Ozone Levels Trigger Air Pollution Action Day for Chicago and Northwest Indiana

The National Weather Service has issued an air quality alert for the Chicago metropolitan area and Northwest Indiana, which remains in effect through Wednesday night. The Illinois Environmental Protection Agency declared an Air Pollution Action Day due to elevated ozone levels that are expected to persist through midnight Wednesday.

According to the Illinois EPA, harmful ozone levels develop when pollution interacts with sunlight to produce smog. This condition poses health risks to sensitive groups, including older adults, children, teenagers, and individuals with lung or heart diseases. Officials advise people in these categories to consider limiting prolonged outdoor activities, and the EPA recommends that individuals with asthma keep quick-relief medication nearby.

The alert coincides with temperatures forecast to reach the low- to mid-80s on Tuesday and Wednesday, which is warmer than the average for late May. National Weather Service meteorologist Mark Ratzer noted that dangerous air quality can occur even without visible haze. Ratzer explained that unlike wildfire smoke, which contains visible particles, ozone is an odorless, colorless, microscopic chemical that is invisible in the air.