setting work,
and EPA's new Clean Ports USA Initiative (http://www.epa.gov/cleandiesel/ports/index.htm
).

    \5\ Marine diesel engines at or above 30 l/cyl displacement are
not included in this program. See Section III.E, below.
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    Emission levels for locomotive and marine diesel engines remain at
high levels--comparable to the emissions standards for highway trucks
in the early 1990s--and emit high level of pollutants that contribute
to unhealthy air in many areas of the U.S. Nationally, in 2007 these
engines account for about 20 percent of mobile source NOX
emissions and 25 percent of mobile source diesel PM2.5
emissions. Absent new emissions standards, we expect overall emissions
from these engines to remain relatively flat over the next 10 to 15
years due to existing regulations such as lower fuel sulfur
requirements and the phase-in of locomotive and marine diesel Tier 1
and Tier 2 engine standards but starting in about 2025 emissions from
these engines would begin to grow. Under today's proposed program, by
2030, annual NOX emissions from locomotive and marine diesel
engines would be reduced by 765,000 tons and PM2.5 and
28,000 tons. Without new controls, by 2030, these engines would become
a large portion of the total mobile source emissions inventory
constituting 35 percent of mobile source NOX emissions and
65 percent of diesel PM emissions.
    We followed certain principles when developing the elements of this
proposal. First, the program must achieve sizeable reductions in PM and
NOX emissions as early as possible. Second, as we did in the
2007 highway diesel and clean nonroad diesel programs, we are
considering engines and fuels together as a system to maximize
emissions reductions in a highly cost-effective manner. The groundwork
for this systems approach was laid in the 2004 nonroad diesel final
rule which mandated that locomotive and marine diesel fuel comply with
the 15 parts per million sulfur cap for ultra-low sulfur diesel fuel
(ULSD) by 2012, in anticipation of this rulemaking (69 FR 38958, June
29, 2004). The costs, benefits, and other impacts of the locomotive and
marine diesel fuel regulation are covered in the 2004 rulemaking and
are not duplicated here. Lastly, we are proposing standards and
implementation schedules that take full advantage of the efforts now
being expended to develop advanced emissions control technologies for
the highway and nonroad sectors. As discussed throughout this proposal,
the proposed standards represent a feasible progression in the
application of advanced technologies, providing a cost-effective
program with very large public health and welfare benefits.
    The proposal consists of a three-part program. First, we are
proposing more stringent standards for existing locomotives that would
apply when they are remanufactured. The proposed remanufactured
locomotive program would take effect as soon as certified remanufacture
systems are available (as early as 2008), but no later than 2010 (2013
for Tier 2 locomotives). We are also requesting comment on an
alternative under consideration that would apply a similar requirement
to existing marine diesel engines when

they are remanufactured. Second, we are proposing a set of near-term
emission standards, referred to as Tier 3, for newly-built locomotives
and marine engines, that reflect the application of technologies to
reduce engine-out PM and NOX. Third, we are proposing
longer-term standards, referred to as Tier 4, that reflect the
application of high-efficiency catalytic aftertreatment technology
enabled by the availability of ULSD. These standards phase in over
time, beginning in 2014. We are also proposing provisions to eliminate
emissions from unnecessary locomotive idling.
    Locomotives and marine diesel engines designed to these proposed
standards would achieve PM reductions of 90 percent and NOX
reductions of 80 percent, compared to engines meeting the current Tier
2 standards. The proposed standards would also yield sizeable
reductions in emissions of nonmethane hydrocarbons (NMHC), carbon
monoxide (CO), and hazardous compounds known as air toxics. Table I-1
summarizes the PM and NOX emission reductions for the
proposed standards compared to today's (Tier 2) emission standards or,
in the case of remanufactured locomotives, compared to the current
standards for each tier of locomotives covered.

                            Table I.-1.--Reductions From Levels of Existing Standards
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                     Sector                               Proposed standards tier             PM         NOX
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Locomotives.....................................  Remanufactured Tier 0..................       60%       15-20%
                                                  Remanufactured Tier 1..................        50
                                                  Remanufactured Tier 2..................        50
                                                  Tier 3.................................        50
                                                  Tier 4.................................        90           80
Marine Diesel Engines \a\.......................  Remanufactured Engines \b\.............     25-60     up to 20
                                                  Tier 3.................................        50           20
                                                  Tier 4.................................        90           80
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\a\ Existing and proposed standards vary by displacement and within power categories. Reductions indicated are
  typical.
\b\ This proposal asks for comment on an alternative under consideration that would reduce emissions from
  existing marine diesel engines. See section VII.A(2).

    Combined, these reductions would result in substantial benefits to
public health and welfare and to the environment. We project that by
2030 this program would reduce annual emissions of NOX and
PM by 765,000 and 28,000 tons, respectively, and the magnitude of these
reductions would continue to grow well beyond 2030. We estimate that
these annual emission reductions would prevent 1,500 premature
mortalities in 2030. These annual emission reductions are also
estimated to prevent 1,000,000 minor restricted-activity days, 170,000
work days lost, and other quantifiable benefits. All told, the
estimated monetized health benefits of this rule in 2030 would be
approximately $12 billion, assuming a 3 percent discount rate (or $11
billion assuming a 7 percent discount rate). The annual cost of the
program in 2030 would be significantly less, at approximately $600
million.

A. What Is EPA Proposing?

    This proposal is a further step in EPA's ongoing program to control
emissions from diesel engines, including those used in marine vessels
and locomotives. EPA's current standards for newly-built and
remanufactured locomotives were adopted in 1998 and were implemented in
three tiers (Tiers 0, 1, and 2) over 2000 through 2005. The current
program includes Tier 0 emission limits for existing locomotives
originally manufactured in 1973 or later, that apply when they are
remanufactured. The standards for marine diesel engines were adopted in
1998 for engines under 37 kilowatts (kW), in 1999 for commercial marine
engines, and in 2002 for recreational marine engines. These various
Tier 1 and Tier 2 standards phase in from 1999 through 2009, depending
on engine size and application. The most stringent of these existing
locomotive and marine diesel engine standards are similar in stringency
to EPA's nonroad Tier 2 standards that are now in the process of being
replaced by Tier 3 and 4 standards.
    The major elements of the proposal are summarized below. We are
also proposing revised testing, certification, and compliance
provisions to better ensure emissions control in use. Detailed
provisions and our justifications for them are discussed in sections
III and IV and in the draft Regulatory Impact Analysis (RIA). Section
VII of this preamble describes a number of alternatives that we
considered in developing this proposal, including a more simplistic
approach that would introduce aftertreatment-based standards earlier.
Our analysis shows that such an approach would result in higher
emissions and fewer health and welfare benefits than we project will be
realized from the program we are proposing today. After evaluating the
alternatives, we believe that our proposed program provides the best
opportunity for achieving timely and very substantial emissions
reductions from locomotive and marine diesel engines. It best takes
into account the need for appropriate lead time to develop and apply
the technologies necessary to meet these emission standards, the goal
of achieving very significant emissions reductions as early as
possible, the interaction of requirements in this proposal with
existing highway and nonroad diesel engine programs, and other legal
and policy considerations.
    Overall, this comprehensive three-part approach to setting
standards for locomotives and marine diesel engines would provide very
large reductions in PM, NOX, and toxic compounds, both in
the near-term (as early as 2008), and in the long-term. These
reductions would be achieved in a manner that: (1) Is very cost-
effective, (2) leverages technology developments in other diesel
sectors, (3) aligns well with the clean diesel fuel requirements
already being implemented, and (4) provides the lead time needed to
deal with the significant engineering design workload that is involved.
We are asking for comments on all aspects of the proposal, including
standards levels and implementation dates, and on the alternatives
discussed in this proposal.
    (1) Locomotive Emission Standards
    We are proposing stringent exhaust emissions standards for newly-
built and remanufactured locomotives, furthering the initiative for
cleaner locomotives started in 2004 with the establishment of the ULSD
locomotive fuel program, and adding this important category of engines
to the highway and nonroad

diesel applications already covered under EPA's National Clean Diesel
Campaign.\6\
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    \6\ We are not proposing any change to the current definition of
a ``new locomotive'' in 40 CFR Sec.  92.2. The terms ``new
locomotive'', ``new locomotive engine'', ``freshly manufactured
locomotive'', ``freshly manufactured locomotive engine'',
``repower'', ``remanufacture'', ``remanufactured locomotive'', and
``remanufactured locomotive engine'' all have formal definitions in
40 CFR 92.2. In this notice, the term ``newly-built locomotive'' is
synonymous with ``freshly manufactured locomotive''.
---------------------------------------------------------------------------

