The U.S. Environmental Protection Agency on Thursday proposed rolling back emission standards for new heavy-duty trucks, including buses, garbage trucks and semis.

Under the proposal, EPA is looking to scale back future warranty mandates from 10 years to 5 and to delay requirements to extend the period in which the vehicles are subject to pollution limits. If finalized, this action could result in lower costs for truck manufacturers while potentially also boosting air pollution.

The 10-year warranty rules, which were created by the Biden administration, are “the single biggest cost of all to the trucking industry,” said EPA Administrator Lee Zeldin at a press event announcing the rule change on the National Mall. “We’re proposing to roll it back while keeping the underlying emissions standards in place.”

This is the latest effort by the Trump administration to unwind pollution regulations for vehicles and other sources finalized by former President Joe Biden. In May, the agency proposed delaying emission standards set to kick in for new light- and medium-duty cars and trucks starting with model year 2027.

Heavy-duty trucks are far more polluting than smaller cars and trucks, releasing higher levels of nitrogen oxides, or NOx, that can cause shortness of breath and other respiratory problems in the short term. They also contribute to ozone and smog conditions.

Under the current rules that took effect in 2023, Biden’s EPA reduced the federal NOx limit for these trucks by nearly 90%. It also extended the heaviest trucks’ useful life – meaning the time frame when they are expected to meet the federal limits – from 435,000 miles or 10 years to 650,000 miles or 11 years. The time period during which this class of vehicles has to be under warranty, meaning manufacturers are legally required to repair or replace defective emissions-related components, went from 100,000 miles or 5 years to 450,000 miles or 10 years.

These changes were designed to cut truck-related pollution. Biden’s EPA estimated at the time that in 2045, the final rule would have prevented 6,700 hospital and emergency department visits, 18,000 cases of asthma onset in children, and 78,000 lost work days.

Under the proposal, Trump’s EPA is keeping the stricter NOx thresholds but relaxing warranty requirements for new vehicles. Specifically, the EPA recommends extending the current 5-year warranty rule for model year 2026 trucks for the foreseeable future, among other changes to warranty structures.

The warranty change “is a really big deal,” said Jennifer Rumsey, chair and CEO of engine manufacturer Cummins Inc, at the Thursday event, “because we are no longer requiring that everyone buy up front an emissions warranty over the whole life of a product. They have choice.”

Trucks would need to comply with the Biden-era useful-life extension, but until 2030 instead of 2027 as mandated by the original rule.

The agency estimates these changes could collectively result in up to $12 billion in savings for the trucking industry, although Zeldin stressed to Bloomberg News the numbers are preliminary and subject to change as the rule is finalized.

Critics said this rollback will boost pollution and hurt people’s health. “Warranty and useful life requirements sound so dry and like corporate fine print, but they’re the actual teeth of this clean air rule,” said Guillermo Ortiz, a senior clean vehicles advocate at the nonprofit Natural Resources Defense Council. “The public needs to realize that a standard becomes completely meaningless if the technology isn’t built to last.”

The EPA is accepting public comment on the proposal until August 29.

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