Photo Credit: Photo by Diego M. Radzinschi/ALM New York Attorney General Barbara Underwood, along with 19 other state attorneys general, promised on Thursday to sue the Trump administration over a proposed rollback of fuel efficiency standards enacted during the Obama administration. The attorneys general said in a joint statement that reversing the Obama-era regulation would be detrimental to the health of their residents and leave them paying more for gas. The U.S. Environmental Protection Agency announced a proposal on Thursday that would require automakers to manufacture vehicles with a fuel efficiency of about 37 miles per gallon on average between cars and light trucks after 2020. That's a significant decrease from the Obama-era rule , which required those vehicles to operate at 54.5 miles per gallon by model year 2025. Acting EPA Administrator Andrew Wheeler said the regulations were proposed to increase fuel efficiency standards from where they are now while lowering the future cost of cars for consumers. “Our proposal aims to strike the right regulatory balance based on the most recent information and create a 50-state solution that will enable more Americans to afford newer, safer vehicles that pollute less,” Wheeler said in a statement. “More realistic standards can save lives while continuing to improve the environment.” The agency said in its proposal that the new standards were created based on the most recent information, part of which is the current median household income. According to the EPA, new vehicle prices have risen faster than the median household income in the United States. The agency wants to freeze the fuel economy standards to make cars more affordable as the median income increases, according to the proposal. The EPA said it expects more consumers to purchase newer cars as a result of the proposed regulation because they will be less expensive than vehicles with higher fuel-efficiency standards. There are a few benefits to increased turnover, the agency said. More consumers will be driving newer, safer cars because they will be less expensive, the proposal said. The agency also argued that because those vehicles will be less expensive, more people will buy them and therefore reduce greenhouse gas emissions at about the same rate as the Obama-era regulation. The proposal is just that—a proposal. It does not change the rule yet, but the state attorneys general said they are preparing litigation if the proposal is finalized. “This decision upends decades of cooperative state and federal action to protect our residents,” a coalition statement said. “We are prepared to go to court to put the brakes on this reckless and illegal plan.” Among that cooperative action is California's Clean Air Act Pre-emption Waiver, which allows the state to set its own, stricter tailpipe emission limits. The EPA's proposal would eliminate that waiver and require that the federal agency's emissions standards apply uniformly to each state. Other states may adopt California's emission standards over the federal standards. At least 13 states, including New York, have adopted California's standards. Those states are home to 74 million people, according to Underwood's office. The EPA said automakers could expect lower production costs if their proposal is finalized, which could be passed on to consumers. “Eliminating California's regulation of fuel economy pursuant to congressional direction will provide benefits to the American public,” the EPA said in the proposal. “This regulatory mandate has required automakers to spend tens of billions of dollars to develop products that a significant majority of consumers have not adopted, and consequently to sell such products at a loss.” The attorneys general, in turn, said in their statement that consumers will bear the brunt of the cost from lower fuel efficiency standards because they will have to spend more to fill up at the pump. Lower standards would also contribute to climate change, they said, which is a threat to public health. “If adopted, the Environmental Protection Agency and National Highway Traffic Safety Administration's rollbacks will cost American drivers hundreds of billions of dollars,” the attorneys general said. “Freezing or weakening these standards puts the health of our children, seniors, and all communities at risk, and increases the rising costs of climate change for our states.” The attorneys general dispute the EPA's claim that the proposal would have a negligible impact on emissions compared to the Obama-era rule. They said lowering fuel efficiency standards would result in increased oil consumption in the United States by 2025, and would add several million additional metric tons of carbon pollution. Underwood was joined in the statement by attorneys general from Massachusetts, Connecticut, Delaware, Hawaii, Illinois, Iowa, Maine, Maryland, Minnesota, New Jersey, New Mexico, North Carolina, Oregon, Pennsylvania, Rhode Island, Vermont, Virginia, Washington, and Washington, D.C. A public comment period is open for 60 days following today's announcement, the EPA said. The EPA did not immediately respond to the lawsuit threat.