intentional venting of fuel from the engine manifold after normal shutdown, and described prospective standards for virtually all pollutants; with some modifications, those standards would ultimately appear in regulations issued in 1983. Also in the early 1980s, ICAO developed similar standards and recommended practices to protect local air quality in the vicinity of airports. Since 1997, airport construction projects that require FAA approval or support have had to show that all emissions resulting from the project, both directly and indirectly, would be consistent with state implementation plans for meeting federal air quality standards. As a result, localities and regions with chronic air quality problems would especially benefit from the availability and use of technology that increases fuel efficiency and reduces aircraft emissions.

Current needs also include better understanding of the health concerns, if any, posed by aircraft emissions of hazardous air pollutants (Ozone Transport Committee, 2001 and Holzman, 1997). Very few data exist for characterizing aircraft exhaust with regard to hazardous air pollutants, many of which are mutagenic and carcinogenic, or for comparing the possible effects of aircraft exhaust with those of other potential sources of hazardous air pollutants, such as automobiles. Although hazardous air pollutants are present in aircraft emissions only in small concentrations, environmental challenges that cite these emissions may be hard to deflect without better data.

Atmospheric Research

Two decades of research have demonstrated the importance of laboratory studies, field observations, and numerical modeling for understanding the effects of aircraft emissions on global climate issues. The federal government continues to support several small research programs, such as NASA’s Atmospheric Effects of Aviation Project, but funding for this effort has been reduced from about $12 million to about $4 million per year. NASA has a stratospheric chemistry program, which studies some aspects of tropospheric chemistry that are important for understanding the stratosphere. NASA also has a tropospheric chemistry program, which is funded at about $4 million per year, but the focus is on the mid- and free troposphere, which encompass altitudes below the region of primary interest to commercial aviation. The Department of Energy’s Atmospheric Radiation Measurement Program studies the effects of aerosols on climate and has provided some information relevant to aviation, but it is not focused on aerosols of particular interest to aviation. The Atmospheric Chemistry Program of the National Science Foundation funds some basic studies of atmospheric and chemical processes that will help assess the effects of aviation.

Recommendation 3-1. Research on Global, Regional, and Local Emissions. NASA should continue to take the lead in supporting federal research to investigate the relationships among aircraft emissions (CO2, water vapor, NOx, SOx, aerosols, particulates, unburned hydrocarbons, and other hazardous air pollutants) in the stratosphere, troposphere, and near the ground, and the resulting changes in cirrus clouds, ozone, climate, and air quality (globally, regionally, and locally, as appropriate). Other agencies interested in aircraft or the environment should also support basic research related to these programmatic goals.

Recommendation 3-2. Eliminating Uncertainties. NASA should support additional research on the environmental effects of aviation to ensure that technology goals are appropriate and to validate that regulatory standards will effectively limit potential environmental and public health effects of aircraft emissions, while eliminating uncertainties that could lead to unnecessarily strict regulations.


IPCC (Intergovernmental Panel on Climate Change). 1999. Aviation and the Global Atmosphere. Cambridge, United Kingdom: Cambridge University Press. Pp. 210.

Holzman, David. 1997. Airports and the Environment. Environmental Health Perspectives 105(12):1300-1305. Available online at <>. March 11, 2001.

Lee, J., S. Lukachko, I. Waitz, and A. Schafer. 2001. Historical and future trends in aircraft performance, cost, and emissions. Annual Review of Energy and the Environment 26:167–200.

Ozone Transport Committee. 2001. Press release. OTC advocated air pollution reductions from airport and clean energy initiatives. Washington, D.C.: State Services Organization. Available online at <>. March 11, 2002.

Spicer, C., M. Holdren, T. Lyon, and R. Riggin. 1984. Composition and photochemical reactivity of turbine engine exhaust. Report ESL-TR-84-28. September. Tyndall Air Force Base, Florida.

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