ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 9 and 94

[EPA-HQ-OAR-2007-0121; FRL_XXXX-X]

RIN 2060-AO38

Control of Emissions from New Marine Compression-Ignition Engines at or
Above 30 Liters per Cylinder

AGENCY:  Environmental Protection Agency (EPA).

ACTION:  Advance notice of proposed rulemaking.

_______________________________________________________________________

SUMMARY:  EPA is issuing this Advance Notice of Proposed Rulemaking
(ANPRM) to invite comment from all interested parties on our plan to
propose new emission standards and other related provisions for new
compression-ignition marine engines with per cylinder displacement at or
above 30 liters per cylinder.  We refer to these engines as Category 3
marine engines.  We are considering standards for achieving large
reductions in oxides of nitrogen (NOx) and particulate matter (PM)
through the use of technologies such as in-cylinder controls,
aftertreatment, and low sulfur fuel, starting as early as 2011.

Category 3 marine engines are important contributors to our nation’s
air pollution today.  This source is projected to continue to generate
large amounts of NOx, PM, and sulfur oxides (SOx) 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 Category 3 marine engines are of particular
concern, as diesel exhaust has been classified by EPA as a likely human
carcinogen.  A program such as the one under consideration would
significantly reduce the contribution of Category 3 marine engines to
national inventories of NOx, PM, and SOx, as well as air toxics, and
would reduce public exposure to those pollutants.

DATES: Comments must be received on or before [insert date, 60 days
after publication in the Federal Register.]

ADDRESSES:  Submit your comments, identified by Docket ID No.
EPA-HQ-OAR-2007-0121, by one of the following methods:

  HYPERLINK "http://www.regulations.gov"  www.regulations.gov : Follow
the on-line instructions for submitting comments.

	(	Email:       HYPERLINK<EMAIL_ADDRESS><EMAIL_ADDRESS>

	(	Fax:<PHONE_NUMBER>

Mail: Environmental Protection Agency, Mail Code: 6102T, 1200
Pennsylvania Ave., NW, Washington, DC, 20460.  Please include two
copies.

Hand Delivery: EPA Docket Center (Air Docket), U.S. Environmental
Protection Agency, EPA West Building, 1301 Constitution Avenue, NW,
Room: 3334 Mail Code: 2822T, Washington, DC.  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-2007-0121.  EPA's policy is that all comments received will
be included in the public docket without change and may be made
available online at   HYPERLINK "http://www.regulations.gov"
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
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your comment.  If you send an e-mail comment directly to EPA without
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Docket: All documents in the docket are listed in the   HYPERLINK
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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   HYPERLINK
"http://www.regulations.gov"  www.regulations.gov  or in hard copy at
the EPA Docket Center, EPA/DC, EPA West, Room 3334, 1301 Constitution
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telephone number for the Public Reading Room is<PHONE_NUMBER>, and the
telephone number for the Air Docket is<PHONE_NUMBER>.

FOR FURTHER INFORMATION CONTACT:  Michael Samulski, Assessment and
Standards Division, Office of Transportation and Air Quality, 2000
Traverwood Drive, Ann Arbor, MI, 48105; telephone number:  (734)
214-4532;  fax number:<PHONE_NUMBER>; email address:     HYPERLINK
<EMAIL_ADDRESS><EMAIL_ADDRESS>.

SUPPLEMENTARY INFORMATION:

I.   General Information

A.  Does this Action Apply to Me?

This action will affect companies that manufacture, sell, or import into
the United States new marine compression-ignition engines for use on
vessels flagged or registered in the United States; companies and
persons that make vessels that will be flagged or registered in the
United States and that use such engines; and the owners or operators of
such U.S. vessels.  Owners and operators of vessels flagged elsewhere
may also be affected, to the extent they use U.S. shipyards or
maintenance and repair facilities; see also Section VII.E regarding
potential application of the standards to foreign vessels that enter
U.S. ports.  Finally, this action may also affect companies and persons
that rebuild or maintain these engines.  Affected categories and
entities include the following:

Category	NAICS Codea	Examples of potentially affected entities

Industry	333618	Manufacturers of new marine diesel engines.

Industry	336611	Manufacturers of marine vessels.

Industry	811310	Engine repair and maintenance.

Industry	483	Water transportation, freight and passenger.

Industry	324110	Petroleum Refineries.

Industry	422710, 422720	Petroleum Bulk Stations and Terminals; Petroleum
and Petroleum Products Wholesalers.

a 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.
To determine whether particular activities may be affected by this
action, you should carefully examine the regulations.  You may direct
questions regarding the applicability of this action as noted in FOR
FURTHER INFORMATION CONTACT.

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

	1.  Submitting CBI.  Do not submit this information to EPA through
www.regulations.gov or e-mail.  Clearly mark the part or all of the
information that you claim to be CBI.  For CBI information in a disk or
CD ROM that you mail to EPA, mark the outside of the disk or CD ROM as
CBI and then identify electronically within the disk or CD ROM the
specific information that is claimed as CBI.  In addition to one
complete version of the comment that includes information claimed as
CBI, a copy of the comment that does not contain the information claimed
as CBI must be submitted for inclusion in the public docket.
Information so marked will not be disclosed except in accordance with
procedures set forth in 40 CFR Part 2.

	2.  Tips for Preparing Your Comments.  When submitting comments,
remember to:

Identify the rulemaking by docket number and other identifying
information (subject heading, Federal Register date and page number).

Follow directions - The agency may ask you to respond to specific
questions or organize comments by referencing a Code of Federal
Regulations (CFR) part or section number.

Explain why you agree or disagree, suggest alternatives, and substitute
language for your requested changes.

Describe any assumptions and provide any technical information and/or
data that you used.

If you estimate potential costs or burdens, explain how you arrived at
your estimate in sufficient detail to allow for it to be reproduced.

Provide specific examples to illustrate your concerns, and suggest
alternatives.

Explain your views as clearly as possible, avoiding the use of profanity
or personal threats.

Make sure to submit your comments by the comment period deadline
identified.

II. Additional Information About This Rulemaking

The current emission standards for new compression-ignition marine
engines with per cylinder displacement at or above 30 liters per
cylinder were adopted in 2003 (see 68 FR 9746, February 28, 2003).  This
ANPRM relies in part on information that was obtained for that rule,
which can be found in Public Docket EPA-HQ-OAR-2003-0045.  This docket
is incorporated into the docket for this action, EPA-HQ-OAR-2007-0121.

Table of Contents

I. Overview

A.  Background:  EPA’s Current Category 3 Standards

B.  Program Under Consideration

II. Why is EPA Considering New Controls?

A. Ozone and PM Attainment

B. Public Health Impacts

1. Particulate Matter

2. Ozone

3. Air Toxics

C. Other Environmental Effects

1. Visibility

2. Plant and Ecosystem Effects of Ozone

3. Acid Deposition

4. Eutrophication and Nitrification

5. Materials Damage and Soiling

III. Relevant Clean Air Act Provisions

IV. International Regulation of Air Pollution from Ships

V. Potential Standards and Effective Dates

A. U.S. Proposal to IMO

1. NOx Standards

2. PM and SOx Standards

B. Other Potential Standards

1. NOx Standards

2. Fuel Quality Standards

VI. Emission Control Technology

A. Engine-Based NOx Control

1.  Traditional In-Cylinder Controls

2.  Water-Based Technologies

3.  Exhaust Gas Recirculation

B. NOx Aftertreatment

C. PM and SOx Control

1.  In-Cylinder Controls

2.  Fuel Quality

3.  Exhaust Gas Scrubbers

VII. Compliance

A.  Testing

1.  PM Sampling

2.  Off-Cycle Emissions

3.  Test Fuel

B.  On-off Technologies

C.  Parameter Adjustment

D.  Certification of Existing Engines

E.  Other Compliance Issues

1. Engines on Foreign-Flagged Vessels

2. Non-Diesel Engines

VIII. Potential Regulatory Impacts

A. Emission Inventory

1. Estimated Inventory Contribution

2. Inventory Calculation Methodology

B. Potential Costs

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

J. Executive Order 12898:  Federal Actions to Address Environmental
Justice in Minority Populations and Low-Income Populations

I. Overview

	In recent years, EPA has adopted major new programs designed to reduce
emissions from diesel engines.  When fully phased in, these new programs
for highway and land-based nonroad diesel engines will lead to the
elimination of over 90 percent of harmful regulated pollutants from
these sources.  The public health and welfare benefits of these actions
are very significant, projected at over $70 billion and $83 billion for
our highway and land-based nonroad diesel programs, respectively.  In
contrast, the corresponding cost of these programs will be a small
fraction of this amount.  We have estimated the annual cost at $4.2
billion and $2 billion, respectively in 2030.  These programs are being
implemented over the next decade.

We have also recently proposed a new emission control program for
locomotives and marine diesel engines.  The proposed standards would
address all types of diesel locomotives (line-haul, switch, and
passenger rail) and all types of marine diesel engines below 30 liters
per cylinder displacement (including propulsion engines used on vessels
from recreational and small fishing boats to super-yachts, tugs and
Great Lakes freighters, and auxiliary engines ranging from small
generator sets to large generators on ocean-going vessels).  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; we are also requesting comment on a program that
would apply a similar requirement to existing marine diesel engines up
to 30 liters per cylinder displacement 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 up to 30
liters per cylinder displacement that reflect the application of
in-cylinder technologies to reduce engine-out NOx and PM.  Third, we are
proposing longer-term standards for locomotive engines and certain
marine diesel engines, referred to as Tier 4 standards, that reflect the
application of high-efficiency catalytic aftertreatment technology
enabled by the availability of ultra-low sulfur diesel (ULSD) fuel.

Marine diesel engines above 30 liters per cylinder, called Category 3
marine diesel engines, are significant contributors to our national
mobile source emission inventory.  Category 3 marine engines are
predominantly used in ocean going vessels.  The contribution of these
engines to national inventories is expected to grow significantly due to
expected increases in foreign trade.  Without new controls, we
anticipate that their overall contribution to mobile source oxides of
nitrogen (NOx) and fine diesel particulate matter (PM2.5) emissions will
increase to about 34 and 45 percent respectively by 2030.  Their
contribution to emissions in port areas on a percentage basis would be
expected to be significantly higher.

