The Trump administration is rescinding the Environmental Protection Agency's 2009 'endangerment finding' on greenhouse gases' environmental harm.
Approximately 120 million people were living in places that got unhealthy grades, according to the report.
The tailpipe standards would also help cut planet-warming pollution from cars in half. Transportation accounts for nearly 30% of all greenhouse gas emissions in the US, according to the EPA.
The EPA is considering emissions standards that could make up to two-thirds of new passenger vehicles sold in the US electric by 2032, according to a source familiar with the proposal.
The EPA memo comes a day after the White House released a national cybersecurity strategy that calls for software makers to be held liable when their products leave gaping holes for hackers to exploit.
"In no way, shape or form, will Norfolk Southern get off the hook for the mess that they created," EPA Administrator Michael Regan said