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 and these engines are projected to continue to generategenerating 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 

PMOzone and ozone precursors from these enginesPM2.5 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 a source of diesel exhaust, which 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, 6090 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: 

• www.regulations.gov: Follow the on-line instructions for submitting comments. 

• Email: a-and-r-docket@epa.gov

• Fax: (202) 566-9744 

• 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 
2

made available online at www.regulations.gov, including any personal information provided, 

unless the comment includes information claimed to be Confidential Business Information (CBI) 

or other information whose disclosure is restricted by statute. Do not submit information that you 

consider to be CBI or otherwise protected through www.regulations.gov or e-mail. The 

www.regulations.gov website is an “anonymous access” system, which means EPA will not 

know your identity or contact information unless you provide it in the body of your comment. If 

you send an e-mail comment directly to EPA without going through www.regulations.gov your 

e-mail address will be automatically captured and included as part of the comment that is placed 

in the public docket and made available on the Internet. If you submit an electronic comment, 

EPA recommends that you include your name and other contact information in the body of your 

comment and with any disk or CD-ROM you submit. If EPA cannot read your comment due to 

technical difficulties and cannot contact you for clarification, EPA may not be able to consider 

your comment. Electronic files should avoid the use of special characters, any form of 

encryption, and be free of any defects or viruses. For additional information about EPA’s public 

docket visit the EPA Docket Center homepage at http://www.epa.gov/epahome/dockets.htm. 

Docket: All documents in the docket are listed in the www.regulations.gov index. Although 

listed in the index, some information is not publicly available, e.g., CBI or other information 

whose disclosure is restricted by statute. Certain other material, such as copyrighted material, 

will be publicly available only in hard copy. Publicly available docket materials are available 

either electronically in www.regulations.gov or in hard copy at the EPA Docket Center, 

EPA/DC, EPA West, Room 3334, 1301 Constitution Avenue, NW, Washington, DC. The Public 

Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal 

holidays. The telephone number for the Public Reading Room is (202) 566-1744, and the 

telephone number for the Air Docket is (202) 566-1742. 

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: (734) 214-4050; email 

address: samulski.michael@epa.gov.

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: 
3

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 
4

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 

2B. 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. Certification and Compliance 

A. Testing 

1. PM Sampling 

2. Off-Cycle Emissions

2. Low Power Operation

3. Test Fuel 
5

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 highway1

 and land-based 

nonroad2

 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.3

 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 

 

1

 66 FR 5001, January 18, 2001 

2

 69 FR 38957, June 29, 2004 

3

 72 FR 15937, April 3, 2007 
6

from small generator sets to large generators on ocean-going vessels).4 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 nearterm 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 (OGV). The contribution of 

these engines to national inventories is described in section VIII.A of this preamble. These 

inventories are 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 toare associated with 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.5 Recent studies 

are showing that populations living near large diesel emission sources such as major roadways6

, 

rail yards, and marine ports7

 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 

 

4

 Marine diesel engines at or above 30 l/cyl displacement are not included in this program. 5

 U.S. EPA (2002) Health Assessment Document for Diesel Engine Exhaust. EPA/600/8-90/057F. Office of 

Research and Development, Washington DC. This document is available electronically at 

http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=29060. This document is available in Docket EPA-HQ-OAR2007-0121. 

6

 Kinnee,E.J.; Touman, J.S.; Mason, R.; Thurman,J.; Beidler, A.; Bailey, C.; Cook, R. (2004) Allocation of onroad 

mobile emissions to road segments for air toxics modeling in an urban area. Transport. Res. Part D 9: 139-150. 

7

 State of California Air Resources Board. Roseville Rail Yard Study. Stationary Source Division, October 14, 

2004. This document is available electronically at: http://www.arb.ca.gov/diesel/documents/rrstudy.htm and State 

of California Air Resources Board. Diesel Particulate Matter Exposure Assessment Study for the Ports of Los 

Angeles and Long Beach, April 2006. This document is available electronically at: 

http://www.arb.ca.gov/regact/marine2005/portstudy0406.pdf. This document is available in Docket EPA-HQ-OAR2007-0121. 
7

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, 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 
8

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.8 

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.9 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.10 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 

 8

 68 FR 9748, February 28, 2003. 9

 “Revision of the MARPOL Annex VI, the NOx Technical Code and Related Guidelines; Development of 

Standards for NOx, PM, and SOx,” submitted by the United States, BLG 11/5, Sub-Committee on Bulk Liquids and 

Gases, 11th Session, Agenda Item 5, February 9, 2007, Docket ID EPA-HQ-OAR-2007-0121-0034. This document 

is also available on our website: www.epa.gov/otaq/oceanvessels.com 10 See “Maersk Line Announces Fuel Switch for Vessels Calling California” at 

http://www.maerskline.com/globalfile/?path=/pdf/environment_fuel_initiative 
9

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 highefficiency 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. 
10

 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. ports11 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 correctThe emission standards that EPA is 

considering for Category 3 marine diesel engines would help address this market failure and 

reduce the negative externality from these emissions, it is necessary to give producers 

 

11 American Association of Port Authorities (AAPA), Industry Statistics, 2005 port rankings by cargo tonnage. 
11

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 

providing a technologically feasible limit accountingpositive incentive for social costs more 

fullyengine manufacturers to produce engines that emit fewer harmful pollutants and for vessel

builders and owners to use those cleaner engines. 

 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.12 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..

13 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 are associated with 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.14 

Recent studies are showing that populations living near large diesel emission sources 

such as major roadways15, railyards, and marine ports16 are likely to experience greater diesel 

 

12 In general, the United States Exclusive Economic Zone (EEZ) extends to 200 nautical miles from the U.S. coast. 

Exceptions include geographic regions near Canada, Mexico and the Bahamas where the EEZ extends less than 200 

nautical miles from the U.S. coast. See map in Figure VIII-1, below. 

13 These projections are based on growth rates ranging from 1.7 to 5.0 percent per year, depending on the geographic 

region. The growth rates are described in Section VIII.A.

14 U.S. EPA (2002) Health Assessment Document for Diesel Engine Exhaust. EPA/600/8-90/057F. Office of 

Research and Development, Washington DC. This document is available electronically at 

http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=29060. This document is available in Docket EPA-HQ-OAR2007-0121. 

15 Kinnee,E.J.; Touman, J.S.; Mason, R.; Thurman,J.; Beidler, A.; Bailey, C.; Cook, R. (2004) Allocation of onroad 

mobile emissions to road segments for air toxics modeling in an urban area. Transport. Res. Part D 9: 139-150. 

16 State of California Air Resources Board. Roseville Rail Yard Study. Stationary Source Division, October 14, 

2004. This document is available electronically at: http://www.arb.ca.gov/diesel/documents/rrstudy.htm and State 

of California Air Resources Board. Diesel Particulate Matter Exposure Assessment Study for the Ports of Los 

Angeles and Long Beach, April 2006. This document is available electronically at: 
12

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 the

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.17 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. As discussed above, EPA recently 

completed estimates of the contribution of Category 3 engines to emission inventories. We 

recognize that air quality effects may vary from one port/coastal area to another with differences 

in meteorology, because of spatial differences in emissions with ship movements within regional 

areas. In addition, these emissions may also affect adjacent coastal areas. For these reasons, we 

 

http://www.arb.ca.gov/regact/marine2005/portstudy0406.pdf. These documents are available in Docket EPA-HQOAR-2007-0121. 

17 Memorandum to Docket A–2001–11 from Jean-Marie Revelt, Santa Barbara County Air Quality News, Issue 62, 

July-August 2001 and other materials provided to EPA by Santa Barbara County,’’ March 14, 2002. 
13

plan to study several different port areas to better assess the air quality effects of emissions from 

Category 3 engines. We believe that there are additional port and adjacent coastal areas affected 

by emissions from Category 3 marine engines. We will be performing air quality modeling

specific to this issue to better assess these impacts.
14

 Figure II-1 Air Quality Problems are Widespread Especially in U.S. Port Areas 
15

 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 areas18 indicate that ocean-going vessels (OGVs) contribute about 30 tons per day 

(tpd) of NOx and 21⁄2 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 2009.19 In the Corpus Christi area, 

OGVs in 2001 were responsible for about 16 tpd of NOx.20 Finally, in the New York/Northern 

New Jersey nonattainment area, 2000 inventories21 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 studies22 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. 

 

18 California Air Resources Board (2006). Emission Reduction Plan for Ports and Goods Movements, (April 2006) 

Appendix B-3, Available electronically at www.arb.ca.gov/gmp/docs/finalgmpplan090905.pdf ; 

19 Texas Commission On Environmental Quality (2006) Houston-Galveston-Brazoria 8-Hour Ozone State 

Implmental Plan & Rules, Informational Meeting Presentation, Kelly Keel, Air Quality Planning Section. 

20 Air consulting and Engineering Solutions, Final Report PhassII Corpus Christi Regional Airshed, (August 2001) 

Project Number 21-01-0006. 

21 The Port Authority of New York & New Jersey, (2003), The New York, Northern New Jersey, Long Island 

Nonattainment Area Commercial Marine Vessel Emissions Inventory, Prepared by Starcrest Consulting Group, 

LLC. 

22 State of California Air Resources Board. Roseville Rail Yard Study. Stationary Source Division, October 14, 

2004. This document is available electronically at: http://www.arb.ca.gov/diesel/documents/rrstudy.htm and State 

of California Air Resources Board and State of California Air Resources Board. Diesel Particulate Matter Exposure 

Assessment Study for the Ports of Los Angeles and Long Beach, April 2006. This document is available 

electronically at: ftp://ftp.arb.ca.gov/carbis/msprog/offroad/marinevess/documents/portstudy0406.pdf. These 

documents are available in Docket EPA-HQ-OAR-2007-0121. 
16

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 Athe 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.23 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.24 

 

23 For example, see: California Air Resources Board (2006). Emission Reduction Plan for Ports and Goods 

Movements, (April 2006), Available electronically at www.arb.ca.gov/gmp/docs/finalgmpplan090905.pdf 24 For example, see letter dated November 29, 2006 from California Environmental Protection Agency to Administrator Stephen 

L. Johnson and January 20, 2006 letter from Executive Director, Puget Sound Clean Air Agency to Administrator Stephen L. 

Johnson. 
17

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. 

(a) Background 

 Particulate matter (PM) represents a broad class of chemically and physically diverse 

substances. It can be principally characterized as discrete particles that exist in the condensed 

(liquid or solid) phase spanning several orders of magnitude in size. PM is further described by 

breaking it down into size fractions. PM10 refers to particles generally less than or equal to 10 

micrometers (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).25 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 

 

25US EPA, Air Quality Designations and Classifications for the Fine Particles (PM2.5) National Ambient Air Quality 

Standards, December 17, 2004. (70 FR 943, Jan 5. 2005) This document is available in Docket EPA-HQ-OAR2007-0121. This document is also available on the web at: http://www.epa.gov/pmdesignations/ 
18

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.26,27,28 

 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.29 In addition, a reanalysis of the American 

Cancer Society Study shows an association between fine particle and sulfate concentrations and 

 

26U.S.EPA (1996) Air Quality Criteria for Particulate Matter, EPA 600-P-95-001aF, EPA 600-P-95-001bF. This 

document is available in Docket EPA-HQ-OAR-2007-0121. 

27U.S. EPA (2004) Air Quality Criteria for Particulate Matter (Oct 2004), Volume I Document No. EPA600/P99/002aF and Volume II Document No. EPA600/P-99/002bF. This document is available in Docket EPA-HQOAR-2007-0121. 

