Select Committee on Science and Technology Written Evidence

Memorandum by Association of Flight Attendants

  On behalf of our 55,000 members of the Association of Flight Attendants-CWA, AFL-CIO (AFA), employed at 20 airlines here in the United States, the Association is responding to the call for evidence for the "Air Travel and Health" follow up inquiry.

  Specifically, we wish to provide information that has emerged since your 2000 inquiry on the following two health concerns for occupants on commercial aircraft: (1) Exposure to insecticides applied in the cabin and flight deck, largely to comply with foreign quarantine regulations of 47 countries; and (2) Exposure to pyrolyzed engine oil and hydraulic fluid that sometimes contaminate the aircraft air supply.


  1.  Paragraph 4.28 of the 2000 Report notes that "some health authorities have queried the wisdom of aircraft disinsection", but still concludes that "insect control procedures are not a significant health issue" based on the apparent paucity of specific reports. The shortage of independently verified data must be noted in the context of the following facts:

    (i)  Neither passengers nor crewmembers are informed of residual spraying requirements so they do not know what they have been exposed to;

    (ii)  Passengers and crew are only informed of in-flight spraying requirements during the flight and are formally assured that the sprays are safe;

    (iii)  Airlines need not provide either passengers or crew information on the contents of either the residual or inflight sprays;

    (iv)  Passengers and crew can and do report symptoms to the airlines and to their physicians, but airlines need not publicise or share these reports and physicians need not report them to a centralised database to facilitate public health alerts; and

    (v)  There is no centralised reporting system that monitors this or any other crew or passenger health concern. For these five reasons, it seems premature—and even irresponsible—to dismiss the health concerns associated with disinsection practices without conducting a formal and independent investigation into the prevalence of reported symptoms on such flights.

  2.  In 2000-01, the California Department of Health Services investigated reports of acute illness reported to physicians by cabin crew and attributed to insecticide exposure on aircraft. Recently, a peer-reviewed paper was published on the results of that investigation (Sutton, 2007). Chronic health effects attributed to exposure to pyrethroid insecticides on aircraft have been reported widely to crewmembers' physicians and to our union, but funding to conduct a controlled, detailed investigation has not been available.

  3.  In early 2002, the United States (US) Department of Transportation (DOT) initiated an inter-agency task group with input from six other US Government agencies. Its goal is to develop and assess the efficacy and feasibility of a method of disinsection that could be achieved through mechanical means instead of chemical spraying. Since then, members of the inter-agency task group have tested the efficacy of simple air curtain technology to keep insects off aircraft (or on aircraft, depending on the direction of the airflow and according to the arrival or departure point in question), intended to protect a passenger boarding door equipped with a boarding bridge. This work has since been published in the peer-reviewed literature (Carlson, 2006). The group is now finalising testing on a custom net curtain solution intended to prevent insect entry through the aircraft service doors and through passenger boarding doors equipped with stairs. The group is also in talks with several interested countries.

  4.  Finally, since your 2000 inquiry, the International Civil Aviation Organization updated its Standard 2.24 to allow countries to adopt WHO-approved non-chemical methods of disinsection as an alternative to the typical chemical methods (ICAO, 2004). I encourage you to investigate these options further as part of your follow-up inquiry.

Pyrolyzed engine oils in the aircraft air supply ("contaminated bleed air")

  5.  There is little dispute that engine oil and hydraulic fluid can and does contaminate commercial aircraft air supply systems (Bobb, 2003; NRC, 2002; SAE, 1997), and that when this happens, flight safety can be compromised (AAIB, 2007; AAIB, 2004; CAA, 2001; CAA, 2000). However, despite the volume of documented crewmember symptoms that span decades of flying (Michaelis, 2003; Witkowski, 1999; Rayman, 1983; Montgomery, 1977), there is still a diversity of opinion on the severity of health impact because there are no air quality monitoring data collected during an event, no standardized medical test to definitively prove exposure, and no diagnostic tests to definitively prove the relationship between exposure and reported symptoms.

  6.  The frequency of air supply contamination events is also under dispute because of underreporting and the absence of a comprehensive source of reports. In March 2007, James Burin, Director of Technical Programs for the Flight Safety Foundation, estimated that five to ten aircraft per day are diverted around the world due to smoke-fire-fumes events, most of them smoke. This estimate was based on accident/incident research and discussions during international meetings with airlines and manufacturers, but he did not know how many of these were caused by oil or hydraulic fluid. Other sources of smoke/fumes include in-flight fires and electrical faults. Of course, any source of smoke or fumes in the flightdeck/cabin creates a potential health and safety hazard, but AFA has been especially concerned about such fumes that contain engine oils or hydraulic fluids because they contain some very toxic ingredients.

