California's pollution cops crack down on big rigs. That might start a fight with Trump

California is already wrestling the Trump administration over the levels of air pollution spewed by cars. Now the state is set to tangle with the White House over pollution from big rigs.

The state's powerful air pollution agency, the California Air Resources Board, voted earlier this month to impose a broad set of regulations to reduce greenhouse gases, nitrogen oxide and other pollutants emitted by trucks and tractor-trailers over the next nine years.

California's new regulations, designed to combat climate change, smog and other problems, are largely in sync with rules established by the U.S. Environmental Protection Agency during the Obama administration. The state is forging ahead with Obama-era regulations that limit pollution caused by trailers and retrofitted trucks known as gliders. But the Trump administration is actively considering repealing those rules.

Gliders in particular are highly controversial. These are vehicles fashioned out of new exteriors but driven by older engines and transmissions, and the EPA's plan to rescind those regulations at the national level has kicked up a storm. The EPA has been relying largely on university research funded by a Tennessee manufacturer of gliders -- research that was just disavowed by the university itself.

California's air agency, known as CARB, voted to move ahead with the rules governing gliders and trailers in spite of the Trump administration's moves. State officials said the vehicles represent major pollution sources and a threat to public health. CARB has hinted it might sue the Trump administration if it rescinds the regulations.

"With the Trump administration moving to roll back some of those standards, it's important for California to step in and assert our continuing leadership role," said Bill Magavern of the Coalition for Clean Air, a Sacramento environmental organization.

But can California simply defy the Trump administration?

Legal experts said it's unclear if California has the authority to set its own rules; generally speaking the state needs permission from Washington if it wants to set air-pollution regulations that are stricter than the feds. Sean Hecht, a UCLA environmental law expert, said California might have to go to court to preserve its rule-making authority.

"You can see the frustration California officials have in trying to address this," Hecht said. "California would be at a lot of risk of having to deal with trucks that don't comply with California law."

For its part, California indicated that it's prepared for a fight if the EPA rescinds the Obama rules on gliders and trailers.

"CARB anticipates fully assessing its available options after U.S. EPA finalizes any proposed amendments or repeal of the existing trailer or glider provisions," said agency spokeswoman Karen Caesar in an email.

Much of the trucking industry supports California's approach, even though the tougher rules will make it more expensive to operate. Trucking companies are under pressure from retailers and other clients to go green. Having dark smoke belching from their vehicles "gives the industry a black eye," said Bob Ramorino, president of Roadstar Trucking in Hayward and a board member of the California Trucking Association.

CARB officials said truckers have another incentive to embrace California's rules: Reductions in greenhouse gas emissions go hand-in-hand with improved fuel efficiency. California projects that the rules will gradually improve trucks' average fuel economy from 6 mpg to 9 mpg, eventually saving them money.

"They feel like it's important to improve efficiency and reduce greenhouse gases," said CARB board member Daniel Sperling, a transportation professor at UC Davis. "This is, in their minds, a fairly reasonable performance target."

Above all, though, the industry is worried about a potential rift between California and the feds. Truckers don't want to have to play by two sets of rules -- one for California and one for every other state. "We would like one unified national standard," said Chris Shimoda, the head of regulatory affairs for the California association.

With hundreds of thousands of trucks on California's roads, there's a lot at stake. The transportation sector accounts for about 40 percent of all the greenhouse gases emitted in California, and trucks generate one-fifth of the transportation total, according to CARB data (Cars are the largest source of transportation greenhouse gases, at 60 percent). The agency says its rules will remove millions of tons of carbon dioxide, the main greenhouse gas, from the atmosphere over the next three decades.

California's disagreements with the White House over air pollution began soon after Donald Trump became president. Last March Trump, at the urging of automakers, announced that the government was rethinking Obama-era rules that would reduce greenhouse-gas emissions from cars and light trucks, starting with the 2022 model years. A week later CARB formally renewed its commitment to impose the Obama rules. The EPA isn't expected to make a final decision on the car regulations until April 1.

The dispute over the truck rules began last August. EPA director Scott Pruitt announced that the federal agency was rethinking the standards governing gliders and trailers. Pruitt vowed to incorporate "the latest technical data" in the reviews.

Pruitt acknowledged that he had been hearing complaints from industry. Trailer manufacturers were already suing the federal government to block the rules, arguing that trailers can't be regulated for air pollution because they don't actually pollute. "They emit nothing, and they lack engines," the manufacturers said in their lawsuit.

California officials said the lack of an engine is irrelevant. The standards adopted by CARB require trailer manufacturers to streamline their aerodynamic design in order to reduce drag and improve fuel mileage.

As for the gliders, CARB's deputy executive officer, Steve Cliff, went to Washington in December to protest the potential rollback of the regulations. He said gliders are heavy emitters of greenhouse gases as well as soot and nitrogen oxide, the key component in the formation of smog.

"Gliders are so much hither emitting than modern trucks that even if only a small number of them operate in California, California's overall air quality progress will be impeded," he told the EPA in prepared testimony. "It is CARB's position that a repeal of the glider (rules) would frankly be illegal."

Gliders have become a growth industry in recent years because they're cheap. It's about 20 percent to 30 percent cheaper to buy an old engine and a "glider kit" than to buy a new truck from scratch. CARB believes at least 862 gliders are operating in California, "with approximately 97 percent of them equipped with pre-2007 engines," Caesar said.

CARB says gliders emit 40 times as much nitrogen oxide as modern trucks. Soot emissions are as many as 450 times higher. That alone gives California justification to crack down on those vehicles, state officials say.

"It seems like such a no-brainer that it didn't require a lot of thought," said Sperling, the CARB board member. "They were really abusing the rules."

The furor over the glider industry has intensified in the past week amid revelations that the EPA has been relying largely on a university study, funded by the nation's largest manufacturer of glider kits, Fitzgerald Glider Kits of Byrdstown, Tenn., in its review of the regulations. On Monday the president of Tennessee Technological University urged the EPA to disregard the study. The study said emissions from glider trucks are no worse than brand-new vehicles with state-of-the-art anti-pollution technology.

"Knowledgeable experts within the University have questioned the methodology and accuracy of the report," Tennessee Tech president Philip Oldham said in the letter to EPA Administrator Scott Pruitt.

The EPA, however, is now insisting it isn't basing its review on the Tennessee Tech study - even though it cited the research in an official rule-making document it released last November. In a statement Wednesday quoted by the New York Times, the EPA said it was revisiting the glider rules because its lawyers had determined the agency really doesn't have the authority to regulate the vehicles.

"EPA did not rely upon the study or even quote directly from it," the agency said.