28U.S. EPA (2005) Review of the National Ambient Air Quality Standard for Particulate Matter: Policy Assessment 

of Scientific and Technical Information, OAQPS Staff Paper. EPA-452/R-05-005. This document is available in 

Docket EPA-HQ-OAR-2007-0121. 

29 Dockery, DW; Pope, CA III: Xu, X; et al. 1993. An association between air pollution and mortality in six U.S. 

cities. N Engl J Med 329:1753-1759. 
19

lung cancer mortality.30 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.31 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.32 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.33,34,35 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. 

 

30 Pope Ca, III; Thun, MJ; Namboodiri, MM; Docery, DW; Evans, JS; Speizer, FE; Heath, CW. 1995. Particulate air 

pollution as a predictor of mortality in a prospective study of U.S. adults. Am J Respir Crit Care Med 151:669-674. 

31Riekider, M.; Cascio, W.E.; Griggs, T.R.; Herbst, M.C.; Bromberg, P.A.; Neas, L.; Williams, R.W.; Devlin, R.B. 

(2003) Particulate Matter Exposures in Cars is Associated with Cardiovascular Effects in Healthy Young Men. Am. 

J. Respir. Crit. Care Med. 169: 934-940. 32 Riediker, M.; Cascio, W.E.; Griggs, T.R.; et al. (2004) Particulate matter exposure in cars is associated with 

cardiovascular effects in healthy young men. Am J Respir Crit Care Med 169: 934–940. 33 Van Vliet, P.; Knape, M.; de Hartog, J.; Janssen, N.; Harssema, H.; Brunekreef, B. (1997). Motor vehicle exhaust 

and chronic respiratory symptoms in children living near freeways. Env. Research 74: 122-132. 34 Brunekreef, B., Janssen, N.A.H.; de Hartog, J.; Harssema, H.; Knape, M.; van Vliet, P. (1997). Air pollution from 

truck traffic and lung function in children living near roadways. Epidemiology 8:298-303. 35 Kim, J.J.; Smorodinsky, S.; Lipsett, M.; Singer, B.C.; Hodgson, A.T.; Ostro, B (2004). Traffic-related air 

pollution near busy roads: The East Bay children’s respiratory health study. Am. J. Respir. Crit. Care Med. 170: 

520-526. 
20

 The science of ozone formation, transport, and accumulation is complex.36 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.37 The 

 

36U.S. EPA Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental 

Protection Agency, Washington, D.C., EPA 600/R-05/004aF-cF, 2006. This document may be accessed 

electronically at: http://www.epa.gov/ttn/naaqs/standards/ozone/s_o3_cr_cd.html. This document is available in 

Docket EPA-HQ-OAR-2007-0121. 

37 EPA proposes to set the 8-hour primary ozone standard to a level within the range of 0.070-0.075 ppm. The 

agency also requests comments on alternative levels of the 8-hour primary ozone standard, within a range from 

0.060 ppm up to and including retention of the current standard (0.084 ppm). EPA also proposes two options for the 

secondary ozone standard. One option would establish a new form of standard designed specifically to protect 

sensitive plants from damage caused by repeated ozone exposure throughout the growing season. This cumulative 

standard would add daily ozone concentrations across a three month period. EPA is proposing to set the level of the 
21

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. 38,39 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, including 

Category 3 marine engines, 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 

 

cumulative standard within the range of 7 to 21 ppm-hours. The other option would follow the current practice of 

making the secondary standard equal to the proposed 8-hour primary standard. 

38 U.S. EPA Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental 

Protection Agency, Washington, D.C., EPA 600/R-05/004aF-cF, 2006. This document is available in Docket EPAHQ-OAR-2007-0121. This document may be accessed electronically at: 

http://www.epa.gov/ttn/naaqs/standards/ozone/s_o3_cr_cd.html 

39 U.S. EPA (2006) Review of the National Ambient Air Quality Standards for Ozone, Policy Assessment of 

Scientific and Technical Information. OAQPS Staff Paper Second Draft.EPA-452/D-05-002. This document is 

available in Docket EPA-HQ-OAR-2007-0121. This document is available electronically at: 

http:www.epa.gov/ttn/naaqs/standards/ozone/s_o3_cr_sp.html. 
22

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 the 1999 NATA, nearly the entire U.S. population was exposed to an 

average level of air toxics that has the potential for adverse respiratory noncancer health effects

(noncancer).. This potential was indicated by a hazard index (HI) greater than 1.40 Mobile 

sources were responsible for 74 percent of the potential noncancer hazard41 from outdoor air 

toxics in 1999. The majorityAbout 91 percent of this potential noncancer hazard was from 

acrolein,;

42 however, the confidence in the RfC for acrolein is medium43 and formaldehyde also 

contributed to the potential hazard. Although not includedconfidence in NATA's estimates of 

population noncancer risk, PMhazard from gasoline and diesel mobile sources contribute 

significantly to the ambient exposure to this pollutant is low.44 It is important to note that 

NATA estimates of noncancer hazard do not include the adverse health effects associated with 

ambient PM. particulate matter identified in EPA’s Particulate Matter Air Quality Criteria 

Document. Gasoline and diesel engine emissions contribute significantly to with particulate 

matter concentration.

 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.45 Even so, this modeling framework is 

 

40 To express chronic noncancer hazards, we used the RfC as part of a calculation called the hazard quotient (HQ), 

which is the ratio between the concentration to which a person is exposed and the RfC. (RfC is defined by EPA as, 

“an estimate of a continuous inhalation exposure to the human population, including sensitive subgroups, with 

uncertainty spanning perhaps an order of magnitude, that is likely to be without appreciable risks of deleterious 

noncancer effects during a lifetime.”) A value of the HQ less than one indicates that the exposure is lower than the 

RfC and that no adverse health effects would be expected. Combined noncancer hazards were calculated using the 

hazard index (HI), defined as the sum of hazard quotients for individual air toxic compounds that affect the same 

target organ or system. As with the hazard quotient, a value of the HI at or below 1.0 will likely not result in 

adverse effects over a lifetime of exposure. However, a value of the HI greater than 1.0 does not necessarily suggest 

a likelihood of adverse effects. Furthermore, the HI cannot be translated into a probability that adverse effects will 

occur and is not likely to be proportional to risk.

41 To express chronic noncancer hazards, we used the RfC as part of a calculation called the hazard quotient (HQ), 

which is the ratio between the concentration to which a person is exposed and the RfC. (RfC is defined by EPA as, 

“an estimate of a continuous inhalation exposure to the human population, including sensitive subgroups, with 

uncertainty spanning perhaps an order of magnitude, that is likely to be without appreciable risks of deleterious 

noncancer effects during a lifetime.”) A value of the HQ less than one indicates that the exposure is lower than the 

RfC and that no adverse health effects would be expected. 42 U.S. EPA. U.S. EPA (2006) National-Scale Air Toxics Assessment for 1999. This material is available 

electronically at http://www.epa.gov/ttn/atw/nata1999/risksum.html. 

 

43U. S. EPA (2003) Integrated Risk Information System File of Acrolein. National Center for Environmental 

Assessment, Office of Research and Development, Washington, D.C. 2003. This material is available electronically 

at http://www.epa.gov/iris/subst/0364.htm.

 

44 U.S. EPA (2006) National-Scale Air Toxics Assessment for 1999. This material is available electronically at 

http://www.epa.gov/ttn/atw/nata1999/risksum.html. 

45 U. S. EPA (2006) National-Scale Air Toxics Assessment for 1999. http://www.epa.gov/ttn/atw/nata1999. 
23

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 includeengines emit 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 (heavyduty, light-duty), engine operating conditions (idle, accelerate, decelerate), and fuel formulations 

(high/low sulfur fuel).46 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. 

(1) Diesel Exhaust: Potential Cancer Effect of Diesel Exhaust 

 In EPA’s 2002 Diesel Health Assessment Document (Diesel HAD),47 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 

 

46 U.S. EPA (2002) Health Assessment Document for Diesel Engine Exhaust. EPA/600/8-90/057F Office of 

Research and Development, Washington DC. Pp1-1 1-2. This document is available in Docket EPA-HQ-OAR2007-0121. This document is available electronically at 

http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=29060 47 U.S. EPA (2002) Health Assessment Document for Diesel Engine Exhaust. EPA/600/8-90/057F Office of 

Research and Development, Washington DC. This document is available in Docket EPA-HQ-OAR-2007-0121. 

This document is available electronically at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=29060 
24

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 metaanalyses, 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.48,49,50 

 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.51,52,53,54 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 exposure to diesel exhaust can exacerbate these effects, but the exposureresponse data were found to be lacking to derive an RfC. The EPA Diesel HAD states, “With 

 

48 U.S. EPA (2002) Health Assessment Document for Diesel Engine Exhaust. EPA/6008-90/057F Office of 

Research and Development, Washington DC. This document is available in Docket EPA-HQ-OAR-2007-0121. 

49 Bhatia, R., Lopipero, P., Smith, A. (1998) Diesel exposure and lung cancer. Epidemiology 9(1):84-91. 50 Lipsett, M: Campleman, S; (1999) Occupational exposure to diesel exhaust and lung cancer: a meta-analysis. Am 

J Public Health 80(7): 1009-1017. 

51Ishinishi, N; Kuwabara, N; Takaki, Y; et al. (1988) Long-term inhalation experiments on diesel exhaust. In: Diesel 

exhaust and health risks. Results of the HERP studies. Ibaraki, Japan: Research Committee for HERP Studies; pp. 

11-84. 

52Heinrich, U; Fuhst, R; Rittinghausen, S; et al. (1995) Chronic inhalation exposure of Wistar rats and two different 

strains of mice to diesel engine exhaust, carbon black, and titanium dioxide. Inhal. Toxicol. 7:553-556. 53Mauderly, JL; Jones, RK; Griffith, WC; et al. (1987) Diesel exhaust is a pulmonary carcinogen in rats exposed 

chronically by inhalation. Fundam. Appl. Toxicol. 9:208-221. 54Nikula, KJ; Snipes, MB; Barr, EB; et al. (1995) Comparative pulmonary toxicities and carcinogenicities of 

chronically inhaled diesel exhaust and carbon black in F344 rats. Fundam. Appl. Toxicol. 25:80-94. 
25

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 nonoccupationally 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).55 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 

 

55 Diesel HAD Page 2-110, 8-12; Woskie, SR; Smith, TJ; Hammond, SK: et al. (1988a) Estimation of the DE 

exposures of railroad workers: II. National and historical exposures. Am J Ind Med 12:381-394. 
26

maintenance rail facility in the western United States.56 This is relevant in that locomotives use 

diesel engines similar to those used in marine vessels. The yard occupies 950 acres along a onequarter 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.57 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 in 2006 to better understand the populations that are 

living near rail yards and marine ports nationally. As part of the study, this effort,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 completecompleted in late 2007 and we intend to add this report to the public 

docket. 

(b) GaseousOther 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. 

