Minnesota Public Radio slideshow:
Bad air days
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This chart shows the air quality in the Twin Cities in 1997. The blue portion indicates that air quality was good 90 percent of the time in that year. (Chart by Jim Erkel, courtesy of gominnesota.org)

This chart shows the air quality in the Twin Cities in 1997. The blue portion indicates that air quality was good 90 percent of the time in that year.

(Chart by Jim Erkel, courtesy of gominnesota.org)
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