My mother said that when she was growing up in Birmingham, "The Pittsburgh of the South", in the 1930's she would walk out the front door and taste the air. My Grandparents lived in Eastlake which was 20 miles away from Bessemer where the iron and steel was smelted and forged.
I had a great aunt (long since joined the Great Majority) who used to tell how when she was growing up not far from the train tracks, the family always had to hang their laundry in the parlor to dry because all of the coal dust from the locomotives would get into anything hung outside.