Airplanes are one of the chief sources of air pollution. Aircraft emissions are mostly carbon dioxide, water vapour and nitrogen oxides but also include other substances of concern: sulphur oxides, lead, carbon monoxide and volatile organic compounds (VOCs). Aircraft size and density of air traffic are increasing at major airports. So the problem is usually seen as one of amenity; there may be complaints of smell and there is inevitably concern over noise; less so pollution. However, at ground level copious emissions are produced during the time airplanes spend taxiing and idling on the runway before takeoff or after landing. And while airports are usually situated in relatively open country, and so aircraft fumes are not often considered to constitute a significant health hazard, nonetheless people who live near airports experience higher levels of respiratory and cardiac problems compared to the population at large.
Increasing use of supersonic aircraft flying at high altitudes may lead to increasing pollution of the upper air, where pollutants may accumulate since natural dispersion at such heights is not very effective. In the 1980's, jet aircraft were estimated to produce 2-3% of nitrogen oxide (NOx) emissions and, more importantly, constitute the only source of high-level NOx (which may be implicated in global warming and ozone depletion). Aircraft also produce high-level water vapour, which forms ice particles which reflect heat back to earth, adding to the greenhouse effect. Air transport constitutes 2-3% of carbon dioxide emissions produced by the use of fossil fuels, equivalent to about 1% of the annual greenhouse forcing effect of carbon dioxide emissions. As a result of increasingly stringent environmental requirements acted on by aircraft manufacturers, it is likely that NOx emissions from aircraft have been reduced by between 30% by the mid-1990s, and by a further 40 to 50% by 2010. Carbon monoxide emissions from aircraft had decreased by 70% in the decade 1982-1992.
The practice of jettsoning surplus air fuel after take-off is now largely disallowed, except in emergency.
Pollution levels within three square miles of an airport are typically 10 times higher than a bit farther out. A joint study by Columbia University and the University of California, reported in 2018, measured carbon monoxide (CO) levels at the 12 largest airports scattered throughout California and then tracked rates of heart and lung disease among the six million nearby residents. The incidence of asthma and respiratory diseases like chronic obstructive pulmonary disease (COPD) was, on average, 17 percent higher among those living within 6.2 miles of an airport compared to the population at large. Cardiac problems were nine percent more common among that same population, with the elderly and very young particularly at risk. The levels of carbon monoxide measured were within the legal limits for air quality safety established by the Environmental Protection Agency, although higher than locales elsewhere. The researchers believe that the established limits are far too liberal and suggest that the EPA would do well to re-evaluate just what levels of CO emissions are actually safe to inhale.
In 2014, researchers found that kids living near Logan Airport in Boston had quadruple the normal rates of asthma, while adults in the same radius had twice the incidence of COPD.
VOCs have been linked to neurological issues and kidney and liver damage, as well as to headaches and eye, nose, and throat irritation; VOC pollution at the levels typical near airports has been linked to cancer, lymphoma, myeloid leukemia, depression and more.