 

56 Hand, R.; Pingkuan, D.; Servin, A.; Hunsaker, L.; Suer, C. (2004) Roseville rail yard study. California Air 

Resources Board. [Online at http://www.arb.ca.gov/diesel/documents/rrstudy.htm] 57 Di, P.; Servin, A.; Rosenkranz, K.; Schwehr, B.; Tran, H. (2006) Diesel particulate matter exposure assessment 

study for the Ports of Los Angeles and Long Beach. California Air Resources Board. [Online at 

http://www.arb.ca.gov/msprog/offroad/marinevess/marinevess.htm] 
27

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. Furthermore, a significant 

portion of total nationwide emissions of these pollutants result from mobile sources. However, 

EPA does not have high confidence in the NATA data for all these compounds. 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,58 subchronic,59 or acute60 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.61 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 

 

58 Chronic exposure is defined in the glossary of the Integrated Risk Information (IRIS) database 

(http://www.epa.gov/iris) as repeated exposure by the oral, dermal, or inhalation route for more than approximately 

10 percent of the life span in humans (more than approximately 90 days to 2 years in typically used laboratory 

animal species). 

59 Defined in the IRIS database as exposure to a substance spanning approximately 10 percent of the lifetime of an 

organism. 60 Defined in the IRIS database as exposure by the oral, dermal, or inhalation route for 24 hours or less. 61 See discussion in U.S. EPA , National Ambient Air Quality Standards for Particulate Matter; Proposed Rule; 

January 17, 2006, Vol71 p 2676. This document is available in Docket EPA-HQ-OAR-2007-0121. 

This information is available electronically at http://epa.gov/fedrgstr/EPA-AIR/2006/January/Day-17/a177.pdf 
28

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 AQCD62 as well as the 2005 PM Staff 

Paper.63

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).64 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.65,66 

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 

 

62 U.S. EPA (2004) Air Quality Criteria for Particulate Matter (Oct 2004), Volume I Document No. EPA600/P99/002aF and Volume II Document No. EPA600/P-99/002bF. This document is available in Docket EPA-HQOAR-2007-0121. 

63 U.S. EPA (2005) Review of the National Ambient Air Quality Standard for Particulate Matter: Policy Assessment 

of Scientific and Technical Information, OAQPS Staff Paper. EPA-452/R-05-005. This document is available in 

Docket EPA-HQ-OAR-2007-0121. 

64These areas are defined in section 162 of the Act as those national parks exceeding 6,000 acres, wilderness areas 

and memorial parks exceeding 5,000 acres, and all international parks which were in existence on August 7, 1977. 

65US EPA, Air Quality Designations and Classifications for the Fine Particles (PM2.5) National Ambient Air Quality 

Standards, December 17, 2004. (70 FR 943, Jan 5. 2005) This document is available in Docket EPA-HQ-OAR2007-0121. 

This document is also available on the web at: http://www.epa.gov/pmdesignations/ 

66U.S. EPA. Regional Haze Regulations, July 1, 1999. (64 FR 35714, July 1, 1999) This document is available in 

Docket EPA-HQ-OAR-2007-0121. 
29

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)67 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. 

 

67U.S. EPA Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). U.S. Environmental 

Protection Agency, Washington, D.C., EPA 600/R-05/004aF-cF,2006. This document is available in Docket EPAHQ-OAR-2007-0121. This document may be accessed electronically at: 

http://www.epa.gov/ttn/naaqs/standards/ozone/s_o3_cr_cd.html 
30

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.68 

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.69 

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.70 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 

 

68 Deposition of Air Pollutants to the Great Waters, Third Report to Congress, June 2000, EPA-453/R-00-005. This 

document is available in Docket EPA-HQ-OAR-2007-0121. It is also available at 

www.epa.gov/oar/oaqps/gr8water/3rdrpt/obtain.html. 

69 Bricker, Suzanne B., et al, National Estuarine Eutrophication Assessment, Effects of Nutrient Enrichment in the 

Nation's Estuaries, National Ocean Service, National Oceanic and Atmospheric Administration, September, 1999. 70 U.S EPA (2005) Review of the National Ambient Air Quality Standards for Particulate Matter: Policy Assessment 

of Scientific and Technical Information, OAQPS Staff Paper. This document is available in Docket EPA-HQ-OAR2007-0121. 
31

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.71 

 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 Act72 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.73 

 

71 See www.imo.org Go to Conventions, Status of Conventions – Summary. 72 46 USCS Appx § 688 

73 Final Regulatory Support Document: Control of Emissions from New Marine Compression-Ignition Engines at or 

Above 30 Liters per Cylinder. EPA420-R-03-004, January 2003, pg. 3-50. This document is available at 

http://www.epa.gov/otaq/regs/nonroad/marine/ci/r03004.pdf . We will update these statistics for more recent years; 

however, these results are not expected to change significantly given the U.S. share of the ownership of ocean-going 

vessels. MARAD data from 2005 indicates that while about 4.7 percent of all ocean-going vessels are owned by 

citizens of the United States (5th largest fleet) only about 1.9 percent of all ocean-going vessels are flagged here. 

Also according to that data, while Greece, Japan, China, and Germany account for the largest fleets in terms of 

ownership (15.3, 13.0, 11, and 8.9 percent, respectively), Panama and Liberia account for the largest fleets by flag 

(21.6 and 8.9 percent, respectively). 
32

 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.”74 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 1999.75 

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. That approach forms the basis of the program

outlined in this ANPRM.76 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 land-based 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 In this rulemaking, we are considering a comprehensive program that 

would set long-term standards that, if adopted, would based on the use of high-efficiency 

catalytic aftertreatment. These standards 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 . 

The program we are considering is based on the the U.S. Government proposal to IMO, 

which consists of near- and long-term NOx limits for new engines based on engine controls and 

 

74 Proposal to Initiate a Revision Process, Submitted by Finland, Germany, Italy, the Netherlands, Norway, Sweden 

and the United Kingdom. MEPC 53/4/4, 15 April 2005. Marine Environment Protection Committee, 53rd Session, 

Agenda Item 4. 

75 Revision of the NOx Technical Code, Tier 2 Emission Limits for Diesel Marine Engines At or Above 130 kW, 

submitted by the United States. MEPC 44/11/7, 24 December 1999. Marine Environment Protection Committee, 

44th Session, Agenda Item 11. 76 “Revision of the MARPOL Annex VI, the NOx Technical Code and Related Guidelines; Development of 

Standards for NOx, PM, and SOx,” submitted by the United States, BLG 11/5, Sub-Committee on Bulk Liquids and 

Gases, 11th Session, Agenda Item 5, February 9, 2007, Docket ID EPA-HQ-OAR-2007-0121-0034. This document 

is also available on our website: www.epa.gov/otaq/oceanvessels.com 
33

aftertreatment technology; NOx limits for Category 3 marinecertain existing engines based on 

engine controls; and PM/SOx limits that can be achieved through the use of exhaust gas cleaning 

or low sulfur fuel. To reduce the costs of the international program, the long-term new engine 

NOx limits and the PM/SOx limits would not apply while ships are operating on the open ocean; 

instead, they would in specified geographic areas to be defined under the treaty. 

1This section describes in greater detail how we are considering that emission control 

program for our federal action under the Clean Air Act.

A. 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 to new engines 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 costeffective 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 
34

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 slidevalve 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. 

2B. 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 
35

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.77 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. 

 

77 Freidrich, A., Heinen, F., Kamakate, F., Kojak, D., “Air Pollution and Greenhouse Gas Emissions from OceanGoing Ships: Impacts, Mitigation Options and Opportunities for Managing Growth,” The International Council on 

Clean Transportation, March 2007, Docket ID EPA-HQ-OAR-2007-0121-0033.
36

VI. Emission Control Technology 

A. Engine-Based NOx Control 

1. Traditional In-Cylinder Controls 

 Engine manufacturers are meeting the Tier 1 NOx standards78 for Category 3 marine 

engines today through traditional in-cylinder fuel and air management approaches. These incylinder 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.79 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.80 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 whetherthe costs and other business impacts of retrofitting Category 3 

 

78 This NOx standard is the same as the internationally negotiated NOx standards established by the International 

Maritime Organization (IMO) in Annex VI to the International Convention on the Prevention of Pollution from 

Ships, 1973, as Modified by the Protocol of 1978 Relating Thereto (MARPOL). 

79 “MARPOL Annex VI Revision - Proposals Related to Future Emission Limits and Issues for Clarification,” 

Submitted by EUROMOT to the IMO Subcommittee on Bulk Liquids and Gases, BLG 10/14/12, January 26, 2006, 

Docket ID EPA-HQ-OAR-2007-0121-0014. 

80 Henningsen, S., “2007 Panel Discussion on Emission Reduction Solutions for Marine Vessels; Engine 

Technologies” presentation by MAN B&W at the Clean Ships: Advanced Technology for Clean Air Conference, 

February 8, 2007, Docket ID EPA-HQ-OAR-2007-0121-0031. 
37

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.81,82,83 However, some 

increase in PM may result due to the lower combustion temperatures, depending on the water 

introduction strategy.84 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 

 

81 Heim, K., “Future Emission Legislation and Reduction Possibilities,” presentation by Wartsila at the CIMAC 

Circle 2006, September 28, 2006, Docket ID EPA-HQ-OAR-2007-0121-0017. 

82 Aabo, K., Kjemtrup, N., “Latest on Emission Control Water Emulsion and Exhaust Gas Re-Circulation,” MAN 

B&W, CIMAC paper number 126, presented at International Council on Combustion Engines Congress, 2004, 

Docket ID EPA-HQ-OAR-2007-0121-0005. 

83 Hagström, U., “Humid Air Motor (HAM) and Selective Catalytic Reduction (SCR) Viking Line,” presented by 

Viking Line at Swedish Maritime Administration Conference on Emission Abatement Technology on Ships, May 

24-26, 2005, Docket ID EPA-HQ-OAR-2007-0121-0027. 

84 Koehler, H., “Field Experience with Considerably Reduced NOx and Smoke Emissions,” MAN B&W, 2004, 

Docket ID EPA-HQ-OAR-2007-0121-0019. 
38

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 costs associated with 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.85 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.86 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.87 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, costeffective 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.88,89,90,91 These systems are used 

 

85 Aabo, K., Kjemtrup, N., “Latest on Emission Control Water Emulsion and Exhaust Gas Re-Circulation,” MAN 

B&W, CIMAC paper number 126, presented at International Council on Combustion Engines Congress, 2004, 

Docket ID EPA-HQ-OAR-2007-0121-0005. 

86 Henningsen, S., “2007 Panel Discussion on Emission Reduction Solutions for Marine Vessels; Engine 

Technologies” presentation by MAN B&W at the Clean Ships: Advanced Technology for Clean Air Conference, 

February 8, 2007, Docket ID EPA-HQ-OAR-2007-0121-0031. 

87 Weisser, G., “Emission Reduction Solutions for Marine Vessels – Wartsila Perspective” presentation by Wartsila 

at the Clean Ships: Advanced Technology for Clean Air Conference, February 8, 2007, Docket ID EPA-HQ-OAR2007-0121-0032. 

88 “DEC SCR Convertor System,” Muenters, May 1, 2006, Docket ID EPA-HQ-OAR-2007-0121-0013. 89 Hagström, U., “Humid Air Motor (HAM) and Selective Catalytic Reduction (SCR),” Viking Line, presented at 

Air Pollution from Ships, May 24-26, 2005, Docket ID EPA-HQ-OAR-2007-0121-0027. 

