The administration billed the proposed rollback from Obama-era fuel efficiency standards as a way to help auto companies and lower vehicle prices for consumers, but critics said the plan would accelerate climate change and increase fuel prices.
More than a third of US auto buyers live in the 13 states plus Washington, DC, that have already adopted Clean Car standards requiring vehicles to have stronger emission controls.
So far, 19 attorneys general have joined California Attorney General Xavier Bacerra, who has vowed that the state would "use every legal tool at its disposal to defend today's national standards and reaffirm the facts and science behind them", according to a report from The Washington Post. The affordability argument also ignores thousands of dollars of saving in fuel costs for each driver over the life of a auto, opponents of the rollbacks said.
While the chief executives of auto companies previous year asked Trump to loosen the Obama-era rules, they have since asked him not to pull them as far back as he has sought to do in Thursday's proposal.
The decision, announced jointly by the U.S. Environmental Protection Agency and National Highway Traffic Safety Administration, had been expected for weeks by clean-air advocates, but turned out be worse than anticipated, according to environmentalists. It says keeping the Obama-era standards in place would increase the cost of an average vehicle by $2,340, prompting consumers to hold back in buying newer, safer vehicles and end up aging the nation's fleet of cars on the road. "Americans shouldn't be denied the ability to purchase a auto or truck that meets their needs". "Our nation's Clean Car Standards save consumers thousands of dollars, protect our families' health, and ensure that we continue tackling climate change, the most important global environmental issue of our time". "We need to speed up that progress, not slide backward".
The release of the administration's proposal was repeatedly delayed in recent weeks as officials debated how aggressively to push.
"More realistic standards will promote a healthy economy by bringing newer, safer, cleaner and more fuel-efficient vehicles to USA roads and we look forward to receiving input from the public", said Chao. Toyota Motor Corp would save $34 billion and Volkswagen AG $20 billion.
"We are going to remain committed to improving fuel economy, reducing emissions and working toward an all-electric future, but we believe it is in everybody's best interest to have one national set of requirement that comprehends the new technologies", she said.
The administration also contends that hiking USA oil consumption by 2 to 3 percent over forecast levels would have a minimal impact on the environment, boosting global average temperature by just "3/1000th of a degree Celsius by 2100".
California has had the authority under the half-century-old Clean Air Act to set its own mileage standards to combat its chronic smog problem.
The Trump administration proposal said California's zero emission vehicle rules, adopted by nine other states, are "technologically infeasible".
California Gov. Jerry Brown said his state "will fight this stupidity in every conceivable way possible".
Democrats hope to make any rollback of the emissions rules a key part of November's midterm elections, when they will try to regain control of one or both chambers of Congress.
"A key goal of this rule-making is to reduce the barriers to enabling Americans to purchase newer, safer, cleaner cars", they wrote.
Speaking to a Senate panel Wednesday, Wheeler, the acting head of the EPA, said he would like to find a way to avoid a legal showdown with California.
EPA Assistant Administrator Bill Wherum says the Department of Transportation and the EPA estimate the proposed rule could lead to 12,000 fewer fatalities over the lifetime of vehicles built through 2029.
In Pennsylvania, nearly 23 percent of greenhouse gases and 37 percent of nitrogen-oxide emissions come from the transportation sector.
"The administration's effort to roll back these standards is a denial of basic science and a denial of American automakers' engineering capabilities and ingenuity", said John DeCicco, an expert on transportation technology at the University of MI.