Smoke from Canadian wildfires is leading to very unhealthy air quality for much of Michigan, including all of Southeast Michigan. As of noon Thursday, Detroit has the fifth-worst air quality in the world.

Smoke from Canadian wildfires continues to plague the Upper Midwest and Great Lakes region, with multiple states under air quality alerts.

Wildfire smoke was helping raise ozone to hazardous levels. No alerts have been issued, but the air quality may approach “code orange” levels again late Thursday afternoon in parts of the region, as it appears that the ozone factory will still be operating while the Canadian wildfire smoke persists in the skies over Philly.