Figure 2 shows the distribution of national total emissions estimates by source category for specific pollutants in 2008. Electric utilities contribute about 70 percent of national SO2 emissions. Agricultural operations (other processes) contribute over 80 percent of national NH3 emissions. Almost 50 percent of the
Air Pollution
Figure 2. Distribution of national total emissions estimates by source category for specific pollutants, 2008.
national VOC emissions originate from solvent use (other processes) and highway vehicles. Highway vehicles and non-road mobile sources together contribute approximately 80 percent of national CO emissions. Pollutant levels differ across regions of the country and within local areas, depending on the size and type of sources present.