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Wes Lowe uses so much Claritin that he started an Amazon subscription to avoid running out. His kids take two asthma medications. This reflects the normalcy of pollution in California’s San Joaquin Valley, where residents breathe some of the dirtiest air in the nation.

Lowe lives about 20 miles outside of Fresno, in the valley’s heart. More than a dozen highways, including Interstate 5, run through the region, carrying almost half of the state’s truck traffic. The sky is usually hazy, the air often deemed hazardous, and 1 in 6 children live with asthma. “You don’t realize how bad it is until you leave,” Lowe said. 

He understands California’s urgent need to clear the air by electrifying the trucking industry and pushing older, more polluting machinery off the road. That would reduce nitrogen oxide emissions by 17.1 tons annually by 2037, significantly reduce the amount of smog-forming ozone,and go a long way toward meeting federal air quality requirements. But as a partner at Kingsburg Truck Center, a dealership in Kingsburg, he’s seen how difficult this transition will be.

More than 15 percent of medium- and heavy-duty trucks sold statewide in 2023 were zero-emission. But the road has been bumpy amid growing uncertainty about California’s regulations and the Trump administration’s hostility toward electric vehicles, the clean energy transition, and the state’s climate policies.

The Golden State started its trucking transition in 2021 when it required manufacturers to produce an increasing number of zero-emission big rigs, known as Advanced Clean Trucks, or ACT. The following year, it mandated that private and public fleets buy only those machines by 2036, establishing what are called Advanced Clean Fleets, or ACF. 

The Environmental Protection Agency granted the waiver California needed to adopt ACT in 2023. But it had not acted on the exemption required to enforce ACF by the time President Donald Trump took office, prompting the state to rescind its application as a “strategic move” to keep “options on the table,” according to the California Air Resources Board.

The U.S. Senate threw the fate of the Advanced Clean Trucks rule into question when it revoked the state’s EPA waiver on May 22, stripping the state of its ability to mandate the electrification of private fleets, though it can still regulate public ones. Now the one bright side for the state’s efforts to clean up trucking is the Clean Trucks Partnership, under which several manufacturers have already agreed to produce zero-emission rigs regardless of any federal challenges.

All of this limits California’s........

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