Health Impact Of Exposure To Contaminated Supply Air On Commercial Aircraft

Quick Reference Guide for use by and reference use 

                           For Health Care Providers:


Summary of exposure and substance: Outside air is bled off the engines/auxiliary power unit and supplied to the cabin/ flight deck on commercial aircraft. Under certain failure conditions, toxins such as pyrolyzed (burned at high temperatures)  engine oils and hydraulic fluids may leak into the aircraft cabin and flight deck air supply systems. Airline workers may develop acute and/or chronic health effects and seek attention from health care providers. This quick guide focuses on oil exposures. The complete reference guide is available at

Exposures: These are often called "Fume Events".  The "bleed air" is not filtered and contaminant levels are not monitored. Airborne toxins include a complex mixture of oil-based compounds, irritant gases, and ultra-fine particles. Exposures of particular concern include tricresylphosphates (TCPs) and N-phenyl-L-naphthylamine (PAN), and carbon monoxide (CO). The primary exposure pathway is inhalation. Some crewmembers describe low-level chronic exposures to fumes (e.g., routine and transient fumes on engine start up); others describe acute, visible fume events, which may result in a flight diversion or cancellation. Other exposures in the cabin/flight deck include ozone gas, insecticides, de-icing fluid, exhaust and fuel fumes, and cleaning products. Also, the cabin altitude is typically 6,000-8,000 feet inflight, with a corresponding reduction in the partial pressure of oxygen.

Documentation: Crewmembers submit written reports of smoke, fumes and/or odor to their airline. Aircraft mechanical records and pilot log book entries sometimes document air supply contamination. Health care providers can request Material Safety Data Sheets for the particular oil/hydraulic fluid. Healthcare providers or the exposed injured person should ask for the date, flight number, aircraft number, aircraft type, phase of flight when the problem was noted, whether there was odor or visible smoke/fumes, duration, whether the aircraft was sprayed with insecticides, the last maintenance record especially involving the oil seals and any supplementary documentation from the airline/maintenance regarding cause. Obtain past medical history, occupational history, and family/social health history.

Health Effects: The most common symptoms reported are acute respiratory, neurological, systemic, and/or psychiatric symptoms. These typically occur within minutes to a few hours following the contaminated bleed air event or exposure. Symptoms vary depending on the duration and magnitude of exposure, plus individual factors. Chronic and sometimes delayed neurological, psychiatric, resperatory, systemic, and dermal symptoms have been reported.  Toxic encephalopathy is the primary concern. 

Suggested Case Definition: If there is either a documented exposure to bleed air contaminants or a history of flying on aircraft type(s) documented to have an increased risk of air supply contamination events, and Initial symptoms occur within 48 hours following exposure, a medical professional should look for  acute and/or persistent respiratory, neurological, systemic, or psychiatric symptoms.  Toxic exposure and toxic encephalopathy due to exposure to TOCP in the cabin has been mistaken for panic disorder or other non related psychiatric conditions.  Note that crewmembers with routine, low-level exposures may also develop chronic symptoms but may not have documented acute, individual exposure events. Symptoms may start many months or years prior to examination by the HCP. Attempt to identify the exposure and make a precise diagnosis (e.g., avoid generic terminology such as "inhalation exposure") based on a combination of symptoms and objective evidence of health effects (physical examination findings and/or medical tests).  Familiarize yourself with potential symptoms such  as those referenced on this website under "experiences" and "my story".  Please take the time to consider exposure to toxic cabin air.  Pet scans and MRI's can be of value in diagnosing and evaluating exposure and effects of toxic cabin air.