    In the Advance Notice of Proposed Rulemaking (ANPRM) for this
proposal (69 FR 39276, June 29, 2004), we suggested a program for
comment that would bring about the introduction of high-efficiency
exhaust aftertreatment to this sector in a single step. Although it has
taken longer than expected to develop, the proposal we are issuing
today is far more comprehensive than we envisioned in 2004. Informed by
extensive analyses documented in the draft RIA and numerous discussions
with stakeholders since then, this proposal goes significantly beyond
that vision. It sets out standards for locomotives in three steps to
more fully leverage the opportunities provided by both the already-
established clean fuel programs, and the migration of clean diesel
technology from the highway and nonroad sectors. It also addresses the
large and long-lived existing locomotive fleet with stringent new
emissions requirements at remanufacture starting in 2008. Finally, it
sets new requirements for idle emissions control on newly-built and
remanufactured locomotives.
    Briefly, for newly-built line-haul locomotives we are proposing a
new Tier 3 PM standard of 0.10 grams per brake horsepower-hour (g/bhp-
hr), based on improvements to existing engine designs. This standard
would take effect in 2012. We are also proposing new Tier 4 standards
of 0.03 g/bhp-hr for PM and 1.3 g/bhp-hr for NOX, based on
the evolution of high-efficiency catalytic aftertreatment technologies
now being developed and introduced in the highway diesel sector. The
Tier 4 standards would take effect in 2015 and 2017 for PM and
NOX, respectively. We are proposing that remanufactured Tier
2 locomotives meet a PM standard of 0.10 g/bhp-hr, based on the same
engine design improvements as Tier 3 locomotives, and that
remanufactured Tier 0 and Tier 1 locomotives meet a 0.22 g/bhp-hr PM
standard. We also propose that remanufactured Tier 0 locomotives meet a
NOX standard of 7.4 g/bhp-hr, the same level as current Tier
1 locomotives, or 8.0 g/bhp-hr if the locomotive is not equipped with a
separate loop intake air cooling system. Section III provides a
detailed discussion of these proposed new standards, and section IV
details improvements being proposed to the applicable test,
certification, and compliance programs.
    In setting our original locomotive emission standards in 1998, the
historic pattern of transitioning older line-haul locomotives to road-
and yard-switcher service resulted in our making little distinction
between line-haul and switch locomotives. Because of the increase in
the size of new locomotives in recent years, that pattern cannot be
sustained by the railroad industry, as today's 4000+ hp (3000+ kW)
locomotives are poorly suited for switcher duty. Furthermore, although
there is still a fairly sizeable legacy fleet of older smaller line-
haul locomotives that could find their way into the switcher fleet,
essentially the only newly-built switchers put into service over the
last two decades have been of radically different design, employing one
to three smaller high-speed diesel engines designed for use in nonroad
applications. In light of these trends, we are establishing new
standards and special certification provisions for newly-built and
remanufactured switch locomotives that take these trends into account.
    Locomotives spend a substantial amount of time idling, during which
they emit harmful pollutants and consume fuel. Two ways that idling
time can be reduced are through the use of automated systems to stop
idling locomotive engines (restarting them on an as-needed basis), and
through the use of small low-emitting auxiliary engines to provide
essential accessory power. Both types of systems are installed in a
number of U.S. locomotives today for various reasons, including to save
fuel, to help meet current Tier 0 emissions standards, and to address
complaints from railyard neighbors about noise and pollution from
idling locomotives.
    We are proposing that idle control systems be required on all
newly-built Tier 3 and Tier 4 locomotives. We also propose that they be
installed on all existing locomotives that are subject to the proposed
remanufactured engine standards, at the point of first remanufacture
under the proposed standards, unless already equipped with idle
controls. We are proposing that automated stop/start systems be
required, but encourage the use of auxiliary power units by allowing
their emission reduction to be factored into the certification test
program as appropriate.
    Taken together, the proposed elements described above constitute a
comprehensive program that would address the problems caused by
locomotive emissions from both a near-term and long-term perspective,
and do so more completely than would have occurred under the concept
described in the ANPRM. It would do this while providing for an orderly
and cost-effective implementation schedule for the railroads, builders,
and remanufacturers.
(2) Marine Engine Emission Standards
    We are also proposing emissions standards for newly-built marine
diesel engines with displacements under 30 liters per cylinder
(referred to as Category 1 and 2, or C1 and C2, engines). This would
include engines used in commercial, recreational, and auxiliary power
applications, and those below 37 kW (50 hp) that were previously
regulated separately in our nonroad diesel program. As with
locomotives, our ANPRM described a one-step marine diesel program that
would bring about the introduction of high-efficiency exhaust
aftertreatment in this sector. Just as for locomotives, our subsequent
extensive analyses (documented in the draft RIA) and numerous
discussions with stakeholders since then have resulted in this proposal
for standards in multiple steps, with the longer-term implementation of
advanced technologies focused especially on the engines with the
greatest potential for large PM and NOX emission reductions.
    The proposed marine diesel engine standards include stringent
engine-based Tier 3 standards for newly-built marine diesel engines
that phase in beginning in 2009. These are followed by aftertreatment-
based Tier 4 standards for engines above 600 kW (800 hp) that phase in
beginning in 2014. The specific levels and implementation dates for the
proposed Tier 3 and Tier 4 standards vary by engine sub-groupings.
Although this results in a somewhat complicated array of emissions
standards, it will ensure the most stringent standards feasible for
each group of newly-built marine engines, and will help engine and
vessel manufacturers to implement the program in a cost effective
manner that also emphasizes early emission reductions. The proposed
standards and implementation schedules, as well as their technological
feasibility, are described in detail in section III of this preamble.
    We are also requesting comment on an alternative we are considering
to address the considerable impact of emissions from large marine
diesel

engines installed in vessels currently in the fleet. We have in the
past considered but not finalized a program to regulate such engines as
``new'' engines at the time of remanufacture, similar to the approach
taken in the locomotive program. We are again considering such a
program in the context of this rulemaking and are soliciting comments
on this alternative.
    Briefly summarized, it would consist of two parts. In the first
part, which could begin as early as 2008, vessel owners and rebuilders
would be required to install a certified emissions control system when
the engine is remanufactured, if such a system were available.
Initially, we would expect the systems installed on remanufactured
marine engines to be those certified for the remanufactured locomotive
program, although this alternative would not limit the program to only
those engines. Eventually manufacturers would be expected to provide
systems for other large engines as well. In the second part, to take
effect in 2013, marine diesel engines identified by EPA as high-sales
volume engine models would have to meet specified emissions standards
when remanufactured. The rebuilder or owner would be required to either
use a system certified to meet the standards or, if no certified
systems were available, to either retrofit an emission reduction
technology for the engine that demonstrates at least a 25 percent
reduction or to repower (replace the engine with a new one). The
alternative under consideration is described in more detail in section
VII.A(2). We request comment on the elements of this alternative as
well as other possible approaches to achieve this goal, with the view
that EPA may adopt a remanufacture program in the final rule if
appropriate.

B. Why Is EPA Making This Proposal?

(1) Locomotives and Marine Diesels Contribute to Serious Air Pollution
Problems
    Locomotive and marine diesel engines subject to today's proposal
generate significant emissions of fine particulate matter
(PM2.5) and nitrogen oxides (NOX) that contribute
to nonattainment of the National Ambient Air Quality Standards for
PM2.5 and ozone. NOX is a key precursor to ozone
and secondary PM formation. These engines also emit hazardous air
pollutants or air toxics, which are associated with serious adverse
health effects. Emissions from locomotive and marine diesel engines
also cause harm to public welfare, including contributing to visibility
impairment and other harmful environmental impacts across the US.
    The health and environmental effects associated with these
emissions are a classic example of a negative externality (an activity
that imposes uncompensated costs on others). With a negative
externality, an activity's social cost (the cost borne to society
imposed as a result of the activity taking place) exceeds its private
cost (the cost to those directly engaged in the activity). In this
case, as described below and in Section II, emissions from locomotives
and marine diesel engines and vessels impose public health and
environmental costs on society. However, these added costs to society
are not reflected in the costs of those using these engines and
equipment. The market system itself cannot correct this externality
because firms in the market are rewarded for minimizing their
production costs, including the costs of pollution control. In
addition, firms that may take steps to use equipment that reduces air
pollution may find themselves at a competitive disadvantage compared to
firms that do not. To correct this market failure and reduce the
negative externality from these emissions, it is necessary to give
producers the signals for the social costs generated from the
emissions. The standards EPA is proposing will accomplish this by
mandating that locomotives and marine diesel engines reduce their
emissions to a technologically feasible limit. In other words, with
this proposed rule the costs of the transportation services produced by
these engines and equipment will account for social costs more fully.
    Emissions from locomotive and marine diesel engines account for
substantial portions of the country's ambient PM2.5 and
NOX levels. We estimate that today hese engines account for
about 20 percent of mobile source NOX emissions and about 25
percent of mobile source diesel PM 2.5 emissions. Under
today's proposed standards, by 2030, annual NOX emissions
from these diesel engines would be reduced by 765,000 tons and
PM2.5 emissions by 28,000 tons, and those reductions would
continue to grow beyond 2030 as fleet turnover to the clean engines is
completed.
    EPA has already taken steps to bring emissions levels from light-
duty and heavy-duty highway, and nonroad diesel vehicles and engines to
very low levels over the next decade, as well as certain stationary
diesel engines also subject to these standards, while the emission
levels for locomotive and marine diesel engines remain at much higher
levels--comparable to the emissions for highway trucks in the early
1990s.
    Both ozone and PM2.5 contribute to serious public health
problems, including premature mortality, aggravation of respiratory and
cardiovascular disease (as indicated by increased hospital admissions
and emergency room visits, school absences, lost work days, and
restricted activity days), changes in lung function and increased
respiratory symptoms, altered respiratory defense mechanisms, and
chronic bronchitis. Diesel exhaust is of special public health concern,
and since 2002 EPA has classified it as likely to be carcinogenic to
humans by inhalation at environmental exposures.\7\ Recent studies are
showing that populations living near large diesel emission sources such
as major roadways,\8\ rail yards, and marine ports \9\ are likely to
experience greater diesel exhaust exposure levels than the overall U.S.
population, putting them at greater health risks. We are currently
studying the size of the U.S. population living near a sample of
approximately 60 marine ports and rail yards, and will place the
information in the docket upon completion prior to the final rule.
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    \7\ U.S. EPA (2002) Health Assessment Document for Diesel Engine
Exhaust. EPA/600/8-90/057F. Office of Research and Development,
Washington DC. This document is available electronically at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=29060
.

    \8\ Kinnee, E.J.; Touman, J.S.; Mason, R.; Thurman, J.; Beidler,
A.; Bailey, C.; Cook, R. (2004) Allocation of onroad mobile
emissions to road segments for air toxics modeling in an urban area.
Transport. Res. Part D 9: 139-150.
    \9\ State of California Air Resources Board. Roseville Rail Yard
Study. Stationary Source Division, October 14, 2004. This document
is available electronically at: http://www.arb.ca.gov/diesel/documents/rrstudy.htm
 and State of California Air Resources Board.

Diesel Particulate Matter Exposure Assessment Study for the Ports of
Los Angeles and Long Beach, April 2006. This document is available
electronically at: http://www.arb.ca.gov/regact/marine2005/portstudy0406.pdf
.