Reducing emissions from these engines can lead to improvements in public
health and would help states and localities attain and maintain the PM
and ozone national ambient air quality standards.  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, loss work days, and restricted activity days), changes
in lung function and increased respiratory symptoms, altered respiratory
defense mechanisms, and chronic bronchitis.  In addition, diesel exhaust
is of special public health concern.  Since 2002 EPA has classified
diesel exhaust as likely to be carcinogenic to humans by inhalation at
environmental exposures.  Recent studies are showing that populations
living near large diesel emission sources such as major roadways, rail
yards, and marine ports 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 US
population living near a sample of approximately 50 marine ports and
will place this information in the docket for this ANPRM upon
completion.

	Category 3 marine engines are currently subject to emission standards
that rely on engine-based technologies to reduce emissions.  These
standards, which were adopted in 2003 and went into effect in 2004, are
equivalent to the NOx limits in Annex VI to the MARPOL Convention,   SEQ
CHAPTER \h \r 1 adopted by a Conference of the Parties to the Convention
in 1997.  The opportunity to gain large additional public health
benefits through the application of advanced emission control
technologies, including aftertreatment, lead us to consider more
stringent standards for these engines.  In order to achieve these
emission reductions on the ship, however, it may be necessary to control
the sulfur content of the fuel used in these engines.  Finally, because
of the international nature of ocean-going marine transportation, and
the very large inventory contribution from foreign flagged vessels, we
may also consider the applicability of federal standards to foreign
vessels that enter U.S. ports (see Section VII.E).

In this ANPRM, we describe the emission program we are considering for
Category 3 marine diesel engines and technologies we believe can be used
to achieve those standards.  The remainder of this section provides
background on our current emission control program and gives an overview
of the program we are considering.  Section II provides a brief
discussion of the health and human impacts of emissions from Category 3
marine diesel engines.  Section III identifies relevant Clean Air Act
provisions and Section IV summarizes our interactions with the
International Maritime Organization (IMO).  In Sections V and VI, we
describe the potential emission limits and the emission control
technologies that can be used to meet them.  Section VII discusses
several compliance issues.  In Section VIII, we summarize the
contribution of these engines to current mobile source NOx and PM
inventories in the United States and describe our plans for our future
cost analysis.  Finally, Section IX contains information on statutory
and executive order reviews covering this action.  We are interested in
comments covering all aspects of this ANRPM.

A.  Background:  EPA’s Current Category 3 Standards

	EPA currently has emission standards for Category 3 marine diesel
engines.  The standards, adopted in 2003, are equivalent to the MARPOL
Annex VI NOx limits.  They apply to any Category 3 engine installed on a
vessel flagged or registered in the United States, beginning in 2004.

In our 2003 final rule, we considered adopting standards that would
achieve greater emission reductions through expanding the use and
optimization of in-cylinder controls as well as through the use of
advanced emission control technologies including water technologies
(water injection, emulsification, humidification) and selective
catalytic reduction (SCR).  However, we determined that it was
appropriate to defer a final decision on the longer-term Tier 2
standards to a future rulemaking.  While there was a certain amount of
information available at the time about the advanced technologies, there
were several outstanding technical issues concerning the widespread
commercial use of those technologies.  Deferring the Tier 2 standards to
a second rulemaking allowed us the opportunity to obtain important
additional information on the use of these advanced technologies that we
expected to become available over the next few years.  This new
information was expected to include: (1) new developments as
manufacturers continue to make various improvements to the technology
and address any remaining concerns, (2) data or experience from recently
initiated in-use installations using the advanced technologies, and (3)
information from longer-term in-use experience with the advanced
technologies that would be helpful for evaluating the long-term
durability of emission controls.  An additional reason to defer the
adoption of long-term standards for Category 3 engines was to allow the
United States to pursue further negotiations in the international arena
to achieve more stringent global emission standards for marine diesel
engines.

Finally, because the standards adopted in our 2003 rulemaking were
equivalent to the international standards, we determined that it was
appropriate to defer a decision on the application of federal standards
to engines on foreign-flagged vessels that enter U.S. ports.  We
indicated that we would consider this issue again in our future
rulemaking, and we intend to evaluate how best to address emissions from
foreign vessels in this action.  We expect our proposal to reflect an
approach similar to the emission program recently proposed by the United
States in the current discussions at the IMO to amend the MARPOL Annex
VI standards to a level that achieves significant reductions in NOx, PM,
and SOx emissions from Category 3 marine diesel engines.  We will
evaluate progress at the IMO and, as appropriate, consider the
application of new EPA national standards to engines on foreign-flagged
vessels that enter U.S. ports under our Clean Air Act authority.

B.  Program Under Consideration

As described in Section VI, continuing advancements in diesel engine
control technology support the adoption of long-term technology-forcing
standards for Category 3 engines.  With regard to NOx control, SCR has
been applied to many land-based applications, and the technology
continues to be refined and improved.  More propulsion engines have been
fitted with the technology, especially on vessels operating in the
Baltic Sea, and it is being found to be very effective and durable
in-use.  These improvements, in addition to better optimization of
engine-based controls, have the potential for significant NOx
reductions.  PM and SOx emissions from Category 3 engines are primarily
due to the sulfur content of the fuel they use.  In the short term,
these emissions can be decreased by using fuel with a reduced sulfur
content or through the use of exhaust gas cleaning technology; this is
the idea behind the SOx Emission Control Areas (SECAs) provided for in
Annex VI.  More significant reductions can be obtained by using
distillate fuel, and at least one company has been voluntarily switching
from residual fuel to distillate fuel while their ships are operating
within 24 nautical miles of certain California ports.  Their experience
demonstrates that this type of fuel switching can be done safely and
efficiently, although the higher price of distillate fuel may limit this
approach to near-coast and port areas.  In addition, emission scrubbing
techniques are improving, which have the potential for significant PM
reductions from Category 3 engines.

	We are currently considering an emission control program for new
Category 3 marine diesel engines that takes advantage of these new
emission reduction approaches.  The program we are considering,
described in more detail in Section V, would focus on NOx, PM, and SOx
control from new and existing engines.  This program is similar to the
one recently proposed at the IMO by the U.S. government.

	For NOx control for new engines, we are considering a two-phase
approach.  In the first phase, called Tier 2, we are considering a NOx
emission limit for new engines that would be 15 to 25 percent below the
current NOx limits as defined by the NOx curve in the current Tier 1
standards.  These standards would apply at all times.  In the second
phase, called Tier 3, we are considering a NOx emission limit that would
achieve an additional 80 percent reduction from the Tier 2 limits.  We
are considering the Tier 2 limits as early as 2011 and Tier 3 limits in
the 2016 time frame.  Because Tier 3 standards are likely to be achieved
using aftertreatment technologies, the application of the standards
could be geographically-based thereby allowing operators to turn the
system off while they are outside of a specified geographic area.  That
area could be the same as the compliance area for PM and SOx reductions
(see below).  This two-part approach would permit near-term emission
reductions while achieving deeper reductions through long-term
standards.

	We believe a two-phase approach under consideration is an effective way
to maximize NOx emission reductions from these engines.  While we
continue to believe that the focus of the emission control program
should be on meaningful long-term standards that would apply
high-efficiency catalytic aftertreatment to these engines, short-term
emission reductions could be achieved through incremental improvements
to existing engine designs.  These design improvements can be consistent
with a long-term, after-treatment-based Tier 3 program.  The recent
experience of engine manufacturers in applying advanced control
technologies to other mobile sources suggests that incremental changes
of the type that would be used to achieve the Tier 2 standards may also
be used in strategies to achieve the Tier 3 standards.  For example,
Tier 2 technologies may allow engine manufactures to size their
aftertreatment control systems smaller.  A more stringent Tier 2 control
program, however, may risk diverting resources away from Tier 3 and may
result in the application of emission reduction strategies that are not
consistent with high-efficiency catalytic aftertreatment-based controls.

For PM and SOx control, we are considering a performance standard that
would reflect the use of low-sulfur distillate fuels or the use of
exhaust gas cleaning technology (e.g., scrubbers), or a combination of
both.  These standards would apply as early as 2011 and would
potentially achieve SOx reductions as high as 95 percent and substantial
PM reductions as well. We believe a performance standard would be a
cost-effective approach for PM emission reductions since it allows ship
owners to choose from a variety of mechanisms to achieve the standard,
including fuel switching or the use of emission scrubbers.  Compliance
with the PM and SOx emissions could be limited to operation in a defined
geographical area.  For example, ships operating in the defined coastal
areas (i.e., within a specified distance from shore) would be required
to meet the requirements while operating within the area, but could
“turn off” the control mechanism while on the open sea.  This type
of performance standard could apply to all vessels, new or existing,
that operate within the designated area.  An important advantage of a
geographic approach for PM and SOx control, as well as the Tier 3
standards, is that it would result in emission reductions that are
important for health and human welfare while reducing the costs of the
program since ships will not be required to comply with the limits while
they are operating across large areas of the open sea.

	We are also considering NOx emission controls for existing Category 3
engines that would begin in 2012.  There are at least two approaches
that could be used for setting NOx emission limits for existing engines.
 The first would be to set a performance standard, for example a
reduction of about 20 percent from the Tier 1 NOx limits; how this
reduction is achieved would be left up to the ship owner.
Alternatively, the second approach would be to express the requirement
as a specified action, for example an injector change known to achieve a
particular reduction; this approach would simplify verification, but the
emission reduction results may vary across engines.  We will be
exploring both of these alternative approaches and seek comment on the
relative merits of each.

II. Why is EPA Considering New Controls?

	Category 3 marine engines subject to today’s ANPRM generate
significant emissions of fine particulate matter (PM2.5), nitrogen
oxides (NOx) and sulfur oxides (SOx) 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 while SOx is a
significant contributor to ambient PM2.5.  These engines also emit
volatile organic compounds (VOCs), carbon monoxide (CO), and hazardous
air pollutants or air toxics, which are associated with adverse health
effects.  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.  In addition, emissions from
these engines also cause harm to public welfare, contributing to
visibility impairment, and other detrimental environmental impacts
across the U.S.

A. Ozone and PM Attainment

	Many of our nation’s most serious ozone and PM2.5 nonattainment areas
are located along our coastlines where vessels using Category 3 marine
engine emissions contribute to air pollution in or near urban areas
where significant numbers of people are exposed to these emissions.  The
contribution of these engines to air pollution is substantial and is
expected to grow in the future.  Currently more than 40 major U.S. ports
along our Atlantic, Great Lakes, Gulf of Mexico, and Pacific coast lines
are located in nonattainment areas for ozone and/or PM2.5 (See Figure
II-1).

	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 by 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, emissions from
Category 3 marine engines 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 negative externality because firms in the
market are rewarded for minimizing their operating 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 economic 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 responsibility for
the social costs associated with emissions.  Emission standards proposed
by EPA will accomplish this by mandating that Category 3 marine engines
reduce their emissions to a technologically feasible limit accounting
for social costs more fully.

