Air pollutants emitted from turbine engine aircraft may have adverse effects on man and his environment. Carbon monoxide, nitrogen oxides, various organic compounds, and particulate matter are the primary pollutants produced by jet engines. Carbon monoxide at low levels may cause impairment of both time interval discriminations and of visual acuity. Nitrogen dioxide has been associated with reduced ventilatory performance and an increase in acute respiratory illness. Some organic compounds, such as formaldehyde and acrolein, may cause eye irritation, and excess of particulate matter in the atmosphere has been associated with increased chronic respiratory disease. In addition to effects on human health, pollutants emitted from turbine engines may adversely affect plants, animals, soil, water, and man-made materials. Much more research is needed before effects on health and welfare can be specifically related to aircraft emissions.