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    Today millions of Americans continue to live in areas that do not
meet existing air quality standards. Currently, ozone concentrations
exceeding the 8-hour ozone NAAQS occur over wide geographic areas,
including most of the nation's major population centers. As of October
2006 there are approximately 157 million people living in 116 areas
(461 full or partial counties) designated as not in attainment with the
8-hour ozone NAAQS. These numbers do not include people living in areas
where there is a potential that the area may fail to maintain or
achieve the 8-hour ozone NAAQS. With regard to PM2.5
nonattainment, EPA has recently finalized nonattainment designations

(70 FR 943, Jan 5, 2005), and as of October 2006 there are 88 million
people living in 39 areas (which include all or part of 208 counties)
that either do not meet the PM2.5 NAAQS or contribute to
violations in other counties. These numbers do not include individuals
living in areas that may fail to maintain or achieve the
PM2.5 NAAQS in the future.
    In addition to public health impacts, there are public welfare and
environmental impacts associated with ozone and PM2.5
emissions which are also serious. Specifically, ozone causes damage to
vegetation which leads to crop and forestry economic losses, as well as
harm to national parks, wilderness areas, and other natural systems.
NOX and direct emissions of PM2.5 can contribute
to the substantial impairment of visibility in many part of the U.S.,
where people live, work, and recreate, including national parks,
wilderness areas, and mandatory class I federal areas. The deposition
of airborne particles can also 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. Finally, NOX emissions
from diesel engines contribute to the acidification, nitrification, and
eutrophication of water bodies.
    While EPA has already adopted many emission control programs that
are expected to reduce ambient ozone and PM2.5 levels,
including the Clean Air Interstate Rule (CAIR) (70 FR 25162, May 12,
2005) and the Clean Air Nonroad Diesel Rule (69 FR 38957, June 29,
2004), the Heavy Duty Engine and Vehicle Standards and Highway Diesel
Fuel Sulfur Control Requirements (66 FR 5002, Jan. 18, 2001), and the
Tier 2 Vehicle and Gasoline Sulfur Program (65 FR 6698, Feb. 10, 2000),
the additional PM2.5 and NOX emission reductions
resulting from the standards proposed in this action would assist
states in attaining and maintaining the Ozone and the PM2.5
NAAQS near term and in the decades to come.
    In September 2006, EPA finalized revised PM2.5 NAAQS
standards and over the next few years the Agency will undergo the
process of designating areas that are not able to meet this new
standard. EPA modeling, conducted as part of finalizing the revised
NAAQS, projects that in 2015 up to 52 counties with 53 million people
may violate either the daily, annual, or both standards for
PM2.5 while an additional 27 million people in 54 counties
may live in areas that have air quality measurements within 10 percent
of the revised NAAQS. Even in 2020 up to 48 counties, with 54 million
people, may still not be able to meet the revised PM2.5
NAAQS and an additional 25 million people, living in 50 counties, are
projected to have air quality measurements within 10 percent of the
revised standards. The locomotive and marine diesel PM2.5
reductions resulting from this proposal will be needed by states to
both attain and maintain the revised PM2.5 NAAQS.
    State and local governments are working to protect the health of
their citizens and comply with requirements of the Clean Air Act (CAA
or ``the Act''). As part of this effort they recognize the need to
secure additional major reductions in both diesel PM2.5 and
NOX emissions by undertaking numerous state level
actions,\10\ while also seeking Agency action, including the setting of
stringent new locomotive and marine diesel engine standards being
proposed today.\11\ The emission reductions in this proposal will play
a critical part in state efforts to attain and maintain the NAAQS
through the next two decades.
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    \10\ Two examples of state and local actions are: California Air
Resources Board (2006). Emission Reduction Plan for Ports and Goods
Movements, (April 2006). Available electronically at http://www.arb.ca.gov/gmp/docs/finalgmpplan090905.pdf
; Connecticut Department of

Environmental Protection. (2006). Connecticut's Clean Diesel Plan,
(January 2006). See http://www.dep.state.ct.us/air2/diesel/index.htm

for description of initiative.
    \11\ For example, see letter dated September 23, 2006 from
Northeast States for Coordinated Air Use Management to Administrator
Stephen L. Johnson; September 7, 2006 letter from Executive Officer
of the California Air Resources Board to Acting Assistant
Administrator William L. Wehrum; August 9, 2006 letter from State
and Territorial Air Pollution Program Administrators and Association
of Local Air Pollution Control Officials (and other organizations)
to Administrator Stephen L. Johnson; January 20, 2006 letter from
Executive Director, Puget Sound Clean Air Agency to Administrator
Stephen L. Johnson; June 30, 2005 letter from Western Regional Air
Partnership to Administrator Stephen L. Johnson.
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    While the program we are proposing today will help many states and
communities achieve cleaner air, for some areas, the reductions will
not be large enough or early enough to assist them in meeting near term
ozone and PM air quality goals. More can be done, beyond what we are
proposing today, to address the emissions from locomotive and marine
diesel engines. For example, as part of this proposal we are requesting
comment on a concept to set emission standards for existing large
marine diesel engines when they are remanufactured. Were we to finalize
such a concept, it could provide substantial emission reductions,
beginning in the next few years, from some of the large legacy fleets
of dirtier diesel engines.
    At the time of our previous locomotive rulemaking, the State of
California worked with the railroads operating in southern California
to develop and implement a corollary program, ensuring that the
cleanest technologies are expeditiously introduced in these areas with
greatest air quality improvement needs. Today's proposal includes
provisions, such as streamlined switcher locomotive certification using
clean nonroad engines, that are well-suited to encouraging early
deployment of cleaner technologies through the development of similar
programs.
    In addition to regulatory programs, the Agency has a number of
voluntary programs that partner government, industry, and local
communities together to help address challenging air quality problems.
The EPA SmartWay program has initiatives to reduce unnecessary
locomotive idling and to encourage the use of idle reduction
technologies that can substantially reduce locomotive emissions while
reducing fuel consumption. EPA's National Clean Diesel Campaign,
through its Clean Ports USA program, is working with port authorities,
terminal operators, and trucking and rail companies to promote cleaner
diesel technologies and strategies today through education, incentives,
and financial assistance for diesel emissions reductions at ports. Part
of these efforts involves voluntary retrofit programs that can further
reduce emissions from the existing fleet of diesel engines. Finally,
many of the companies operating in states and communities suffering
from poor air quality have voluntarily entered into Memoranda of
Understanding (MOUs) designed to ensure that the cleanest technologies
are used first in regions with the most challenging air quality issues.
    Together, these approaches can augment the regulations being
proposed today helping states and communities achieve larger reductions
sooner in the areas of our country that need them the most. The Agency
remains committed to furthering these programs and others so that all
of our citizens can breathe clean healthy air.
(2) Advanced Technology Solutions
    Air pollution from locomotive and marine diesel exhaust is a
challenging problem. However, we believe it can be addressed
effectively through the use of existing technology to reduce engine-out
emissions combined with high-efficiency catalytic aftertreatment
technologies. As discussed in greater detail in section III.D, the
development of these aftertreatment technologies for

highway and nonroad diesel applications has advanced rapidly in recent
years, so that very large emission reductions in PM and NOX
(in excess of 90 and 80 percent, respectively) can be achieved.
    High-efficiency PM control technologies are being broadly used in
many parts of the world, and in particular to comply with EPA's heavy-
duty truck standards now taking effect with the 2007 model year. These
technologies are highly durable and robust in use, and have also proved
extremely effective in reducing exhaust hydrocarbon (HC) emissions.
However, as discussed in detail in section III.D, these emission
control technologies are very sensitive to sulfur in the fuel. For the
technology to be viable and capable of controlling an engine's
emissions over the long term, we believe it will require diesel fuel
with sulfur content capped at the 15 ppm level.
    Control of NOX emissions from locomotive and marine
diesel engines can also be achieved with high-efficiency exhaust
emission control technologies. Such technologies are expected to be
used to meet the stringent NOX standards included in EPA's
heavy-duty highway diesel and nonroad Tier 4 programs, and have been in
production for heavy duty trucks in Europe since 2005, as well as in
many stationary source applications throughout the world. These
technologies are also sensitive to sulfur.
    Section III.D discusses additional engineering challenges in
applying these technologies to newly-built locomotive and marine
engines, as well as the development steps that we expect to be taken to
resolve the challenges. With the lead time available and the assurance
of ULSD for the locomotive and marine sectors in 2012, as provided by
our 2004 final rule for nonroad engines and fuel, we are confident the
proposed application of advanced technology to locomotives and marine
diesels will proceed at a reasonable rate of progress and will result
in systems capable of achieving the proposed standards on the proposed
schedule.
(3) Basis for Action Under the Clean Air Act
    Authority for the actions promulgated in this documents is granted
to the Environmental Protections Agency (EPA) by sections 114, 203,
205, 206, 207, 208, 213, 216, and 301(a) of the Clean Air Act as
amended in 1990 (CAA or ``the Act'') (42 U.S.C. 7414, 7522, 7524, 7525,
7541, 7542, 7547, 7550 and 7601(a)).
    EPA is promulgating emissions standards for new marine diesel
engines pursuant to its authority under section 213(a)(3) and (4) of
the Clean Air Act (CAA). EPA is promulgating emission standards for new
locomotives and new engines used in locomotives pursuant to its
authority under section 213(a)(5) of the CAA.
    CAA section 213(a)(3) directs the Administrator to set
NOX, VOCs, or carbon monoxide, standards for classes or
categories of engines that contribute to ozone or carbon monoxide
concentrations in more than one nonattainment area, like marine diesel
engines. These ``standards shall achieve the greatest degree of
emission reduction achievable through the application of technology
which the Administrator determines will be available for the engines or
vehicles, giving appropriate consideration to cost, lead time, noise,
energy, and safety factors associated with the application of such
technology.''
    CAA section 213(a)(4), authorizes the Administrator to establish
standards to control emissions of pollutants which ``may reasonably be
anticipated to endanger public health and welfare,'' where the
Administrator determines, as it has done for emissions of PM, that
nonroad engines as a whole contribute significantly to such air
pollution. The Administrator may promulgate regulations that are deemed
appropriate, taking into account costs, noise, safety, and energy
factors, for classes or categories of new nonroad vehicles and engines
which cause or contribute to such air pollution, like diesel marine
engines.
    Finally, section 213(a)(5) directs EPA to adopt emission standards
for new locomotives and new engines used in locomotives that achieve
the ``greatest degree of emissions reductions achievable through the
use of technology that the Administrator determines will be available
for such vehicles and engines, taking into account the cost of applying
such technology within the available time period, the noise, energy,
and safety factors associated with the applications of such
technology.'' Section 213(a)(5) does not require any review of the
contribution of locomotive emissions to pollution, though EPA does
provide such information in this proposal. As described in section III
of this Preamble and in Chapter 4 of the draft RIA, EPA has evaluated
the available information to determine the technology the will be
available for locomotives and engines proposed to be subject to EPA
standards.
    EPA is also acting under its authority to implement and enforce
both the marine diesel emission standards and the locomotive emissions
standards. Section 213(d) provides that the standards EPA adopts for
both new locomotive and marine diesel engines ``shall be subject to
sections 206, 207, 208, and 209'' of the Clean Air Act, with such
modifications that the Administrator deems appropriate to the
regulations implementing these sections. In addition, the locomotive
and marine standards ``shall be enforced in the same manner as [motor
vehicle] standards prescribed under section 202'' of the Act. Section
213(d) also grants EPA authority to promulgate or revise regulations as
necessary to determine compliance with, and enforce, standards adopted
under section 213.
    As required under section 213(a)(3), (4), and (5) we believe the
evidence provided in section III.D of this Preamble and in Chapter 4 of
draft RIA indicates that the stringent emission standards proposed
today for newly-built and remanufactured locomotive engines and newly-
built marine diesel engines are feasible and reflect the greatest
degree of emission reduction achievable through the use of technology
that will be available in the model years to which they apply. We also
believe this may be the case for the alternative identified for
existing marine engines in section VII.A(2) of this preamble. We have
given appropriate consideration to costs in proposing these standards.
Our review of the costs and cost-effectiveness of these standards
indicate that they will be reasonable and comparable to the cost-
effectiveness of other emission reduction strategies that have been
required. We have also reviewed and given appropriate consideration to
the energy factors of this rule in terms of fuel efficiency as well as
any safety and noise factors associated with these proposed standards.
    The information in section II of this Preamble and Chapter 2 of the
draft RIA regarding air quality and public health impacts provides
strong evidence that emissions from marine diesel engines and
locomotives significantly and adversely impact public health or
welfare. EPA has already found in previous rules that emissions from
new marine diesel engines contribute to ozone and carbon monoxide (CO)
concentrations in more than one area which has failed to attain the
ozone and carbon monoxide NAAQS (64 FR 73300, December 29, 1999). EPA
has also previously determined that it is appropriate to establish
standards for PM from marine diesel engines under section 213(a)(4),
and the additional information on diesel exhaust carcinogenicity noted
above reinforces

