CHICAGO (WLS) — An air quality alert has been extended for part of the Chicago area through Thursday.

McHenry, Lake, Kane, DuPage, Kendall, Grundy, Cook, and Will counties in Illinois, as well as parts of southern Wisconsin, are under an alert until midnight on Friday.

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The Illinois Environmental Protection Agency previously issued an Air Pollution Action Day for Wednesday for the Chicago area.

Lake, Porter, Newton and Jasper counties in Indiana are also under alert all day Tuesday.

The alert was also issued because of unhealthy ozone levels in addition to smoke particles.

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The Chicago area has been under air quality alerts for most of last week, due to smoke from Canadian wildfires.

At one point last week, Chicago had the worst air quality in the world.

Health professionals point out that the poor air quality is particularly concerning for active kids and adults who have respiratory issues. It is advised that those affected should move indoors and seek medical help if needed.

Experts recommend using an N95 mask when outdoors, and ensuring that home air filters are updated to maximize the effectiveness of air conditioning systems.

The video in the player above is from an earlier report.

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