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NAAQS levels of annual mean concentrations of respirable particulate matter (PM 10 ), 2000 to 2010. Measurements taken at air quality monitoring stations during 2000 to 2010. *NAAQS is National Ambient Air Quality Standards. Low/Moderate, High, and Critical refer to annual mean concentrations of less than 60, 60-90, and more than 90 PM10 micrograms/meter, respectively [23].