	When considering vessel operations in the United States’ Exclusive
Economic Zone (EEZ), emissions from Category 3 marine engines account
for a substantial portion of the United States’ ambient PM2.5 and NOx
mobile source emissions.  We estimate that annual emissions in 2007 from
these engines totaled more than 870,000 tons of NOx emissions and 66,000
tons of PM2.5.  This represents more than 8 percent of U.S. mobile
source NOx and 15 percent of U.S. mobile source PM2.5 emissions.   These
numbers are projected to increase significantly through 2030 due to
growth in the use of Category 3 marine engines to transport overseas
goods to U.S. markets and U.S. produced goods overseas.  Furthermore,
their proportion of the emission inventory is projected to increase
significantly as regulatory controls on other major emission categories
take effect.  By 2030, NOx emissions from these ships are projected to
more than double, growing to 2.1 million tons a year or 34 percent of
U.S. mobile source NOx emissions while PM2.5 emissions are expected to
almost triple to 170,000 tons annually comprising 45 percent of U.S.
mobile source PM2.5 emissions.  In 2007 annual emission of SOx from
Category 3 engines totaled almost 530,000 tons or more than half of
mobile source SOx and by 2030 these emissions are expected to increase
to 1.3 million tons or 94 percent of mobile source emissions.

	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), 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.

Recent studies are showing that populations living near large diesel
emission sources such as major roadways, railyards, and marine ports are
likely to experience greater diesel exhaust exposure levels than the
overall U.S. population, putting them at greater health risks.  As part
of our current locomotive and marine diesel engine rulemaking (72 FR
15938, April 3, 2007), we are studying the US population living near a
sample of 47 marine ports which are located along the entire east and
west coasts of the U.S. as well as the Gulf of Mexico and the Great
Lakes region.  This information will be placed in the docket for this
rulemaking when the study is completed.  The PM2.5 and NOx reductions
which would occur as a result of applying advanced emissions control
strategies to Category 3 marine engines could both reduce that amount of
emissions that the populations near these sources are exposed to and
assist state and local governments as they work to reduce NOx and PM2.5
inventories.

	Today millions of Americans continue to live in areas that do not meet
existing air quality standards.  As of June 2007 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 149 million people
living in 94 areas (which include all or part of 391 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 and
depicts counties which are currently (as of March 2007) 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.  Superimposed on this map are top U.S. ports many of which
receive significant port stops from ocean going vessels operating with
Category 3 marine engines.  Currently more than 40 major U.S. deep sea
ports are located in these nonattainment areas.  Many ports are located
in areas rated as class I federal areas for visibility impairment and
regional haze.  It should be noted that emissions from ocean-going
vessels are not simply a localized problem related only to cities that
have commercial ports.  Virtually all U.S. coastal areas are affected by
emissions from ships that transit between those ports, using shipping
lanes that are close to land.  Many of these coastal areas also have
high population densities.  For example, Santa Barbara, which has no
commercial port, estimates that engines on ocean-going marine vessels
currently contribute about 37 percent of total NOx in their area.  These
emissions are from ships that transit the area, and “are comparable to
(even slightly larger than) the amount of NOx produced onshore by cars
and truck.”  By 2015 these emissions are expected to increase 67
percent, contributing 61 percent of Santa Barbara’s total NOx
emissions. This mix of emission sources led Santa Barbara to point out
that they will be unable to meet air quality standards for ozone without
significant emission reductions from these vessels, even if they
completely eliminate all other sources of pollution.  Interport
emissions from OGV also contribute to other environmental problems,
affecting sensitive marine and land ecosystems.

	Figure II-  SEQ Figure \* ARABIC \s 1  1  Air Quality Problems are
Widespread Especially in U.S. Port Areas

	Emissions from Category 3 marine engines account for a substantial and
growing portion of the U.S.’s coastal ambient PM2.5 and NOx levels.
The emission reductions from tightened Category 3 marine engine
standards could play an important part in states efforts to attain and
maintain the NAAQS in the coming decades, especially in coastal
nonattainment areas, where these engines comprise a large portion of the
remaining NOx and PM2.5 emissions inventories.  For example, 2001
emission inventories for California’s South Coast ozone and PM
nonattainment areas indicate that ocean-going vessels (OGVs) contribute
about 30 tons per day (tpd) of NOx and 2½ tpd of PM2.5 to regional
inventories -- and absent additional emission controls, this number
would almost triple in 2020 to 86 tpd of NOx and 8 tpd of PM2.5 as port
related activities continue to grow.  The Houston-Galveston-Beaumont
area is also faced with growing OGV inventories which continue to hamper
their area’s effort to achieve and maintain clean air.  Today, OGVs in
the Houston nonattainment area annually contribute about 27 tpd of NOx
emissions and this is projected to climb to 30 tpd by 2009.  In the
Corpus Christi area, OGVs in 2001 were responsible for about 16 tpd of
NOx.  Finally, in the New York/Northern New Jersey nonattainment area,
2000 inventories indicated that OGVs contributed 12 tpd of NOx emissions
and about 0.75 tpd of PM2.5 emissions to PM inventories.  We request
comment on the impact Category 3 marine engines have on state and local
emission inventories as well as their efforts to meet the ozone and
PM2.5 NAAQS.

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

In addition to public health impacts, there are serious public welfare
and environmental impacts associated with ozone and PM2.5.
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, SOx and PM2.5 can contribute to
the substantial impairment of visibility in many parts 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 and SOx 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), 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 PM2.5 and NOx
emission reductions resulting from tightened standards for Category 3
marine diesel engines would greatly assist nonattainment areas,
especially along our nation’s coasts, in attaining and maintaining the
ozone and the PM2.5 NAAQS in the near term and in the decades to come.

	In September 2006, EPA finalized revised PM2.5 NAAQS.  Nonattainment
areas will be designated with respect to the revised PM2.5 NAAQS in
early 2010.  EPA modeling, conducted as part of finalizing the revised
NAAQS, projects that in 2015 up to 52 counties with 53 million people
may violate 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 PM2.5 inventory
reductions that would be achieved from applying advanced emissions
control strategies to Category 3 engines could be useful in helping
coastal nonattainment areas, 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 PM2.5 and NOx emissions by
undertaking state level action.  However, they also seek further Agency
action for national standards, including the setting of stringent new
Category 3 marine engine standards since states are preempted from
setting new engine emissions standards for this class of engines.

B. Public Health Impacts

1. Particulate Matter

	The emission control program for Category 3 marine engines has the
potential to significantly reduce their contribution to PM2.5
inventories.  In addition, these engines emit high levels of NOx which
react in the atmosphere to form secondary PM2.5, ammonium nitrate.
Category 3 marine engines also emit large amounts of SO2 and HC which
react in the atmosphere to form secondary PM2.5 composed of sulfates and
organic carbonaceous PM2.5.  The emission control program being
considered would reduce the contribution of Category 3 engines to both
directly emitted diesel PM and secondary PM emissions.

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 (µm).  PM2.5 refers to
fine particles, those particles generally less than or equal to 2.5 µm
in diameter.   Inhalable (or “thoracic”) coarse particles refer to
those particles generally greater than 2.5 µm but less than or equal to
10 µm in diameter.  Ultrafine PM refers to particles less than 100
nanometers (0.1 µm).  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 65µg/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 15µg/m3 averaged over three years.  EPA has recently finalized
PM2.5 nonattainment designations for the 1997 standard (70 FR 943, Jan
5, 2005).   All areas currently in nonattainment for PM2.5 will be
required to meet these 1997 standards between 2009 and 2014.

	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 65μg/m3 to 35 μg/m3 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
15μg/m3, 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.

(b) Health Effects of PM 2.5

	Scientific studies show ambient PM is associated with a series of
adverse health effects.  These health effects are discussed in detail in
the 2004 EPA Particulate Matter Air Quality Criteria Document (PM AQCD),
and the 2005 PM Staff Paper.,,

	Health effects associated with short-term exposures (hours to days) to
ambient PM include premature mortality, increased hospital admissions,
heart and lung diseases, increased cough, adverse lower-respiratory
symptoms, decrements in lung function and changes in heart rate rhythm
and other cardiac effects.  Studies examining populations exposed to
different levels of air pollution over a number of years, including the
Harvard Six Cities Study and the American Cancer Society Study, show
associations between long-term exposure to ambient  PM2.5 and both total
and cardiovascular and respiratory mortality.  In addition, a reanalysis
of the American Cancer Society Study shows an association between fine
particle and sulfate concentrations and lung cancer mortality.  The
Category 3 marine engines covered in this proposal contribute to both
acute and chronic PM2.5 exposures.

	The 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.  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.  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.,,  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  Category 3 marine engines.  By reducing their
contribution to PM2.5  inventories, the emissions controls under
consideration also would reduce exposure to these emissions,
specifically exposure near marine ports and shipping routes.

2. Ozone

	The emissions reduction program under consideration for Category 3
marine engines would reduce the contribution of these engines NOx
inventories.  These engines currently have high NOx emissions due to the
size of the engine and because they are relatively uncontrolled.    NOx
contributes 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 VOCs and 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.
 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 downwind, resulting
in elevated ozone levels even in areas with low local VOC or NOx
emissions.

	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 NAAQS has an 8-hour averaging time.  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.  On
June 20, 2007 EPA proposed to strengthen the ozone NAAQS.  The proposed
revisions reflect new scientific evidence about ozone and its effects on
public health and welfare.  The final ozone NAAQS rule is scheduled for
March 2008.

 (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. ,   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.  As of the 2006 review, there was suggestive
evidence that certain people may have greater genetic susceptibility.
Those with greater exposures to ozone, for instance due to time spent
outdoors (e.g., children and outdoor workers), are also of concern.

	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.  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.

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 exposure.  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 among the 133 pollutants quantitatively assessed in the 1999 NATA.
Benzene is the largest contributor to cancer risk of all the assessed
pollutants and mobile sources were responsible for,  about 68 percent of
all benzene emissions in 1999.  Although the 1999 NATA did not quantify
cancer risks associated with exposure to 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 potential noncancer hazard from outdoor air toxics
in 1999.   The majority of this potential noncancer hazard was from
acrolein, and formaldehyde also contributed to the potential hazard.
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 website.   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.

	The following section provides a brief overview of air toxics which are
associated with nonroad engines, including Category 3 marine engines,
and provides a discussion of the health risks associated with each air
toxic.