this finding. In addition, we have already found that emissions from
nonroad engines as a whole significantly contribute to air pollution
that may reasonably be anticipated to endanger public welfare due to
regional haze and visibility impairment (67 FR 68241, Nov. 8, 2002). We
propose to find here, based on the information in section II of this
preamble and Chapters 2 and 3 of the draft RIA that emissions from the
new marine diesel engines likewise contribute to regional haze and to
visibility impairment.
    The PM and NOX emission reductions resulting from the
standards proposed in this action would be important to states' efforts
in attaining and maintaining the Ozone and the PM2.5 NAAQS
in the near term and in the decades to come. As noted above, the risk
to human health and welfare would be significantly reduced by the
standards proposed today.

II. Air Quality and Health Impacts

    The locomotive and marine diesel engines subject to today's
proposal generate significant emissions of particulate matter (PM) and
nitrogen oxides (NOX) that contribute to nonattainment of
the National Ambient Air Quality Standards (NAAQS) for PM2.5
and ozone. These engines also emit hazardous air pollutants or air
toxics which are associated with serious adverse health effects.
Finally, emissions from locomotive and marine diesel engines cause harm
to the public welfare, contribute to visibility impairment, and
contribute to other harmful environmental impacts across the U.S.
    By 2030, the proposed standards are expected to reduce annual
locomotive and marine diesel engine PM2.5 emissions by
28,000 tons; NOX emissions by 765,000 tons; and volatile
organic compound (VOC) emissions by 42,000 tons as well as reductions
in carbon monoxide (CO) and toxic compounds known as air toxics.\12\
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    \12\ Nationwide locomotive and marine diesel engines comprise
approximately 3 percent of the nonroad mobile sources hydrocarbon
inventory. EPA National Air Quality and Emissions Trends Report
1999. March 2001, Document Number: EPA 454/R-0-004. This document is
available electronically at:http://www.epa.gov/air/airtrends/aqtrnd99/
.

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    We estimate that reductions of PM2.5, NOX,
and VOC emissions from locomotive and marine diesel engines would
produce nationwide air quality improvements. According to air quality
modeling performed in conjunction with this proposed rule, if
finalized, all 39 current PM2.5 nonattainment areas would
experience a decrease in their 2020 and 2030 design values. Likewise
all 116 mandatory class I federal areas would see improvements in their
visibility. This rule would also result in substantial nationwide ozone
benefits. The air quality modeling conducted for ozone estimates that
in 2020 and 2030, 114 of the current 116 ozone nonattainment areas
would see improvements in ozone air quality as a result of this
proposed rule.

A. Overview

    From a public health perspective, we are concerned with locomotive
and marine diesel engines' contributions to atmospheric levels of
particulate matter in general, diesel PM2.5 in particular,
and various gaseous air toxics, and ozone. Today, locomotive and marine
diesel engine emissions represent a substantial portion of the U.S.
mobile source diesel PM2.5 and NOX emissions
accounting for approximately 20 percent of mobile source NOX
and 25 percent of mobile source diesel PM2.5. These
proportions are even higher in some urban areas. Over time, the
relative contribution of these diesel engines to air quality problems
is expected to increase as the emission contribution from other mobile
sources decreases and the usage of locomotives and marine vessels
increases. By 2030, without further emissions controls beyond those
already adopted for these engines, locomotive and marine diesel engines
nationally will emit more than 65 percent of the total mobile source
diesel PM2.5 emissions and 35 percent of the total mobile
source NOX emissions.
    Based on the most recent data available for this rule, air quality
problems continue to persist over a wide geographic area of the United
States. As of October 2006 there are approximately 88 million people
living in 39 designated areas (which include all or part of 208
counties) that either do not meet the current PM2.5 NAAQS or
contribute to violations in other counties, and 157 million people
living in 116 areas (which include all or part of 461 counties)
designated as not in attainment for the 8-hour ozone NAAQS. These
numbers do not include the people living in areas where there is a
significant future risk of failing to maintain or achieve either the
PM2.5 or ozone NAAQS. Figure II-1 illustrates the widespread
nature of these problems. This figure depicts counties which are
currently designated nonattainment for either or both the 8-hour ozone
NAAQS and PM2.5 NAAQS. It also shows the location of
mandatory class I federal areas for visibility.
BILLING CODE 6560-50-P

[GRAPHIC] [TIFF OMITTED] TP03AP07.000

BILLING CODE 6560-50-C
    The engine standards proposed in this rule would help reduce
emissions of PM, NOX, VOCs, CO, and air toxics and their
associated health and

environmental effects. Emissions from locomotives and diesel marine
engines contribute to PM and ozone concentrations in many, if not all,
of these nonattainment areas.\13\ The engine standards being proposed
today would become effective as early as 2008 making the expected
PM2.5, NOX, and VOC inventory reductions from
this rulemaking critical to states as they seek to either attain or
maintain the current PM2.5 or ozone NAAQS.
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    \13\ See section II.B.(1)(d) and II.B.(2)(d) for a summary of
the impact emission reductions from locomotive and marine diesel
engines will have on air quality in current PM2.5 and
ozone nonattainment areas.
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    Beyond the impact locomotive and marine diesel engines have on our
nation's ambient air quality the diesel exhaust emissions emanating
from these engines are also of particular concern since diesel exhaust
is classified as a likely human carcinogen.\14\ Many people spend a
large portion of time in or near areas of concentrated locomotive or
marine diesel emissions, near rail yards, marine ports, railways, and
waterways. Recent studies show that populations living near large
diesel emission sources such as major roadways,\15\ rail yards \16\ and
marine ports \17\ are likely to experience greater diesel exhaust
exposure levels than the overall U.S. population, putting them at a
greater health risk. We are currently studying the size of the U.S.
population living near a sample of approximately 60 marine ports and
rail yards, and will place that information in the docket upon
completion prior to the final rule. The diesel PM2.5
reductions which occur as a result of this proposed rule would benefit
the population near these sources and also assist state and local
governments as they work to meet the NAAQS.
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    \14\ U.S. EPA (2002) Health Assessment Document for Diesel
Engine Exhaust. EPA/600/8-90/057F. Office of Research and
Development, Washington, DC. This document is available
electronically at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=29060
.

    \15\ Kinnee, E.J.; Touma, J.S.: Mason, R.; Thurman, J.; Beidler,
A.; Bailey, C.; Cook, R. (2004) Allocation of onroad mobile
emissions to road segments for air toxics modeling in an urban area.
Transport. Res. Part D 9:139-150; also see Cohen, J.; Cook, R;
Bailey, C.R.; Carr, E. (2005) Relationship between motor vehicle
emissions of hazardous pollutants, roadway proximity, and ambient
concentrations in Portland, Oregon. Environ. Modeling & Software 20:
7-12.
    \16\ Hand, R.; Di, P; Servin, A.; Hunsaker, L.; Suer, C. (2004)
Roseville Rail Yard Study. California Air Resources Board. [Online
at http://www.arb.ca.gov/diesel/documents/rrstudy.htm]

    \17\ Di P.; Servin, A.; Rosenkranz, K.; Schwehr, B.; Tran, H.
(April 2006); Diesel Particulate Matter Exposure Assessment Study
for the Ports of Los Angeles and Long Beach. State of California Air
Resources Board. This document is available electronically at:http://www.arb.ca.gov/regact/marine2005/portstudy0406.pdf
.

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    In the following three sections we review important public health
effects linked to pollutants emitted from locomotive and marine diesel
engines first describing the human health effects and the current and
expected future ambient levels of direct or indirectly caused
pollution. Following the discussion of health effects, we will discuss
the modeled air quality benefits which are estimated to result from
regulating these engines. We also discuss a number of other welfare
effects associated with emissions from diesel engines. These effects
include visibility impairment, ecological and property damage caused by
acid deposition, eutrophication and nitrification of surface waters,
environmental threats posed by polycyclic organic matter (POM)
deposition, and plant and crop damage from ozone.
    Finally, in section E we describe the locomotive and marine engine
emission inventories for the primary pollutants affected by the
proposal. We present current and projected future levels of emissions
for the base case, including anticipated reductions from control
programs already adopted by EPA and the States, but without the
controls proposed today. Then we identify expected emission reductions
from nonroad locomotive and marine diesel engines. These reductions
would make important contributions to controlling the health and
welfare problems associated with ambient PM and ozone levels and with
diesel-related air toxics.
    Taken together, the materials in this section describe the need for
tightening emission standards from both locomotive and marine diesel
engines and the air quality and public health benefits we expect as a
result of this proposed rule. This section is not an exhaustive
treatment of these issues. For a fuller understanding of the topics
treated here, you should refer to the extended presentations in Chapter
2 of the Draft Regulatory Impact Analysis (RIA) accompanying this
proposal.

