HIGHWAY MOTOR VEHICLES AS SOURCES OF ATMOSPHERIC PARTICLES - PROJECTED TRENDS 1977 TO 2000

The characteristics of long-term national and mesoscale (citywide) exposures and short-term localized (congested freeway, city street canyon) exposures to mobile source particles were examined for 1977 and 1988, and estimated for 2000. Urban concentrations of mobile source particles ranged from about 2 to 10 mu g/m**3 in 1977; lower concentrations occurred in suburban areas and higher concentrations occurred in city central core areas. However, concentrations of nearly 80 mu g/m**3 could be experienced on congested freeways with low velocity, near parallel winds. Due primarily to decreases in the number of vehicles using leaded gasoline, the mobile source particulate matter burden is projected to be less in 1988 and 2000 than in 1977; the degree to which the burden will lessen depends upon the level of dieselization and the degree of regulation. The compositional characteristics of the particles will also change.