(a) Diesel Exhaust (DE)

	Category 3 marine 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 (< 2.5µm),
including a subgroup with a large number of ultrafine particles (< 0.1
µm).   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).  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.

Diesel Exhaust: Potential Cancer Effect of Diesel Exhaust

	In EPA’s 2002 Diesel Health Assessment Document (Diesel HAD), 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.

	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.,,

	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.

(2) 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.,,,  The RfC is 5 µg/m3 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
were found to be 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).

	(3) Ambient PM2.5 Levels and Exposure to Diesel Exhaust PM

	The Diesel HAD  briefly summarizes health effects associated with
ambient PM and discusses the EPA’s annual NAAQS of 15 µg/m3.  In
addition, both the 2004 AQCD and the 2005 Staff Paper for PM2.5 have
more recent information.    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.

	(4) 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.

	Occupational Exposures

	Occupational exposures to diesel exhaust from mobile sources, including
Category 3 marine 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 µg/m3 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).   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.

	Elevated Concentrations and Ambient Exposures in Mobile Source-Impacted
Areas

	Regions immediately downwind of marine ports and shipping channels
experience elevated ambient concentrations of directly-emitted PM2.5
from Category 3 marine engines.  Due to the unique nature of marine
ports, emissions from a large number of Category 3 marine engines are
concentrated in a relatively 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 service and maintenance rail facility in
the western United States.  This is relevant in that locomotives use
diesel engines similar to those used in marine vessels.  The yard
occupies 950 acres along a one-quarter mile wide and four mile long
section of land in Roseville, CA.  The study developed an emissions
inventory for the facility for the year 2000 and modeled ambient
concentrations of diesel PM using a well-accepted dispersion model
(ISCST3).  The study estimated substantially elevated concentrations in
an area 5,000 meters from the facility, with higher concentrations
closer to the rail yard.  Using local meteorological data, annual
average contributions from the rail yard to ambient diesel PM
concentrations under prevailing wind conditions were 1.74, 1.18, 0.80,
and 0.25 µg/m3 at receptors located 200, 500, 1000, and 5000 meters
from the yard, respectively.  Several tens of thousands of people live
within the area estimated to experience substantial increases in annual
average ambient PM2.5 as a result of rail yard emissions.

	Another study from CARB evaluated air quality impacts of diesel engine
emissions within the Ports of Long Beach and Los Angeles in California,
one of the largest ports in the U.S.   The study found that ocean going
vessels comprised 53% of the diesel PM emissions while ship auxiliary
engines’ hoteling comprised another 20% of  PM emissions for the
marine ports.   Like the earlier rail yard study, the port study
employed the ISCST3 dispersion model.  Also using local meteorological
data, annual average concentrations were substantially elevated over an
area exceeding 200,000 acres.  Because the ports are located near
heavily-populated areas, the modeling indicated that over 700,000 people
lived in areas with at least 0.3 µg/m3 of port-related diesel PM in
ambient air, about 360,000 people lived in areas with at least 0.6
µg/m3 of diesel PM, and about 50,000 people lived in areas with at
least 1.5 ug/m3 of ambient diesel PM directly from the port.  The study
found that impacts could be discerned up to 15 miles from the marine
port.

	Overall, while these studies focus on only two large marine port and
railroad facilities, they highlight the substantial contribution these
facilities make to elevated ambient concentrations in populated areas.

	We have recently initiated a study to better understand the populations
that are living near rail yards and marine ports nationally.  As part of
the study, a computer geographic information system (GIS) is being used
to identify the locations and property boundaries of these facilities
nationally, and to determine the size and demographic characteristics of
the population living near these facilities.  We anticipate that the
results of this study will be complete in 2007 and we intend to add this
report to the public docket.

(b) Gaseous Air Toxics—benzene, 1,3-butadiene, formaldehyde,
acetaldehyde, acrolein, POM, naphthalene

	Category 3 marine engine emissions contribute to ambient levels of
other air toxics known or suspected as human or animal carcinogens, or
that have non-cancer health effects.  These other compounds include
benzene, 1,3-butadiene, formaldehyde, acetaldehyde, acrolein, polycyclic
organic matter (POM), and naphthalene.   All of these compounds, except
acetaldehyde, were identified as national or regional risk drivers in
the 1999 National-Scale Air Toxics Assessment (NATA) and have
significant inventory contributions from mobile sources.  That is, for a
significant portion of the population, these compounds pose a
significant portion of the total cancer and noncancer risk from
breathing outdoor air toxics.  Reducing the emissions from Category 3
marine engines would help reduce exposure to these harmful substances.

	Air toxics can cause a variety of cancer and noncancer health effects.
A number of the mobile source air toxic pollutants described in this
section are known or likely to pose a cancer hazard in humans. Many of
these compounds also cause adverse noncancer health effects resulting
from chronic, subchronic, or acute inhalation exposures. These include
neurological, cardiovascular, liver, kidney, and respiratory effects as
well as effects on the immune and reproductive systems.

C. Other Environmental Effects

There are a number of public welfare effects associated with the
presence of ozone and PM2.5 in the ambient air including the impact of
PM2.5 on visibility and materials and the impact of ozone on plants,
including trees, agronomic crops and urban ornamentals.

1. Visibility

Visibility can be defined as the degree to which the atmosphere is
transparent to visible light.  Visibility impairment manifests in two
principal ways:  as local visibility impairment and as regional haze.
Local visibility impairment may take the form of a localized plume, a
band or layer of discoloration appearing well above the terrain as a
result of complex local meteorological conditions.  Alternatively, local
visibility impairment may manifest as an urban haze, sometimes referred
to as a “brown cloud.”  This urban haze is largely caused by
emissions from multiple sources in the urban areas and is not typically
attributable to only one nearby source or to long-range transport.   The
second type of visibility impairment, regional haze, usually results
from multiple pollution sources spread over a large geographic region.
Regional haze can impair visibility in large regions and across states.

Visibility is important because it has direct significance to people’s
enjoyment of daily activities in all parts of the country.  Individuals
value good visibility for the well-being it provides them directly,
where they live and work, and in places where they enjoy recreational
opportunities.  Visibility is also highly valued in significant natural
areas such as national parks and wilderness areas and special emphasis
is given to protecting visibility in these areas.  For more information
on visibility see the final 2004 PM AQCD as well as the 2005 PM Staff
Paper.

Fine particles are the major cause of reduced visibility in parts of the
United States.  EPA is pursuing a two-part strategy to address
visibility.  First, to address the welfare effects of PM on visibility,
EPA set secondary PM 2.5 standards which would act in conjunction with
the establishment of a regional haze program. In setting this secondary
standard EPA concluded that PM2.5 causes adverse effects on visibility
in various locations, depending on PM concentrations and factors such as
chemical composition and average relative humidity.  Second, section 169
of the Clean Air Act provides additional authority to address existing
visibility impairment and prevent future visibility impairment in the
156 national parks, forests and wilderness areas categorized as
mandatory class I federal areas (62 FR 38680-81, July 18, 1997).  In
July 1999 the regional haze rule (64 FR 35714) was put in place to
protect the visibility in mandatory class I federal areas.  Visibility
can be said to be impaired in both PM2.5 nonattainment areas and
mandatory class I federal areas.

Category 3 marine engines contribute to visibility concerns in these
areas through their primary PM2.5 emissions and their NOx and SO2
emissions which contribute to the formation of secondary PM2.5.

Recently designated PM2.5 nonattainment areas indicate that, as of June
20, 2007, almost 90 million people live in nonattainment areas for the
1997 PM2.5 NAAQS.  Thus, at least these populations would likely be
experiencing visibility impairment, as well as many thousands of
individuals who travel to these areas.   In addition, while visibility
trends have improved in mandatory Class I federal areas the most recent
data show that these areas continue to suffer from visibility
impairment.  In summary, visibility impairment is experienced throughout
the U.S., in multi-state regions, urban areas, and remote mandatory
class I federal areas.,

2. Plant and Ecosystem Effects of Ozone

Ozone contributes to many environmental effects, with impacts to plants
and ecosystems being of most concern. Ozone can produce both acute and
chronic injury in sensitive species depending on the concentration level
and the duration of the exposure. Ozone effects also tend to accumulate
over the growing season of the plant, so that even lower concentrations
experienced for a longer duration have the potential to create chronic
stress on vegetation. Ozone damage to plants includes visible injury to
leaves and a reduction in food production through impaired
photosynthesis, both of which can lead to reduced crop yields, forestry
production, and use of sensitive ornamentals in landscaping.  In
addition, the reduced food production in plants and subsequent reduced
root growth and storage below ground, can result in other, more subtle
plant and ecosystems impacts.  These include increased susceptibility of
plants to insect attack, disease, harsh weather, interspecies
competition and overall decreased plant vigor.  The adverse effects of
ozone on forest and other natural vegetation can potentially lead to
species shifts and loss from the affected ecosystems, resulting in a
loss or reduction in associated ecosystem goods and services. Lastly,
visible ozone injury to leaves can result in a loss of aesthetic value
in areas of special scenic significance like national parks and
wilderness areas.  The final 2006 ozone Air Quality Criteria Document
(ozone AQCD) presents more detailed information on ozone effects on
vegetation and ecosystems.

As discussed above, Category 3 marine engine emissions of NOx contribute
to ozone and therefore the NOx standards discussed in this action would
help reduce crop damage and stress on vegetation from ozone.

3. Acid Deposition

Acid deposition, or acid rain as it is commonly known, occurs when NOx
and SO2 react in the atmosphere with water, oxygen and oxidants to form
various acidic compounds that later fall to earth in the form of
precipitation or dry deposition of acidic particles. It contributes to
damage of trees at high elevations and in extreme cases may cause lakes
and streams to become so acidic that they cannot support aquatic life.
In addition, acid deposition accelerates the decay of building materials
and paints, including irreplaceable buildings, statues, and sculptures
that are part of our nation’s cultural heritage.

The proposed NOx and SOx standards would help reduce acid deposition,
thereby helping to reduce acidity levels in lakes and streams throughout
the coastal areas of our country and help accelerate the recovery of
acidified lakes and streams and the revival of ecosystems adversely
affected by acid deposition.  Reduced acid deposition levels will also
help reduce stress on forests, thereby accelerating reforestation
efforts and improving timber production.  Deterioration of historic
buildings and monuments, vehicles, and other structures exposed to acid
rain and dry acid deposition also will be reduced, and the costs borne
to prevent acid-related damage may also decline.  While the reduction in
nitrogen acid deposition will be roughly proportional to the reduction
in NOx emissions, the precise impact of new standards would differ
across different areas.

