Measurement | Region | Annual Average, 2000–2002 | Annual Average, 2018–2020 | Percent Change | Number of Sites |
---|---|---|---|---|---|
Ambient Particulate Sulfate Concentration (µg/m³) | Mid-Atlantic | 4.8 | 1 | -79 | 13 |
Midwest | 4.3 | 1.1 | -74 | 16 | |
North Central | 1.3 | 0.6 | -54 | 2 | |
Northeast | 2.6 | 0.6 | -77 | 6 | |
Pacific | 0.8 | 0.5 | -37 | 5 | |
Rocky Mountain | 0.7 | 0.4 | -45 | 10 | |
South Central | 2.9 | 1.2 | -59 | 2 | |
Southeast | 4.2 | 1 | -76 | 12 | |
Ambient Sulfur Dioxide Concentration (µg/m³) | Mid-Atlantic | 8 | 1 | -88 | 13 |
Midwest | 6.8 | 0.6 | -91 | 16 | |
North Central | 1 | 0.4 | -60 | 2 | |
Northeast | 3.4 | 0.3 | -91 | 6 | |
Pacific | 0.4 | 0.3 | -32 | 5 | |
Rocky Mountain | 0.5 | 0.2 | -60 | 10 | |
South Central | 1.1 | 0.4 | -64 | 2 | |
Southeast | 3.4 | 0.3 | -91 | 12 | |
Ambient Total Nitrate Concentration (µg/m³) | Mid-Atlantic | 3 | 1.3 | -57 | 13 |
Midwest | 4.1 | 1.9 | -54 | 16 | |
North Central | 1.2 | 0.8 | -33 | 2 | |
Northeast | 1.9 | 0.8 | -58 | 6 | |
Pacific | 1.8 | 0.9 | -50 | 5 | |
Rocky Mountain | 0.8 | 0.5 | -38 | 10 | |
South Central | 1.5 | 0.9 | -40 | 2 | |
Southeast | 2.3 | 0.9 | -61 | 12 |