Minnesota and other states are weighing their options as the U.S. Environmental Protection Agency plans to weaken vehicle emission standards.
The efficiency rules, known as Corporate Average Fuel Economy or CAFE, were created during the Obama administration. President Trump's EPA says they're a burden on American automakers and would make cars and trucks more expensive.
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But they could also put a significant dent in future greenhouse gas emissions.
"These vehicle emission standards are a broad tool that help reduce air pollution from vehicles. Vehicles are the No. 1 source of air pollution in Minnesota," Minnesota Pollution Control Agency Commissioner John Linc Stine said.
Stine and MnDOT Commissioner Charles Zelle sent a letter to EPA Administrator Scott Pruitt last week urging the agency to reconsider.
The vehicle standards for cars and light trucks are set to go into effect in 2022.
Stine said there's no evidence showing a need to weaken standards.
"The letter is intended to communicate our strong opinion that they should remain in place, that the automotive industry was planning on them being in place and that they're beneficial to health and the environment," he said.
States and other groups are setting up for a legal fight if the EPA ends up repealing the emissions standards.