B. Public Health Impacts

(1) Particulate Matter
    The proposed locomotive and marine engine standards would result in
significant reductions of primary PM2.5 emissions from these
sources. In addition, locomotive and marine diesel engines emit high
levels of NOX which react in the atmosphere to form
secondary PM2.5, ammonium nitrate. Locomotive and marine
diesel engines also emit SO2 and HC which react in the
atmosphere to form secondary PM2.5 composed of sulfates and
organic carbonaceous PM2.5. This proposed rule would reduce
both the directly emitted diesel PM and secondary PM emissions.
(a) Background
    Particulate matter (PM) represents a broad class of chemically and
physically diverse substances. It can be principally characterized as
discrete particles that exist in the condensed (liquid or solid) phase
spanning several orders of magnitude in size. PM is further described
by breaking it down into size fractions. PM10 refers to
particles generally less than or equal to 10 micrometers ([mu]m).
PM2.5 refers to fine particles, those particles generally
less than or equal to 2.5 [mu]m in diameter. Inhalable (or
``thoracic'') coarse particles refer to those particles generally
greater than 2.5 [mu]m but less than or equal to 10 [mu]m in diameter.
Ultrafine PM refers to particles less than 100 nanometers (0.1 [mu]m).
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 VOCs) in the atmosphere. The chemical and physical
properties of PM2.5 may vary greatly with time, region,
meteorology, and source category. Thus, PM2.5, may include a
complex mixture of different pollutants including sulfates, nitrates,
organic compounds, elemental carbon and metal compounds. These
particles can remain in the atmosphere for days to weeks and travel
through the atmosphere hundreds to thousands of kilometers.
    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/
m3 based on the 98th percentile concentration averaged over
three years. (This air quality statistic compared to the standard is
referred to as the ``design value.'') The annual standard specifies an
expected annual arithmetic mean not to exceed 15 [mu]g/m3
averaged over three years. EPA has recently finalized PM2.5
nonattainment designations for the 1997 standard (70 FR 943, Jan 5,
2005).\18\ All areas currently in nonattainment for

PM2.5 will be required to meet these 1997 standards between
2009 and 2014.
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    \18\ US EPA, Air Quality Designations and Classifications for
the Fine Particles (PM2.5) National Ambient Air Quality
Standards, December 17, 2004. (70 FR 943, Jan 5. 2005) This document
is also available on the web at: http://www.epa.gov/pmdesignations/.

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    As can be seen in Figure II-1 ambient PM2.5 levels
exceeding the 1997 PM2.5 NAAQS are widespread throughout the
country. As of October 2006 there were approximately 88 million people
living in 39 areas (which include all or part of 208 counties) that
either do not meet the 1997 PM2.5 NAAQS or contribute to
violations in other counties. These numbers do not include the people
living in areas where there is a significant future risk of failing to
maintain or achieve the PM2.5 NAAQS.
    EPA has recently amended the NAAQS for PM2.5 (71 FR
61144, October 17, 2006). The final rule, signed on September 21, 2006
and published in the Federal Register on October 17, 2006, 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\ to provide increased protection against health
effects associated with short-term exposures to fine particles. The
current form of the 24-hour PM2.5 standard was retained
(e.g., based on the 98th percentile concentration averaged over three
years). The level of the annual PM2.5 NAAQS was retained at
15 [mu]g/m\3\, continuing protection against health effects associated
with long-term exposures. The current form of the annual
PM2.5 standard was retained as an annual arithmetic mean
averaged over three years, however, the following two aspects of the
spatial averaging criteria were narrowed: (1) The annual mean
concentration at each site shall be within 10 percent of the spatially
averaged annual mean, and (2) the daily values for each monitoring site
pair shall yield a correlation coefficient of at least 0.9 for each
calendar quarter.
    With regard to the secondary PM2.5 standards, EPA has
revised these standards to be identical in all respects to the revised
primary standards. Specifically, EPA has revised the current 24-hour
PM2.5 secondary standard by making it identical to the
revised 24-hour PM2.5 primary standard and retained the
annual PM2.5 secondary standard. This suite of secondary
PM2.5 standards is intended to provide protection against
PM-related public welfare effects, including visibility impairment,
effects on vegetation and ecosystems, and material damage and soiling.
    The 2006 standards became effective on December 18, 2006. As a
result of the 2006 PM2.5 standard, EPA will designate new
nonattainment areas in early 2010. The timeframe for areas attaining
the 2006 PM NAAQS will likely extend from 2015 to 2020.
    Table II-1 presents the number of counties in areas currently
designated as nonattainment for the 1997 PM2.5 NAAQS as well
as the number of additional counties which have monitored data that is
violating the 2006 PM2.5 NAAQS. In total more than 106
million U.S. residents, in 257 counties are living in areas which
either violate either the 1997 PM2.5 standard or the 2006
PM2.5 standard.

  Table II-1.--Fine Particle Standards: Current Nonattainment Areas and
                        Other Violating Counties
------------------------------------------------------------------------
                                             Number of
                                             counties     Population \a\
------------------------------------------------------------------------
1997 PM2.5 Standards: 39 areas currently             208      88,394,000
 designated.............................
2006 PM2.5 Standards: Counties with                   49      18,198,676
 violating monitors \b\.................
                                         -------------------------------
    Total...............................             257     106,595,676
------------------------------------------------------------------------
\a\ Population numbers are from 2000 census data.
\b\ This table provides an estimate of the counties violating the 2006
  PM2.5 NAAQS based on 2003-05 air quality data. The areas designated as
  nonattainment for the 2006 PM2.5 NAAQS will be based on 3 years of air
  quality data from later years. Also, the county numbers in the summary
  table includes only the counties with monitors violating the 2006
  PM2.5 NAAQS. The monitored county violations may be an underestimate
  of the number of counties and populations that will eventually be
  included in areas with multiple counties designated nonattainment.

    EPA has already adopted many emission control programs that are
expected to reduce ambient PM2.5 levels and as a result of
these programs, the number of areas that fail to achieve the 1997
PM2.5 NAAQS is expected to decrease. Even so, EPA modeling
projects that in 2015, with all current controls, up to 52 counties
with 53 million population may not attain some combination of the
current annual standard of 15 [mu]g/m\3\ and the revised daily standard
of 35 [mu]g/m\3\, and that even in 2020 up to 48 counties with 54
million population will still not be able to attain either the annual,
daily, or both the annual and daily PM2.5 standards.\19\
This does not account for additional areas that have air quality
measurements within 10 percent of the 2006 PM2.5 standard.
These areas, although not violating the standards, would also benefit
from the additional reductions from this rule ensuring long term
maintenance of the PM NAAQS.
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    \19\ Final RIA PM NAAQS, Chapter 2: Defining the
PM2.5 Air Quality Problem. October 17, 2006.
---------------------------------------------------------------------------

    States have told EPA that they need the reductions this proposed
rule would provide in order to meet and maintain both the current 1997
PM2.5 NAAQS and the 2006 PM2.5 NAAQS. Based on
the final rule designating and classifying PM2.5
nonattainment areas, most PM2.5 nonattainment areas will be
required to attain the 1997 PM2.5 NAAQS in the 2009 to 2015
time frame, and then be required to maintain the NAAQS thereafter. The
emissions standards for engine remanufacturing being proposed in this
action would become effective as early as 2008, but no later than 2010,
and states would rely on these expected PM2.5 reductions to
help them to either attain or maintain the 1997 PM2.5 NAAQS.
In the long term, the emission reductions resulting from the proposed
locomotive and marine diesel engine standards would be important to
states efforts to attain and maintain the 2006 PM2.5 NAAQS.
(b) 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)
for PM, and the 2005 PM Staff Paper.\20\ \21\ \22\ Further discussion
of health effects associated

with PM can also be found in the draft RIA for this proposal.
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    \20\ U.S. EPA (1996) Air Quality Criteria for Particulate
Matter, EPA 600-P-95-001aF, EPA 600-P-95-001bF. This document is
available in Docket EPA-HQ-OAR.
    \21\ 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.
    \22\ 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.
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    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 cardio respiratory mortality.\23\
In addition, a reanalysis of the American Cancer Society Study shows an
association between fine particle and sulfate concentrations and lung
cancer mortality.\24\ The locomotive and marine diesel engines, covered
in this proposal contribute to both acute and chronic PM2.5
exposures. Additional information on acute exposures is available in
Chapter 2 of the draft RIA for this proposal.
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    \23\ 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.
    \24\ Pope Ca, III; Thun, MJ; Namboodiri, MM; Docery, DW; Evans,
JS; Speizer, FE; Heath, CW. 1995. Particulate air pollution as a
predictor of mortality in a prospective study of U.S. adults. Am J
Respir Crit Care Med 151:669-674.
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    These health effects of PM2.5 have been further
documented in local impact studies which have focused on health effects
due to PM2.5 exposures measured on or near roadways.\25\
Taking account of all air pollution sources, including both spark-
ignition (gasoline) and diesel powered vehicles, these latter studies
indicate that exposure to PM2.5 emissions near roadways,
dominated by mobile sources, are associated with potentially serious
health effects. For instance, a recent study found associations between
concentrations of cardiac risk factors in the blood of healthy young
police officers and PM2.5 concentrations measured in
vehicles.\26\ Also, a number of studies have shown associations between
residential or school outdoor concentrations of some constituents of
fine particles found in motor vehicle exhaust and adverse respiratory
outcomes, including asthma prevalence in children who live near major
roadways.\27\ \28\ \29\ Although the engines considered in this
proposal differ with those in these studies with respect to their
applications and fuel qualities, these studies provide an indication of
the types of health effects that might be expected to be associated
with personal exposure to PM2.5 emissions from large marine
diesel and locomotive engines. The proposed controls would help to
reduce exposure, and specifically exposure near marine ports and rail
yard related PM2.5 sources.
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    \25\ Riekider, 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.
    \26\ Riediker, M.; Cascio, W.E.; Griggs, T.R.; et al. (2004)
Particulate matter exposure in cars is associated with
cardiovascular effects in healthy young men. Am. J. Respir. Crit.
Care Med. 169: 934-940.
    \27\ Van Vliet, P.; Knape, M.; de Hartog, J.; Janssen, N.;
Harssema, H.; Brunekreef, B. (1997). Motor vehicle exhaust and
chronic respiratory symptoms in children living near freeways. Env.
Research 74: 122-132.
    \28\ Brunekreef, B., Janssen, N.A.H.; de Hartog, J.; Harssema,
H.; Knape, M.; van Vliet, P. (1997). Air pollution from truck
traffic and lung function in children living near roadways.
Epidemiology 8:298-303.
    \29\ Kim, J.J.; Smorodinsky, S.; Lipsett, M.; Singer, B.C.;
Hodgson, A.T.; Ostro, B. (2004). Traffic-related air pollution near
busy roads: The East Bay children's respiratory health study. Am. J.
Respir. Crit. Care Med. 170: 520-526.
---------------------------------------------------------------------------

    Recently, new studies \30\ from the State of California provide
evidence that PM2.5 emissions within marine ports and rail
yards contribute significantly to elevated ambient concentrations near
these sources. A substantial number of people experience exposure to
locomotive and marine diesel engine emissions, raising potential health
concerns. Additional information on marine port and rail yard emissions
and ambient exposures can be found in section.B.3 of this preamble.
---------------------------------------------------------------------------

    \30\ State of California Air Resources Board. Roseville Rail
Yard Study. Stationary Source Division, October 14, 2004. This
document is available electronically at: http://www.arb.ca.gov/diesel/documents/rrstudy.htm
 and State of California Air Resources

Board and State of California Air Resources Board. Diesel
Particulate Matter Exposure Assessment Study for the Ports of Los
Angeles and Long Beach, April 2006. This document is available
electronically at: ftp://ftp.arb.ca.gov/carbis/msprog/offroad/marinevess/documents/portstudy0406.pdf
.

