Cabin air quality frequently asked questions

Concerns have been raised in the media about the possibility of air crew and passengers being exposed to fumes in cabin air. The Department for Transport (DfT) has received a number of enquiries, and these are our answers to the most Frequently Asked Questions.  There is more information on the website of the Committee on Toxicity (http://cot.food.gov.uk/).

Is aircraft cabin air contaminated?

Studies such as the European CabinAir project have shown that normally the levels of chemical and biological contaminants in aircraft are less than in many work environments such as office buildings.

There are however occasional bad smells or 'fume events' during flights, and these have been reported on a number of aircraft types which are in use around the world. Reports to the Civil Aviation Authority (CAA) show that sometimes one pilot reports a bad smell and the other detects nothing.  An unpleasant smell is undesirable but does not necessarily harm health.  Conversely carbon monoxide has no smell yet kills people in the home every year.

Some pilots who have experienced these events report a variety of short or long term symptoms or ill health.  But it is not certain that these symptoms are work related.

The independent Committee on Toxicity (a panel including toxicologists from various universities) completed a substantial review of evidence in September 2007 and concluded that the evidence available did not establish a link between cabin air and pilot ill health, but nor did it rule one out.

How frequent are fume events?

The independent Committee on Toxicity estimated in 2007 that fume events occur on roughly 0.05% of flights overall (1 in 2000). The most recent figures show that in 2008 there were 97 contaminated air events reported to the CAA mandatory reporting scheme (MORS) out of 1.2 million passenger and cargo flights by UK carriers. (Not all fume events are reported, but even if the number was doubled or tripled this would still be a very small proportion.)

How many passengers have been affected?

There are very few passenger complaints about health issues to airlines or the authorities.
According to recent figures from the Air Transport Users Council, out of a total of 29,000 written complaints since January 2001, 64 were categorised as medical and the main issues raised were pregnancy; ski injuries; allergies, typically from peanuts; and infectious diseases.

What is the Government doing?

Both the Committee on Toxicity and the House of Lords Select Committee on Science and Technology have identified a gap in the world's knowledge.  We are now trying to fill that gap.  No-one has previously captured samples of cabin air during normal conditions and fume events and analysed them to see what substances they contain and in what concentrations. 
The science is difficult because fume events are unpredictable and can last just a couple of minutes.

• DfT has this work in hand as a priority.  To date we have:
  commissioned first functionality tests to identify equipment capable of capturing fume events in real time.  The report was published on 21 February 2008.  We are confident we now have equipment that will do the job.
• commissioned a data analysis study of fume events and operational parameters – especially whether there is any link between “full power take-offs” and fume events.
• begun a second and more substantive phase of in-flight functionality tests to assemble data on substances in cabin air during fume events. This work builds on the equipment and methodology tested in the first phase. Several airlines have volunteered to take part by allowing an independent scientist to come on board with sampling equipment.  Testing began in 2008 and will continue in 2009.
• The first functionality tests were peer-reviewed by scientists in the UK, Europe and the USA. Future work in this area will be similarly peer–reviewed before publication.

Does the research involve wipe / swab samples?

Not yet but we are planning to commission some swab tests in the UK with control samples taken from non-aircraft locations for comparison.

Who is doing the research?

The project manager is Professor Helen Muir, an aviation safety expert at Cranfield University, who has support from Cranfield Health and two external laboratories.  The research design was overseen by a Steering Group which includes an independent occupational hygiene expert, a pilot nominated by BALPA (the main trade union representing pilots) and the Health Protection Agency.

The project reports to the Aviation Health Working Group which includes the Air Transport Users Council, trade unions, airlines, the Department of Health, Health and Safety Executive and Civil Aviation Authority.  Its minutes are published on the DfT website (www.dft.gov.uk/pgr/aviation/hci/ahwg/).

When will the research report?

We cannot give an exact date. Cranfield University is actively engaged on the cabin air sampling programme with the participating airlines.  The findings will then need to be written up and peer-reviewed before being published as a whole. It is important that we maintain the integrity of this research; because it is a peer-reviewed study we cannot release the results until the work is completed. Nevertheless, both DfT and Cranfield University agree that it would be proper for DfT to be alerted of any findings out of the ordinary.  Should that happen the DfT will consider what action might be appropriate to ensure that people can continue to fly without risk to their health.

Why not just fit filters to aircraft?

DfT has discussed this with a major filter manufacturer who said that, to produce an effective filtration system, they would first need to know what particular substance had to be filtered out. 

That is why it is logical to analyse cabin air first, to identify what remedy might be needed.
 
Compulsory fitting of filters would have to be required by regulators (e.g. the European Aviation Safety Agency) on the basis of evidence that cabin air contains a particular substance in a harmful concentration and that a particular specification of filter could remove that substance.  It is important to remember that the same aircraft types are flown world wide.

Why do fume events happen?

In any mechanical system malfunctions can occur which result in abnormal operating conditions. The CAA has already taken remedial action to help operators of particular aircraft reduce the incidence of fume events e.g. engine oil servicing procedures and engine sealing modifications.
   

Should there be a public enquiry?

There have already been 2 public enquiries:

1) In 2006/7 the Committee on Toxicity – an independent panel of toxicologists – was commissioned to look into the evidence on the subject. They reported in 2007 and found that no connection between pilot ill health and cabin air could be proved or disproved, but that more research was needed. That research is currently in progress.

2) In 2007/8 the issue was revisited by the House of Lords Select Committee on Science and Technology. The Select Committee urged the Government to complete the air sampling research.

We doubt if a third public enquiry would reach a different conclusion. Rather we favour continuation with the Cranfield research project to reach a result.

Is there TCP in cabin air?

DfT has published the results of two functionality tests of sampling equipment, one in the air and one on the ground. A number of compounds were measured in low concentrations including TCP.  So we are confident that if there are higher concentrations of TCP during fume events, our methodology would detect these. The methodology is capable of detecting different isomers of TCP.  It is the concentration of a substance which determines its health effect.

Why not use engine oil containing no TCP?

TCP is an organophosphate. Organophosphates are anti-wear agents and are used as aviation lubricants to make engines safe.  Although there is a lubricant on the market which uses an alternative organophosphate to TCP, according to the manufacturer it is not typically used in civil aviation and research about its health impacts is under way. So we do not know if it would be safer or healthier.

Will you do an epidemiological study?

The logical first step in research is to examine potential exposure as recommended by the Committee on Toxicity (COT). That is what we have under way. The COT said epidemiological research would best be done on an international basis. The scale of pilots and control group needed for reliable results would be large. We are also aware that it could be difficult to recruit pilots, who in the UK would be legally obliged to report any health impairments found (related or not to cabin air) to the CAA who licenses them.