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(Al Hartmann | The Salt Lake Tribune) Man walks through a ghostly scene at Sugarhouse Park Monday Dec. 11. Winters first... (Rick Egan | The Salt Lake Tribune) Sun and blue skies above the smog in the valley, Monday, December 11, 2017. (Rick Egan | The Salt Lake Tribune) Austin Lau, of San Francisco, watches the sunset above the fog in the valley from Ensi... (Rick Egan | The Salt Lake Tribune) A cyclist wears a mask as he pedals up State Street in Salt Lake City on a foggy day, M... (Al Hartmann | The Salt Lake Tribune) Man walks through a ghostly scene at Sugarhouse Park Monday Dec. 11. Winters first... (Al Hartmann | The Salt Lake Tribune) Traffic on State Street at 400 S. Monday Dec. 11. The state capitol at top is bare... (Al Hartmann | The Salt Lake Tribune) Utah State Capitol fades from a one-half block distance Monday Dec. 11. Winters fir... (Al Hartmann | The Salt Lake Tribune) Ghostly scene of the Eagle Gate at State Street and North Temple looking south Mond... (Al Hartmann | The Salt Lake Tribune) Downtown Salt Lake City sklyline is obscured looking north at State Street and 1000... (Al Hartmann | The Salt Lake Tribune) Traffic and pedestrians on State Street at 300 S. Monday Dec. 11. Winters first tem... (Al Hartmann | The Salt Lake Tribune) Ghostly scene of the Eagle Gate at State Street and North Temple looking south Mond... (Francisco Kjolseth | The Salt Lake Tribune) The Salt Lake Valley sees an increase in pollution as a winter inversion sett... (Rick Egan | The Salt Lake Tribune) Austin Lau, of San Francisco, watches the sunset above the fog in the valley from Ensi... (Rick Egan | The Salt Lake Tribune) Sun and blue skies above the smog in the valley, Monday, December 11, 2017.