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(c) PM2.5 Air Quality Modeling Results
    Air quality modeling performed for this proposal shows that in 2020
and 2030 all 39 current PM2.5 nonattainment areas would
experience decreases in their PM2.5 design values. For areas
with PM2.5 design values greater than 15 [mu]g/m3
the modeled future-year PM2.5 design values are expected to
decrease on average by 0.06 [mu]g/m3 in 2020 and 0.14 [mu]g/
m3 in 2030. The maximum decrease for future-year
PM2.5 design values in 2020 would be 0.35 [mu]g/
m3 and 0.90 [mu]g/m3 in 2030. The reductions are
discussed in more detail in Chapter 2 of the draft RIA.
    The geographic impact of the proposed locomotive and marine diesel
engine controls in 2030 on PM2.5 design values (DV) in
counties across the US, can be seen in Figure II-2.
BILLING CODE 6560-50-P

[GRAPHIC] [TIFF OMITTED] TP03AP07.001

BILLING CODE 6560-50-C

    Figure II-2 illustrates that the greatest emission reductions in
2030 are projected to occur in Southern California where 3 counties
would experience reductions in their PM2.5 design values of
-0.50 to -0.90 [mu]g/m3. The next level of emission
reductions would occur among 13 counties geographically dispersed in
the southeastern U.S., southern Illinois, and southern California. An
additional 325 counties spread across the U.S. would see a decrease in
their PM2.5 DV ranging from -0.05 to -0.24 [mu]g/
m3.
(d) PM Air Quality Modeling Methodology
    A national scale air quality modeling analysis was performed to
estimate future year annual and daily PM2.5 concentrations
and visibility for this proposed rule. To model the air quality
benefits of this rule we used the Community-Scale Air Quality (CMAQ)
model. CMAQ simulates the numerous physical and chemical processes
involved in the formation, transport, and destruction of ozone and
particulate matter. In addition to the CMAQ model, the modeling
platform includes the emissions, meteorology, and initial and boundary
condition data which are inputs to this model. Consideration of the
different processes that affect primary directly emitted and secondary
PM at the regional scale in different locations is fundamental to
understanding and assessing the effects of pollution control measures
that affect PM, ozone and deposition of pollutants to the surface. A
complete description of the CAMQ model and methodology employed to
develop the future year impacts of this proposed rule are found in
Chapter 2.1 of the draft RIA.
    It should be noted that the emission control scenarios used in the
air quality and benefits modeling are slightly different than the
emission control program being proposed. The differences reflect
further refinements of the regulatory program since we performed the
air quality modeling for this rule. Emissions and air quality modeling
decisions are made early in the analytical process. Chapter 3 of the
draft RIA describes the changes in the inputs and resulting emission
inventories between the preliminary assumptions used for the air
quality modeling and the final proposed regulatory scenario. These
refinements to the proposed program would not significantly change the
results summarized here or our conclusions drawn from this analysis.

(2) Ozone

    The proposed locomotive and marine engine standards are expected to
result in significant reductions of NOX and VOC emissions.
NOX and VOC 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.
(a) Background
    Ground-level ozone pollution is formed by the reaction of volatile
organic compounds (VOCs) and nitrogen oxides (NOX) in the
atmosphere in the presence of heat and sunlight. These two 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.\31\ Ground-level ozone is produced and destroyed in a cyclical
set of chemical reactions, many of which are sensitive to temperature
and sunlight. When ambient temperatures and sunlight levels remain high
for several days and the air is relatively stagnant, ozone and its
precursors can build up and result in more ozone than typically would
occur on a single high-temperature day. Ozone also can be transported
from pollution sources into areas hundreds of miles upwind, resulting
in elevated ozone levels even in areas with low local VOC or
NOX emissions.
---------------------------------------------------------------------------

    \31\ 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 may be accessed electronically at: http://www.epa.gov/ ttn/

naaqs/standards/ ozone/s--o3-- cr--cd.html.
---------------------------------------------------------------------------

    The highest levels of ozone are produced when both VOC and
NOX emissions are present in significant quantities on clear
summer days. Relatively small amounts of NOX enable ozone to
form rapidly when VOC levels are relatively high, but ozone production
is quickly limited by removal of the NOX. Under these
conditions NOX reductions are highly effective in reducing
ozone while VOC reductions have little effect. Such conditions are
called ``NOX-limited.'' Because the contribution of VOC
emissions from biogenic (natural) sources to local ambient ozone
concentrations can be significant, even some areas where man-made VOC
emissions are relatively low can be NOX-limited.
    When NOX levels are relatively high and VOC levels
relatively low, NOX forms inorganic nitrates (i.e.,
particles) but relatively little ozone. Such conditions are called
``VOC-limited.'' Under these conditions, VOC reductions are effective
in reducing ozone, but NOX reductions can actually increase
local ozone under certain circumstances. Even in VOC-limited urban
areas, NOX reductions are not expected to increase ozone
levels if the NOX reductions are sufficiently large.
    Rural areas are usually NOX-limited, due to the
relatively large amounts of biogenic VOC emissions in many rural areas.
Urban areas can be either VOC- or NOX-limited, or a mixture
of both, in which ozone levels exhibit moderate sensitivity to changes
in either pollutant.
    Ozone concentrations in an area also can be lowered by the reaction
of nitric oxide with ozone, forming nitrogen dioxide (NO2);
as the air moves downwind and the cycle continues, the NO2
forms additional ozone. The importance of this reaction depends, in
part, on the relative concentrations of NOX, VOC, and ozone,
all of which change with time and location.
    The current ozone National Ambient Air Quality Standards (NAAQS)
has an 8-hour averaging time.\32\ The 8-hour ozone NAAQS, established
by EPA in 1997, is based on well-documented science demonstrating that
more people were experiencing adverse health effects at lower levels of
exertion, over longer periods, and at lower ozone concentrations than
addressed by the previous one-hour ozone NAAQS. The current ozone NAAQS
addresses ozone exposures of concern for the general population and
populations most at risk, including children active outdoors, outdoor
workers, and individuals with pre-existing respiratory disease, such as
asthma. The 8-hour ozone NAAQS is met at an ambient air quality
monitoring site when the average of the annual fourth-highest daily
maximum 8-hour average ozone concentration over three years is less
than or equal to 0.084 ppm.
---------------------------------------------------------------------------

    \32\ EPA's review of the ozone NAAQS is underway and a proposal
is scheduled for May 2007 with a final rule scheduled for February
2008.
---------------------------------------------------------------------------

    Ozone concentrations exceeding the level of the 8-hour ozone NAAQS
occur over wide geographic areas, including most of the nation's major
population centers.\33\ As of October 2006 there are approximately 157
million people living in 116 areas (which include all or part

of 461 counties) designated as not in attainment with the 8-hour ozone
NAAQS. These numbers do not include the people living in areas where
there is a future risk of failing to maintain or achieve the 8-hour
ozone NAAQS.
---------------------------------------------------------------------------

    \33\ A listing of the 8-hour ozone nonattainment areas is
included in the draft RIA for this proposed rule.
---------------------------------------------------------------------------

    EPA has already adopted many emission control programs that are
expected to reduce ambient ozone levels. These control programs are
described in section I.B.(1) of this preamble. As a result of these
programs, the number of areas that fail to meet the 8-hour ozone NAAQS
in the future is expected to decrease.
    Based on recent ozone modeling performed for the CAIR analysis,\34\
which does not include any additional local ozone precursor controls,
we estimate that in 2010, 24 million people are projected to live in 37
Eastern counties exceeding the 8-hour ozone NAAQS. An additional 61
million people are projected to live in 148 Eastern counties expected
to be within 10 percent of violating the 8-hour ozone NAAQS in 2010.
---------------------------------------------------------------------------

    \34\ Technical Support Document for the Final Clean Air
Interstate Rule Air Quality Modeling. This document is available in
Docket EPA-HQ-OAR-2003-0190.
---------------------------------------------------------------------------

    States with 8-hour ozone nonattainment areas will be required to
take action to bring those areas into compliance in the future. Based
on the final rule designating and classifying 8-hour ozone
nonattainment areas (69 FR 23951, April 30, 2004), most 8-hour ozone
nonattainment areas will be required to attain the 8-hour ozone NAAQS
in the 2007 to 2013 time frame and then be required to maintain the 8-
hour ozone NAAQS thereafter.\35\ We expect many of the 8-hour ozone
nonattainment areas will need to adopt additional emission reduction
programs. The expected NOX and VOC reductions from the
standards proposed in this action would be important to states as they
seek to either attain or maintain the 8-hour ozone NAAQS.
---------------------------------------------------------------------------

    \35\ The Los Angeles South Coast Air Basin 8-hour ozone
nonattainment area will have to attain before June 15, 2021.
---------------------------------------------------------------------------

(b) 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 papers. 36 37 38 Ozone can irritate the
respiratory system, causing coughing, throat irritation, and/or
uncomfortable sensation in the chest. Ozone can reduce lung function
and make it more difficult to breathe deeply, and breathing may become
more rapid and shallow than normal, thereby limiting a person's
activity. Ozone can also aggravate asthma, leading to more asthma
attacks that require a doctor's attention and/or the use of additional
medication. Animal 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 include children, the elderly, and
individuals with respiratory disease such as asthma. There is also
suggestive evidence that certain people may have greater genetic
susceptibility. People can also have heightened vulnerability to ozone
due to greater exposures (e.g., children and outdoor workers).
---------------------------------------------------------------------------

    \36\ 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
may be accessed electronically at: http://www.epa.gov/ttn/naaqs/standards/ozone/s_o3_cr_cd.html
.