90 “Reference List - SINOx® Systems,” Argillon, December 2006, Docket ID EPA-HQ-OAR-2007-0121-0035. 
39

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 foreign navy vessels for 

both propulsion and auxiliary engines. These SCR units are being used successfully on slow and 

medium speed Category 3 propulsion engines and on Category 2 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.92,93, 94 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. WeTo the extent that SCR has been used in additional 

marine applications, we request further information on the use of SCR on marine vessels and the 

potential emissionsemission reductions that may behave been 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.95,96,97 Below this 

temperature, the vanadium-oxide catalyst in the SCR unit would not be hot enough to efficiently 

 91 “Reference List January 2005 Marine Applications,” Hug Engineering, January 2005, Docket ID EPA-HQ-OAR2007-0121-0036. 

92 Heim, K., “Future Emission Legislation and Reduction Possibilities,” Wärtsilä, presented at CIMAC Circle 2006, 

September 28, 2006, Docket ID EPA-HQ-OAR-2007-0121-0017. 

93 Argillon, “Exhaust Gas Aftertreatment Systems; SCR – The Most Effective Technology for NOx Reduction,” 

presented at Motor Ship Marine Propulsion Conference, May 7-8, 2003, Docket ID EPA-HQ-OAR-2007-0121-

0010. 

94 Holmström, Per, “Selective Catalytic Reduction,” presentation by Munters at Clean Ships: Advanced Technology 

for Clean Air, February 7-9, 2007, Docket ID EPA-HQ-OAR-2007-0121-0013. 

95 Rasmussen, K., Ellegasrd, L., Hanafusa, M., Shimada, K., “Large Scale SCR Application on Diesel Power Plant,” 

CIMAC paper number 179, presented at International Council on Combustion Engines Congress, 2004, Docket ID 

EPA-HQ-OAR-2007-0121-0007. 

96 “Munters SCR ConverterTM System,” downloaded from www.munters.com, November 21, 2006, Docket ID EPAHQ-OAR-2007-0121-0023. 

97 Argillon, “Exhaust Gas Aftertreatment Systems; SCR – The Most Effective Technology for NOx Reduction,” 

presented at Motor Ship Marine Propulsion Conference, May 7-8, 2003, Docket ID EPA-HQ-OAR-2007-0121-

0010. 
40

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.98 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.99 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 

 

98 MAN B&W, “Emission Control Two-Stroke Low-Speed Diesel Engines,” December 1996, Docket ID EPA-HQOAR-2007-0121-0020. 

99 “NOx Emissions from M/V Hamlet,” Data provided to W. Charmley, U.S. EPA. by P. Holmström, DEC Marine, 

February 5, 2007, Docket ID EPA-HQ-OAR-2007-0121-0015. 
41

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 commentIf commenters have additional information on 

the feasibility of using SCR for effective NOx emission control at low power operation, we 

request that this information be submitted for our consideration as we continue developing 

proposed standards for Category 3 marine engines. 

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.100 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.101 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, 

 

100 U.S. Department of the Interior, "Mineral Commodity Summaries 2006," page 118, U.S. Geological Survey, 

January 13, 2006, Docket ID EPA-HQ-OAR-2007-0121-0022. 

101 Tokunaga, Y., Kiyotaki, G., “Development of NOx Reduction System for Marine Diesel Engines by SCR using 

Liquid Hydrocarbon Distilled from Fuel Oil as Reductant,” CIMAC paper number 63, presented at International 

Council on Combustion Engines Congress, 2004, Docket ID EPA-HQ-OAR-2007-0121-0002. 
42

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.102,103,104 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.105,106 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.107 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.108 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 

 

102 Paro, D., “Effective, Evolving, and Envisaged Emission Control Technologies for Marine Propulsion Engines,” 

presentation from Wartsila to EPA on September 6, 2001, Docket ID EPA-HQ-OAR-2007-0121-0028. 

103 Koehler, H., “Field Experience with Considerably Reduced NOx and Smoke Emissions,” MAN B&W, 2004, 

Docket ID EPA-HQ-OAR-2007-0121-0019. 

104 Heim, K., “Future Emission Legislation and Reduction Possibilities,” presentation by Wartsila at the CIMAC 

Circle 2006, September 28, 2006, Docket ID EPA-HQ-OAR-2007-0121-0017. 

105 “Emission Factors for Compression Ignition Nonroad Engines Operated on No. 2 Highway and Nonroad Diesel 

Fuel,” U.S. EPA, EPA420-R-98-001, March 1998, Docket ID EPA-HQ-OAR-2007-0121-0025. 

106 Lyyranen, J., Jokiniemi, J., Kauppinen, E., Joutsensaari, J., “Aerosol Characterization in Medium-Speed Diesel 

Engines Operating with Heavy Fuel Oils,” Aerosol Science Vol. 30, No. 6, pp. 771-784, 1999, Docket ID EPA-HQOAR-2007-0121-0009. 

107 Maeda, K., Takasaki, K., Masuda, K., Tsuda, M., Yasunari, M., “Measurement of PM Emission from Marine 

Diesel Engines,” CIMAC paper number 107 presented at International Council on Combustion Engines Congress, 

2004, Docket ID EPA-HQ-OAR-2007-0121-0004. 

108 Kasper, A., Aufdenblatten, S., Forss, A., Mohr, M., Burtscher, H., “Particulate Emissions from a Low-Speed 

Marine Diesel Engine,” Aerosol Science and Technology, 41:24-32, 2007. 
43

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.109 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. 

 

109 Takasaki, K., Tayama, K., Tanaka, H., Baba, S., Tajima, H., Strom, A., “NOx Emission from Bunker Fuel 

Combustion,” CIMAC paper number 87, presented at International Council on Combustion Engines Congress, 2004, 

Docket ID EPA-HQ-OAR-2007-0121-0003. 
44

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 adsorbabsorb 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.110 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.111 We request comment on the effectiveness offurther experience with 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.112 Although exhaust gas scrubbers are only used in a few 

demonstration vessels today, this technology is widely used in land-based applications. We 

 

110 Skawinski, C., “Seawater Scrubbing Advantage,” Presentation by Marine Exhaust Solutions at the Conference 

for Emission Abatement Technology on Ships held by the Swedish Maritime Administration, May 24-26, 2005, 

Docket ID EPA-HQ-OAR-2007-0121-0021. 

111 “Krystallon Seawater Scrubber,” downloaded from www.krystallon.com on February 14, 2007, Docket ID EPAHQ-OAR-2007-0121-0018. 

112 “Cloud Chamber Scrubber Performance Results for Diesel Exhaust,” Tri-Mer Corporation, April 14, 2005, 

Docket ID EPA-HQ-OAR-2007-0121-0026. 
45

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.113 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.114 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.115 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. 

 

113 Skawinski, C., “Seawater Scrubbing Advantage,” Presentation by Marine Exhaust Solutions at the Conference 

for Emission Abatement Technology on Ships held by the Swedish Maritime Administration, May 24-26, 2005, 

Docket ID EPA-HQ-OAR-2007-0121-0021. 

114 An, S., Nishida, O., “Marine Air Pollution Control System Development Applying Seawater and Electrolyte,” 

SAE Paper 2002-01-2295, July 2002, Docket ID EPA-HQ-OAR-2007-0121-0024. 

115 Houng-Soo, K., “Development of Diesel Engine Emission Control System on NOx and SOx by Seawater 

Electrolysis,” CIMAC paper number 25 presented at International Council on Combustion Engines Congress, 2004, 

Docket ID EPA-HQ-OAR-2007-0121-0001. 
46

VII. Certification and Compliance 

We In general, we expect generally to continue withretain the certification and 

compliance program provisions finalized with the Tier 1 standards. These include testing, 

durability, labeling, maintenance, prohibited acts, etc. However, we believe additional testing 

and compliance provisions will be necessary for new standards requiring more advanced 

technology and more challenging calibrations. These changes, as well as other modifications to 

our certification and compliance provisions, are discussed below.

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. The U.S. government 

recently submitted proposed procedures for PM measurement to IMO.116 We request comment 

on the feasibility of these procedures for accurately measuring PM emissions from Category 3 

marine engines operating on residual fuel. 

2. Off-Cycle Emissions

Low Power Operation

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-toexceed” 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 defeatdevice 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 effectivelyoperated 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 

 

116 Measurement Method for Particulate Matter Emitted from Marine Engines, submitted by the United States. 

BLG-WGAP 2, October 2007. Intersessional Meeting of the BLG Working Group on Air Pollution, 2nd Session.
47

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 would include 

targets for engine speeds other than the test points speeds. Equivalent control could involve 

either using of the same injection timing map for the tested and non-tested engine speeds, or 

following a linear interpolation between test points for NOx emissions at non-test speeds. For 

example, manufacturers might provide operators with a series of NOx maps that relate allowable 

NOx emission levels to various operating parameters. Operators would then be required to 

adjust their engine until it was below the NOx targets. We also request comment on other 

methods of addressing this adjustability.

In addition, we remain concerned thatlow power. Category 3 engines operate at 

relatively low power levels when they are operating in port areas. Ship pilots generally operate 

engines at reduced power for several miles to approach a port, with even lower power levels very 

close to shore. Because of the relatively low weighting of the low-power test modes in the ISO 

E3 test cycleThe ISO E3 and E2 test cycles are used for emission testing of propulsion marine 

engines. These test cycles are heavily weighted towards high power. Therefore, it is very 

possible that manufacturers could meet the cycle-weighted average emission standards without 

significantly reducing emissions at the low-power modes that are . Because low power operation 

is more prevalent for thesepropulsion engines aswhen they operate close to commercial ports. 

This, of course, has the potential to reduce, it is important that the emission control strategy be 

effective at low power operation to maximize on-shore emission benefits. This issue would 

generally not apply to vessels that rely on multiple engines providing electric-drive propulsion, 

sincebecause these engines can be shut down as needed to maintain the desired engine loading. 

We are considering a variety of options to address this concern. We could re-weight the modes 

of the duty cycle to emphasize low-power operation. This has several potential drawbacks. For 

example, we have no information to provide a basis for applying different weighting factors. 

Also, changing the duty cycle would depart from the historic norm for marine engine testing. 

This would make it more difficult to make use of past emission data, which is all based on the 

established modal weighting.

An alternative approach would be to cap emission rates at the two and therefore may not 

operate at low-power modes. We could set the cap at the same level as the emission standard, or 

allow for a small variation above the emission standard. For mechanically controlled engines, 

such an approach could dictate the overall design of the engine. On the other hand, there is 

increasing use of electronic controls, which would enable the manufacturer to target emission 

controls specifically for low-power operation with little or no effect on controlling emissions at 

higher power settings. We request comment on the need for addressing emissions at low power 

operation and whether and how the test procedure should be changed to accommodate this 

operation. See section VI.B for additional discussion of low power NOx emissions for engines 

equipped with exhaust aftertreatment. 

3. Test Fuel 

 Appropriate test procedures need to represent in-use operating conditions as much as 

possible, including specification of test fuels consistent with the fuels that compliant engines will 

use over their lifetimes. For the Tier 1 standards, we allow engine testing using distillate fuel, 
48

even though vessels with Category 3 marine engines primarily use the significantly less 

expensive residual fuel. This provision is consistent with the specifications of the NOx 

Technical Code. Also, most manufacturers have test facilities designed to test engines using 

distillate fuel. Distillate fuel is easier to test with because it does not need to be heated to remain 

a liquid and manufacturers have indicated that it is difficult to obtain local permits for testing 

with residual fuel. However, we believe it is important to specify a test fuel that is consistent 

with the in-use fuel with which engines will operate in service. This is especially true for PM 

measurements. We request comment on the appropriate test fuel for emission testing and if this 

fuel should be representative on the fuel on which a specific engine is designed to operate. 

