BOX 15-A
Transportation Air Emissions Data
National
data on air emissions are estimated by the U.S. Environmental Protection Agency
(EPA). EPA's National Emissions Inventory (NEI) is updated annually and covers
mobile, stationary, and area sources of pollution regulated under the Clean Air
Act. These pollutants include the so-called "criteria" and hazardous air
pollutants.1 Most criteria emissions have been
estimated since 1970, hazardous emissions only since 1996.
EPA's
mobile source category contains "onroad" (highway)
and "nonroad" (all other modes) emissions. However,
its nonroad category includes nontransportation sources such as farming and construction equipment, lawn and garden equipment,
and logging, industrial, and light commercial equipment. To more accurately
assess transportation air emissions, the Bureau of Transportation Statistics
removes the nontransportation components from EPA's
criteria mobile source emissions. It is this subset that is presented here as
transportation emissions.
1 For details on transportation's contribution to
hazardous air pollutants, see U.S. Department of Transportation, Bureau of
Transportation Statistics, Transportation Statistics Annual Report 2000, available at
http://www.bts.gov/, as of August 2005.
|
