Aircraft Engine Emissions

Engine Types and Fuels

Thrust for forward propulsion and to develop lift in airplanes is provided by a range of engine systems designed around one of two main types: piston-driven propeller models, and reactive or jet engines. “Avgas” is the term used to refer to the aviation fuel used in piston engines. Jet engines burn jet fuel, a kerosene-based, low-volatility formula similar to diesel. Avgas—in contrast to automotive gasoline, where legislation reduced and ultimately removed lead—still includes lead in most formulations, specifically tetraethyl-lead, which has proven toxic qualities.

Jet fuels incorporate a vast array of additives that provide a range of important performance-enhancing and protective functions; but each of these may be suspect in terms of carcinogenic or other toxic outcomes.

Makeup of Emissions

With its lead content (used to increase octane levels and support better performance), avgas has been shown in various studies to be a factor in increased blood-lead levels in children residing near general aviation airports where many small aircraft take off [Page 63]and land. There are some 20,000 such airports in the United States alone. The U.S. Environmental Protection Agency (EPA) has stated: “Emissions of lead from piston-engine aircraft using leaded avgas comprise approximately half of the national inventory of lead emitted to air.” The EPA has also noted as recently as 2010 that “serious health effects occur at much lower levels of lead in blood than previously identified” and that there is no known safe level of lead exposure.

Kerosene-based jet engine fuel, also called aviation turbine fuel, or ATF, embodies a group of fuel types that are chemically tuned to provide a range of performance standards for use in different atmospheric conditions and operational functions, as well as safety standards for storage, handling, and use. In recent decades, more adjustments to ATF have been tested and adopted with an eye to cutting air pollution and greenhouse gas emission. Synthetic fuel formulas, as well as biofuels, have been important in this regard. One example from among the key pollutants from ATF is benzopyrene, which is often found in smoke from other sources as well, such as cigarettes, forest fires, and petroleum combustion. This soot-carried chemical is absorbed through the skin and by inhalation; it is strongly linked to lung cancer and is highly suspect in many other cancers, as it has powerful mutagenic, or DNA-altering, qualities.

Both types of aircraft fuel emit hydrocarbon or greenhouse gases, in particular, carbon dioxide, nitrogen oxides, sulfur oxides, and water vapor. Besides atmospheric warming, these chemicals can also contribute to acid rain, ocean acidification, and health threats.

...