Indianapolis officials issued an air quality advisory for Wednesday, July 15 in advance of an influx of air pollution that poses a health risk for vulnerable Hoosiers.
The alert marks the city’s second “Knozone Action Day” of 2026, an advisory that denotes hazardous levels of ozone and particulate matter.
Indiana’s Department of Environmental Management predicts ground-level ozone will reach levels unhealthy for sensitive groups in more than 40 counties across the state on Wednesday. The Indianapolis Office of Sustainability encourages vulnerable Hoosiers – children, older adults, people with asthma and outdoor laborers – to “remain indoors on Wednesday as much as possible.”
Ozone is a crucial ingredient in the medley of gases that form layers of the earth’s atmosphere. But when a series of sun-induced chemical reactions form dense pockets of ground-level ozone, it can become a human health threat, especially for individuals with asthma and respiratory illnesses.
In Indiana, most of the chemicals that form ozone can be traced back to car exhaust.
So to mitigate even more local ozone production on Wednesday, city officials recommend that Hoosiers avoid activities that might inadvertently pump the chemical precursors of ozone into Indianapolis air.
Experts recommend driving less; avoiding idling vehicles, including waiting in a drive-thru line; and postponing refuels and the use of gas-powered lawn equipment until temperatures dip in the evening.
To learn more about local air pollution and track developments, Hoosiers can sign up for text alerts at smogwatch.in.gov.
IndyStar’s environmental reporting is made possible through the generous support of the nonprofit Nina Mason Pulliam Charitable Trust.
Sophie Hartley is an IndyStar environment reporter. You can reach her at sophie.hartley@indystar.com or on X at @sophienhartley.
This article originally appeared on Indianapolis Star: City warns sensitive groups to stay indoors as air quality plummets
Reporting by Sophie Hartley, Indianapolis Star / Indianapolis Star
USA TODAY Network via Reuters Connect
By Sophie Hartley, Indianapolis Star | USA TODAY Network