  7.  In 2002, the US National Research Council published the following frequency estimates for air supply contamination with engine oil or hydraulic fluid for a small selection of aircraft types, all presented as number of events per 1,000 flight cycles: 3.88 for the BAe146; 1.29 for the A320; 1.25 for the B747; 1.04 for the DC-10, 1.02 for the MD80, 0.63 for the B767, and 0.09 for the B737 (NRC, 2002). These estimates were based on several years of data from three airlines. To put these numbers in context, there were an estimated 10,556,000 departures on US airlines last year (BTS, 2007), so even the most conservative estimate of 0.09 events per 1,000 flight cycles fleet-wide, for example, translates into 950 events per year in the US fleet or an average of two to three events every day.

  8.  I am in the midst of compiling smoke/fumes incident data from the following four sources:

    (i)  Copies of reports that our members submitted to their airlines, assuming that they also reported the events to AFA;

    (ii)  News media reports, typically of diversions or major delays due to smoke or fumes (not always specific as to source of smoke);

    (iii)  Reports that US airlines submitted to the Federal Aviation Administration (FAA) Service Difficulty Reporting system (per 14 CFR 703); and

    (iv)  Reports that US airlines submitted to the Aviation Incident Database System. The dataset is restricted to those events that involved a smoke, fume, mist, haze, or odor likely or definitely caused by pyrolyzed engine oil or hydraulic fluid.

  Events for which another cause (such as an electrical fault or de-icing fluid) could be identified are excluded. Data collection and analysis is ongoing but from these four incomplete and largely underused sources of information, I have documentation on 293 events for a 16.5 month period (1 January 2006-11 May 2007), translating into an average of 0.59 events per day on the US fleet alone that likely or definitely involved engine oil or hydraulic fluid in the cabin/flight deck. These four data sources are a starting point, but aside from the fact that the data collection is ongoing, they are guaranteed to underestimate reality for the following reasons:

    (i)  Our union, AFA, only represents about half of the flight attendants in the US, so we only have the potential to review about half of the contamination events reported by flight attendants, assuming that these events are neither more nor less common at AFA airlines. Further, there is no guarantee that AFA members will send a copy of their airline report to the union, or if they do, that our particular department will get a record from either the member or the local union office. So, at best, we had access to a fraction of the events documented by US flight attendants with their airlines.

    (ii)  Airlines under-report to the FAA. Specifically, the FAA requires airlines to report "each failure, malfunction, or defect concerning an aircraft component that causes accumulation or circulation of smoke, vapor, or toxic or noxious fumes in the crew compartment or passenger cabin during flight" to its Service Difficulty Reporting (SDR) system per Federal Aviation Regulation (FAR) 703(a)(5). Airlines must also report ground-based events that involve a failure, malfunction, or defect that has endangered or may endanger the safe operation of the aircraft per FAR 703(c). However, in May 2006, the FAA distributed a bulletin to its inspectors stating that "it appears as though there are numerous air carriers/operators who may not have reported these [smoke/fumes in the flight deck/cabin] events as required by regulation" (FAA, 2006). Put simply, even the FAA recognises that airline compliance with its reporting rules is poor. As an example, of the 105 events recently documented by our members with their airlines, I was only able to identify four in the FAA databases. Similarly, of the 39 smoke/fume events identified in the media (typically serious enough to require a diversion), I was only able to identify three in the FAA databases.[4]

    (iii)  Airlines need not monitor the air so for an event to be reported, there must be sufficient contamination for crewmembers to either smell or see the problem, and they must fill in the paperwork knowing that there is a high probability that the incident will get ignored and any associated workers' compensation claim will be denied. Under-reporting (both intentional and unintentional) by crew is a real problem and it is hard to overcome the obstacles of no inflight warning systems, low morale, and low expectations of an appropriate response from the airlines.

  9.  Of the events with complete phase of flight information, a little more than half diverted. Many of those that did not divert were either in descent or taxi-in, so instead conducted emergency landings. We do not have enough information to know if the subsequent flights were cancelled, but presumably they would have at least been delayed so that maintenance staff would have time to troubleshoot.