 For any NOx measurements from engines operating on residual fuel we recognize that 

there may be emission-related effects due to fuel quality, specifically fuel-bound nitrogen. If the 

standards were based on distillate fuel, we would consider a NOx correction factor to account for 

the impact of fuel quality when testing on residual fuel. This correction would be useful because 

of the high levels of nitrogen contained in residual fuel. Such a correction factor would likely 

involve measuring fuel-bound nitrogen and correcting measured values to what would occur with 

a nitrogen concentration of 0.4 weight percent. This corrected value would be used to determine 

whether the engine meets emission standards or not. We request comment on the need for 

corrections and, if so, how the appropriate corrections would be developed. 

B. On-off Technologies 

One of the features of the emission control technologies that could be used to achieve 

significant NOx and PM reductions from C3 engines is that they are not integral to the engine 

and the engine can be operated without them. Aftertreatment systems such as SCR or emission 

scrubbing, or the use of lower sulfur fuel, require a positive action on the part of the ship owner 

to make sure the emission control system is in operation or that the appropriate fuel is used. 

These types of technologies are often called “on-off” technologies. 

The increased operating costs of such controls associated with urea or other catalysts or 

with distillate usage suggest that it may be reasonable to allow these systems to be turned off 

while a ship is operated on the open ocean, far away from sensitive areas that are affected by 

ship emissions. In other words, EPA could elect to set geographically-based NOx and PM 

standards, with one limit that would apply when ships are operated within a specified distance 

from U.S. coasts, and another that would apply when ships are operated outside those limits. 

If EPA were to adopt such an approach, we would need to determine the areas in which 

ships would have to comply with the standards. We are currently exploring this issue through 

the air quality modeling for our proposed standards. There are other issues associated with such 

an approach, including: the technological feasibility of by-pass systems and their impacts on the 

emission control systems when they are not in use; the level of the standard that would apply 

when the system is turned off; and how compliance would be demonstrated. There may also be 

additional certification requirements for ships equipped with such systems. 

We request comment on all aspects of this alternative, especially with regard to how such 

systems could be designed to ensure no loss of emission reductions. 
49

C. Parameter Adjustment 

 Given the broad range of ignition properties for in-use residual fuels, we expect that our 

in-use adjustment allowance for Category 3 engines would result in a broad range of adjustment. 

We are therefore considering a requirement for operators to perform a simple field measurement 

test to confirm emissions after parameter adjustments or maintenance operations, using onboard 

emission measurement systems with electronic-logging equipment. We expect this issue will be 

equally important for more advanced engines that rely on water injection or aftertreatment for 

emission reductions. Onboard verification systems could add significant assurance that engines 

have properly operating emission controls. 

 We envision a simpler measurement system than the type specified in Chapter 6 of the 

NOx Technical Code. As we described in the 2003 final rule, we believe that onboard emission 

equipment that is relatively inexpensive and easy to use could verify that an engine is properly 

adjusted and is operating within the engine manufacturer’s specifications. Note that Annex VI 

includes specifications allowing operators to choose to verify emissions through onboard testing, 

which suggests that Annex VI also envisioned that onboard measurement systems could be of 

value to operators. We request comment on requiring onboard verification systems on ships with 

Category 3 marine engines and on a description of such a system. 

D. Certification of Existing Engines 

 While we normally require certification only for newly built engines, we are considering 

emission standards that would apply to remanufactured engines in the existing fleet. This leads 

to questions about how one would certify the modified engines. We are considering adoption of 

one or more of the following simplified certification procedures for in-use engines: 

• Basing certification for any engine on a pre-existing certificate if the engine is modified 

to be the same as a later engine that is already certified to the Tier 1 NOx standard. 

• Testing in-use engines using portable emission measurement equipment, with appropriate 

consideration for any necessary deviations in the engine test cycle. 

• Broadening the engine family concept for in-use engines to reduce the amount of testing 

necessary to certify a range of engines. This would require the same or similar hardware 

and calibration requirements to ensure that a single test engine can properly represent all 

the engines in the broader engine family. 

• Developing alternatives to the NOx Technical File117 to simplify the certification burdens 

for existing vessels while ensuring that the modified engines and emission components 

may be appropriately surveyed and inspected. 

 We request comment on the best approach for ensuring compliance from existing 

engines. We also request comment on the simplified certification procedures listed above. 

 

117 The NOx Technical File, required pursuant to Section 2.4 of the Technical Code on Control of Emissions of 

Nitrogen Oxides from Marine Diesel Engines, is a record containing details of engine parameters, including 

components and settings, which may influence the NOx emissions of the engine. The NOx Technical File also 

contains a description of onboard NOx verification procedures required for engine surveys. The NOx Technical File 

is developed by the engine manufacturer and must be approved by the authority issuing the engine certificate. 
50

E. Other Compliance Issues 

In addition to the compliance issues described above we are also seeking comment on to 

addition issues, described in this section: (1) the application of the standards engines on foreignflagged vessels that enter U.S. ports; and (2) whether the standards should apply to gas turbines 

or natural gas engines.

We intend to apply the same exemptions to any new tier of Category 3 marine diesel 

engine standards as currently apply under our Tier 1 program. These exemptions, including the 

national security exemption, are set out in 40 CFR 94 Subpart J. We will also consider whether 

to include engines on foreign vessels in the program and whether we should also adopt standards 

for non-diesel engines such as gas turbine engines.

1. Engines on Foreign-Flagged Vessels 

 Our current federal marine diesel engine standards do not apply to Category 1, 2, and 3 

marine diesel engines installed on foreign-flagged vessels. In our 2003 Final Rule we 

acknowledged the contribution of engines on foreign-flagged vessels to U.S. air pollution but did 

not apply federal standards to foreign vessels (see 68 FR 9759, February 28, 2003). This section 

summarizes the discussion from that 2003 Final Rule. We will continue to evaluate this issue as 

we develop the proposal for this rule. 

Section 213 of the Clean Air Act (42 U.S.C. 7547), authorizes regulation of “new 

nonroad engine” and “new nonroad vehicle.” However, Title II of the Clean Air Act does not 

define either “new nonroad engine” or “new nonroad vehicle.” Section 216 defines a “new 

motor vehicle engine” to include an engine that has been “imported.” EPA modeled the current 

regulatory definitions of “new nonroad engine” and “new marine engine” at 40 CFR 89.2 and 40 

CFR 94.2, respectively, after the statutory definitions of “new motor vehicle engine” and “new 

motor vehicle.” This was a reasonable exercise of the discretion provided to EPA by the Clean 

Air Act to interpret “new nonroad engine” or “new nonroad vehicle.” See Engine Manufacturers 

Assoc. v. EPA, 88 F.3d 1075, 1087 (D.C. Cir. 1996). 

 The 1999 marine diesel engine rule did not apply to marine engines on foreign vessels. 

40 CFR 94.1(b)(3). At that time, we concluded that engines installed on vessels flagged or 

registered in another country, that come into the United States temporarily, will not be subject to 

the emission standards. At that time, we believed that they were not considered imported under 

the U.S. customs law. As a result, we did not apply the standards adopted in that rule to those 

vessels (64 FR 73300, Dec. 29, 1999). 

 The May 29, 2002 proposed rule for Category 3 marine diesel engines solicited comment 

on whether to exercise our discretion and modify the definition of a “new marine engine” to find 

that engine emission standards apply to foreign vessels that enter U.S. ports. However, in the 

February 28, 2003 final rule we determined that we did not need to determine whether we have 

the discretion to interpret “new” nonroad engine or vessel in such a manner. 

 Foreign vessels were expected to comply with the MARPOL standards whether or not 

they were also subject to the equivalent Clean Air Act standards being adopted in that final rule. 

Consequently, we concluded that no significant emission reductions would be achieved by 

treating foreign vessels as “new” for purposes of the Tier 1 standards and there would be no 

significant loss in emission reductions by not including them. Therefore, we did not include 
51

foreign engines and vessels in our 2003 rulemaking and we did not revise the definition of “new 

marine engine” at that time. 

In this rule we will evaluate under what circumstances we may and should define new 

nonroad engine and vessel to include foreign engines and vessels. As part of that evaluation, we 

will also assess the progress made by the international community toward the adoption of new 

more stringent international consensus standards that reflect advanced emission-control 

technologies. 

2. Non-Diesel Engines 

Gas turbine engines are internal combustion engines that can operate using diesel fuel, 

residual fuel, or natural gas, but do not operate on a compression-ignition or other reciprocating 

engine cycle. Power is extracted from the combustion gas using a rotating turbine rather than 

reciprocating pistons. While gas turbine engines are used primarily in naval ships, a small 

number are being used in commercial ships. In addition, we have received indication that their 

use is growing in some applications such as cruise ships and liquid natural gas carriers. As we 

develop the proposal for this rule we will consider whether it is appropriate to regulate emissions 

from gas turbine engines and, if so, whether special provisions would be needed for testing and 

certifying turbine engines. For example, since turbine engines have no cylinders, we may need 

to address how to apply any regulatory provisions that depend on a specified value for percylinder displacement. We would welcome any emissions information that is available for 

turbine engines. 

 Marine engines have been developed that can operate either on natural gas or a dualfuel.118 In a dual-fuel application, a mixture of marine diesel oil and natural gas is used for the 

main engine that provides a means to comply with the low-sulfur fuel requirement. Natural gas 

engines are especially attractive to vessels that carry a cargo of liquefied petroleum gas due to 

the readily available fuel supply. Natural gas powered engines are similar to Category 3 marine 

engines operating on traditional diesel fuels, and we would consider including these engines in 

this rulemaking. 

We request comment on other fuels and engine types that we should consider in the scope 

of this rulemaking. We also request comments on test procedure or other compliance issues that 

would need to be considered for these other fuels and engines.

VIII. Potential Regulatory Impacts 

A. Emission Inventory 

The inventory contribution of Category 3 engines consists of two parts: emissions that 

occur in port areas and emissions that occur at various distances from the coast while vessels are 

underway. Although the issue of emissions transport is common to all of our air pollution 

control programs , these underway emissions suggest that Category 3 emissions are different 

from emissions from other mobile sources. and result in at least two implications for the analysis 

 

118 Nylund, I., “Status and Potentials of the Gas Engines,” Wartsila, CIMAC paper number 163, presented at 

International Council on Combustion Engines Congress, 2004, Docket ID EPA-HQ-OAR-2007-0121-0006. 
52

we will perform for our proposal. First, the definition of the inventory modeling domain 

becomes important. In the inventory analysis described below we use a distance of 200 nautical 

miles from shore (see Figure VIII-1 below and associated text). This distance is reasonable 

based on both particle dynamics119 and results from air quality modeling for other programs 

which has shown that PM and NOx emissions can be transported significant distances.120 

Second, it will be important to analyze the air quality impacts of these emissions at various 

distances to determine how offshore emissions affect air quality both along the coasts and inland. 

We will use the CMAQ model, modified to accommodate at-sea emissions, to track the impacts 

of underway emissions and estimate the air quality benefits of the proposal.

This section contains our updated inventory estimates for Category 3 marine engines in 

the 200 nautical mile domain and a brief discussion of our inventory estimation methodology.