    \37\ U.S. EPA (1996) Review of National Ambient Air Quality
Standards for Ozone, Assessment of Scientific and Technical
Information. OAQPS Staff Paper First Draft. EPA-452/R-96-007. This
document is available electronically at: http:http://www.epa.gov/ ttn/

naaqs/ standards/ ozone/s--o3-- cr--sp. html.
    \38\ U.S. EPA (2006) Review of the National Ambient Air Quality
Standards for Ozone, Policy Assessment of Scientific and Technical
Information. OAQPS Staff Paper Second Draft. EPA-452/D-05-002. This
document is available electronically at: http:http://www.epa.gov/ttn/naaqs/standards/ozone/s_o3_cr_sp.html
.

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    The recent ozone AQCD also examined relevant new scientific
information which has emerged in the past decade, including the impact
of ozone exposure on such health effect indicators 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. In addition to supporting
and building further on conclusions from the 1996 AQCD, the 2006 AQCD
included new information on the health effects of ozone. 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.
    EPA typically quantifies ozone-related health impacts in its
regulatory impact analyses (RIAs) when possible. In the analysis of
past air quality regulations, ozone-related benefits have included
morbidity endpoints and welfare effects such as damage to commercial
crops. EPA has not recently included a separate and additive mortality
effect for ozone, independent of the effect associated with fine
particulate matter. For a number of reasons, including (1) advice from
the Science Advisory Board (SAB) Health and Ecological Effects
Subcommittee (HEES) that EPA consider the plausibility and viability of
including an estimate of premature mortality associated with short-term
ozone exposure in its benefits analyses and (2) conclusions regarding
the scientific support for such relationships in EPA's 2006 Air Quality
Criteria for Ozone and Related Photochemical Oxidants (the CD), EPA is
in the process of determining how to appropriately characterize ozone-
related mortality benefits within the context of benefits analyses for
air quality regulations. As part of this process, we are seeking advice
from the National Academy of Sciences (NAS) regarding how the ozone-
mortality literature should be used to quantify the reduction in
premature mortality due to diminished exposure to ozone, the amount of
life expectancy to be added and the monetary value of this increased
life expectancy in the context of health benefits analyses associated
with regulatory assessments. In addition, the Agency has sought advice
on characterizing and communicating the uncertainty associated with
each of these aspects in health benefit analyses.
    Since the NAS effort is not expected to conclude until 2008, the
agency is currently deliberating how best to characterize ozone-related
mortality benefits in its rulemaking analyses in the interim. For the
analysis of the proposed locomotive and marine standards, we do not
quantify an ozone mortality benefit. So that we do not provide an
incomplete picture of all of the benefits associated with reductions in
emissions of ozone precursors, we have chosen not to include an
estimate of total ozone benefits in the proposed RIA. By omitting ozone
benefits in this proposal, we acknowledge that this analysis
underestimates the benefits associated with the proposed standards. For
more information regarding the quantified benefits included in this
analysis, please refer to Chapter 6 of this RIA.

(c) Air Quality Modeling Results for Ozone
    This proposed rule would result in substantial nationwide ozone
benefits. The air quality modeling conducted for ozone as part of this
proposed rulemaking projects that in 2020 and 2030, 114 of the current
116 ozone nonattainment areas would see improvements in ozone air
quality as a result of this proposed rule.
    Results from the air quality modeling conducted for this rulemaking
indicates that the average and population-weighted average
concentrations over all U.S. counties would experience broad
improvement in ozone air quality. The decrease in average ozone
concentration in current nonattainment counties shows that the proposed
rule would help bring these counties into attainment. The decrease in
average ozone concentration for counties below the standard, but within
ten percent, shows that the proposed rule would also help those
counties to maintain the standard. All of these metrics show a decrease
in 2020 and a larger decrease in 2030, indicating in four different
ways the overall improvement in ozone air quality. For example, in
nonattainment counties, on a population-weighted basis, the 8-hour
ozone design value would decrease by 0.29 ppb in 2020 and 0.87 ppb in
2030.
    The impact of the proposed reductions has also been analyzed with
respect to those areas that have the highest design values at or above
85 ppb in 2030. We project there would be 27 U.S. counties with design
values at or above 85 ppb in 2030. After implementation of this
proposed action, we project that 3 of these 27 counties would drop
below 85 ppb. Further, 17 of the 27 counties would be at least 10
percent closer to a design value of less than 85 ppb, and on average
all 27 counties would be about 30 percent closer to a design value of
less than 85 ppb.
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[GRAPHIC] [TIFF OMITTED] TP03AP07.002

BILLING CODE 6560-50-C
    Figure II-3 shows those U.S. counties in 2030 which are projected
to experience a change in their ozone design values as a result of this

proposed rule. The most significant decreases, equal or greater than -
2.0 ppb, would occur in 7 counties across the U.S. including: Grant (-
2.1 ppb) and Lafayette (-2.0 ppb) Counties in Louisiana; Montgomery (-
2.0 ppb), Galveston (-2.0 ppb), and Jefferson (-2.0 ppb) Counties in
Texas; Warren County (-2.9 ppb) in Mississippi; and Santa Barbara
County (-2.7 ppb) in California. One hundred eighty-seven (187)
counties would see annual ozone design value reductions from -1.0 to -
1.9 ppb while an estimated 217 additional counties would see annual
design value reductions from -0.5 to -0.9 ppb. Note that 5 counties
including: Suffolk (+1.5 ppb) and Hampton (+0.8 ppb) Counties in
Virginia; Cook County (+0.7 ppb) in Illinois; Lake County (+0.2 ppb) in
Indiana; and San Bernardino County (+0.1 ppb) in California are
projected to experience an increase in ozone design values because of
the NOX disbenefit that occurs under certain conditions.\39\
It is expected that future local and national controls that decrease
VOC, CO, and regional ozone will mitigate any localized disbenefits.
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    \39\ NOX reductions can at certain times and in some
areas cause ozone levels to increase. Such ``disbenefits'' are
predicted in our modeling for this proposed rule. For a discussion
of the phenomenon see the draft RIA Chapter 2.2. In spite of this
disbenefit, the air quality modeling we conducted makes clear that
the overall effect of this proposed rule is positive with 456
counties experiencing a decrease in both their 2020 and 2030 ozone
design value.
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    EPA's review of the ozone NAAQS is currently underway and a
proposed decision in this review is scheduled for May 2007 with a final
rule scheduled for February 2008. If the ozone NAAQS is revised then
new nonattainment areas could be designated. While EPA is not relying
on it for purposes of justifying this proposal, the emission reductions
from this rulemaking would also be helpful to states if there is an
ozone NAAQS revision.
(d) Ozone Air Quality Modeling Methodology
    A national scale air quality modeling analysis was performed to
estimate future year ozone concentrations for this proposed rule. To
model the air quality benefits of this rule we used the Community-Scale
Air Quality (CMAQ) model. CMAQ simulates the numerous physical and
chemical processes involved in the formation, transport, and
destruction of ozone and particulate matter. In addition to the CMAQ
model, the modeling platform includes the emissions, meteorology, and
initial and boundary condition data which are inputs to this model.
Consideration of the different processes that affect primary directly
emitted and secondary PM at the regional scale in different locations
is fundamental to understanding and assessing the effects of pollution
control measures that affect PM, ozone and deposition of pollutants to
the surface. A complete description of the CAMQ model and methodology
employed to develop the future year impacts of this proposed rule are
found in Chapter 2.1 of the draft RIA.
    It should be noted that the emission control scenarios used in the
air quality and benefits modeling are slightly different than the
emission control program being proposed. The differences reflect
further refinements of the regulatory program since we performed the
air quality modeling for this rule. Emissions and air quality modeling
decisions are made early in the analytical process. Chapter 3 of the
draft RIA describes the changes in the inputs and resulting emission
inventories between the preliminary assumptions used for the air
quality modeling and the final proposed regulatory scenario. These
refinements to the proposed program would not significantly change the
results summarized here or our conclusions drawn from this analysis.
(3) Air Toxics
    People experience elevated risk of cancer and other noncancer
health effects from exposure to air toxics. Mobile sources are
responsible for a significant portion of this risk. According to the
National Air Toxic Assessment (NATA) for 1999, mobile sources were
responsible for 44 percent of outdoor toxic emissions and almost 50
percent of the cancer risk. Benzene is the largest contributor to
cancer risk of all 133 pollutants quantitatively assessed in the 1999
NATA. Mobile sources were responsible for 68 percent of benzene
emissions in 1999. Although the 1999 NATA did not quantify cancer risks
associated with exposure to this diesel exhaust, EPA has concluded that
diesel exhaust ranks with the other air toxic substances that the
national-scale assessment suggests pose the greatest relative risk.
    According to 1999 NATA, nearly the entire U.S. population was
exposed to an average level of air toxics that has the potential for
adverse respiratory health effects (noncancer). Mobile sources were
responsible for 74 percent of the noncancer (respiratory) risk from
outdoor air toxics in 1999. The majority of this risk was from
acrolein, and formaldehyde also contributed to the risk of respiratory
health effects. Although not included in NATA's estimates of noncancer
risk, PM from gasoline and diesel mobile sources contribute
significantly to the health effects associated with ambient PM.
    It should be noted that the NATA modeling framework has a number of
limitations which prevent its use as the sole basis for setting
regulatory standards. These limitations and uncertainties are discussed
on the 1999 NATA Web site.\40\ Even so, this modeling framework is very
useful in identifying air toxic pollutants and sources of greatest
concern, setting regulatory priorities, and informing the decision
making process.
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    \40\ U.S. EPA (2006) National-Scale Air Toxics Assessment for
1999. http://www.epa.gov/ttn/atw/nata1999.

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    The following section provides a brief overview of air toxics which
are associated with nonroad engines, including locomotive and marine
diesel engines, and provides a discussion of the health risks
associated with each air toxic.
(a) Diesel Exhaust (DE)
    Locomotive and marine diesel engine emissions include diesel
exhaust (DE), a complex mixture comprised of carbon dioxide, oxygen,
nitrogen, water vapor, carbon monoxide, nitrogen compounds, sulfur
compounds and numerous low-molecular-weight hydrocarbons. A number of
these gaseous hydrocarbon components are individually known to be toxic
including aldehydes, benzene and 1,3-butadiene. The diesel particulate
matter (DPM) present in diesel exhaust consists of fine particles (< 2.5
[mu]m), including a subgroup with a large number of ultrafine particles
(< 0.1 [mu]m). These particles have large surface area which makes them
an excellent medium for adsorbing organics and their small size makes
them highly respirable and able to reach the deep lung. Many of the
organic compounds present on the particles and in the gases are
individually known to have mutagenic and carcinogenic properties.
Diesel exhaust varies significantly in chemical composition and
particle sizes between different engine types (heavy-duty, light-duty),
engine operating conditions (idle, accelerate, decelerate), and fuel
formulations (high/low sulfur fuel). Also, there are emissions
differences between on-road and nonroad engines because the nonroad
engines are generally of older technology. This is especially true for
locomotive and marine diesel engines.\41\
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    \41\ U.S. EPA (2002) Health Assessment Document for Diesel
Engine Exhaust. EPA/600/8-90/057F Office of Research and
Development, Washington, DC. Pp 1-1, 1-2. This document is available
electronically at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=29060
.

