Bureau of Transportation Statistics (BTS)
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Table 1
Mobile Source Air Toxics (MSATs): 1996

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MSAT Highway motor vehicles Nonroad vehicles and engines Total mobile sources
Short tons National total (percent) Short tons National total (percent) Short tons National total (percent)
Acetaldehyde 28,700 29.0 40,800 41.0 69,500 70.0
Acrolein 5,000 16.0 7,400 23.0 12,400 39.0
Arsenic compounds 0.25 0.06 2.01 0.51 2.26 0.57
Benzene 168,200 48.0 98,700 28.0 266,900 76.0
1,3-butadiene 23,500 42.0 9,900 18.0 33,400 60.0
Chromium compounds 14 1.2 35 3.0 49 4.2
Dioxin/furans 0.0001 0.2 NA   0.0001 0.2
Diesel exhaust (PM) data not yet available          
Ethylbenzene 80,800 47.0 62,200 37.0 143,000 84.0
Formaldehyde 83,000 24.0 864,000 25.0 169,400 49.0
Lead compounds 19 0.8 546 21.8 565 22.6
Manganese compounds 5.80 0.2 35.50 1.3 41.30 1.5
Mercury compounds 0.20 0.1 6.60 4.1 6.80 4.2
MTBE 65,100 47.0 53,900 39.0 119,000 86.0
n-Hexane 63,300 26.0 43,600 18.0 106,600 44.0
Naphthalene data not yet available          
Nickel compounds 10.70 0.9 92.80 7.6 103.50 8.5
POM (sum of 7 PAHs) 42 4.0 19.30 2.0 61.30 6.0
Styrene 16,300 33.0 3,500 7.0 19,800 40.0
Toluene 549,900 51.0 252,200 23.0 802,100 74.0
Xylene 311,000 43.0 258,400 36.0 569,400 79.0
Totals 1,394,892   1,695,337   2,312,329  

KEY: MTBE = methy-tertiary-butyl-ether; NA = not applicable; PAHs = polycyclic aromatic hydrocarbons; PM = particulate matter; POM = polycyclic organic matter.

NOTE: EPA estimates these data based on engine type. Thus, highway motor vehicles includes both gasoline- and diesel-powered vehicles such as light duty vehicles and trucks, heavy duty vehicles, and motorcycles. The nonroad vehicles and engines category data are estimated based on engine types normally used by aircraft, marine vessels, and locomotives. However, this category can also include engines for lawn, construction, and other equipment that the Bureau of Transportation Statistics does not consider to be transportation-related sources of nonroad emissions. Currently, it is not possible to subtract these data from the totals, as is done for criteria pollutants.

SOURCE: U.S. Environmental Protection Agency, National Vehicle and Fuels Emission Laboratory, “Control of Emissions of Hazardous Air Pollutants from Mobile Sources,” 65 Federal Register 48058, 2001.