The Environmental Protection Agency on Thursday proposed to loosen limits on smog-causing pollution from a variety of heavy-duty vehicles, including tractor-trailers, fire engines and delivery trucks.
It was the latest effort by the Trump administration to encourage the use of vehicles that burn fossil fuels rather than running on electricity. The Biden administration, in contrast, had made a rapid transition to electric vehicles a centerpiece of its plans for tackling both climate change and hazardous air pollution.
President Trump has derided Biden-era electric vehicle initiatives as an “E.V. mandate” and a “green new scam.” Last week, the president pardoned nine men who had been convicted of selling or installing devices that illegally disabled the emissions controls of diesel trucks, making them far more polluting.
The E.P.A. said on Thursday that it would repeal some, but not all, provisions in a clean-air rule that the Biden administration finalized in 2023. That rule was designed to significantly reduce emissions of nitrogen oxides from truck tailpipes.
Nitrogen oxides are toxic gases that form when fossil fuels are burned. They create smog when they mix with other pollutants in the air on hot, sunny days. Breathing in smog can irritate the lungs, exacerbating asthma and other respiratory conditions.
The Biden-era rule did not mandate the sale of electric trucks. Rather, it increasingly limited the amount of nitrogen oxides a manufacturer’s diesel engines could emit over time. Manufacturers could comply by strengthening the emissions controls in their diesel engines, or they could choose to forego those extra costs by making more electric trucks.
Lee Zeldin, the E.P.A. administrator, said the Trump administration would largely maintain a Biden-era requirement that manufacturers cut nitrogen oxide emissions by 80 percent starting with model year 2027. Several manufacturers have already designed new diesel engines that meet this requirement.
But under the proposal from the Trump administration, trucks would have to meet the emissions standards for only the first 435,000 miles that they drove. The Biden administration had mandated compliance for the first 650,000 miles, saying the change would compel manufacturers to design more durable emissions controls that would not break down in older engines.
In addition, the new proposal would require manufacturers to offer warranties for their emissions controls for the first 100,000 miles. The Biden administration had required warranties for the first 450,000 miles, reasoning that once a truck was out of warranty, the driver might disable faulty emissions controls instead of paying for costly repairs.
Mr. Zeldin said the changes would lift burdensome restrictions that threatened to take trucks off the roads, erasing jobs and restricting the flow of goods.
“When I took this job, I inherited a set of rules that just weren’t working for truckers, for farmers and for so many other American families who count on them,” Mr. Zeldin said during a news conference at the Great American State Fair, an event on the National Mall organized by Freedom 250, a Trump-backed organization.
Speaking in front of a bright red big rig, Mr. Zeldin said the Trump administration was making “key fixes to the last administration’s problematic truck engine rule.” He added that the proposal would shave $6,000 off the average sticker price of each new truck, though it was not immediately clear how the E.P.A. arrived at that number.
John O’Leary, the chief executive of Daimler Trucks North America, one of the largest truck makers, thanked the Trump administration for listening to the industry’s concerns.
“We don’t expect to dictate regulations, but we definitely have opinions and we represent vast constituencies, and we just want to be heard,” Mr. O’Leary said at the event on the National Mall, adding, “For us now to feel like we actually are being heard means a lot to us.”
The changes announced Thursday were part of a proposed rule, an early step in the regulatory process. After soliciting public comments for 45 days, the E.P.A. will unveil a final rule, likely by the end of the year.
While medium- and heavy-duty trucks account for 13 percent of all vehicles in the United States, they are responsible for 58 percent of nitrogen oxide emissions from road transportation, according to the Union of Concerned Scientists, an environmental group.
Under the Biden administration, the E.P.A. estimated that 72 million people lived within a mile of a truck freight route, increasing their exposure to unhealthy air. People of color and those with lower incomes were more likely to live in these areas, the agency found.
Isella Ramirez is the executive director of the Moving Forward Network, a coalition of groups that work with communities to reduce diesel pollution. She grew up in Commerce, Calif., an industrial city southeast of Los Angeles with a predominantly Hispanic population and four major freight rail yards.
Ms. Ramirez said tens of thousands of trucks rumble through the 6.5-square-mile city each day. She called the community a “diesel death zone,” noting that diesel exhaust also contains fine particulate matter, which is linked to premature death as well as asthma and heart disease.
“The E.P.A. is continuing to act against its own mission to protect public health and the environment,” Ms. Ramirez said. “It’s another slap in the face to communities that are already overburdened.”
The Truck and Engine Manufacturers Association, an industry group, said that it was still reviewing the proposal. But in general, the group supports “the agency’s continued engagement on cost-effective and achievable requirements for manufacturers, truck customers and equipment operators,” according to Jacqueline Gelb, the group’s president and C.E.O.
Despite the efforts of the Biden administration, electric trucks remain a rarity on U.S. roads. Out of roughly 416,000 medium- and heavy-duty trucks sold in the United States in 2025, around 17,000 were electric.
With significantly larger batteries than electric cars, electric trucks require powerful chargers that are not yet widely available. And many electric models cost hundreds of thousands of dollars, two or three times the sticker price of a diesel truck. But going electric can lead to lower fuel and maintenance costs in the long run. That is especially true as the war in the Middle East drives up diesel prices.
