Key: NOx = oxides of nitrogen; PM-10 and PM-2.5 = airborne particulates of less than 10 microns or 2.5 microns, respectively; CO = carbon monoxide; VOC = volatile organic compounds.
Note: Transportation emissions include all onroad mobile sources and thefollowing nonroad mobile sources: recreational vehicles and boats, airportservice equipment, aircraft, commercial marine vessels, and railroads. Othernonroad sources, such as lawnmowers and farming equipment, are not included. Lead estimates include onroad mobile sources only.