4. Eutrophication and Nitrification

The NOx standards discussed in this action would help reduce the
airborne nitrogen deposition that contributes to eutrophication of
watersheds, particularly in aquatic systems where atmospheric deposition
of nitrogen represents a significant portion of total nitrogen loadings.

Eutrophication is the accelerated production of organic matter,
particularly algae, in a water body.  This increased growth can cause
numerous adverse ecological effects and economic impacts, including
nuisance algal blooms, dieback of underwater plants due to reduced light
penetration, and toxic plankton blooms.  Algal and plankton blooms can
also reduce the level of dissolved oxygen, which can adversely affect
fish and shellfish populations.  In recent decades, human activities
have greatly accelerated nutrient impacts, such as nitrogen and
phosphorus, causing excessive growth of algae and leading to degraded
water quality and associated impairment of fresh water and estuarine
resources for human uses.

Severe and persistent eutrophication often directly impacts human
activities.  For example, losses in the nation’s fishery resources may
be directly caused by fish kills associated with low dissolved oxygen
and toxic blooms.  Declines in tourism occur when low dissolved oxygen
causes noxious smells and floating mats of algal blooms create
unfavorable aesthetic conditions.  Risks to human health increase when
the toxins from algal blooms accumulate in edible fish and shellfish,
and when toxins become airborne, causing respiratory problems due to
inhalation.  According to the NOAA report, more than half of the
nation’s estuaries have moderate to high expressions of at least one
of these symptoms – an indication that eutrophication is well
developed in more than half of U.S. estuaries.

5. Materials Damage and Soiling

The deposition of airborne particles can reduce the aesthetic appeal of
buildings and culturally important articles through soiling, and can
contribute directly (or in conjunction with other pollutants) to
structural damage by means of corrosion or erosion.  Particles affect
materials principally by promoting and accelerating the corrosion of
metals, by degrading paints, and by deteriorating building materials
such as concrete and limestone.  Particles contribute to these effects
because of their electrolytic, hygroscopic, and acidic properties, and
their ability to adsorb corrosive gases (principally sulfur dioxide).
The rate of metal corrosion depends on a number of factors, including
the deposition rate and nature of the pollutant; the influence of the
metal protective corrosion film; the amount of moisture present;
variability in the electrochemical reactions; the presence and
concentration of other surface electrolytes; and the orientation of the
metal surface. The PM standards discussed in this action would help
reduce the airborne particles that contribute to materials damage and
soiling.

III. Relevant Clean Air Act Provisions

	Section 213 of the Clean Air Act (the Act) gives us the authority to
establish emission standards for nonroad engines and vehicles.  Section
213(a)(3) requires the Administrator to set (and from time to time
revise) standards for NOx, VOCs, or carbon monoxide emissions from new
nonroad engines, to reduce ambient levels of ozone and carbon monoxide.
That section specifies that the “standards shall achieve the greatest
degree of emission reductions achievable through the application of
technology which the Administrator determines will be available for the
engines or vehicles.”  As part of this determination, the
Administrator must give appropriate consideration to lead time, noise,
energy, and safety factors associated with the application of such
technology.  Section 213(a)(4) authorizes the Administrator to establish
standards on new engines to control emissions of pollutants, such as PM,
which “may reasonably be anticipated to endanger public health and
welfare.”  In setting appropriate standards, EPA is instructed to take
into account costs, noise, safety, and energy factors.

Section 211(c) of the CAA allows us to regulate fuels where emission
products of the fuel either: (1) Cause or contribute to air pollution
that reasonably may be anticipated to endanger public health or welfare,
or (2) will impair to a significant degree the performance of any
emission control device or system which is in general use, or which the
Administrator finds has been developed to a point where in a reasonable
time it will be in general use were such a regulation to be promulgated.

IV. International Regulation of Air Pollution from Ships

	Annex VI to the International Convention for the Prevention of
Pollution from Ships (MARPOL) addresses air pollution from ships.  Annex
VI was adopted by the Parties to MARPOL at a Diplomatic Conference on
September 26, 1997, and it went into force May 20, 2005.  As of July 31,
2007, the Annex has been ratified by 44 countries, representing 74.1
percent of the world’s merchant shipping tonnage.

	Globally harmonized regulation of ship emissions is generally
recognized to be the preferred approach for addressing air emissions
from ocean-going vessels.  It reduces costs for ship owners, since they
would not be required to comply with a patchwork of different standards
that could occur if each country was setting its own standards, and it
can simplify environmental protection for port and coastal states.

The significance of international shipping to the United States can be
illustrated by port entrance statistics.  In 1999, according to U.S.
Maritime Administration (MARAD) data, about 90 percent of annual
entrances to U.S. ports were made by foreign-flagged vessels (75,700
total entrances; 67,500 entrances by foreign vessels; entrances are for
vessels engaged in foreign trade and do not include Jones Act vessels).
At the same time, however, only a small portion of those vessels account
for most of the visits.  In 1999, of the 7,800 foreign vessels that
visited U.S. ports, about 12 percent accounted for about 50 percent of
total vessel entrances; about 30 percent accounted for about 75 percent
of the vessel entrances.

	The emission control program contained in Annex VI was the first step
for the international control of air pollution from ships.  However, as
early as the 1997 conference, many countries “already recognized that
the NOx emission limits established in Regulation 13 were very modest
when compared with current technology developments.”  Consequently, a
Conference Resolution was adopted at the 1997 conference that invited
the Marine Environment Protection Committee (MEPC) to review the NOx
emission limits at a minimum of five-year intervals after entry into
force of the protocol and, if appropriate, amend the NOx limits to
reflect more stringent controls.

The United States began advocating a review of the NOx emission limits
in 1999.  However, MEPC did not formally consider the issue until 2005,
after the Annex went into effect.  Negotiations for amendments to the
Annex VI standards, including NOx and SOx emission limits, officially
began in April 2006, with the most recent round of negotiations taking
place in April 2007.  The United States submitted a paper to that
meeting (April 2007 Bulk Liquids and Gases Sub-Committee meeting,
referred to as BLG-11) setting out an approach for new international
engine and fuel standards that is outlined in this ANPRM.  Discussions
are expected to continue through Summer 2008 and are expected to
conclude at the October 2008 MEPC meeting.  We will continue to
coordinate our national rule for Category 3 emission limits with our
activities at IMO.

V. Potential Standards and Effective Dates

A. U.S. Proposal to IMO

	Over the past several years, remarkable progress has been made for
highway and nonroad diesel engines in reducing NOx and PM emissions.
Current EPA standards for those land-based sources are anticipated to
achieve emission reductions of more than 90 percent relative to
uncontrolled NOx and PM levels.  In contrast, Category 3 marine engines
are subject to modest NOx standards only.  As discussed above, the U.S.
submitted a proposal to IMO for new exhaust emission standards that, if
adopted, would achieve substantial reductions in NOx, PM, and SOx
exhaust emissions from engines on marine vessels.  Here, we present the
concepts in the IMO submission that we are considering for Category 3
marine engines.

1. NOx Standards

Tier 2 NOx limits:  We are considering new NOx emission standards for
Category 3 marine diesel engines.  As discussed in Section VI, emission
control technology for Category 3 marine engines has progressed
substantially in recent years.  Significant reductions can be achieved
in the near term through in-cylinder controls with little or no impact
on overall vessel performance.  These technologies include traditional
engine-out controls such as electronically controlled high pressure
common-rail fuel systems, turbocharger optimization, compression-ratio
changes, and electronically controlled exhaust valves.  Further emission
reductions could be achieved through the use of water-based technologies
such as water emulsification, direct water injection, or intake-air
humidification or through exhaust gas recirculation.  We request comment
on setting a near term NOx emission standard requiring a reduction of 15
to 25 percent below the current Tier 1 standard.  We are considering
applying this near term standard as early as 2011 for new engines.

	Tier 3 NOx limits:  In the longer term, we believe that much greater
emission reductions could be achieved through the use of selective
catalytic reduction (SCR).  More than 300 SCR systems have been
installed on marine vessels, some of which have been in operation for
more than 10 years and have accumulated 80,000 hours of operation.
While many of these applications have been limited to certain vessel
classes, we believe that the technology is feasible for application to
most engines given adequate lead time.  As discussed in Section VI, SCR
systems are capable of reducing NOx on the order of 90 to 95 percent
compared to current emission levels.  We further believe that an 80
percent reduction from the Tier 2 levels discussed above is achievable
throughout the life of the vessel.  We are requesting comment on setting
a NOx standard 80 percent below the Tier 2 standards in the 2016
timeframe.  Low sulfur distillate fuel would help in achieving these
limits due to the impact of sulfur on catalyst operation; however, we do
not believe low sulfur fuel is necessary to achieve these reductions.
SCR systems have been used on residual fuel, with sulfur levels as high
as 2.5 to 3 percent.  However low sulfur distillate fuel would allow SCR
systems to be smaller, more efficient, less costly, and simpler to
operate.  We request comment on the need for fuel controls to enable low
emission NOx technology.

	NOx limits for existing engines:  Due to the very long life of
ocean-going vessels and the availability of known in-cylinder technical
modifications that provide significant and cost-effective NOx
reductions, the U.S. proposal to IMO presents potential NOx emission
limits for engines on vessels built prior to the Tier 1 limits.  We are
requesting comment on requiring engines on these vessels to be
retrofitted to meet the Tier 1 standard.  The U.S. submittal proposed
that this requirement would start in 2012.  Although the Tier 1
standards went into effect in the United States in 2004, manufacturers
have been building engines with emissions that meet this limit since
2000 due to the MARPOL Annex VI NOx standard.  Although the Annex VI
standards did not go into force until 2005, they apply to engines
installed on vessels built on or after January 1, 2000.

Engines may be retrofitted to achieve meaningful emission reduction by
applying technology used by manufacturers to meet the Tier 1 limits.
These technologies include slide-valve fuel injectors and injection
timing retard.  Manufacturers have indicated that they can reduce NOx
emissions by approximately 20 percent using this technology.  However,
some engines have higher baseline emissions than average and would
require more than a 20 percent emission reduction to meet Tier 1
standards.  Manufacturers have expressed concerns that they would not
necessarily be able to reduce emissions to the Tier 1 standards for such
engines through a simple retrofit.  Therefore, the U.S. proposal to IMO
considers a standard based on percent reduction rather than an absolute
numerical limit.  Specifically, these engines would need to be modified
to reduce NOx emissions by 20 percent from their existing baseline
emission rate.  Alternatively, we request comment on requiring vessel
operators to perform a specific action, such as a valve or injector
change, that would be known to achieve a particular NOx reduction.  In
this case, the certification and compliance provisions would be based on
the completion of this action rather than achieving a specified emission
reduction.

