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Particulate matter days
This indicator shows the annual number of days with maximum 24-hour average PM 2.5 concentration over the National Ambient Air Quality Standard. Air Quality Standard monitoring data were used for counties and days with monitors and hierarchical Bayesian data were used for any county or day without monitors. The spatial resolution of the HB grid cell used is 36 Km. The grid cell values were transferred to counties based on a population weighted approach. The indicators are available for counties/states in the conterminous US (Lower 48 + Washington DC). HB modeled data are not available for AK and HI. The state and national values are an average of county values weighted by population size.
Measurement Period: 2005
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