While Ohio’s air has been getting cleaner, health advocates fear that progress could be erased as the Trump administration works to roll back pollution regulations.

On Wednesday, the American Lung Association released its “State of the Air” report for the 20th year, which chronicles air quality by examining high ozone days in 220 metro areas.

“We’re very concerned about that," said Janice Nolen, national assistant vice president for policy for the American Lung Association, who authored the report. "This report covers the three warmest years in history and what we’re seeing are areas that had done better traditionally are now worse."

More than 134 million Americans live in counties that received an "F" grade for ozone pollution, according to the report. That's a 4 percent increase compared to last year with nearly 129 million Americans living in high ozone pollution areas.

The air quality in Franklin County has improved since the 1990s but has never received a passing grade in the report. This year, the county received an “F” for high ozone days.

Contrast that to Delaware County, which received a “B” and Licking County which received a “C.”

Other Ohio counties that received F grades for high ozone days include Ashtabula, Butler, Clark, Clermont, Clinton, Cuyahoga, Geauga, Hamilton, Lake, Stark and Warren.

The Columbus metro area, which includes Delaware, Fairfield, Franklin and Licking counties, ranked 45th out of 220 U.S. metro areas for ozone pollution.

The 2019 study averages the three previous years with complete data, meaning 2015 to 2017, and then assigns values to each day in which the county hits an orange level or above on the air-quality index. An orange air quality alert means the air is dangerous for sensitive groups, such as those with asthma or the elderly. A red alert indicates it is becoming dangerous for everyone.

For example, Franklin County had 5.3 unhealthy ozone days on average during that period, the report found, which was one day less compared to the 2018 report. In the late 1990s, Franklin County had 49.3 unhealthy ozone days on average.

What improved the air quality?

“A lot of reasons and the Clean Air Act is behind them all," Nolen said, citing reduced emissions from cars and trucks, vehicles running on cleaner fuels, and cleaner power plant emissions. The latter, she said, has "been a big contributor to the reduction in pollution in the Midwest and in Ohio particularly because a lot of coal-fired power plants — we’ve cleaned up a lot of emissions from those in the last 20 years.”

Ozone pollution is produced from heated nitrogen oxides and organic volatile compounds. The sources for ozone include cars, trucks, buses and power plants. The pollution season for ozone runs from April to October. Conditions are worse on hot, sunny days as the pollution cooks in the atmosphere.

That can make it harder to breathe for those with asthma or other lung conditions.

The Trump administration continues to roll back environmental regulations, including repealing the Clean Power Plan and proposing the Affordable Clean Energy rule, which would have states develop their own plans to address emissions from coal-fired plants. States could potentially opt to scale back regulations or step up to fill that regulatory void. Ohio Environmental Protection Agency officials aren't saying how the state would handle the rule change.

"We will not know what will be in our state plan until we can see the final rule that U.S. EPA adopts and the data that the federal plan will require of affected facilities. Then we will create our state plan accordingly," said James Lee, an Ohio EPA spokesman.

Last year, the Columbus metro area was given a deadline of 2021 by the U.S. Environmental Protection Agency to come into compliance with Clean Air Act standards and was labeled “marginal non-attainment” — along with the Cleveland and Cincinnati metro areas — when it comes to failing ozone pollution standards.

On Tuesday, Ohio EPA filed a 54-page request to redesignate the Columbus metro area as achieving attainment.

A letter from Ohio EPA Director Laurie Stevenson cited monitoring of existing air quality data and emission projections as indications "that current controls, existing state rules, existing federal rules ...will be more than sufficient to maintain the (National Ambient Air Quality Standards) indefinitely into the future."

bburger@dispatch.com

@ByBethBurger