POTENTIAL ENVIRONMENTAL IMPACTS RELATED TO PROPOSED RUNWAY EXPANSION AT TORONTO INTERNATIONAL AIRPORT

Major emissions from aircraft jet engines include CO, CO2, NO(x), N2O, SO(x), and NMHC. Although all internal combustion engines produce the se emissions, jet engines cycle large amounts of air under high temper ature and pressure and hence produce significant quantities of the oxi des of nitrogen. These emissions affect the environment at local, regi onal, and global levels. Lester B. Pearson International Airport (LBPI A), situated in the northwest portion of metropolitan Toronto, is the busiest in Canada, acting as a hub with at least one-third of all sche duled air carrier operations in Canada itinerant through LBPIA. In ord er to relieve the congestion and delay in air traffic passing through LBPIA, Transport Canada has proposed the construction of three more ru nways. An alternative to runway expansion is to cap the existing facil ities and shift the short-haul traffic to alternate modes (train or au tomobile). Comparison of the three modes on a short-haul trip (Toronto -Montreal) shows that, on a grams per passenger kilometer basis, the L RC train produces the least amounts of CO, NMHC, N2O, and CO2, and the 1988 automobile the least amount of NO(x). Travel by DC10-30 aircraft always produces the highest quantity of each gas emitted. Of the emis sions from combustion processes in aircraft, none contribute more than 3% of the total emissions of that gas per year in Canada. Thus, any r eductions achieved through modal substitution will be less than 1% of the totals for each gas generated annually in Canada, which is not a s ignificant reduction in absolute terms. These reductions, however, rep resent a step toward the goals of emission reduction and, moreover, wo uld cause an improvement in the distribution of these gases in the env ironment.