California regulators have issued a proposal focused at lowering particulate matter emissions for new trucks built beginning in 2024, but federal regulators are still working to craft a separate nationwide low-NOx and PM proposal scheduled to take effect in 2027. Additionally, California Air Resources Board (CARB) and the U.S. Environmental Protection Agency staff hope to synchronize their regulations.
The Environmental Protection Agency (EPA) participates on the U.S. delegation to the International Maritime Organization (IMO), which is part of the United Nations. The Marine Environment Protection Committee (MEPC) is a group of member states within IMO that works on maritime safety and security and the prevention of marine pollution. The resulting global standards are embodied in the International Convention on the Prevention of Pollution from Ships, a treaty called "MARPOL." In particular, MARPOL Annex VI defines engine and vessel requirements related to air pollution.