Days with poor air quality have declined in Indiana despite ozone levels worsening in some Hoosier counties, according to an EPA report released this summer.

The U.S. Environmental Protection Agency report titled “Our Nation’s Air: Status and Trends Through 2018” shows that air pollutant concentrations have dropped since 1990 but some pollutants are continuing to pose serious problems.

“Emissions of all key air pollutants dropped between 2016 and 2018, and lead and sulfur dioxide concentrations dropped by double-digit percentages during the same period,” EPA Administrator Andrew Wheeler said in a statement last month.

“Emissions of all key air pollutants dropped between 2016 and 2018, and lead and sulfur dioxide concentrations dropped by double-digit percentages during the same period,” Wheeler said. “The U.S. is a global leader in clean air progress, and we’ve proven that we can protect the environment while growing our economy.”

The report shows that, from 1970 through 2018, the combined emissions of six key pollutants dropped by 74 percent, while the U.S. economy grew 275 percent.

Ground-level ozone, however, is increasing in some of Indiana’s industrial centers.

Gabriel Fillpelli, a professor at Indiana University Purdue University Indianapolis, told the Indiana Environmental Reporter that improvement in air quality can be linked to strict federal regulations, but regulatory rollbacks under the administration of President Donald Trump might result in poorer air quality.

Unhealthy days for air quality are decreasing overall, according to the report.

For example, Boone County has had 87 good days out of 87 days monitored in 2019, compared to 88 percent in all of 2018.

However, Elkhart County in northern Indiana has had 46 good days of 90, or about 51 percent, compared to 78 percent in 2018.