to the EPA, two-thirds of CO emissions and nearly half then
ozone-forming emissions come from mobile sources, such as motor vehicles.
Typically, the older the car, the more pollution it emits. The EPA has
found that 30 percent of five-year-old cars emit far more than they were
designed to emit, contributing to air pollution more than the other 70
percent of vehicles of a similar age. Fifty-five percent of seven-year-old
cars are "gross emitters." Overall, 10 to 30 percent of the
vehicles on the road create the majority of the pollution from cars and
Source Contribution to Air Pollutant Inventories — 1995
Excludes natural sources, fugitive dust, and smoke from controlled burning
and forest fires. Transportation sources represent about 33 percent of
total carbon emissions.