We are also considering whether standards for existing engines should
apply to all engines, regardless of age.  Over time, engine
manufacturers have changed their engine platforms as new technologies
have become available.  Many of the technologies that can be used to
reduce NOx emissions on modern engines may not be easily applied to
older engine designs.  Based on conversations with engine manufacturers
we believe that engines built in the mid-1980s and later are compatible
with the lower NOx components.  Therefore we are requesting comment on
excluding engines installed on a vessel prior to 1985 from this
requirement.  We request comment on what generation of engines can be
retrofitted to achieve NOx reductions.  Also, we request comment on the
feasibility, costs, and other business impacts that would result from
retrofitting existing engines to meet a NOx standard as discussed above.

2. PM and SOx Standards

	For PM and SOx emission control, we are considering emission
performance standards that would reflect the use of low-sulfur
distillate fuels or the use of exhaust gas cleaning technology, or a
combination of both.  As discussed in Section VI, SOx emissions and the
majority of the direct PM emissions from Category 3 marine engines
operated on residual fuels are a direct result of fuel quality, most
notably the sulfur in the fuel.  In addition, SOx emissions form
secondary PM in the atmosphere.  Other components of residual fuel, such
as ash and heavy metals, also contribute directly to PM.  Significant PM
and SOx reductions could be achieved by using low sulfur fuel residual
fuel or distillate fuel.  Alternatively, direct and indirect
sulfur-based PM can be reduced through the use of a seawater scrubber in
the exhaust system.  Recent demonstration projects have shown that
scrubbers are capable of reducing SOx emissions on the order of 95
percent and can achieve substantial reductions in PM as well.

We request comment on setting a PM standard on the order of 0.5 g/kW-hr
and a SOx standard on the order of 0.4 g/kW-hr.  We believe that the
combination of these two performance-based standards would be a
cost-effective way to approach both primary and secondary PM emission
reductions because ship owners would have a variety of mechanisms to
achieve the standard, including fuel switching or the use of emission
scrubbers.  This standard would apply as early as 2011 and would result
in more than a 90 percent reduction in SOx and approximately a 50-70
percent reduction in PM.  We request comment on performance based PM and
SOx standards for Category 3 marine engines, what the standards should
be, and an appropriate implementation date.  We also request comment on
allowing vessel operators the option to comply with the standards by
simply using a distillate fuel with a maximum allowable sulfur level,
such as 1,000 ppm.  Under this option, no exhaust emission testing would
be required to demonstrate compliance with the standard.

B. Other Potential Standards

	A number of other emission control strategies have been discussed at
IMO and other forums.  One study describes many approaches ranging from
exhaust emission standards and operational requirements to port fee and
credit programs.  Below, we discuss an intermediate tier of NOx
standards and a fuel-based approach to emission reductions.

1. NOx Standards

	The Tier 2 and Tier 3 NOx standards discussed above consider
traditional in-cylinder technologies and advanced aftertreatment
technologies, respectively.  It may be appropriate to consider
intermediate standards based on water technology or exhaust gas
recirculation.  As discussed in Section VI, these technologies have been
demonstrated to reduce NOx by 30 to 80 percent from Category 3 marine
engines.  We request comment if this technology could be used to achieve
a more stringent Tier 2 NOx standard or to achieve an intermediate
standard between the Tier 2 and 3 NOx standards discussed above.  A
potential emission standard based on this technology would be on the
order of 50 percent below the Tier 1 NOx standard.

2. Fuel Quality Standards

	We are asking comment on whether EPA should regulate marine fuel
quality for vessels propelled by Category 3 marine engines.  For
example, we could require a distillate fuel with a sulfur content at or
below 1,000 ppm.  The advantage of this approach would be that there
would be a substantial reduction in fuel-bound contaminants such as
sulfur, ash, and heavy metals that enter the engine.  Because the
contaminants would not be in the fuel, they would not be emitted to the
atmosphere.  In addition, fuel-based controls would remove the concern
that fuel quality might impact in-use degradation of exhaust cleaning
devices and thus, emissions.  We request comment on the feasibility and
cost of supplying low sulfur distillate fuel to all ships operating in
U.S. waters.  We also request comment on negative environmental impacts
of wastewater from exhaust scrubbers and on the in-use durability of
exhaust aftertreatment devices used on ships.

VI. Emission Control Technology

A. Engine-Based NOx Control

1.  Traditional In-Cylinder Controls

	Engine manufacturers are meeting the Tier 1 NOx standards for Category
3 marine engines today through traditional in-cylinder fuel and air
management approaches.  These in-cylinder emission control technologies
include electronic controls, optimizing the turbocharger, higher
compression ratio, valve timing, and optimized fuel injection which may
include common rail systems, timing retard, increased injection
pressure, rate shaping, and changes to the number and size of injector
holes to increase fuel atomization.  Although U.S. standards became
effective in 2004, most manufacturers began selling marine engines in
2000 that met the MARPOL Annex VI NOx standard in anticipation of its
ratification.

Manufacturers have indicated that they would be able to use in-cylinder
engine control strategies to achieve further NOx emission reductions
beyond the Tier 1 standards.  EUROMOT, which is an association of engine
manufacturers, submitted a proposal to the International Maritime
Organization for new Category 3 marine engine NOx standards 2 g/kW-hr
below the Tier 1 NOx standard.  In this submission, they pointed to the
following technologies for Category 3 marine engines operating on
residual fuel: fuel injection timing, high compression ratio, modified
valve timing on 4-stroke engines, late exhaust valve closing on 2-stroke
engines, and optimized fuel injection system and combustion chamber.
EUROMOT stated that the limiting factors for NOx design and optimization
are increases in low load smoke and thermal load, PM and CO2 emissions,
fuel consumption, and concerns about engine reliability and load
acceptance.  We request comment on potential emission reductions beyond
the Tier 1 NOx standards that may be achieved through traditional
in-cylinder technology and what the impact of the low NOx designs would
be on fuel consumption, maintenance, and on PM exhaust emissions.

Many of the same in-cylinder control technologies used to meet the Tier
1 NOx standards can be used as retrofit technology on existing engines
built prior to the Tier 1 standards.  An example of this is retrofitting
older fuel injectors with new injectors using slide-valve nozzle tips.
The slide-valve in the nozzle tip limits fuel “dripping” which leads
to higher HC, PM, and smoke emissions and engine fouling.  This fuel
nozzle can be combined with low-NOx engine calibration to achieve about
a 20 percent reduction in NOx emissions through an engine retrofit.
This retrofit is relatively simple on engine platforms similar to those
used for the Tier 1 compliant engines, but the slide-valve injectors may
not be compatible with older engines.  We request comment on whether
Category 3 marine engines built before 2000 could be retrofitted to meet
the Tier 1 NOx standard.  We also request comment on what impacts there
may be on costs and business practices if a retrofit program were
implemented.

2.  Water-Based Technologies

	NOx emissions from Category 3 marine engines can be reduced by
introducing water into the combustion process in combination with
appropriate in-cylinder controls.  Water can be used in the combustion
process to lower the maximum combustion temperature, and therefore lower
NOx formation without a significant increase in fuel consumption.  Water
has a high heat capacity which allows it to absorb enough of the energy
in the cylinder to reduce peak combustion temperatures.  Data from
engine manufacturers suggest that, depending on the amount of water and
how it is introduced into the combustion chamber, a 30 to 80 percent
reduction in NOx can be achieved from Category 3 marine engines.,,
However, some increase in PM may result due to the lower combustion
temperatures, depending on the water introduction strategy.  We request
comment on the potential NOx reductions achievable from water-based
technologies and what the impact on other pollutants or fuel consumption
may be.

	Water may be introduced into the combustion process through
emulsification with the fuel, direct injection into the combustion
chamber, or saturating the intake air with water vapor.  Water
emulsification refers to mixing the fuel and water prior to injection.
This strategy is limited by the instability of the water in the fuel,
but can be improved by mixing the water into the fuel just prior to
injection into the cylinder.  More effective control can be achieved
through the use of an independent injection nozzle in the cylinder for
the water.  Using a separate injector nozzle for water allows larger
amounts of water to be added to the combustion process because the water
is injected simultaneously with the fuel, and larger injection pumps and
nozzles can be used for the water injection.  In addition, the fuel
injection timing and water flow rates can be better optimized at
different engine speeds and loads.  Even higher water-to-fuel ratios can
be achieved through the use of combustion air humidification and steam
injection.  With combustion air humidification, a water nozzle is placed
in the engine intake and an air heater is used to offset condensation.
With steam injection, waste heat is used to vaporize water, which is
then injected into the combustion chamber during the compression stroke.

	Depending on the targeted NOx emission reduction, the amount of water
used can range from half as much as the fuel volume to more than three
times as much.  Fresh water is necessary for the water-based NOx
reduction techniques.  Introducing saltwater into the engine could
result in serious deterioration due to corrosion and fouling.  For this
reason, a ship using water strategies would need either to produce fresh
water through the use of a desalination or distillation system or to
store fresh water on-board.  Often, waste heat in the exhaust is used to
generate fresh water for on-board use.  We request comment on the
capabilities of marine vessels, especially ocean-going ships, to
generate sufficient fresh water on-board to support the use of
water-based NOx control technologies.  For vessels making shorter trips,
we request comment on the practicality of storing fresh water on board
and replenishing the water supply when at port.  We also request comment
on the hardware and operating costs associated with this emission
control technology.

3.  Exhaust Gas Recirculation

	Exhaust gas recirculation (EGR) is a strategy similar to water-based
NOx reduction approaches in that a non-combustible fluid (in this case
exhaust gas) is added to the combustion process.  The exhaust gas is
inert and reduces peak combustion temperatures, where NOx is formed, by
slowing reaction rates and absorbing some of the heat generated during
combustion.  One study concluded that EGR could be used to achieve
similar NOx emission reductions as water emulsion.  However, due to the
risk of carbon deposits and deterioration due to sulfuric acid in the
exhaust gas when high sulfur fuel is used, any exhaust gases
recirculated to the cylinder intake would have to be cleaned before
being routed back into the cylinder.  One method of cleaning the exhaust
would be to use a seawater scrubber.  Another alternative is to use
internal EGR where a portion of the exhaust gases is held in the
cylinder after combustion based on the cylinder scavenging design.  We
request comment on the potential of using EGR as a NOx reduction
strategy for Category 3 marine engines.