  10.  The fact that about half of these events required a diversion and likely all caused potentially expensive and unpopular delays is important because it presents a business case for preventing these events with improved maintenance practices and air cleaning equipment, and it justifies the investment in sensor equipment designed to identify an event in its early stages. In 2006, the FAA estimated the average cost of a diversion at $207,000, obviously varying by size of aircraft and requisite ground time to troubleshoot and fix any mechanical failure. So, some or all of the cost of air cleaning equipment for the outside air will clearly reduce diversion costs associated with smoke and fumes. Similarly, some or all of the expense of chemical sensor equipment that allows an airline to identify and address minor problems before they become serious and costly may be offset by saved diversion costs. For example, one major US airline submitted a report to the FAA last year of an extremely foul odour from the air packs after liftoff. It described the forward and aft cabin air quality as poor but noted that maintenance found no evidence of an oil leak. On that same aircraft eight days later, strong fumes entered the flight deck at takeoff and remained through the climb. Maintenance finally identified three oil leaks and replaced the engine. That later event could have been prevented had there been some objective indication of oil leaking in the cabin on the earlier flight or if the aircraft had been equipped with air cleaning equipment.

  11.  In closing, we know that, by definition, the outside air supplied to the cabin and flight deck is first processed in the engines or APU where it can be contaminated with pyrolyzed engine oil or hydraulic fluid. The only exception to this rule is the B787 that will enter service in 2008 and rely on a non-bleed air system, both on the ground and inflight. To this end, the frequency and potential severity of air supply contamination events present an obligation for government bodies to investigate and promote preventive and remedial measures. Options include installing commercially viable air cleaning devices on the outside air supply, prompt and effective cleaning of contaminated systems, and an obligation to inform crew and passengers of onboard exposures.

  On behalf of our members, we thank you for your interest in these exposures onboard commercial flights.

18 June 2007


AAIB (2007) Bulletin no 4/2/07, Bombardier DHC -8-400, G-JECE (EW/C2005/08/10), UK Air Accidents Investigation Board.

AAIB (2004) Report no 1/2004, BAe146, G-JEAK (EW/C2000/11/4) UK Air Accidents Investigation Board.

Bobb, AJ (2003) Known harmful effects of constituents of jet oil smoke TOXDET-03-04 Naval Health Research Center Detachment (Toxicology), Wright-Patterson AFB, OH.

BTS (2007) Airline Activity: National Summary (US Flights). Bureau of Transportation Statistics, US Department of Transportation, Washington, DC. See

CAA (2001) Flight Operations Department Communication (FODCOM) 14/2001 UK Civil Aviation Authority, Safety Regulation Group, Aviation House, Gatwick, West Sussex, England.

CAA (2000) Flight Operations Department Communication (FODCOM) 17/2000 UK Civil Aviation Authority, Safety Regulation Group, Aviation House, Gatwick, West Sussex, England.

Carlson, D A; Hogsette, J A; Kline, DL; et al (2006) "Prevention of mosquitoes and house flies from entering simulated aircraft with commercial air curtain units" J Econ Entomol, 99(1): 182-193.

FAA (2006) Flight Standards Information Bulletin for Air Worthiness (FSAW) 06-05A "Guidance for smoke/fumes in the cockpit/cabin" US Federal Aviation Administration, Washington, DC.

ICAO (2004) Meeting of the Facilitation (FAL) Division of the International Civil Aviation Organization, Working Paper 117 (FAL/12—WP/117), Cairo, Egypt.

Michaelis, S (2003) "A survey of health symptoms in BALPA B757 pilots" J Occup Health Safety-Aust NZ, 19(3): 253-61.

Montgomery, MR; Wier, GT; Zieve, FJ; et al (1977) "Human intoxication following inhalation exposure to synthetic jet lubricating oil" Clinical Toxicol, 11(4): 423-26.

NRC (2002) The airliner cabin environment and the health of passengers and crew US National Research Council, ISBN 0-309-08289-7, National Academy Press, Washington, DC.

SAE (1997) Aerospace Information Report 1539 Rev A. Society of Automotive Engineers International, Warrendale, PA.

Sutton PM, Vergara X, Beckman J, Nicas M, Das R. (2007) "Pesticide illness among flight attendants due to aircraft disinsection" Am J Ind Med, 50: 345-356.

Witkowski CJ (1999) "Remarks on airliner air quality" Presentation at semi-annual conference of the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE), Chicago, IL.

4   The compilation of reports submitted to the FAA during this period is about 90% complete so we may ultimately conclude that the airlines reported a greater number of events to the FAA than these numbers suggest, but dramatic under-reporting is still evident. Back

previous page contents next page

House of Lords home page Parliament home page House of Commons home page search page enquiries index

© Parliamentary copyright 2007