AIR POLLUTANT EMISSIONS FROM TRANSPORTATION
AIR POLLUTANT EMISSIONS FROM TRANSPORTATION
Index of Key Air Pollutant Emissions from Transportation (annual data)
Modal Shares of Key Air Pollutants from Transportation, 1998
Despite rapid growth in vehicle use over the past two decades, emissions of carbon monoxide (CO) and volatile organic compounds (VOC) have declined, and lead emissions have been almost eliminated, leading to improved air quality. There have been reductions in particulate emissions (PM) at the 10 micron classification. Only emissions of nitrogen oxides (NOX) remain above 1970 levels. (Ammonia and PM-2.5 were added to the list of regulated pollutants recently.)
With the exception of lead, onroad vehicles contribute the largest share of air pollutants among all modes.
| Thousands of Short Tons of Transportation Air Emissions | 1997 | 1998 |
|---|---|---|
| Carbon monoxide (CO) | 55,437 | 54,170 |
| Oxides of nitrogen (NOx) | 10,077 | 9,975 |
| Volatile organic compounds (VOC) | 6,513 | 6,510 |
| Particulate matter < 10 microns (PM-10) | 420 | 405 |
| Particulate matter < 2.5 microns (PM-2.5) | 336 | 323 |
| Ammonia | 250 | 260 |
| Lead | 0.5 | 0.5 |
SOURCE: U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards (OAQPS). 1998a. National Air Pollutant Emission Trends, Update: 1970-1997 (Research Triangle Park, NC: December 1998).