Maryland Attorney General Joins Coalition Opposing Rollback of Heavy-Duty Vehicle Emission Standards

Maryland Attorney General Anthony G. Brown has joined a coalition of state and local legal officers in opposing a proposed rule by the U.S. Environmental Protection Agency (EPA) that would weaken regulations on emissions from heavy-duty vehicles. The proposed changes, if finalized, could allow for increased pollution from semi-trucks and other large commercial vehicles, potentially leading to negative impacts on public health and air quality, particularly in communities that already bear a disproportionate burden of environmental pollution.

The coalition’s argument centers on the belief that the EPA’s proposal fails to meet the requirements of the Clean Air Act. The transportation sector is identified as the primary source of nitrogen oxides (NOx) emissions in the United States, with heavy-duty vehicles being the second-largest contributor within this sector. Exposure to NOx is linked to a variety of respiratory issues, including asthma, inflammation of the respiratory tract, and impaired lung function and growth. Vulnerable populations, such as communities of color and low-income communities, often reside near major transportation arteries and industrial sites that emit these pollutants, making them more susceptible to these adverse health effects.

The EPA’s proposed rule, released in July 2026, aims to revise emission regulations for heavy-duty vehicles that were established in 2023. Key provisions of the proposed rollback include shortening the emission warranty period for heavy-duty vehicles from ten years to five years for model year 2027 and later. The EPA’s own projections indicate this change could result in an additional 36,000 tons of NOx emissions annually. Furthermore, the proposal seeks to delay the implementation of longer regulatory useful life periods for these vehicles, pushing back the enforcement from model year 2027 to model year 2030. This delay would shorten the duration over which emission standards apply, consequently increasing overall NOx emissions. The coalition also argues that the proposed rule weakens mechanisms designed to ensure that emission control systems are properly maintained and functioning effectively.

The comment letter submitted by the coalition asserts that the proposed rule, by weakening emission standards for heavy-duty vehicles and potentially hindering state and local efforts to achieve mandated air quality standards, would violate federal law. The coalition further contends that the EPA has not adequately considered the health consequences associated with the anticipated increase in pollution. Attorney General Brown is joined in this opposition by the attorneys general of California, Colorado, Connecticut, Delaware, the District of Columbia, Hawaiʻi, Illinois, Maine, Massachusetts, Michigan, Minnesota, New Jersey, New York, North Carolina, Oregon, Rhode Island, Washington, and Wisconsin. Additionally, chief legal officers from the cities of Chicago, Denver, New York, and the City and County of San Francisco have also signed onto the comment letter.

Article by Mel Anara, based upon information from the Maryland Attorney General’s Office.

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