The standards would "clean up our air, improve access to crucial air quality information, and protect those most at-risk—our children, our elderly, and people already suffering from lung diseases like asthma," McCarthy wrote in an editorial.
The proposal, which will apply not only to power plants but to cars and oil and gas facilities, is expected to face opposition from industry groups.
The tougher standards would be closer to the proposal drafted in 2011 by former EPA Administrator Lisa Jackson, which was withdrawn by President Barack Obama before its release because of cost concerns amid the nation's economic recovery.
Although Obama had directed the EPA to come up with a new proposal, the agency did not take action, prompting the American Lung Association and green groups Earthjustice, the Sierra Club, the Environmental Defense Fund and the Natural Resources Defense Council to sue and get a court-ordered deadline.
Read MoreHigh court to review EPA mercury limits
Health and environment groups say the new standards can lower the risk of early deaths, asthma and other respiratory illnesses from the pollutant.
"President Obama is not up for re-election. This should be a centerpiece of his environmental legacy," said Terry Maguire, the Sierra Club's Washington representative on smog pollution.