WASHINGTON — The political war between California and the Trump administration escalated Monday with a letter from Andrew Wheeler, the head of the Environmental Protection Agency, warning that Washington would withhold federal highway funds from the state if it did not rapidly address a decades-long backlog of state-level pollution control plans.
The letter is the latest parry between President Trump and the liberal West Coast state that he appears to relish antagonizing. California’s recent actions on clean air and climate change policy have blindsided and enraged him, according to two people familiar with the matter.
While California has angered Mr. Trump with its efforts to adhere to stricter state standards on climate change pollution from vehicles even as Mr. Trump has sought to roll back such standards nationally, Mr. Wheeler’s new letter to the state offers a twist on the narrative.
It states that California “has the worst air quality in the United States,” including 82 areas within the state with air quality that does not meet federal law. It says that by law, the state is required to submit plans for reducing that pollution, but that California has a backlog of about 130 incomplete or inactive plans, “many dating back decades.”
The letter notes that California has more than 34 million people living in areas that do not meet federal air pollution standards for pollutants like soot and smog — “more than twice as many people as any other state in the country.”
Mr. Wheeler says in the letter that he is calling attention to California’s backlog as part of a broader effort to “dramatically reduce” such backlogs nationally.
He says that California’s failure to address the backlogged plans may result in penalties such as the withholding of federal highway funds, or the implementation of federal plans.
The letter requests a response from the state by Oct. 10.
California’s governor, Gavin Newsom, called the E.P.A.’s administrator pure politics.
“The White House has no interest in helping California comply with the Clean Air Act to improve the health and well-being of Californians,” he said in a statement Tuesday. “This letter is a threat of pure retaliation. While the White House tries to bully us and concoct new ways to make our air dirtier, California is defending our state’s clean air laws from President Trump’s attacks. We won’t go back to the days when our air was the color of mud. We won’t relive entire summers when spending time outside amounted to a public health risk. We won’t be intimidated by this brazen political stunt.”
The E.P.A. letter, made public on Monday but dated Sept. 24, was first reported by The Sacramento Bee. California officials said Monday night that they had only just received it, and they declined to respond until they had time to review it. A spokesman for the White House referred questions to the E.P.A., and a spokesman for the agency did not immediately respond to an emailed request for comment.
The letter follows Mr. Trump’s announcement last week that his administration would revoke California’s legal authority to set its own stringent state-level regulations on planet-warming pollution from vehicle tailpipes. On Friday, California and more than 20 other states retaliated by filing a sweeping lawsuit expected to be resolved only before the Supreme Court, accusing Mr. Trump of trampling on both states’ rights and on major efforts to fight climate change.
In fact, one of the key legal arguments made by the California lawsuit last week is that those tailpipe standards are required for the state to control emissions of the other pollutants, like soot and smog, at levels required to meet even federal standards.
“We need the extra clean cars to meet the standards set by the federal government,” Mary Nichols, California’s top clean air regulator, said at a news conference last week. “If this prevails, millions of people in California will breathe dirty air. There will be more pollution, more asthma, more hospitalizations, more premature deaths.”
Mr. Trump’s move to revoke California’s authority to set climate standards from vehicle pollution came after an announcement in July that four automakers that opposed Mr. Trump’s plan to roll back the national vehicle tailpipe pollution standard signed a deal with California to comply with tighter emissions standards if the broader rollback goes through.
Mr. Trump, who was surprised and angered by that announcement, according to two people familiar with the matter, has since sought to push policies that would punish California.
Earlier this month, the Justice Department opened an investigation into whether the automakers’ deal with California violates antitrust laws, although a person familiar with the investigation said that it was not started at the request of Mr. Trump or any administration officials.
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