The U.S. Environmental Protection Agency (EPA) on Friday said it was approving California‘s plans to require a rising number of zero-emission heavy-duty trucks as the state pushes to cut pollution.

California Governor Gavin Newsom said as a result of the plan, “half of all heavy duty trucks sold in CA will be electric by 2035.”

“Time to stop playing small ball,” he added.

Under an executive order Newsom signed in 2020, California plans to mandate by 2045 that all operations of medium- and heavy-duty vehicles be zero emission where feasible, shifting away from diesel-powered trucks.

The California Air Resources Board (CARB) had sought waivers from the Clean Air Act to set heavy-duty vehicle and engine emission standards. California has been joined by Massachusetts, New Jersey, New York, Oregon, Washington and Vermont in adopting the rules.

CARB has noted heavy-duty vehicles greater than 14,000 pounds comprised 3 percent of vehicles on California roads, but account for more than 50 percent of nitrogen oxides and fine particle diesel pollution.

The Union of Concerned Scientists said the waivers are “a vital step to building a cleaner transportation system” and said heavy-duty truck emissions disproportionately impact “marginalized communities that are more likely to be exposed to major highways and trucking routes.”

American Trucking Associations CEO Chris Spear criticized the Biden administration decision, saying “by allowing the state to proceed with these technologically infeasible rules on unworkable and unrealistic timelines, the EPA is sowing the ground for a future supply chain crisis.”

The EPA said it is not yet approving California’s request to set new regulations on pollutant exhaust emission standards for nitrogen oxide (NOx) and particulate matter for 2024 and future medium- and heavy-duty engines and vehicles.

Separately, California in August moved to require all new light-duty cars and trucks sold in the state by 2035 to be either electric or plug-in electric hybrids. California needs an EPA waiver for that regulation.

In December, the EPA finalized new emissions standards to drastically cut smog- and soot-forming emissions from heavy-duty trucks.

Transportation is the largest source of U.S. greenhouse gas emissions, making up 29 percent of emissions, and heavy-duty vehicles are the second-largest contributor, at 23 percent.