On good days, St. Louis’s Air Quality Index sits on the high end of green—polluted, but not dangerously so. During these days, the city’s air is often just about to slip from the green “good,” to the yellow “moderate.”. As summer intensifies, the year-round pollution caused by the coal industry, tobacco use, and radon gas starts to take its toll. Original version published at http://www.2014missouriexhibit.org/ and short-text version displayed at Material Monster's physical exhibit.