Definition: Annual average concentration of fine particulate matter in the air (e.g., in 2016, the average concentration of fine particulate matter in the air in Los Angeles County was 12.0 micrograms per cubic meter). State-level data are averaged from county-level data and should be treated with caution.
Data Source: California Environmental Protection Agency, Air Resource Board: (iADAM) Air Quality Data Statistics; U.S. Environmental Protection Agency, Particulate Matter (PM 2.5) Trends (Jul. 2017).
Footnote: "Fine particulate matter" (PM 2.5) is an air pollutant commonly found in diesel exhaust. PM 2.5 refers to particles with a diameter of less than 2.5 microns, or about 1/10,000 of an inch. The national annual PM 2.5 standard is 12 micrograms per cubic meter (µg/m³); concentrations at or above 12 µg/m³ are considered potentially harmful to health, especially for sensitive groups such as young children and those with asthma. Data are limited because (i) monitoring stations are usually in urban areas, and (ii) PM 2.5 samples are taken every three days or during times of the year when air pollution is very high. In addition, not all counties are monitored, and data are only provided for counties with monitors that pass completeness criteria. N/A means that data are not available.