Measurement | Region | Annual Average, 2000–2002 | Annual Average, 2017–2019 | Percent Change | Number of Sites |
---|---|---|---|---|---|
Ambient Particulate Sulfate Concentration (µg/m³) | Mid-Atlantic | 4.8 | 1.1 | -77 | 13 |
Midwest | 4.3 | 1.2 | -72 | 16 | |
North Central | 1.3 | 0.7 | -46 | 2 | |
Northeast | 2.6 | 0.7 | -73 | 6 | |
Pacific | 0.82 | 0.54 | -34 | 5 | |
Rocky Mountain | 0.66 | 0.37 | -44 | 10 | |
South Central | 2.9 | 1.4 | -52 | 2 | |
Southeast | 4.2 | 1.1 | -74 | 12 | |
Ambient Sulfur Dioxide Concentration (µg/m³) | Mid-Atlantic | 8 | 1 | -88 | 13 |
Midwest | 6.8 | 0.8 | -88 | 16 | |
North Central | 1 | 0.5 | -50 | 2 | |
Northeast | 3.4 | 0.4 | -88 | 6 | |
Pacific | 0.37 | 0.3 | -19 | 5 | |
Rocky Mountain | 0.48 | 0.24 | -50 | 10 | |
South Central | 1.1 | 0.5 | -55 | 2 | |
Southeast | 3.4 | 0.4 | -88 | 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 | 0.9 | -2 | 2 | |
Northeast | 1.9 | 0.8 | -58 | 6 | |
Pacific | 1.8 | 1 | -44 | 5 | |
Rocky Mountain | 0.78 | 0.49 | -37 | 10 | |
South Central | 1.5 | 0.9 | -40 | 2 | |
Southeast | 2.3 | 1 | -57 | 12 |