Local
Stagnant air puts parts of Cook and DuPage counties in elevated pollution category
AirNow readings early Friday showed air quality at “unhealthy for sensitive groups” in parts of Cook County and into DuPage County, including Chicago Heights, Elmhurst and Tinley Park. Light winds and stagnant air contributed as a dense fog advisory covered parts of the region.
Parts of the Chicago area were under elevated air pollution readings early Friday, Oct. 23, with sections of Cook County and DuPage County rated “unhealthy for sensitive groups,” according to AirNow data recorded at 6 a.m.
The affected areas included Tinley Park, Elmhurst, Downers Grove, York, Oak Lawn, Frankfort and Chicago Heights. The rating is level three on AirNow’s six-level scale. Other areas were rated “moderate,” level two.
The conditions were not driven by ozone, said meteorologist Iisha Scott. Instead, light winds allowed pollution to accumulate near the ground. Fog also contributed to the conditions, Scott said.
The National Weather Service describes stagnant air as a buildup of pollution in the atmosphere. When the same air mass lingers, light winds may not disperse smoke, dust, gases and other pollution, the agency says.
A dense fog advisory was in effect until 9 a.m. Friday for Illinois’ Lake County and Kenosha County, Wisconsin. Visibility could fall to one-quarter mile or less, with the worst conditions expected in northeastern parts of Lake County and near the Wisconsin state line. The Weather Service warned that visibility could change quickly.
Scott said moderate air quality was expected to continue through the weekend and urged people sensitive to pollutants to take note. The region’s weekend forecast called for sunny, mild conditions, with temperatures reaching the low 70s away from the lake.