The Environmental Protection Agency (EPA) on Thursday unveiled a proposal to relax emissions limits on nitrogen oxides from medium- and heavy-duty vehicles, including tractor-trailers, fire engines, and delivery trucks. The move signals a shift from the Biden administration’s regulatory approach, which had aimed to tighten pollution controls in favor of accelerating electric vehicle adoption.

The rule under reconsideration was finalized last year and sought to drastically reduce nitrogen oxide emissions from truck tailpipes—a key contributor to smog and associated respiratory health issues. Under the Biden-era standards, manufacturers were required to meet emissions limits over the first 650,000 miles a truck was driven, with warranty coverage extending for 450,000 miles. The new proposal reduces those mileage requirements to 435,000 miles for emissions standards compliance and 100,000 miles for emissions control warranties.

EPA Administrator Lee Zeldin defended the changes as necessary to alleviate what he described as burdensome regulations that risked removing trucks from the roads, potentially leading to job losses and disruptions in goods transportation. Speaking at an event on the National Mall, Zeldin said the updated rule would cut approximately $6,000 from the average cost of a new truck, though details on the calculation were not immediately provided. The proposal retains an 80% emissions reduction target starting with model year 2027, a standard that several manufacturers have already met with new diesel engine designs.

Industry stakeholders welcomed the proposal. John O’Leary, CEO of Daimler Trucks North America, expressed appreciation for the EPA’s engagement with manufacturers’ concerns, emphasizing the importance of being heard in regulatory discussions. The Truck and Engine Manufacturers Association also indicated general support for the agency’s efforts to balance cost-effective, achievable requirements for manufacturers and operators, though it noted it was still reviewing the details of the proposal.

Environmental advocates and community leaders voiced strong opposition. The Union of Concerned Scientists highlights that while medium- and heavy-duty trucks constitute just 13% of vehicles on U.S. roads, they are responsible for 58% of nitrogen oxide emissions from transportation. The EPA further noted that approximately 72 million Americans live within a mile of truck freight routes, with populations of color and lower-income communities disproportionately affected by exposure to diesel pollution.

Isella Ramirez, executive director of the Moving Forward Network, criticized the EPA’s proposal as counter to its mission to protect public health and the environment. Ramirez highlighted Commerce, California, an industrial city with heavy truck traffic, as an example of a community severely impacted by diesel emissions, describing it as a “diesel death zone” due to elevated rates of pollution-linked illnesses.

Despite regulatory efforts to increase electric truck adoption, they continue to represent a small fraction of new sales. The EPA reported that in 2025, only about 17,000 electric medium- and heavy-duty trucks were sold out of roughly 416,000 total vehicles. High costs, limited charging infrastructure, and large battery requirements pose challenges for broader market penetration, though proponents note potential long-term savings on fuel and maintenance, especially amid rising diesel prices influenced by geopolitical tensions.

The EPA is seeking public input on the proposal over the next 45 days before finalizing the rule, expected by the end of the year.