1. Estimated Inventory Contribution 

 Category 3 marine engines contribute to the formation of ground level ozone and 

concentrations of fine particles in the ambient atmosphere. Based on our current emission 

inventory analysis of U.S. and foreign-flag vessels, we estimate that these engines contributed 

nearly 6 percent of mobile source NOx, over 10 percent of mobile source PM2.5, and about 40 

percent of mobile source SO2 in 2001. We estimate that their contribution will increase to about 

34 percent of mobile source NOx, 45 percent of mobile source PM2.5, and 94 percent of mobile 

source SO2 by 2030 without further controls on these engines. Our current estimates for NOx, 

PM2.5, SO2 inventories are set out in Tables VIII-1 through VIII-3. The inventory projections for 

2020 and 2030 include the impact of existing emission mobile source and stationary source 

control programs previously adopted by EPA (excluding the recently adopted MSAT regulations, 

signed on February 9, 2007 which will have an impact on future highway non-diesel PM2.5

levels). 

 

 

119 U.S. EPA. Air Quality Criteria for Particulate Matter (October 2004). U.S. Environmental Protection Agency, 

Washington, DC, EPA 600/P-99/002aF-bF, 2004.

120 U.S. EPA Technical Support Document for the Final Clean Air Interstate Rule Air Quality Modeling (March 

2005) U.S. Environmental Protection Agency, Washington, DC,
53

Table VIII-1: 50-State Annual NOx Baseline Emission Levels 

for Mobile and Other Source Categories 

2001a Category 2020 2030 

short tons % of 

mobile 

source 

% of 

total 

short tons % of 

mobile 

source 

% of 

total 

short tons % of 

mobile 

source 

% of 

total 

Commercial Marine (C3)b 744,444745

,224

5.7% 3.3% 1,399,8341,

368,420

23.2%2

2.8%

11.5%3

%

2,076,2602,

023,974

34.3%

33.7%

17.1%16

.7%

Locomotive 1,118,786 8.6% 5.0% 860,474 14.2%3

%

7.1% 854,226 14.1% 7.0% 

Recreational Marine Diesel 40,437 0.3% 0.2% 45,477 0.8% 0.4% 48,102 0.8% 0.4% 

Commercial Marine (C1 & C2) 834,025 6.4% 3.7% 676,154 11.2%3

%

5.6% 680,025 11.2%

3%

5.6% 

Land-Based Nonroad Diesel 1,548,236 11.9% 6.9% 678,377 11.2%3

%

5.6% 434,466 7.2% 3.6% 

Small Nonroad SI 114,319 0.9% 0.5% 114,881 1.9% 0.9% 133,197 2.2% 1.1% 

Recreational Marine SI 44,732 0.3% 0.2% 86,908 1.4% 0.7% 96,143 1.6% 0.8% 

SI Recreational Vehicles 5,488 0.0% 0.0% 17,496 0.3% 0.1% 20,136 0.3% 0.2% 

Large Nonroad SI (>25hp) 321,098 2.5% 1.4% 46,319 0.8% 0.4% 46,253 0.8% 0.4% 

Aircraft 83,764 0.6% 0.4% 105,133 1.7% 0.9% 118,740 2.0% 1.0% 

Total Off Highway 4,855,3294,

856,109

37.5% 21.8% 4,031,0543,

999,640

66.7%6

%

33.2%0

%

4,507,5474,

455,262

74.4%

2%

37.0%36

.8%

Highway Diesel 3,750,886 28.9% 16.8% 646,961 10.7%8

%

5.3% 260,915 4.3% 2.1%2%

Highway non-diesel 4,354,430 33.6% 19.5% 1,361,276 22.5%7

%

11.2% 1,289,780 21.3%

5%

10.6% 

Total Highway 8,105,316 62.5% 36.3% 2,008,237 33.3%4

%

16.5%6

%

1,550,695 25.6%

8%

12.7%8

%

Total Mobile Sources 12,960,645

12,961,425

100% 58.1% 6,039,2916,

007,877

100% 49.7%6

%

6,058,2426,

005,957

100% 49.8%6

%

Stationary Point & Area Sources 9,355,659 - 41.9% 6,111,866 - 50.3%4

%

6,111,866 - 50.2%4

%

Total Man-Made Sources 22,316,304

22,317,084

- 100% 12,151,157

12,119,743

- 100% 12,170,108

12,117,823

- 100% 

a

 The locomotive, commercial marine (C1 & C2), and recreational marine diesel estimates are for calendar year 2002. b

 This category includes emissions from Category 3 (C3) propulsion engines and C2/3 auxiliary engines used on ocean-going 

vessels. 
54

Table VIII-2: 50-State Annual PM2.5 Baseline Emission Levels 

for Mobile and Other Source Categories 

2001a Category 2020 2030 

short tons % of 

mobile 

source 

% of 

total 

short tons % of 

mobile 

source 

% of 

total 

short tons % of 

mobile 

source 

% of 

total 

Commercial Marine (C3)b 54,599667 10.9% 2.2% 111,188110

,993

33.6% 5.2% 166,751161 45.4% 7.6% 

Locomotive 29,660 5.9% 1.2% 26,301 8.0% 1.2% 25,109 6.8% 1.1% 

Recreational Marine Diesel 1,096 0.2% 0.0% 1,006 0.3% 0.0% 1,140 0.3% 0.1% 

Commercial Marine (C1 & C2) 28,730 5.7% 1.2% 22,236 6.7% 1.0% 23,760 6.5% 1.1% 

Land-Based Nonroad Diesel 164,180 32.8% 6.7% 46,075 13.9% 2.1% 17,934 4.9% 0.8% 

Small Nonroad SI 25,466 5.1% 1.0% 32,904 10.0% 1.5% 37,878 10.3% 1.7% 

Recreational Marine SI 16,837 3.4% 0.7% 6,367 1.9% 0.3% 6,163 1.7% 0.3% 

SI Recreational Vehicles 12,301 2.5% 0.5% 11,773 3.6% 0.5% 9,953 2.7% 0.5% 

Large Nonroad SI (>25hp) 1,610 0.3% 0.1% 2,421 0.7% 0.1% 2,844 0.8% 0.1% 

Aircraft 5,664 1.1% 0.2% 7,044 2.1% 0.3% 8,569 2.3% 0.4% 

Total Off Highway 340,143211 68.0% 13.8% 267,315120 80.9% 12.4% 300,101299

,511

81.8% 13.7% 

Highway Diesel 109,952 22.0% 4.5% 15,800 4.8% 0.7% 10,072 2.7% 0.5% 

Highway non-diesel 50,277 10.0% 2.0% 47,354 14.3% 2.2% 56,734 15.5% 2.6% 

Total Highway 160,229 32.0% 6.5% 63,154 19.1% 2.9% 66,806 18.2% 3.1% 

Total Mobile Sources 500,372440 100% 20.3% 330,469274 100% 15.4% 366,907317 100% 16.8% 

Stationary Point & Area Sources 1,963,264 - 79.7% 1,817,722 - 84.6% 1,817,722 - 83.2% 

Total Man-Made Sources 2,463,6367

04

- 100% 2,148,1912,

147,996

- 100% 2,184,6290

39

- 100% 

a

 The locomotive, commercial marine (C1 & C2), and recreational marine diesel estimates are for calendar year 2002. b

 This category includes emissions from Category 3 (C3) propulsion engines and C2/3 auxiliary engines used on ocean-going 

vessels. 
55

Table VIII-3: 50-State Annual SO2 Baseline Emission Levels 

for Mobile and Other Source Categories 

2001a Category 2020 2030 

short tons % of 

mobile 

source 

% of 

total 

short tons % of 

mobile 

source 

% of 

total 

short tons % of 

mobile 

source 

% of 

total 

Commercial Marine (C3)b 432,496457

,948

41.0%

42.4%

2.7%8

%

883,520932

,820

92.8%

93.2%

9.6%10.

1%

1,326,9201,

398,598

94.3%

5%

13.8%

14.4%

Locomotive 76,727 7.3%1

%

0.5% 400 0.0% 0.0% 468 0.0% 0.0% 

Recreational Marine Diesel 5,145 0.5% 0.0% 162 0.0% 0.0% 192 0.0% 0.0% 

Commercial Marine (C1 & C2) 80,353 7.6%4

%

0.5% 3,104 0.3% 0.0% 3,586 0.3% 0.0% 

Land-Based Nonroad Diesel 167,615 15.9%

5%

1.0% 999 0.1% 0.0% 1,078 0.1% 0.0% 

Small Nonroad SI 6,710 0.6% 0.0% 8,797 0.9% 0.1% 10,196 0.7% 0.1% 

Recreational Marine SI 2,739 0.3% 0.0% 2,963 0.3% 0.0% 3,142 0.2% 0.0% 

SI Recreational Vehicles 1,241 0.1% 0.0% 2,643 0.3% 0.0% 2,784 0.2% 0.0% 

Large Nonroad SI (>25hp) 925 0.1% 0.0% 905 0.1% 0.0% 1,020 0.1% 0.0% 

Aircraft 7,890 0.7% 0.0% 9,907 1.0% 0.1% 11,137 0.8% 0.1% 

Total Off Highway 781,840807

,293

74.1%

7%

4.9%5

.0%

913,401962

,700

95.9%

96.1%

10.0%4

%

1,360,5231,

432,202

96.6%

8%

14.1%

8%

Highway Diesel 103,632 9.8%6

%

0.6% 3,443 0.4%3

%

0.0% 4,453 0.3% 0.0% 

Highway non-diesel 169,125 16.0%

15.7%

1.0% 35,195 3.7%5

%

0.4% 42,709 3.0%2

.9%

0.4% 

Total Highway 272,757 25.9%

3%

1.7% 38,638 4.1%3

.9%

0.4% 47,162 3.4%2

%

0.5% 

Total Mobile Sources 1,054,5971,

080,050

100% 6.5%7

%

952,0391,0

01,338

100% 10.4%9

%

1,407,6851,

479,364

100% 14.6%

15.3%

Stationary Point & Area Sources 15,057,420 - 93.5%

3%

8,215,016 - 89.6%1

%

8,215,016 - 85.4%

84.7%

Total Man-Made Sources 16,112,017

16,137,470

- 100% 9,167,0559,

216,354

- 100% 9,622,7019,

694,380

- 100% 

a

 The locomotive, commercial marine (C1 & C2), and recreational marine diesel estimates are for calendar year 2002. b

 This category includes emissions from Category 3 (C3) propulsion engines and C2/3 auxiliary engines used on ocean-going 

vessels. 

 The United States is actively engaged in international trade and is frequently visited by 

ocean-going marine vessels. As shown in Figure II-1, the ports which accommodate these 

vessels are located along the entire coastline of the United States. Commercial marine vessels, 

powered by Category 3 marine engines, contribute significantly to the emissions inventory for 

many U.S. ports. This is illustrated in Table VIII-4 which presents the mobile source inventory 

contributions of these vessels for several ports. The ports in this table were selected to present a 

sampling over a wide geographic area along the U.S. coasts. In 2005, these twenty ports 

received approximately 60 percent of the vessel calls to the U.S. from ships of 10,000 DWT or 

greater.121

 

121 “Vessel Calls at U.S. & World Ports; 2005,” U.S. Maritime Administration, Office of Statistical and Economic 

Analysis, April 2006, Docket ID EPA-HQ-OAR-2007-0121-0040. 
56

Table VIII-4: Contribution of Commercial Marine Vesselsa

to Mobile Source Inventories for Selected Ports in 2002 

Port Area NOx PM2.5 SOx 

Valdez, AK 

Seattle, WA 

Tacoma, WA 

San Francisco, CA 

Oakland, CA 

LA/Long Beach, CA 

Beaumont, TX 

Galveston, TX 

Houston, TX 

New Orleans, LA 

South Louisiana, LA 

Miami, FL 

Port Everglades, FL 

Jacksonville, FL 

Savannah, GA 

Charleston, SC 

Wilmington, NC 

Baltimore, MD 

New York/New Jersey 

Boston, MA 

4% 

10% 

20% 

1% 

8% 

5% 

6% 

5% 

3% 

14% 

12% 

13% 

9% 

5% 

24% 

22% 

7% 

12% 

4% 

4% 

10% 

20% 

38% 

1% 

14% 

10% 

20% 

12% 

10% 

24% 

24% 

25% 

20% 

11% 

39% 

33% 

16% 

27% 

9% 

5% 

43% 

56% 

74% 

31% 

80% 

71% 

55% 

47% 

41% 

59% 

58% 

66% 

56% 

52% 

80% 

87% 

73% 

69% 

39% 

30% b

 This category includes emissions from Category 3 (C3) propulsion engines and C2/3 auxiliary engines used on 

ocean-going vessels. 

