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The Environmental Protection Agency (EPA) uses the Air Quality Index (AQI) for reporting daily air quality to help us understand what air quality means to our health. In northern Indiana, the EPA calculates the AQI for two pollutants regulated by the Clean Air Act: ground-level ozone and particulate matter, or PM2.5. The AQI is divided into color categories outlining how these pollutant levels can affect our health.

Current Conditions


Ground-Level Ozone

While ozone high in the atmosphere protects us from ultraviolet (UV) light, ground-level zone can be harmful to our health. Ground level ozone is formed when pollutants from vehicles and industry become heated up by sunlight. Higher levels of ground-level ozone typically occur during hot summer days and can irritate your eyes, nose, throat, and lungs causing coughing, sneezing, and aggravating asthma.


Particulate Matter

Particulate matter (PM2.5) is the term for a mixture of solid particles and moisture found in the air. PM2.5 is composed of particles such as dirt, smoke, and dust as well as particles unseen by the naked eye. Unlike ground level ozone, unhealthy levels of PM2.5 can occur year round but can cause similar health effects.

Both Ground-Level Ozone and PM2.5 can have negative health effects on people with respiratory diseases.


Air Quality Action Days

An Air Quality Action Day is declared by the Indiana Department of Environmental Management when the air quality data and weather conditions indicate the potential for hazardous levels of ground-level ozone or particulate matter levels at or greater than the Orange category (Unhealthy for Sensitive Groups). On these days, it is particularly important we take actions to reduce air pollution. Sign up to receive alerts for Air Quality Action Days on the Get Involved page.