Groups file comments vigorously opposing EPA’s proposal to weaken life-saving protections against air pollution from cars

(Washington, D.C. - July 7, 2026) The Trump EPA's proposed weakening of standards to reduce air pollution from cars, passenger trucks, and SUVs "unlawfully abdicates [the agency's] statutory duty to protect public health and the environment from dangerous vehicle emissions," according to comments filed by Environmental Defense Fund, Natural Resources Defense Council (NRDC), Center for Biological Diversity, Environmental Law and Policy Center and Sierra Club.

The Trump EPA has proposed a two-year delay of the 2024 Tier 4 emissions standards, which reduce smog and soot-forming nitrogen oxides (NOx), fine particulate matter, and volatile organic compounds from new light- and medium-duty vehicles in model years 2027 to 2032.

These types of pollution are extremely dangerous. Fine particulate matter, for instance, can permanently impair lung development in children and is directly linked to heart attacks, strokes, and premature death. Pollution from vehicles is the largest source of air-pollution-related early deaths each year in the U.S. Low-cost technologies are already being deployed that dramatically reduce this pollution in cars and light trucks.

"Although EPA describes its Proposal as a temporary 'delay' … EPA is in fact proposing to eliminate those standards for Model Year (MY) 2027-2028 vehicles and replace them with outdated requirements from more than a decade ago that fail to protect public health and reflect modern technology as the Clean Air Act requires," the groups write in their comments to EPA. "This rollback would result in … additional dangerous pollution as well as premature deaths and other health harms in communities across the country, and is patently unreasonable and unlawful."

The groups' comments outline the "many legal and technical errors" in the proposal to delay the Tier 4 protections and include extensive new technical analysis documenting those flaws and the harms that will result from the proposal. For instance:

• The comments include a new, detailed analysis of vehicle certification data that shows many vehicles are already deploying commonsense pollution control technologies and certifying to levels at or below the strengthened standards that EPA has proposed to delay. The analysis reinforces that manufacturers are well positioned to comply, especially since manufacturers already deploy these lifesaving technologies in other countries around the world.
• The comments include a new analysis of pollution and health impacts that shows the weakening of the standards will cause up to 595 more premature deaths and up to $12.4 billion in health harms.

In light of these serious flaws and the increase in pollution, health harms, and costs that will result, the groups comments call on the agency to "abandon this illegal and misguided Proposal and instead fully implement and enforce its existing criteria-pollutant emissions standards" for cars and passenger trucks.