B. NOx Aftertreatment

NOx emissions can be reduced substantially using selective catalytic
reduction (SCR), which is a commonly-used technology reducing NOx
emissions standards in diesel applications worldwide.  Stationary power
plants fueled with coal, diesel, and natural gas have used SCR for three
decades as a means of controlling NOx emissions.  European heavy-duty
truck manufacturers are using this technology to meet Euro 5 emissions
limits and several heavy-duty truck engine manufacturers have indicated
that they will use SCR technology to meet stringent U.S. NOx limits
beginning in 2010.  Collaborative research and development activities
between diesel engine manufacturers and SCR catalyst suppliers suggest
that SCR is a mature, cost-effective solution for NOx reduction on
diesel engines.

SCR has also been demonstrated for use with marine diesel engines.  More
than 300 SCR systems have been installed on marine vessels, some of
which have been in operation for more than 10 years and have accumulated
80,000 hours of operation.,,,  These systems are used in a wide range of
ship types including ferries, supply ships, ro ros (roll-on roll-off),
tankers, container ships, icebreakers, cargo ships, workboats, cruise
ships, and navy vessels for both propulsion and auxiliary engines.  The
fuel used on ships with SCR systems ranges from low sulfur distillate
fuel to high sulfur residual fuel.  SCR is capable of reducing NOx
emissions in marine diesel exhaust by more than 90 percent and can have
other benefits as well.,,   Fuel consumption improvements may also be
gained with the use of an SCR system.  By relying on the SCR unit for
NOx emissions control, the engine can be optimized for better fuel
consumption, rather than for low NOx emissions.  When an oxidation
catalyst is used in conjunction with the SCR unit, significant
reductions in HC, CO, and PM may also be achieved.  The SCR unit
attenuates sound, so it may use the space on the vessel that would
normally hold a large muffler generally referred to as an exhaust gas
silencer.  We request further information on the use of SCR on marine
vessels and the potential emissions reductions that may be achieved.  We
also request comment on the durability, packaging, and cost of these
systems.

An SCR catalyst reduces nitrogen oxides to elemental nitrogen (N2) and
water by using a small amount of ammonia (NH3) as the reducing agent.
The most-common method for supplying ammonia to the SCR catalyst is to
inject an aqueous urea-water solution into the exhaust stream.  In the
presence of high-temperature exhaust gases (>200°C), the urea in the
injected solution hydrolyzes to form NH3.  The NH3 is stored on the
surface of the SCR catalyst where it is used to complete the NOx
reduction reaction.  In theory, it is possible to achieve 100 percent
NOx conversion if the exhaust temperature is high enough and the
catalyst is large enough.  Low temperature NOx conversion efficiency can
be improved through use of an oxidation catalyst upstream of the SCR
catalyst to promote the conversion of NO to NO2.  Because the reduction
of NOx can be rate limited by NO reductions, converting some of the NO
to NO2 also allows manufacturers to use a smaller reactor.

Manufacturers report minimum exhaust temperatures for SCR units to be in
the range of 250 to 300°C, depending on the catalyst system design and
fuel sulfur level.,,  Below this temperature, the vanadium-oxide
catalyst in the SCR unit would not be hot enough to efficiently reduce
NOx.  With very low sulfur fuels, a highly reactive oxidation catalyst
can be used upstream of the SCR reactor to convert NO to NO2.  NO2
reacts in the SCR catalyst at lower temperatures than NO; therefore, the
oxidation catalyst lowers the exhaust temperature at which the SCR unit
is effective.  However, as the sulfur concentration increases, a less
reactive oxidation catalyst must be used to prevent excessive formation
of sulfates and poisoning of the oxidation catalyst.  When operating on
marine distillate fuel with a sulfur level of 1,000 ppm, the minimum
exhaust temperature for effective reductions through a current SCR
system would be on the order of 270°C.  On typical heavy fuel oils,
which have sulfur concentrations on the order of 2.5 percent, the
exhaust temperature would need to be about 300°C due to high sulfur
concentrations.  We request comment on the relationship between SCR
operating temperatures and the quality of the fuel used.

SCR can be operated in exhaust streams at or above 500°C before
heat-related degradation of the catalyst becomes significant.  This
maximum exhaust temperature is sufficient for use with Category 3 marine
engines.  Exhaust valve temperatures are generally maintained below
450°C to minimize high temperature corrosion and fouling caused by
vanadium and sodium present in residual fuel.

Modern SCR systems should be able to achieve very high NOx conversion
for all operation covered by the E3 test cycle, which includes power
levels from 25 to 100 percent.  A properly designed system can generally
maintain exhaust temperatures high enough at these power levels to
ensure proper functioning of the improved SCR catalysts.  However,
exhaust temperatures at lower power levels on current vessels may be
below the minimum temperature threshold for SCR systems, especially when
operated on high sulfur fuels.  We believe that it is important that NOx
emission control is achieved even at low power due to the concern that
much of the engine operation that occurs near the shore may be at less
than 25 percent power.  As described in Section VII.A.2, we are
considering the need for changes to the test cycle or other supplemental
requirements to account for the fact that the current test cycle does
not include any operation below 25 percent power.  We request comment on
engine power levels, and corresponding exhaust temperature profiles,
when maneuvering, operating at low speeds, or during other operation
near shore.

We believe there are several approaches that can be used to ensure that
the exhaust temperature during low power operation is sufficiently high
for the SCR unit to function properly.  By positioning the SCR system
ahead of the turbocharger, the heat to the SCR system can be maximized.
This approach was used with vessels equipped with slow-speed engines
that operated at low loads near the coast.  Exhaust temperatures could
be increased by adjusting engine parameters, such as reduced charge air
cooling and modified injection timing.  In one case, SCR was used on a
short passage car ferry which originally had exhaust temperatures below
200°C when the engine was operated at low load.  When the SCR unit was
installed, controls were placed on the intercooler in the air intake
system.  By reducing the cooling on the intake air, the exhaust
temperature was increased to be within the operating range of the SCR
unit, even during low power operation.  In a ship using multiple
propulsion engines, one or more engines could be shut down such that the
remaining engine or engines are operating at higher power.  Another
approach to increase the exhaust temperature could be to use burner
systems during low power operation.  We request comment on the
feasibility of using SCR for effective NOx emission control at low power
operation.

SCR grade urea is a widely used industrial chemical around the world.
Although an infrastructure for widespread transportation, storage, and
dispensing of SCR-grade urea does not currently exist in most places, we
believe that it would develop as needed based on market forces.
Concerning urea production capacity, the U.S. has more-than-sufficient
capacity to meet the additional needs of the marine engines.  Currently,
the U.S. consumes 14.7 million tons of ammonia resources per year, and
relies on imports for 41 percent of that total (of which, urea is the
principal derivative).  In 2005, domestic ammonia producers operated
their plants at 66 percent of rated capacity, resulting in 4.5 million
tons of reserve production capacity.  Thus we do not project that urea
cost or supply will be an issue.  As an alternative, one study looked at
using hydrocarbons distilled from the marine fuel oil as a reductant for
an SCR unit.  We request comment on any issues related using urea, or
any other reductant, on ships such as costs, on-board storage
requirements, and supply infrastructure.

C. PM and SOx Control

	As discussed above, we are considering PM and SOx emission control
approaches based on both fuel sulfur limits and performance based
requirements.  This section discusses traditional in-cylinder emission
controls, fuel quality, and exhaust gas scrubbing technology.

1.  In-Cylinder Controls

	For typical diesel engines operating on distillate fuel, particulate
matter formation is primarily the result of incomplete combustion of the
fuel and lube oil.  The traditional in-cylinder technologies discussed
above for NOx emission control can be optimized for PM control while
simultaneously reducing NOx emissions.  If aftertreatment, such as SCR,
is used to control NOx, then the in-cylinder technologies can be used
primarily for PM reductions.  However, the PM reduction through
in-cylinder technologies is limited for engines operating on high-sulfur
fuel because the majority of the PM emissions in this case are due to
compounds in the fuel rather than due to incomplete combustion, as
discussed below.

2.  Fuel Quality

	The majority of Category 3 engines are designed to run on residual fuel
which has the highest viscosity and lowest price of the petroleum fuel
grades.  Residual fuels are known by several names including heavy fuel
oil (HFO), bunker C fuel, and marine fuel oil.  This fuel is made from
the very end products of the oil refining process, formulated from
residues remaining in the primary distilling stages of the refining
process.  It has high content of ash, metals, nitrogen, and sulfur that
increase emissions of exhaust PM pollutants.  Typical residual fuel
contains about 2.7 percent sulfur, but may have a sulfur content as high
as 4.5 percent.

	When a diesel engine is operating on very low sulfur distillate fuel,
80 to 90 percent of the PM in the exhaust is unburned hydrocarbons from
the fuel and lubricating oil and carbon soot.  When residual fuel is
used, only about 25 to 35 percent of the PM from the engine is made up
of unburned hydrocarbon compounds.,,  In this case, the majority of the
PM from the engine is made up of sulfur, metal, and ash components
originating from the fuel itself.  On a mass basis, the vast majority of
this fuel-based PM is due to the sulfur which oxidizes in the combustion
process and associates with water to form an aqueous solution of
sulfuric acid, known as sulfate PM.  Data suggest that about two percent
of the sulfur in the fuel is converted directly to sulfate PM.,  The
rest of the sulfur in the fuel forms SOx emissions.  These SOx emissions
lead to indirect PM formation in the atmosphere.

	We believe that substantial PM and SOx reductions could be achieved
through the use of lower sulfur fuel.  Using a residual fuel with a
lower sulfur content would reduce the fraction of PM from sulfate
formation.  One study showed a decrease of PM emissions from more than
1.0 g/kW-hr on 2.4 percent sulfur fuel to less than 0.5 g/kW-hr with 0.8
percent sulfur fuel for a medium-speed generator engine on a ship.
Using distillate fuel would likely have further reduced sulfur-based
emissions and PM emissions from ash and metals.  Another study compared
PM emissions from a large 2-stroke marine engine on both low sulfur
residual fuel oil and marine distillate oil and reported about a 70
percent reduction in PM.  The simpler molecular structure of distillate
fuel may result in more complete combustion and reduced levels of
carbonaceous PM (soot and heavy hydrocarbons).  Because SOx emissions
are directly related to the concentration of sulfur in the fuel, a given
percent reduction in sulfur in the fuel would be expected to result in
about the same percent reduction in SOx emissions from the engine.  We
request comment on the potential PM and SOx emission reductions that
could be achieved through the use of lower sulfur residual fuel or
through the use of distillate fuel in Category 3 marine engines.

