Despite evidence that dirty air still endangers millions of Americans with asthma and other respiratory diseases, the Trump administration on Monday declined to tighten national standards for lung-damaging smog.

The decision to retain an Obama-era regulation came less than a week after the Chicago area suffered its longest streak of bad air days in more than a decade.

Business groups lobbied the administration for months to keep in place the latest federal limit on smog concentrations — after saying just five years ago it would bankrupt the U.S. economy.

“Current scientific information continues to support the conclusion that the primary standard established in 2015 protects public health,” Andrew Wheeler, head of the U.S. Environmental Protection Agency, said during a brief conference call with reporters.

The announcement marked the second time this year that Wheeler, a former coal lobbyist, rejected pleas from public health experts to redouble the nation’s fight against air pollution.

In April, the Trump political appointee disregarded scientific advice to require more rigorous control of industrial soot emissions, which researchers have determined can trigger respiratory problems, cause heart disease and prompt early deaths.

Wheeler opted to leave current smog and soot standards unchanged after his predecessor, Scott Pruitt, fired the EPA’s independent scientific advisers and replaced them with a panel dominated by industry-backed researchers.

Though the new group concluded the existing smog standard should be retained, it included an attachment in a February letter to Wheeler acknowledging “legitimate questions about whether the current standard provides an adequate margin of safety for people with asthma.”

“I think this will be troubling to federal courts,” one of the fired advisers, H. Christopher Frey, said in an email.

Frey, a civil and environmental engineering professor at North Carolina State University, chaired a group that advised the Obama EPA before the agency adopted its latest smog standard in 2015.

Research since then shows more clearly how air pollution triggers asthma attacks, Frey said, suggesting that keeping the current standard in place violates the federal Clean Air Act.

“The law uses the term ‘protect public health,’ which is understood to err on the side of protection when there are uncertainties,” Frey said. “Administrator Wheeler has used uncertainty as an excuse to do nothing.”

Smog, also known as ground-level ozone, is created when the sun’s heat bakes a mixture of chemicals emitted mostly by car tailpipes, diesel engines and the smokestacks of coal-fired power plants.

Regulating sources of smog-forming pollution is supposed to be grounded in science. But politics often play a role.

President George W. Bush was told in 2007 that the strictest standard under consideration by the EPA would have reduced smog-related deaths by 75%. His administration favored a far less stringent limit, significantly reducing the number of counties required to adopt smog-fighting measures.

A year later, candidate Barack Obama vowed to update the Bush-era standard, then blocked the EPA’s efforts to follow through on that promise as the White House shifted its focus to President Obama’s 2012 reelection campaign.

Trump, meanwhile, has spent the past three years attempting to roll back regulations intended to improve air quality across the nation.

Nearly 214 million people nationwide and 10 million in Illinois live in counties where average smog levels exceed 60 parts per billion — the strictest standard EPA officials have considered, according to a Chicago Tribune analysis of federal monitoring data.

Tightening the standard from the current 70 ppb limit would require Chicago and other big cities to clamp down harder on polluters.

Dozens of smaller cities, mostly in the Midwest, Northeast and Southeast, would be forced to adopt smog-fighting measures for the first time. Many are election-year battlegrounds where the air is considered relatively clean, at least according to the EPA.

“The EPA is ensuring millions of people will repeatedly be told the air is healthy when the agency knows it’s not,” said Brian Urbaszewski, director of environmental health policy at the Chicago-based Respiratory Health Association. “It won’t be protecting at-risk groups like children living with asthma, needlessly causing families more trauma, emergency room visits and hospital stays.”

Like many other Trump-era regulatory decisions, the smog standard almost assuredly will end up in the courts. Even if judges determine the EPA failed to follow the law, it will take years to reach that point, effectively delaying new requirements for industry.

Original Article from Chicago Tribune