UK Air Safety Group (ASG) Statement on Airliner ‘Cabin Air Quality’

On the subject of Cabin Air Quality aboard passenger-carrying aircraft:

The Air Safety Group (ASG) believes there is disagreement within the aviation industry about the levels of risk that passengers and crews are facing from the quality of the pressurised (conditioned) air aboard many modern aircraft. This disagreement is hindering the promotion of safe flight and, if not resolved, may seriously damage the reputation of the aviation industry.
The ASG was disappointed by the rather unconvincing and disrespectful answers given to Her Majesty’s Coroner by BA and the CAA regarding the death of the BA pilot, Richard Westgate.
The ASG believes that:

  1. There may be an unaccountably-high incidence of crew-members being affected by serious illnesses; this is deeply concerning. Furthermore, passengers are largely unaware that they may be being subjected to contaminated air and because the presentation of some symptoms is delayed, the symptoms may not be linked by the passengers (or their doctors) to recent in-flight events.
  2. While not all fumes events are created by oil-contaminated air, there may exist a culture of under-reporting of fume events (“Why bother because nothing happens!”) and also a possible mis-categorization of the causes of the event in the subsequent engineering reporting process. e.g “Air Conditioning failure” could hide a multitude of sins.
  3. There is a belief amongst some experts that cabin air may, on some occasions, contain organo-phosphate (OP) type compounds and toxins at harmful levels. Furthermore, there is a belief amongst the same experts that exposure to such contaminated air may result in harm, either as a result of;
    • Acute exposure in ‘fume events’ or
    • Chronic (long-term) exposure to frequent-fliers (and, importantly, crews).
  4. Medium to longer-term symptoms (many of which are akin to organo-phosphate (OP) poisoning) may include neurological degradation, sensory perception and cognitive impairment and possibly cancers and heart-problems; which has obvious safety concerns for operating crews and their passengers.
  5. As awareness amongst crew increases, there is a growing concern of a causative link between aero-engine oil in cabin air and unexplained symptoms in crew and passengers.
  6. Scientific evidence is available that there exists a serious potential problem in using ‘bleed air’ to condition the airliner cabins, as evidenced by the recent HM Coroner’s Inquest into the death of Richard Westgate, an airline pilot. Questions need to be answered - both the airline and the regulator have actions against them from HM Coroner.
  7. It appears that governments and regulators require those people seeking safer cabin air-quality to ‘prove with scientific evidence’ the dangers of breathing oily/smoky air in an enclosed space. Recent histo-pathological studies and outcomes of Inquests are providing and adding to the evidence of such dangers. But in truth, the onus to prove the ‘safety’ of aero-engine additives rests the manufacturers and operators and always should have done.
  8. The often-quoted ‘Cranfield Study’ of 2011 is thought to be scientifically compromised because of less-than-ideal measurement techniques and the fact that the mere 100-flight study did not capture any significant ‘fume events’ - by Cranfield’s own admission. Despite this, the study did discover evidence of highly-toxic compounds, including organo-phosphates (OPs), being present on the majority of flights in aircraft that use engine or auxiliary power units to provide conditioned air. OPs are related to ‘Nerve Gases’ and fungicidal sheep-dips; the latter have been proven to be dangerously harmful to farmers. OPs are added to many aero-engine oils but they may not be the only toxic substance in these oils.
  9. Even if below occupationally “safe” levels, the presence of OPs (of a number of various varieties/isomers), along with other toxic by-products of aero-engine combustion, may be highly significant because any ‘occupational’ levels are likely to be inappropriate when applied to passengers, (including babies, pregnant women and those medically-compromised) who have to breathe this air, in a confined space, for long periods of time. Despite Cranfield’s recommendation to do so, no further government-funded studies have been carried out that have defined what actually constitutes a ‘safe’ dose of possible cabin air contaminants for passengers.
  10. Nonetheless, taking into account the increasing depth and breadth of evidence indicating links between what is now being more-widely recognised as ‘aerotoxic syndrome’ and poor cabin-air quality, the ASG believes that a more-cautious approach should be taken by our industry. Failure to do so may lead to an irreparable loss of trust in our industry’s leaders, the manufacturers, the airlines and the regulators alike.

The ASG urges the Civil Aviation Authority (CAA), all other NAAs and the European Aviation Safety Agency (EASA) to act immediately in the best long-term interests of the industry, passengers and crew by taking the following measures:

  • Require operators to install, on all passenger aircraft, measures to provide crews with timely warnings of oil-contaminated air in the cabin and cockpit.
  • Require all operators to fit appropriate air-filtration devices that will ensure the safety and long-term health of all air-travellers by reducing any toxic contaminants of cabin air (from all sources) to levels significantly below the ‘occupational’ limits, if not to zero.
  • Commission a wholly-independent and fully-funded scientific study and monitoring programme in order to determine precisely the constituents of real-time ‘fume events’ and the true proportions of the contaminants.
  • Commission another wholly-independent study to define what is the ‘safe dose’ (acute and chronic) of OPs and other toxins for aircraft passengers. This dose should take into account the passengers’ age, illness, frailty and individual/genetic sensitivity to OPs and other aero-oil contaminants and products of thermal degradation/combustion.
  • Sponsor the development and insist upon the introduction of an additive to aero-engine oil that is either benign, or far less toxic than OPs.
  • Encourage more-open reporting of all fume events and unambiguous analysis/statement of the root and contributory causes, which includes the likelihood of oil contamination of the cabin air.
  • Consider any further interim measures which may be used to reduce the risk of exposure to contaminated cabin air until such time as the scientific studies are complete.
  • The authorities should ensure that passengers get the same (or better) medical advice as that which is given to crews. The passengers should be informed of the possibility of illness after acknowledged ‘fume events’, what possible symptoms they may experience and to visit their doctors or their local hospital immediately should the symptoms not clear within a given time.
  • Medical advice should be given to all general practitioners, nurses, pharmacists and hospitals - including which tests and samples are to be taken (e.g. blood, urine and fat tissue) and to which specialist clinics they should be sent for testing. Specifically, they should be advised on any time limits on conducting urine or tissue tests.
  • The medical authorities, unions and research bodies conduct a wholly-independent, epidemiological and histo-pathological study of the cause of death and illness rates amongst present and retired flight-crew and where possible, passengers involved in fume events. The study should be on-going and all Coroners’ and pathologists should be made more aware of the possibility of toxicological poisoning, neural degeneration, heart problems and cancer following on from breathing contaminated cabin air. Accordingly, Coroners and those doctors certifying the cause of death should request post-mortems wherever possible.

In the meantime, the ASG considers that it is the duty of care and a reasonable course of action for all operators and manufacturers of passenger-aircraft to complete full health and safety risk assessments in light of recent medical evidence and recorded crew illnesses. It is also reasonable to expect them to introduce a crew-health monitoring scheme and provide specialist advisors on cabin air quality and related issues.

Air Safety Group


April 2015