CHARLESTON, W.Va. -- The American Lung Association, in its "State of the Air 2013" report, gives Charleston a failing grade even though the city received passing marks in 2012.
"It received a failing grade after its passing mark in 2012 because the air quality standard has since been made more protective of public health," according to a Tuesday release.
"Overall, 'State of the Air 2013' shows that the air quality in Charleston and nationwide continues the long-term trend to much healthier air."
The report lists Charleston and Kanawha County among "Cleanest U.S. Cities" and "Cleanest Counties." Short-term particle pollution levels in the Charleston area have decreased significantly from the 2012 report.
The decrease moved Charleston from the report's list of most polluted cities. It ranked 17th worst in the nation last year.
Kanawha County has improved its short-term particle pollution -- receiving a "C" in 2012 and averaging one unhealthy air day per year but receiving an "A" for the first time this year with zero days of unhealthy particle pollution.
However, the reports indicates that ozone levels in Kanawha County worsened. The county received a "D" in that category this year, down from a "C" in the 2012 report. The county had an additional three unhealthy high ozone days, for a total of eight during the 2009-2011 period.
Created by the reaction of sunlight on vehicle emissions, ozone is the most widespread air pollutant. When ozone is inhaled, it irritates the lungs and can cause wheezing, coughing, asthma attacks and premature death.