A new report by the American Lung Association gives the Big Island a failing grade for particle pollution in the air.
That's because one of the island's main sources of particle pollution is vog, or volcanic smog.
The association gave Hawaii County an F despite a decrease in the number of days with unhealthy particle pollution, from 23.5 days in the 2012 report to 12.5 days in this year's report.
The annual report released Wednesday grades counties nationwide for ozone and particle pollution levels.
Honolulu is the only county in the state that collected data on ozone levels. There were no days of unhealthy levels of ozone, or smog.
Maui County received healthy grades for particle pollution. According to the report, there were incomplete data available for Kauai County.