 

Currently, more than 40 major U.S. deep sea ports are located in areas that are designated 

as being in nonattainment for either or both the 8-hour ozone NAAQS and PM2.5 NAAQS. 

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.122 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. 

2. Inventory Calculation Methodology 

The exhaust emission inventories presented above for commercial marine vessels, with 

Category 3 marine engines, include emissions from vessels in-port and from vessels engaged in 

interport transit. This section gives a general overview of the methodology used to estimate the 

 

122 Memorandum to Docket A–2001–11 from Jean-Marie Revelt, Santa Barbara County Air Quality News, Issue 62, 

July-August 2001 and other materials provided to EPA by Santa Barbara County,’’ March 14, 2002.
57

emission contribution these vessels. A more detailed description of this inventory analysis is 

available in the public docket.123

For the purposes of this analysis, in-port operation includes cruising, reduced speed zone, 

maneuvering, and hotelling. The in-port analysis includes operation out to a 25 nautical mile 

radius from the entrance to the port. Interport operation includes ship traffic, within the U.S. 

Exclusive Economic Zone (EEZ), not included as part of the port emissions analysis. In general, 

the EEZ extends to 200 nautical miles from the U.S. coast. Exceptions include geographic 

regions near Canada, Mexico and the Bahamas where the EEZ extends less than 200 nautical 

miles from the U.S. coast. 

 

The port inventories are based on detailed emission estimates for eleven specific ports. 

The port inventories were estimated using activity data for that port (number of port calls, vessel 

types and typical times in different operating modes) and an emission factor for each mode. 

Emission estimates for all other commercial ports were developed by matching each of the other 

commercial ports to one of the eleven specific ports. Matching was based on characteristics of 

port activity, such as predominant vessel types, harbor craft and region of the country. The 

detailed port emissions were then scaled for the other commercial ports based on relative port 

activity.124 An exception to this is that detailed port inventories for fourteen California ports 

were provided by the California Air Resources Board (ARB). 

To calculate the mobile fractions in Table VIII-4, we compared commercial marine port 

inventory estimates described above to county-level mobile source emission estimates developed 

in support of the recent rulemaking for national PM ambient air quality standards.125 Both 

propulsion engines and auxiliary engines are included in these estimates. The county-level 

inventories were adjusted to include the updated emissions estimates for commercial marine 

vessels. 

 

Recently, the California Air Resources Board (ARB) sponsored the development of new 

national inventory estimates for Category 3 marine engines.126 The new approach captures 

actual interport activity, by using information on ship movements, ship attributes, and the 

distances of routes. We believe that this methodology is an improvement over past evaluations 

of interport shipping emissions which were based on estimates of ton-miles of cargo moved. The 

new methodology captures ship traffic more completely which results in much higher estimates 

of total emissions from commercial marine vessels engaged in interport traffic within the U.S. 

EEZ. 

 

123 “Development of Inventories for Commercial Marine Vessels with Category 3 Engines,” U.S. EPA, 

SeptemberOctober 2007. 124 Browning, L., Hartley, S., Lindhjem, C., Hoats, A., “Commercial Marine Port Inventory Development; Baseline 

Inventories,” prepared by ICF International and Environ for the U.S. Environmental Protection Agency, September 

2006, Docket ID EPA-HQ-OAR-2007-0121-0037. 

125 Regulatory Impact Analysis for the Review of the Particulate Matter National Ambient Air Quality Standards, 

EPA Docket: EPA-HQ-OAR-2006-0834-0048.3. 

126 Corbett, J., Ph.D., Wang, C., Ph.D., Firestone, J., Ph.D, “Estimation, Validation, and Forecasts of Regional 

Commercial Marine Vessel Inventories, Tasks 1 and 2: Baseline Inventory and Ports Comparison; Final Report,” 

University of Delaware, May 3, 2006, Available electronically at http://www.arb.ca.gov/research/seca/jctask12.pdf, 

Docket ID EPA-HQ-OAR-2007-0121-0038. 
58

 Our emission inventory estimates for interport traffic are based on the ARB-sponsored 

study with four primary modifications.127,128 First, we use only the interport traffic estimates 

from the study and rely on our own, more detailed, analysis of in-port emissions. Second, we 

modified the geographic boundaries of the inventory to align with the U.S. EEZ. Third, we use 

adjusted emission factors for PM emissions to better reflect the sum of available PM emissions 

data from engines on marine vessels. 

 

 The detailed inventory studies described above were performed for 2002. To calculate 

emission inventories for future years, we applied separate growth rates for the West Coast, Gulf 

Coast, East Coast, and Great Lakes. These emission inventory growth estimates were 

determined based on economic growth projections of trade between the United States and other 

regions of the world.129 In contrast, the ARB-sponsored study looks at a range of growth rates 

based on extrapolations of historical growth in installed power.130 The approach used by EPA is 

more conservative in that it uses lower growth rate projections. 

 

The inventory estimates include emissions from both U.S. flagged vessels and foreign 

flagged vessels. The majority of the ship operation near the U.S. coast is from ships that are not 

registered in the United States. According to the U.S. Maritime Administration, in 2005, 

approximately 87 percent of the calls by ocean-going vessels (10,000 dead weight tons or 

greater) at U.S. ports were made by foreign vessels.131

This inventory analysis includes emissions from Category 3 propulsion engines and the 

Category 2 and 3 auxiliary engines used on these vessels. Based on our emissions inventory 

analysis, auxiliary engines contribute approximately half of the exhaust emissions from vessels 

in port. In contrast, auxiliary engines only represent about 4 percent of the exhaust emissions 

from ships engaged in interport traffic. 

 The exhaust emission inventory for commercial marine vessels with Category 3 marine 

engines includes operation that extends out to 200 nautical miles from shore. Considering all 

emissions from ships operating in the U.S. EEZ, emissions in ports contribute to less than 20 

percent of the total inventory. However, we recognize that emissions closer to shore are more 

likely to impact human health and welfare because of their proximity to human populations. We 

have initiated efforts to perform air quality modeling to quantify these impacts. The air quality 

modeling will consider transport of emissions over the ocean, meteorological data, population 

densities, emissions from other sources, and other relevant information. We request comment on 

 

127 “Recalculation of Baseline and 2005 Emissions and Fuel Consumption,” memorandum from Lou Browning, ICF 

and Chris Lindhjem and Lyndsey Parker, Environ, to Penny Carey, Mike Samulski, and Russ Smith, U.S. EPA, July 

19, 2007. 

128 “U.S. and Regional Totals of Marine Vessel Emissions and Fuel Consumption under WA 0-2 Tasks 6 and 7,” 

draft memorandum from Abby Hoats and Chris Lindhjem, Environ, to Lou Browning, ICF International, April 23, 

2007. 

129 “RTI Estimates of Growth in Bunker Fuel Consumption,” memorandum from Michael Gallaher and Martin Ross, 

RTI International, to Barry Garelick and Russ Smith, U.S. EPA, April 24, 2006, Docket ID EPA-HQ-OAR-2007-

0121-0039. 

130 Corbett, J., Ph.D., Wang, C., Ph.D., “Estimation, Validation, and Forecasts of Regional Commercial Marine 

Vessel Inventories, Tasks 3 and 4: Forecast Inventories for 2010 and 2020; Final Report,” University of Delaware, 

May 3, 2006, Docket ID EPA-HQ-OAR-2007-0121-0012. 

131 “Vessel Calls at U.S. & World Ports; 2005,” U.S. Maritime Administration, Office of Statistical and Economic 

Analysis, April 2006, Docket ID EPA-HQ-OAR-2007-0121-0040. 
59

the methodology used to develop exhaust inventory estimates for ships with Category 3 engines 

operating near the U.S. coast. 

 As discussed above, the national inventories presented here are for the Exclusive 

Economic Zone around the 50 states. Note that the ship traffic in the EEZ includes not only 

direct movements to and from U.S. ports, but also movements up and down the coast. The 

boundaries for the EEZ are presented in Figure VIII-1. 

61

Figure VIII-1: Regions of U.S. EEZ used for Category 3 Inventory Analysis 
62

Table VIII-5 presents the 2002 national exhaust emission inventory for commercial 

marine vessels, with Category 3 marine engines, subdivided into the seven regions shown in the 

above figure. The Alaska and Hawaii regions contribute to roughly one-fifth of the national 

emissions inventory. The inventory for the Alaska EEZ includes emissions from ships on a great 

circle route, along the Aleutian Islands, between Asia and the U.S. West Coast. Therefore, 

eastern Alaska, which includes most of the state population, is presented separately in the table 

below. The Hawaii EEZ includes major shipping lanes across the Pacific that pass near the 

Hawaiian isles. 

Table VIII-5: 2002 Regional U.S. Emissions from Commercial Marine Vesselsa [tons/yr] 

Region 

NOx 

[short tons] 

PM2.5

[short tons] 

SOx 

[short tons] 

South Pacific 116,057 8,283 62,944 

North Pacific 28,941 2,205 16,469 

East Coast 243,261 17,901 153,597 

Gulf Coast 192,130 14,374 110,382 

Alaska (east) 20,078 1,458 11,037 

Alaska (west) 66,768 4,799 35,998 

Hawaii 60,501 4,372 32,970 

Great Lakes (U.S. only) 16,708 1,207 9,098 

Great Lakes (Canada only) 5,621 405 3,043 

Total (using U.S. only Great Lakes) 744,444 54,599 432,496 

a

 This category includes emissions from Category 3 (C3) propulsion engines and C2/3 auxiliary engines used on 

ocean-going vessels.

B. Potential Costs 

 The emission-control technologies we are considering for Category 3 marine engines are 

already in development or in commercial use in some marine applications. The draft Regulatory 

Impact Analysis132 for the May 29, 2002 proposed rulemaking for Category 3 marine engines (67 

FR 37548) included an analysis of regulatory alternatives which including advanced 

technologies. To estimate costs of this prospective emissions control program, we expect to start 

with cost estimates that were developed as part of that regulatory analysis. We will modify these 

costs as needed to take into account advances in technology, changes in cost structure, and 

comments received on this ANPRM. We encourage commenters to review the information 

covering all aspects of engine costs in the regulatory impact documents for the earlier Category 3 

rulemaking and to provide comments on cost-related issues. In addition, we are interested in 

cost information associated with potential retrofitting concepts and in information about any 

unique costs associated with equipment redesign for the marine market. 