In general, engines that are designed to operate on residual fuel are
capable of operating on distillate fuel.  For example, if the engine is
to be shut down for maintenance, distillate fuel is typically used to
flush out the fuel system.  There are some issues that would need to be
addressed for operating engines on distillate fuel that were designed
primarily for use on residual fuel.  Switching to distillate fuel
requires 20 to 60 minutes, depending on how slowly the operator wants to
cool the fuel temperatures.  According to engine manufacturers,
switching from a heated residual fuel to an unheated distillate too
quickly could cause damage to fuel pumps.  These fuel pumps would need
to be designed to operate on both fuels if a fuel-switching strategy
were employed.  Separate fuel tanks would be needed for distillate fuel
with sufficient capacity for potentially extended operation on this
fuel.  It is common for ships to have several fuel tanks today to
accommodate the variety in different grades of residual fuel which may
be incompatible with each other and, therefore, require segregation.
Also, different lubricating oil is used with each fuel type.  We believe
that properly designed ships would be able to operate on distillate fuel
either under a fuel-switching strategy or for extended use.  We request
comment on the practical implications of operating ships on either lower
sulfur residual or distillate fuel for extended use.

	Fuel quality may also affect NOx emissions.  Residual fuels have
nitrogen bound into the fuel at a concentration on the order of 0.3 to
0.4 weight percent.  In contrast, marine distillate fuel has about a
0.02 to 0.06 weight percent concentration of nitrogen in the fuel.
Approximately half of nitrogen in the fuel will oxidize to form NOx in a
marine diesel engine.  In addition, the ignition quality of the fuel may
be worse for residual fuel than for distillate fuel which can affect NOx
emissions.  These effects are reflected in the MARPOL NOx technical code
which allows an upward adjustment of 10 percent for NOx, under certain
circumstances, when the engine is tested on residual fuel.  We request
comment on the effect of using residual fuel on NOx emissions, both due
to nitrogen in the fuel and any impacts of fuel quality on
ignition-delay or other combustion characteristics.

There are several types of processes refineries use to remove sulfur
from fuels. Traditional sulfur removal technologies include installing a
hydrocracker upstream, or a hydrotreater upstream or downstream, of the
fluidized catalytic cracker (FCC) unit.  Due to high refinery production
costs, it is not likely that much new volume of residual fuel will be
desulfurized to create 1,000 ppm heavy fuel oil.  It is more likely that
additional distillate fuel may be produced by cracking existing residual
fuels or that blends of high and low sulfur fuels will be used.  Some
existing low sulfur residual fuel is already produced, though the volume
is probably insufficient to fully meet fuel volume requirements for both
ships and land-based applications subject to local sulfur emission
requirements.  We request comment on the availability of low sulfur
marine fuels.

3.  Exhaust Gas Scrubbers

Another approach to reduce PM and SOx emissions is to use seawater
scrubbers. Seawater scrubbers are an aftertreatment technology that uses
the seawater’s ability to absorb SO2.  In the scrubber, the exhaust
gases are brought into contact with seawater.  The SO2 in the exhaust
reacts with oxygen to produce sulfur trioxide that subsequently reacts
with water to yield sulfuric acid.  The sulfuric acid in the water then
reacts with carbonate (and other salts) in the seawater to form sulfates
which may be removed from the exhaust.  The carbonate also directionally
neutralizes the pH of the sulfuric acid.

A scrubber system does not necessarily need to use sea water.  An
alternative approach is to circulate fresh water through the scrubber
system.  In this design, the pH of the wash water is monitored and
additional caustic solution is added as necessary.  If the pH becomes
too low, the water will not adsorb any further sulfur.  During typical
operation, a small amount of wash water is bled out of the system and
fresh water is added to maintain volume.  This prevents excessive
build-up of contaminants in the wash water.

Water may be sprayed into the exhaust stream, or the exhaust gasses may
be routed through a water bath.  As the cooled exhaust gas rises out the
stack, demisters are used to separate water droplets that may be
entrained in the exhaust.  The cleaned exhaust passes out of the
scrubber through the top while the water, containing sulfates, is
drained out through the bottom.  Recent demonstration projects have
shown scrubbers are be capable of reducing SOx emissions on the order of
95 percent.  Today, exhaust gas silencers are used on ships to muffle
noise from the exhaust.  Seawater scrubbers would act as mufflers making
the exhaust gas silencers unnecessary.  New seawater scrubber designs
are not much larger than exhaust gas silencers already used on ships,
and could be packaged in the space formerly used by an exhaust gas
silencer.  We request comment on the effectiveness of seawater scrubbers
and on the practical issues related to installing scrubbers on ships,
including space constraints and costs.

Exhaust gas scrubbers can achieve reductions in particulate matter as
well.  By removing sulfur from the exhaust, the scrubber removes most of
the direct sulfate PM.  As discussed above, sulfates are a large portion
of the PM from ships operating on high sulfur fuels.  By reducing the
SOx emissions, the scrubber will also control much of the secondary PM
formed in the atmosphere from SOx emissions.

Simply mixing alkaline water in the exhaust does not necessarily remove
much of the carbonaceous PM, ash, or metals in the exhaust.  While SO2
associates with the wash water, particles can only be washed out of the
exhaust through direct contact with the water.  In simple scrubber
designs, much of the mass of particles can hide in gas bubbles and
escape out the exhaust.  Manufacturers have been improving their
scrubber designs to address carbonaceous soot and other fine particles.
Finer water sprays, longer mixing times, and turbulent action would be
expected to directionally reduce PM emissions through contact
impactions.  One scrubber design uses an electric charge on the water to
attract particles in the exhaust to the water.  Two chambers are used so
that both a positive and a negative charge can be used to attract both
negatively-charged and positively-charged particles.  The manufacturer
reports an efficiency of more than 99 percent for the removal for
particulate matter and condensable organics in diesel exhaust.  Although
exhaust gas scrubbers are only used in a few demonstration vessels
today, this technology is widely used in land-based applications.  We
request comment on potential PM reductions that could be achieved
through the use of exhaust gas scrubbers on vessels and how scrubber
design impacts the amount of PM that is removed from the exhaust.

	It may be possible to achieve NOx reductions through the use of
seawater scrubbers.  In a typical scrubber, the water-soluble fraction
of NOx (NO2) can combine with the water to form nitrates which are
scrubbed out of the exhaust.  However, because NO2 makes up only a small
fraction of total NOx, this results in less than a 10 percent reduction
in NOx emissions exhausted to atmosphere.  Seawater electrolysis systems
have been developed which increase the adsorption rate of NOx in the
water by oxidizing NO to NO2, which is water-soluble.  One study used
electrolysis in an experimental scrubbing system to remove 90 percent of
the NO and nearly all of the NO2 in the feed gas.  We request comment on
the feasibility of achieving significant NOx reductions from Category 3
marine engines through the use of seawater scrubbers.  We also request
comment on the impact of this technology on nitrate loading and
eutrophication of surrounding waters.

Water-soluble components of the exhaust gas such as SO2, SO3, and NO2
form sulfates and nitrates that are dumped overboard in the discharge
water.  Scrubber wash water also includes suspended solids, heavy
metals, hydrocarbons and PAHs.  Before the scrubber water is discharged,
it may be processed to remove solid particles through several
approaches.  Heavier particles may be trapped in a settling or sludge
tank for disposal.  The removal process may include cyclone technology
similar to that used to separate water from residual fuel prior to
delivery to the engine.  However, depending on particle size
distribution and particle density, settling tanks and hydrodynamic
separation may not effectively remove all suspended solids.  Other
approaches include filtration and flocculation techniques.
Flocculation, which is used in many waste water treatment plants, refers
to adding a chemical agent to the water that will cause the fine
particles to aggregate so that they may be filtered out.  Sludge
separated from the scrubber water would be stored on board until it is
disposed of at proper facilities.

We request comment on appropriate waste discharge limits for scrubber
water and how these limits should be defined.  We are concerned that if
limits are based on the concentration of the pollutants in the water,
then the standards could be met simply by diluting the effluent before
it is discharged.  Although diluting the discharge water may have some
local benefits near the vessel, it would not change the total pollutant
load on a given body of water.  We request comment on basing limits for
waste water pollutants on engine load, similar to exhaust emission
standards.

VII. Compliance

	We expect generally to continue with the compliance program finalized
with the Tier 1 standards.  However, we believe additional testing and
compliance provisions will be necessary for new standards requiring more
advanced technology and more challenging calibrations.

A.  Testing

1.  PM Sampling

	In the past, there has been some concern regarding the use of older PM
measurement procedures with high sulfur residual fuels.  The primary
issue of concern was variability of the PM measurement, which was
strongly influenced by the amount of water bound to sulfur.  However, we
believe improvements in PM measurement procedures, such as those
specified in 40 CFR 1065, have addressed these issues of measurement
variability.  We request comment on the feasibility of accurately
measuring PM emissions from Category 3 marine engines operating on
residual fuel.

2.  Off-Cycle Emissions

We are concerned about emission control performance when the engine is
not operating on the ISO E3 test cycle points.  For Category 1 and
Category 2 engines, we adopted “not-to-exceed” provisions to define
an objective measure to ensure that engines would be reasonably
controlling emissions under the whole range of expected normal
operation, as well as the defeat-device prohibition.  Since these
smaller engines are mass produced for a wide range of vessels used in
many different applications, we expected “normal operation” for
these engines to vary considerably around the ideal propeller curve.
Often, Category 3 engines are intended to operate on a propeller curve
matched with a propeller for custom installation on a specific vessel.
However, these engines may have different duty cycles when used with
variable pitched propellers or as auxiliary engines.  We remain
concerned that Category 3 engines may have higher emissions between test
modes, regardless of the intended operation of the engine.  While the
defeat device provisions prohibit manufacturers from producing their
engines to control emissions more effectively at established test points
than at other points not included in the test, it can be a difficult
prohibition to enforce.  We request comment on how to address emissions
during engine operation not captured by the certification test duty
cycle.

This concern is especially important for Category 3 engines, which
generally remain adjustable in use.  In other words, shipboard engineers
are typically employed to maintain Category 3 engines and would be able
to adjust engine calibrations as they deem appropriate.   To address
this adjustability, we are considering a requirement for manufacturers
to develop emission targets to allow the operator to ensure that the
engine has been readjusted to have performance equivalent to the
certified configuration.  Without some form of target, it may be very
difficult for operators to properly adjust their engines to be
equivalent to their certified configurations if the operators cannot
duplicate certification test conditions (speed, load, fuel quality,
etc.).  The emission targets would vary with operating conditions and