Airports, Air Pollution, and Health

Small amounts of ambient air pollution... can have substantial effects on the incidence of local respiratory illness.

Airports are among the largest sources of air pollution in the United States. In fact, Los Angeles International Airport is the largest source of carbon monoxide (CO) in the state of California. Average airplane taxi time -- the amount of time that an airplane spends between the gate and runway -- increased by 23 percent from 1995 to 2007. This increase in average congestion, combined with an increased number of flights, translates to an aggregate increase of over one million airplane hours per year spent idling on runways, leading to significantly higher levels of local ambient air pollution.

In Airports, Air Pollution, and Contemporaneous Health (NBER Working Paper No. 17684), authors Wolfram Schlenker and Reed Walker show how runway traffic congestion from East Coast airports influences runway congestion on the West Coast, subsequently increasing pollution levels in areas surrounding California airports. They find that these East Coast driven changes in California pollution levels, which are arguably unrelated to local weather and other conditions in California, are associated with adverse health outcomes and hence to respiratory and heart related hospital admissions. These effects are larger in areas adjacent to and downwind from airports on a given day. Infants and the elderly are more sensitive to these pollution fluctuations, but even adults ages 20-64 are affected. Schlenker and Walker estimate that a single standard deviation increase in daily pollution levels is responsible for at least $1 million per day in hospitalization costs for the 6 million people living within 10 km of one of the 12 California airports in their study.

In examining the explanation for the observed pollution-health relationship, the authors find that CO, rather than other pollutants such as ozone or nitrogen oxides, is primarily responsible for the observed health effects. They find no evidence of forward displacement or delayed impacts of pollution, or that people in areas with larger pollution shocks are either less susceptible or less responsive to pollution. These findings suggest that relatively small amounts of ambient air pollution, far below current CO ambient air quality standards, can have substantial effects on the incidence of local respiratory illness.

-- Lester Picker