The Windy City was enveloped in smoke Thursday as air pollution from over 800 Canadian wildfires wafted through the city and suburbs.The air contained hazardous levels of PM2.5, a particulate matter that can lodge in the lungs and cause adverse health effects, especially in immunocomprised people an d those with respiratory conditions.Some Chicagoans masked up while others spent a hazy morning swimming in Lake Michigan. Chicago Sun-Times photojournalists were on the ground to document the city grappling with the in-your-face pollution. The Chicago Theatre sign is obscured by smoke from the wildfires in Canada on Thursday.Pat Nabong/Sun-Times Pedestrians wearing masks cross a street in the Loop to protect themselves from wildfire smoke coming from Canada on Thursday.Pat Nabong/Sun-Times North Avenue Beach is obscured by smoke from the wildfires in Canada on Thursday. The poor air quality and high levels of airborne pollution led the city to close beaches along Lake Michigan.Anthony Vazquez/Sun-Times A swimmer in Lake Michigan near Montrose Point Bird Sanctuary as air quality drops Thursday.Pat Nabong/Sun-Times Navy Pier is covered in smoke from the wildfires in Canada on Thursday.Anthony Vazquez/Sun-Times A pedestrian crosses the street while covering her nose in the Loop as air quality drops Thursday.Pat Nabong/Sun-Times A commuter wearing a mask waits for a bus Thursday on West 26th Street in Little Village as air quality drops.Pat Nabong/Sun-Times The Chicago Board of Trade building in the Loop is obscured by smoke from wildfires in Canada on Thursday.Pat Nabong/Sun-Times Buildings on Michigan Avenue are obscured by smoke from wildfires in Canada on Thursday.Pat Nabong/Sun-Times Smoke from the wildfires in Canada obscure the Chicago skyline near Navy Pier on Thursday.Anthony Vazquez/Sun-Times A commuter wears a mask while waiting in Greater Grand Crossing on Thursday, a day of poor air conditions across the greater Chicago area.Candace Dane Chambers/Sun-Times Bronzeville is obscured by smoke from the wildfires in Canada on Thursday.Candace Dane Chambers/Sun-Times Michigan Avenue buildings obscured by smoke from wildfires in Canada on Thursday,Pat Nabong/Sun-Times Wildfire smoke covers the city as viewed from Lincoln Park on Thursday.Anthony Vazquez/Sun-Times Lincoln Park obscured by smoke from the wildfires in Canada on Thursday.Anthony Vazquez/Sun-Times A masked woman in Greater Grand Crossing on Thursday. That neighborhood, like others across Chicago, was enveloped by smoke from the wildfires in Canada.Candace Dane Chambers/Sun-Times Smoke in Grant Park from Canadian wildfires, causing air quality to drop across Chicago on Thursday.Pat Nabong/Sun-Times Nick Bradbury, who is visiting from Tennessee, wears a mask while walking in the Loop to protect himself from smoke from wildfires in Canada on Thursday.Pat Nabong/Sun-Times Smoke from the wildfires in Canada obscure the Chicago skyline Thursday.Anthony Vazquez/Sun-Times ...read more read less