National Ambient Air Pollutant Concentrations by Type of Pollutant: 1990 and 2006
Overall, air quality has improved somewhat over the last 15 years. Other than Ozone levels, all major pollutants fall significantly below national air quality standards.
| Pollutant | Measurment Unit | Air quality standard | 1990 | 2006 |
|---|---|---|---|---|
| Carbon monoxide | ppm | 9 | 6.0 | 2.3 |
| Ozone | ppm | 0.075 | 0.085 | 0.077 |
| Sulfur dioxide | ppm | 0.03 | 0.0081 | 0.0038 |
| Particulates (PM-10) | µg/m3 | 150 | 79.1 | 55.3 |
| Fine particulates (PM-2.5) | µg/m3 | 15 | (NA) | 11.6 |
| Nitrogen dioxide | ppm | 0.053 | 0.020 | 0.014 |
| Lead | µg/m3 | 1.5 | 0.13 | 0.06 |
(Source)
A Few Random Facts:
In 1998 there were 44 counties in the United States that had at least ten days where the Air Quality Index was categorized as Unhealthy. In 2007 there were 10.
In 1998 there were 11 counties in the United States (including San Franciso) that had 365 days where the Air Quality Index was categorized as Good. In 2007 there were 5.
In 1998 there were 84 counties in the United States that had 350 days where the Air Quality Index was categorized as Good. In 2007 there were 62.