CHICAGO — An Air Pollution Action Day is in effect for Tuesday, July 15, across much of the Chicago metro area, as the Illinois Environmental Protection Agency flags deteriorating air quality conditions driven by lingering wildfire smoke from Canada.
Unhealthy air quality for sensitive groups
Tuesday’s alert comes after the Air Quality Index (AQI) climbed to 137 on Monday afternoon, a level considered unhealthy for sensitive groups. According to the EPA, an Air Pollution Action Day is triggered when AQI readings reach 101 or higher for two or more consecutive days. At this level, children, seniors, and individuals with respiratory or cardiovascular conditions are at increased risk of health complications.
The alert remains in effect through midnight Tuesday for McHenry, Lake (IL), Kane, DuPage, Cook, Kendall, Grundy, Will, Lake (IN), Porter, LaPorte, Newton, and Jasper Counties.
The health risks and what to know
The Illinois Department of Public Health (IDPH) warns that air pollution on days like today can aggravate conditions such as asthma or chronic bronchitis, and even cause breathing difficulties in otherwise healthy individuals during outdoor activity.
While surgical or cloth masks offer no protection against wildfire smoke, N95 or N100 respirators can help reduce exposure to fine particulate matter when worn properly. The smoke particles in question measure 2.5 micrometers or smaller—invisible to the naked eye and capable of penetrating deep into the lungs.
What’s causing the haze over Chicago
The thick haze hanging over Chicago is tied to 177 active wildfires currently burning in Saskatchewan and Manitoba. Over the weekend, an upper-level low pressure system passed through the Great Lakes, setting up a pattern that allowed smoke from those fires to drift into the region.
Behind that system, a high-pressure ridge built in, ushering in clear skies but also sinking air, which acts like a lid, trapping pollutants near the surface. These conditions are common during the summer months and can lead to prolonged episodes of poor air quality.
Improvement is on the way
A shift in wind direction is expected on Wednesday, with stronger movement from the northwest by Thursday, which should begin to clear out the smoke and improve air quality across northeastern Illinois. Until then, officials advise staying alert for changing conditions throughout the day.