 We will also consider the economics of desulfurizing residual fuel, using of distillate 

fuel, and blending high and low sulfur fuels. Due to high refinery production costs, it is not 

likely that much new volume of residual fuel will be desulfurized. We expect to employ a world 

wide refinery modeling analysis to estimate the cost for desulfurizing residual fuel and to 

estimate the cost for the production of additional distillate fuel in our analysis for different fuel 

volume scenarios. Additionally, we will estimate scrubbing costs and potential scrubber 

 

132 “Draft Regulatory Support Document: Control of Emissions from Compression-Ignition Marine Diesel Engines 

at or Above 30 Liters per Cylinder,” U.S. Environmental Protection Agency, April, 2002. 
63

penetration rates for ships, as the use of scrubbers is another method that ships may use to 

comply, in lieu of using low sulfur fuel. The resulting fuel cost from our refinery analysis will 

be compared to the costs from scrubbing and fuel blending to determine the most economical 

method for complying with the standards for Category 3 marine engines. We request comment 

on the potential costs of low sulfur marine fuels. 

IX. Statutory and Executive Order Reviews 

A. Executive Order 12866: Regulatory Planning and Review 

 Under section (3)(f)(1) Executive Order 12866 (58 FR 51735, October 4, 1993), the 

Agency must determine whether the regulatory action is “significant” and therefore subject to 

review by the Office of Management and Budget (OMB) and the requirements of this Executive 

Order. This Advance Notice has been sent to the Office of Management and Budget (OMB) for 

review under EO 12866 and any changes made in response to OMB recommendations have been 

documented in the docket for this action. 

B. Paperwork Reduction Act 

We will prepare information collection requirements as part of our proposed rule and 

submit them for approval to the Office of Management and Budget (OMB) under the Paperwork 

Reduction Act, 44 U.S.C. 3501 et seq.

C. Regulatory Flexibility Act 

The Regulatory Flexibility Act (RFA) as amended by the Small Business Regulatory 

Enforcement Fairness Act (SBREFA), requires agencies to endeavor, consistent with the objectives of the rule and applicable statutes, to fit regulatory and information requirements to the 

scale of businesses, organizations, and governmental jurisdictions subject to their regulations. 

SBREFA amended the RFA to strengthen its analytical and procedural requirements and to 

ensure that small entities are adequately considered during rule development. The Agency 

accordingly requests comment on the potential impacts on a small entity of the program 

described in this notice. These comments will help the Agency meet its obligations under 

SBREFA and will suggest how EPA can minimize the impacts of this rule for small entities that 

may be adversely impacted. 

Depending on the number of small entities identified prior to the proposal and the level of 

any contemplated regulatory action, we may convene a Small Business Advocacy Review Panel 

under section 609(b) of the Regulatory Flexibility Act as amended by SBREFA. The purpose of 

the Panel would be to collect the advice and recommendations of representatives of small entities 

that could be impacted by the eventual rule. If we determine that a panel is not warranted, we 

would intend to work on a less formal basis with those small entities identified. 

Although we do not believe that this rule will have a significant economic impact on a 

substantial number of small entities, we are requesting information on small entities potentially 

impacted by this rulemaking. Information on company size, number of employees, annual 

revenues and product lines would be especially useful. Confidential business information may 

be submitted as described under SUPPLEMENTARY INFORMATION. 
64

D. Unfunded Mandates Reform Act 

Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), Public Law 104-4, 

establishes requirements for Federal agencies to assess the effects of their regulatory actions on 

State, local, and tribal governments and the private sector. Under section 202 of the UMRA, 

EPA generally must prepare a written statement, including a cost-benefit analysis, for proposed 

and final rules with "Federal mandates" that may result in expenditures to State, local, and tribal 

governments, in the aggregate, or to the private sector, of $100 million or more in any one year. 

Before promulgating an EPA rule for which a written statement is needed, section 205 of the 

UMRA generally requires EPA to identify and consider a reasonable number of regulatory 

alternatives and adopt the least costly, most cost-effective or least burdensome alternative that 

achieves the objectives of the rule. The provisions of section 205 do not apply when they are 

inconsistent with applicable law. Moreover, section 205 allows EPA to adopt an alternative other 

than the least costly, most cost-effective or least burdensome alternative if the Administrator 

publishes with the final rule an explanation why that alternative was not adopted. Before EPA 

establishes any regulatory requirements that may significantly or uniquely affect small 

governments, including tribal governments, it must have developed under section 203 of the 

UMRA a small government agency plan. The plan must provide for notifying potentially 

affected small governments, enabling officials of affected small governments to have meaningful 

and timely input in the development of EPA regulatory proposals with significant Federal 

intergovernmental mandates, and informing, educating, and advising small governments on 

compliance with the regulatory requirements. 

As part of the development of our Notice of Proposed Rulemaking, we will examine the 

impacts of our proposal with respect to expected expenditures by State, local, and tribal 

governments, in the aggregate, or by the private sector of $100 million or more in any one year. 

E. Executive Order 13132: Federalism 

Executive Order 13132, entitled “Federalism” (64 FR 43255, August 10, 1999), requires 

EPA to develop an accountable process to ensure “meaningful and timely input by State and 

local officials in the development of regulatory policies that have federalism implications.” 

“Policies that have federalism implications” is defined in the Executive Order to include 

regulations that have “substantial direct effects on the States, on the relationship between the 

national government and the States, or on the distribution of power and responsibilities among 

the various levels of government.” 

Under Section 6 of Executive Order 13132, EPA may not issue a regulation that has 

federalism implications, that imposes substantial direct compliance costs, and that is not required 

by statute, unless the Federal government provides the funds necessary to pay the direct 

compliance costs incurred by State and local governments, or EPA consults with State and local 

officials early in the process of developing the proposed regulation. EPA also may not issue a 

regulation that has federalism implications and that preempts State law, unless the Agency 

consults with State and local officials early in the process of developing the proposed regulation. 

Section 4 of the Executive Order contains additional requirements for rules that preempt 

State or local law, even if those rules do not have federalism implications (i.e., the rules will not 

have substantial direct effects on the States, on the relationship between the national government 
65

and the states, or on the distribution of power and responsibilities among the various levels of 

government). Those requirements include providing all affected State and local officials notice 

and an opportunity for appropriate participation in the development of the regulation. If the 

preemption is not based on express or implied statutory authority, EPA also must consult, to the 

extent practicable, with appropriate State and local officials regarding the conflict between State 

law and Federally protected interests within the agency’s area of regulatory responsibility. 

As part of the development of our Notice of Proposed Rulemaking, we will examine the 

impacts of our proposal with respect to the relationship between the national government and the 

States, or on the distribution of power and responsibilities among the various levels of 

government, as specified in Executive Order 13132. 

In the spirit of Executive Order 13132, and consistent with EPA policy to promote 

communications between EPA and State and local governments, EPA specifically solicits 

comment on this proposed rule from State and local officials. 

F. Executive Order 13175: Consultation and Coordination with Indian Tribal 

Governments 

 Executive Order 13175, entitled “Consultation and Coordination with Indian Tribal 

Governments” (65 FR 67249, November 9, 2000), requires EPA to develop an accountable 

process to ensure “meaningful and timely input by tribal officials in the development of 

regulatory policies that have tribal implications.” “Policies that have tribal implications” is 

defined in the Executive Order to include regulations that have “substantial direct effects on one 

or more Indian tribes, on the relationship between the Federal government and the Indian tribes, 

or on the distribution of power and responsibilities between the Federal government and Indian 

tribes.” 

 As part of the development of our Notice of Proposed Rulemaking, we will examine the 

impacts of our proposal with respect to tribal implications. 

G. Executive Order 13045: Protection of Children from Environmental Health 

and Safety Risks 

 Executive Order 13045, “Protection of Children from Environmental Health Risks and 

Safety Risks” (62 FR 19885, April 23, 1997) applies to any rule that: (1) is determined to be 

“economically significant” as defined under Executive Order 12866, and (2) concerns an 

environmental health or safety risk that EPA has reason to believe may have a disproportionate 

effect on children. If the regulatory action meets both criteria, the Agency must evaluate the 

environmental health or safety effects of the planned rule on children, and explain why the 

planned regulation is preferable to other potentially effective and reasonably feasible alternatives 

considered by the Agency. 

 This rule is not subject to the Executive Order because it does not involve decisions on 

environmental health or safety risks that may disproportionately affect children. The EPA 

believes that the emissions reductions from the strategies proposed in this rulemaking will 

further improve air quality and will further improve children’s health. 
66

H. Executive Order 13211: Actions that Significantly Affect Energy Supply, 

Distribution, or Use 

Executive Order 13211, “Actions Concerning Regulations That Significantly Affect 

Energy Supply, Distribution, or Use” (66 Fed. Reg. 28355 (May 22, 2001)) requires that we 

determine whether or not there is a significant impact on the supply of energy caused by our 

rulemaking. These impacts include: reductions in supply, reductions in production, increases in 

energy usage, increases in the cost of energy production and distribution, or other similarly 

adverse outcomes. We anticipate that our proposal will not be a “significant energy action” as 

defined by this order because we are not reducing the supply or production of any fuels or 

electricity, nor are we increasing the use or cost of energy by more than the stated thresholds. 

The proposed standards will have for their aim the reduction of emissions from certain marine 

engines using either exhaust gas cleaning technology or an alternative grade of marine fuel, and 

will have no effect on fuel formulation. 

I. National Technology Transfer Advancement Act 

Section 12(d) of the National Technology Transfer and Advancement Act of 1995 

(“NTTAA”), Public Law 104 113, 12(d) (15 U.S.C. 272 note) directs EPA to use voluntary 

consensus standards in its regulatory activities unless doing so would be inconsistent with 

applicable law or otherwise impractical. Voluntary consensus standards are technical standards 

(e.g., materials specifications, test methods, sampling procedures, and business practices) that are 

developed or adopted by voluntary consensus standards bodies. NTTAA directs EPA to provide 

Congress, through OMB, explanations when the Agency decides not to use available and 

applicable voluntary consensus standards. 

As part of the development of our Notice of Proposed Rulemaking, we will examine the 

availability and use of voluntary consensus standards. 

J. Executive Order 12898: Federal Actions to Address Environmental Justice in 

Minority Populations and Low-Income Populations 

Executive Order (EO) 12898 (59 FR 7629 (Feb. 16, 1994)) establishes federal executive 

policy on environmental justice. Its main provision directs federal agencies, to the greatest 

extent practicable and permitted by law, to make environmental justice part of their mission by 

identifying and addressing, as appropriate, disproportionately high and adverse human health or 

environmental effects of their programs, policies, and activities on minority populations and lowincome populations in the United States. 

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

Liters per Cylinder page 105 of 105 - ANPRM 

EPA has determined that this proposed rule will not have disproportionately high and adverse 

human health or environmental effects on minority or low-income populations because it 

increases the level of environmental protection for all affected populations without having any 

disproportionately high and adverse human health or environmental effects on any population, 

including any minority or low-income population. Rather the opposite as more low-income 

individuals tend to live closer to marine ports, and it is these areas that will receive the most 

benefits in this rule that will reduce emissions of large marine engines. 
67

List of Subjects 

40 CFR Part 9

Reporting and recordkeeping requirements 

40 CFR Part 94 

Environmental protection, Administrative practice and procedure, Air pollution control, 

Confidential business information, Imports, Incorporation by reference, Penalties, Reporting and 

recordkeeping requirements, Vessels, Warranties. 

Dated_____________ 

___________________________________ 

Stephen L. Johnson, 

Administrator.