EPA Collaboration on International Air Pollution Standards for Ships

The revised fuel sulfur limits and engine emission standards adopted in 2008 are geographically-based, with more stringent controls applicable to ships operating in designated Emission Control Areas. Specifically, ships operating in ECAs must meet the following requirements.

• The sulfur content of fuel used in a ship while operating in a fuel sulfur ECA may not exceed 1,000 ppm. This fuel sulfur limit may be met through the use of compliant fuel or an approved equivalent method (for example, a SO_X scrubber, also known as an exhaust gas cleaning system).
  • Outside of a fuel sulfur ECA, the current global fuel sulfur cap is 5,000 ppm.
• Emissions from engines above 130 kW installed on a ship may not exceed the Tier III NO_X limits while operating in a NO_X ECA.
  • The effective dates of the Annex VI NO_X limits are based on the year the ship was built.
  • The Tier III limits apply to engines on ships built beginning January 1, 2016.
  • Outside of a NO_X ECA, engines are subject to Tier I NO_X limits for ships built beginning January 1, 2000, and Tier II NO_X limits for ships built beginning January 1, 2011.

The MARPOL Annex VI standards apply to both U.S. and foreign ships. U.S. ships are also subject to EPA’s Clean Air Act marine diesel engine standards and marine fuel sulfur limits. For more information about those programs, see the links in Related Topics on this page.

U.S. Emissions Control Areas

Together with Canada and France, the U.S. Government successfully petitioned the International Maritime Organization to designate the North American Emission Control Area for both fuel sulfur limits and engine NO_X emission standards. This area extends up to 200 nautical miles from the coasts of the continental United States and large portions of coastal waters around Alaska and Hawaii, in addition to significant portions of the Canadian coasts and the French Islands of Saint Pierre and Miquelon.

The U.S. Government also successfully petitioned the International Maritime Organization to designate the U.S. Caribbean Sea Emission Control Area for both fuel sulfur limits and engine NO_X emission standards. This area includes waters surrounding Puerto Rico and the U.S. Virgin Islands.

• Guidance documents related to Annex VI standards for marine vessels
• Reports related to Emission Control Areas (ECAs) for marine vessels
• Designation of the U.S. Caribbean ECA for marine vessels
• Designation of the North American ECA for marine vessels

New Effort to Review the MARPOL Annex VI Regulation 13 NO_X Limits

In early 2024, the United States joined a group of like-minded countries in submitting a paper to the 81^st session of MEPC expressing concern that the MARPOL Annex VI NO_X emission control program, and the ECA NO_X requirements in particular, are not achieving the anticipated reductions in air pollution from marine diesel engines.

After discussion at its 82nd session, the Committee agreed to include a new work item on its agenda, "Review and development of NOx emission requirements in MARPOL Annex VI and the NOx Technical Code 2008," to ensure that the Regulation 13 NOx standards achieve the intended emission reductions. The Committee assigned the topic to the Sub-Committee on Pollution Prevention and Response, to begin work at their 13th session in January 2026, with a completion date of 2027.

The United States continues to work with several countries to prepare draft revisions to the Regulation 13 NOx control program.

Also at its 82nd session, the Committee approved draft amendments to MARPOL Annex VI Regulation 13 concerning the use of multiple engine operational profiles for a marine diesel engine, as well as associated draft amendments to the NOx Technical Code (NTC) 2008. The amendments to Regulation 13 are expected to be adopted in Autumn 2025, at the same time as other amendments to MARPOL Annex VI, while the amendments to the NTC are expected to be adopted in April 2025. Both sets of amendments are expected to enter into force at the same time, in March 2027.

Learn more:

• PPR 11/INF.4 - ANY OTHER BUSINESS Assessment of the impacts of the MARPOL Annex VI emission control regulations in the United States portion of the North American Emission Control Area (pdf) (774.91 KB, November 2023) (submitted by United States).
• MEPC 81/5/3 - AIR POLLUTION PREVENTION Perceived shortcomings of regulation 13 of MARPOL Annex VI NOX emission air pollution reduction programme (pdf) (213.08 KB, January 2024) (submitted by Submitted by Belgium, Canada, Denmark, Germany, Ireland, Netherlands (Kingdom of the), Norway and United States).
• MEPC 82/14/1 - WORK PROGRAMME OF THE COMMITTEE AND SUBSIDIARY BODIES Proposal for a new output to amend MARPOL Annex VI and the NOX Technical Code 2008 (pdf) (271.44 KB, June 2024) (submitted by Belgium, Canada, Denmark, Finland, Germany, Ireland, Netherlands (Kingdom of the), Norway and United States).
• MEPC 82/17/Add.1, Annex 4 DRAFT AMENDMENTS TO MARPOL ANNEX VI (pdf) (78.1 KB, January 2025) (Use of multiple engine operational profiles for a marine diesel engine including clarifying engine test cycles and clarification of entries in data reporting required by regulations 27 and 28)
• MEPC 82/17/Add.1, Annex 5, DRAFT AMENDMENTS TO THE NOx TECHNICAL CODE 2008 (pdf) (321.39 KB, January 2025) (Use of multiple engine operational profiles for a marine diesel engine, including clarifying engine test cycles)
• Large Marine Engine Technology Evaluation, Final Report (pdf) (3.66 MB, February 2025, EPA-420-R-25-007) (Report prepared for EPA by Southwest Research Institute, SwRI Project Number 03.28987, February 28, 2025)

List of Related Regulations and Other Publications

Below is a list of all international regulations and materials related to emissions from marine compression-ignition (diesel) engines.

• Rule summaries;
• Regulatory impact analyses;
• Comment summaries;
• Rule histories (including proposed rules); and
• Fact sheets.*

* Note: Rule-related materials vary by rule.