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    After being emitted in the engine exhaust, diesel exhaust undergoes
dilution as well as chemical and physical changes in the atmosphere.
The lifetime for some of the compounds present in diesel exhaust ranges
from hours to days.
(i) Diesel Exhaust: Potential Cancer Effect of Diesel Exhaust
    In EPA's 2002 Diesel Health Assessment Document (Diesel HAD),\42\
diesel exhaust was classified as likely to be carcinogenic to humans by
inhalation at environmental exposures, in accordance with the revised
draft 1996/1999 EPA cancer guidelines. A number of other agencies
(National Institute for Occupational Safety and Health, the
International Agency for Research on Cancer, the World Health
Organization, California EPA, and the U.S. Department of Health and
Human Services) have made similar classifications. However, EPA also
concluded in the Diesel HAD that it is not possible currently to
calculate a cancer unit risk for diesel exhaust due to a variety of
factors that limit the current studies, such as limited quantitative
exposure histories in occupational groups investigated for lung cancer.
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    \42\ U.S. EPA (2002) Health Assessment Document for Diesel
Engine Exhaust. EPA/600/8-90/057F Office of Research and
Development, Washington, DC. This document is available
electronically at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=29060
.

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    For the Diesel HAD, EPA reviewed 22 epidemiologic studies on the
subject of the carcinogenicity of workers exposed to diesel exhaust in
various occupations, finding increased lung cancer risk, although not
always statistically significant, in 8 out of 10 cohort studies and 10
out of 12 case-control studies within several industries, including
railroad workers. Relative risk for lung cancer associated with
exposure ranged from 1.2 to 1.5, although a few studies show relative
risks as high as 2.6. Additionally, the Diesel HAD also relied on two
independent meta-analyses, which examined 23 and 30 occupational
studies respectively, which found statistically significant increases
in smoking-adjusted relative lung cancer risk associated with diesel
exhaust, of 1.33 to 1.47. These meta-analyses demonstrate the effect of
pooling many studies and in this case show the positive relationship
between diesel exhaust exposure and lung cancer across a variety of
diesel exhaust-exposed occupations.\43\ \44\ \45\
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    \43\ U.S. EPA (2002) Health Assessment Document for Diesel
Engine Exhaust. EPA/6008-90/057F Office of Research and Development,
Washington, DC. 9-11.
    \44\ Bhatia, R., Lopipero, P., Smith, A. (1998) Diesel exposure
and lung cancer. Epidemiology 9(1):84-91.
    \45\ Lipsett, M: Campleman, S; (1999) Occupational exposure to
diesel exhaust and lung cancer: a meta-analysis. Am J Public Health
80(7): 1009-1017.
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    In the absence of a cancer unit risk, the Diesel HAD sought to
provide additional insight into the significance of the diesel exhaust-
cancer hazard by estimating possible ranges of risk that might be
present in the population. An exploratory analysis was used to
characterize a possible risk range by comparing a typical environmental
exposure level for highway diesel sources to a selected range of
occupational exposure levels. The occupationally observed risks were
then proportionally scaled according to the exposure ratios to obtain
an estimate of the possible environmental risk. A number of
calculations are needed to accomplish this, and these can be seen in
the EPA Diesel HAD. The outcome was that environmental risks from
diesel exhaust exposure could range from a low of 10-\4\ to
10-\5\ to as high as 10-\3\, reflecting the range
of occupational exposures that could be associated with the relative
and absolute risk levels observed in the occupational studies. Because
of uncertainties, the analysis acknowledged that the risks could be
lower than 10-\4\ or 10-\5\, and a zero risk from
diesel exhaust exposure was not ruled out.
    Retrospective health studies of railroad workers have played an
important part in determining that diesel exhaust is a likely human
carcinogen. Key evidence of the diesel exhaust exposure linkage to lung
cancer comes from two retrospective case-control studies of railroad
workers which are discussed at length in the Diesel HAD.
(ii) Diesel Exhaust: Other Health Effects
    Noncancer health effects of acute and chronic exposure to diesel
exhaust emissions are also of concern to the Agency. EPA derived an RfC
from consideration of four well-conducted chronic rat inhalation
studies showing adverse pulmonary effects. \46\ \47\ \48\ \49\ The RfC
is 5 [mu]g/m \3\ for diesel exhaust as measured by diesel PM. This RfC
does not consider allergenic effects such as those associated with
asthma or immunologic effects. There is growing evidence, discussed in
the Diesel HAD, that diesel exhaust can exacerbate these effects, but
the exposure-response data are presently lacking to derive an RfC. The
EPA Diesel HAD states, ``With DPM [diesel particulate matter] being a
ubiquitous component of ambient PM, there is an uncertainty about the
adequacy of the existing DE [diesel exhaust] noncancer database to
identify all of the pertinent DE-caused noncancer health hazards. (p.
9-19).
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    \46\ Ishinishi, N; Kuwabara, N; Takaki, Y; et al. (1988) Long-
term inhalation experiments on diesel exhaust. In: Diesel exhaust
and health risks. Results of the HERP studies. Ibaraki, Japan:
Research Committee for HERP Studies; pp. 11-84.
    \47\ Heinrich, U; Fuhst, R; Rittinghausen, S; et al. (1995)
Chronic inhalation exposure of Wistar rats and two different strains
of mice to diesel engine exhaust, carbon black, and titanium
dioxide. Inhal. Toxicol. 7:553-556.
    \48\ Mauderly, JL; Jones, RK; Griffith, WC; et al. (1987) Diesel
exhaust is a pulmonary carcinogen in rats exposed chronically by
inhalation. Fundam. Appl. Toxicol. 9:208-221.
    \49\ Nikula, KJ; Snipes, MB; Barr, EB; et al. (1995) Comparative
pulmonary toxicities and carcinogenicities of chronically inhaled
diesel exhaust and carbon black in F344 rats. Fundam. Appl. Toxicol.
25:80-94.
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    Diesel exhaust has been shown to cause serious noncancer effects in
occupational exposure studies. One study of railroad workers and
electricians, cited in the Diesel HAD,\50\ found that exposure to
diesel exhaust resulted in neurobehavioral impairments in one or more
areas including reaction time, balance, blink reflex latency, verbal
recall, and color vision confusion indices. Pulmonary function tests
also showed that 10 of the 16 workers had airway obstruction and
another group of 10 of 16 workers had chronic bronchitis, chest pain,
tightness, and hyperactive airways. Finally, a variety of studies have
been published subsequent to the completion of the Diesel HAD. One such
study, published in 2006 \51\ found that railroad engineers and
conductors with diesel exhaust exposure from operating trains had an
increased incidence of chronic obstructive pulmonary disease (COPD)
mortality. The odds of COPD mortality increased with years on the job
so that those who had worked more than 16 years as an engineer or
conductor after 1959 had an increased risk of 1.61 (95% confidence
interval, 1.12--2.30). EPA is assessing the significance of this study
within the context of the broader literature.
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    \50\ Kilburn (2000). See HAD Chapter 5-7.
    \51\ Hart, JE, Laden F; Schenker, M.B.; and Garshick, E. Chronic
Obstructive Pulmonary Disease Mortality in Diesel-Exposed Railroad
Workers; Environmental Health Perspective July 2006: 1013-1016.

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(iii) Ambient PM2.5 Levels and Exposure to Diesel Exhaust PM
    The Diesel HAD also briefly summarizes health effects associated
with ambient PM and discusses the EPA's annual National Ambient Air
Quality Standard (NAAQS) of 15 [mu]g/m \3\. There is a much more
extensive body of human data showing a wide spectrum of adverse health
effects associated with exposure to ambient PM, of which diesel exhaust
is an important component. The PM2.5 NAAQS is designed to
provide protection from the noncancer and premature mortality effects
of PM2.5 as a whole, of which diesel PM is a constituent.
(iv) Diesel Exhaust PM Exposures
    Exposure of people to diesel exhaust depends on their various
activities, the time spent in those activities, the locations where
these activities occur, and the levels of diesel exhaust pollutants in
those locations. The major difference between ambient levels of diesel
particulate and exposure levels for diesel particulate is that exposure
accounts for a person moving from location to location, proximity to
the emission source, and whether the exposure occurs in an enclosed
environment.
1. Occupational Exposures
    Occupational exposures to diesel exhaust from mobile sources,
including locomotive engines and marine diesel engines, can be several
orders of magnitude greater than typical exposures in the non-
occupationally exposed population.
    Over the years, diesel particulate exposures have been measured for
a number of occupational groups resulting in a wide range of exposures
from 2 to 1,280 [mu]g/m \3\ for a variety of occupations. Studies have
shown that miners and railroad workers typically have higher diesel
exposure levels than other occupational groups studied, including
firefighters, truck dock workers, and truck drivers (both short and
long haul).\52\ As discussed in the Diesel HAD, the National Institute
of Occupational Safety and Health (NIOSH) has estimated a total of
1,400,000 workers are occupationally exposed to diesel exhaust from on-
road and nonroad vehicles including locomotive and marine diesel
engines.
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    \52\ Diesel HAD Page 2-110, 8-12; Woskie, SR; Smith, TJ;
Hammond, SK: et al. (1988a) Estimation of the DE exposures of
railroad workers: II. National and historical exposures. Am J Ind
Med 12:381-394.
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2. Elevated Concentrations and Ambient Exposures in Mobile Source-
Impacted Areas
    Regions immediately downwind of rail yards and marine ports may
experience elevated ambient concentrations of directly-emitted
PM2.5 from diesel engines. Due to the unique nature of rail
yards and marine ports, emissions from a large number of diesel engines
are concentrated in a small area. Furthermore, emissions occur at or
near ground level, allowing emissions of diesel engines to reach nearby
receptors without fully mixing with background air.
    A recent study conducted by the California Air Resources Board
(CARB) examined the air quality impacts of railroad operations at the
J.R. Davis Rail Yard, the largest rail facility in the western United