Debate pack: Cabin air safety and aerotoxic syndrome

Background

For a number of years concerns have been expressed about possible health effects relating to the air in the cabins of commercial aircraft. Cabin crew and pilots have reported a number of symptoms that they believe are linked to repeated exposure to episodes of contaminated air within aircraft cabins.  These symptoms have been referred to as aerotoxic syndrome. 

Cabin air in commercial aircraft needs to be pressurised and heated. In order to do this, compressed air is taken from the engine and is cooled and conditioned before entering the cabin.  It is thought that, where there is an engine oil seal failure, substances from the aircraft’s engine oil supply can leak into the cabin through ‘bleed air’ from the engine.^[1]  The resulting episode of contaminated air in the cabin is referred to as a “fume event”.  The Committee on Toxicity (an independent scientific committee that provides advice to Government departments on matters concerning the toxicity of chemicals) have estimated that a fume event occurs in around one in every 2000 flights. [2]

The Boeing Dreamliner aircraft has a new no-bleed air system which uses a different process for providing air to the aircraft cabin and avoids these fume events.  

Scientific reports and Government response

There has been a number of reports on the quality and safety of aircraft cabin air and potential links to health effects. The House of Lords Science and Technology Committee, the Civil Aviation Authority and the Committee on Toxicity have all looked at this issue. The most recent UK report on this issue was a position statement published by the Committee on Toxicity (COT) in 2013. This followed a review of the scientific evidence in this area. 

The findings of COT in its 2013 position paper on cabin air were summarised by the Transport Minister, Robert Goodwill in a letter to Louise Ellman MP in November 2015:

1. 1. The Committee concluded that there is evidence of the occurrence of contamination of cabin air by components and/or combustion products of engine oils. Peaks of higher exposure, lasting seconds, have been reported.
2. 2. While many chemicals have been identified as being present in the bleed air from the aircraft engines, given the short duration of reported fume events, peak exposures of chemicals such as triaryl phosphates would have to occur at very much higher concentrations than was found during the studies to cause serious toxicity.
3. 3. Episodes of acute illness have occurred in temporal relation to perceived episodes of contamination of cabin air. The sufferers of these illnesses have attributed the cause to the fume event.
4. 4. The Committee noted that the range of symptoms reported following fume events was wide-ranging, whereas toxic effects of chemicals tend to be more specific.
5. 5. While it is possible that the acute illness which occurred in relation to perceived episodes of contamination of cabin air might reflect a toxic effect of one or more chemicals, the Committee considered that a toxic mechanism as a cause for the reported illnesses was unlikely.
6. 6. As a toxic mechanism was an unlikely cause for the reported illnesses, a nocebo effect was considered a plausible alternative. There is strong scientific evidence that nocebo effects can lead to illnesses that are in some cases severely disabling, from environmental exposures that are perceived as hazardous. However, there is no simple and reliable way of establishing that nocebo responses are responsible for individual cases of illness.
7. 7. As neither a toxic mechanism nor a nocebo effect could be excluded beyond reasonable doubt as the source of symptoms reported, the Committee concluded more research would be beneficial. It stated, however, that when considering any new research project in conjunction to cabin air quality, it will be necessary to balance the likelihood that it will usefully inform further management of the problem against the costs of undertaking the research. The Committee suggested several lines of research, including database establishment, more monitoring of fume events and biomonitoring of cabin crew. Due to the unpredictability and rareness of the fume events, any new comprehensive research would incur severe costs without certainty of the procurement of any new meaningful evidence.
8. 8. Finally, the Committee emphasised that an illness, whether caused by toxicity or a nocebo effect, can be severely disabling. Therefore, there is a continuing imperative to minimise the risk of the fume events which give rise to symptoms.[3]

The letter also provides information about ongoing and future work in this area. It states that the Government believe that the best approach is for further work in this area to take place on an international basis.  The European Aviation Safety Agency is currently undertaking a preliminary in-flight cabin air measurement campaign, which will put in place the equipment required to undertake cockpit and cabin air measurements.  The results of this campaign are expected in autumn 2016, and then a larger scale piece of research will be planned after this. 

The Government have also said that the Aviation Health unit of the Medical Department of the Civil Aviation Authority will continue to monitor issues around cabin air quality as part of their role as specialist advisor to the Government on aviation health issues.[4] 

Campaign and concerns

Campaigners, including the trade union Unite, which represents passenger transport workers, are calling for an independent public inquiry into cabin air safety and potential health effects. Unite are also supporting a number of their members in pursuing legal claims regarding the symptoms they are suffering, on 15 March they reported that they were pursuing a legal case against airlines on behalf of 61 members of cabin crew staff.^[5]

The potential health effects relating to cabin air were also highlighted during a Coroner’s investigation of the death of a British Airways pilot, Richard Mark Westgate, in 2015. The Coroner sent a report to prevent future deaths to both British Airways (BA) and Civil Aviation Authority (CAA) raising concerns about the presence of organo-phosphate compounds in aircraft cabins and effects on health in February 2015.[6]  The Coroner has a legal power and duty to write a report following an inquest where the investigation reveals something that would give rise to a concern that there is a risk of deaths in the future and that action should be taken to reduce or eliminate that risk.[7]  The responses to this report must be sent within 56 days.  The responses to the report from BA and the CAA have not been made public on the Courts and Tribunals Judiciary website. 

The Civil Aviation Authority responded to concerns relating to cabin air safety in June 2015. It said that its priority is the safety of passengers and crew.  It relies on the guidance from scientific experts based on independent studies and evidence reviews and the overall conclusions of these is that there is no positive evidence of a link between exposure to contaminated cabin air and possible health effects but such a link cannot be excluded:

1. Our priority is always the safety of passengers and crew and we continue to work with airlines, manufacturers and international regulators to drive improvements in safety standards across the industry.
2. We understand the concerns that have been raised about cabin air quality and we take very seriously any suggestions that people have suffered ill health from their experience of aviation.
3. We rely on guidance from scientific experts based on the results of a number of independent studies and evidence reviews – including Government commissioned research. The overall conclusion of those studies is that there is no positive evidence of a link between exposure to contaminants in cabin air and possible acute and long-term health effects, although such a link cannot be excluded. Accordingly, we support the steps being taken by the European Aviation Safety Agency (EASA), which maintains responsibility for approving the safety of aircraft and setting aviation standards for European airlines, and is carrying out further research into cabin air quality.
4. It is important that we continue to support this work, which we believe will help significantly improve the global aviation industry’s understanding of what, if any, impact exposure to fumes has on people’s long-term health.[8]

[1]           Committee on Toxicity, Non-technical lay summary, Statement on the review of the cabin air environment, ill-health in aircraft crews and the possible relationship to smoke/fume events in aircraft,

[2]           Committee on Toxicity, Non-technical lay summary, Statement on the review of the cabin air environment, ill-health in aircraft crews and the possible relationship to smoke/fume events in aircraft,

[3]           Deposited Paper DEP2015-0931 November 2015

[4]           Written Question 8756: Aircraft: Air Conditioning, 9 September 2015

[5]           Unite, Toxic air legal cases rise as MPs prepare to debate cabin air safety, 15 March 2016

[6]           Sheriff Stanhope Payne, Regulation 28, Report to prevent future deaths, 16 February 2016

[7]           Chief Coroner, Chief Coroner’s Guide to the Coroners and Justice Act 2009

[8]           CAA, CAA statement on cabin air quality, 19 June 2015