Aircraft Cabin Air Quality

Based on anecdotal evidence suggesting that air quality in aircraft cabins is sometimes not to a reasonable standard, I make the following comments.

In order to better understand the issue in question, it would be useful to consider buildings, on which considerable investigation has been carried out relating to air quality. “Sick building syndrome” (SBS) has come to the fore since the 1970s with the advent of high rise commercial buildings of curtain-walling exterior cladding, which have no natural ventilation. The ventilation in these buildings relies on mechanical air conditioning.

The presence of fungi within buildings is significant. Often fungi, rather than bacteria, constitute the most significant viable and potentially pathogenic microorganisms in buildings.

Microorganisms may have adverse health effects in indoor environments by causing allergenic or hypersensitivity respiratory responses. Inhalation of spores, cell wall fragments, toxic metabolites or enzymes from these microorganisms can cause symptoms such as general malaise, fever, shortness of breath, runny nose, cough and aching limbs. The symptoms are not usually persistent; they disappear when one is absent from a building for a length of time. The symptoms return when one re-enters an affected building.

There are many legal implications depending on the jurisdictions in various countries.

The discussion of buildings is given to indicate some of the issues involved. Aircraft are similar to buildings insofar as they contain people in close proximity in an enclosed space and are ventilated with mechanical air conditioning systems. There has been previous research carried out relating to the potential effects on passengers due to fuel and hydraulic fluid volatile contamination in aircraft cabins. However, up until about 2001 it appears there had been no significant research on bioaerosol contamination of passengers in aircraft cabins. The Building Research Establishment (BRE) in the UK has carried out some research.

While there is considerable presumptive evidence that SBS is a real issue, and case law has been set based on that evidence, there is every indication that similar health effects would derive from aircraft cabins. It would be tempting to speculate even further and suppose that, assuming there is some bioaerosol contamination in aircraft cabins, then the synergistic effects of that combined with chemical contamination (from fuel and hydraulic fluids), and altitude, could lead to much greater adverse effects on passengers.

The typical anecdotal evidence from passengers on long-distance flights who believe that the aircraft cabin air quality has affected them is of their contracting influenza a short time after completing the flight. There are also isolated reports of some contracting tuberculosis. The air filtration system for aircraft is usually based upon the recommendations of the system manufacturer (such as Boeing), and there appear to be no universal standards for types and sizes of filters or for the rate of air change in the aircraft cabin. The air movement requires the use of fuel, and to economise on fuel use, then it would be possible to reduce the rate of air change inside the cabin.

Some of the smallest potentially harmful bioaerosols are viruses at about 0.02–0.3 microns in size. However, it appears that many filtration systems used may be between 0.3 and 0.65 microns. Based on this, it appears that many filters will not filter out some of the viruses in the cabin air. Most fungal spores are about 2–20 microns; they should therefore be effectively filtered out.

If aircraft manufacturers and airline operators are not carrying out air sampling inside aircraft cabins during long-distance flights, then I believe they should be.

The matter in question is a medical manifestation, insofar there is a cabin air quality problem it affects passengers’ health, but it is in fact a multi-disciplinary matter. The origin of any such problem would be as a result of the engineering of the aircraft. If passengers and/or flight staff are adversely affected, then that becomes a passenger/staff health problem as well.

The engineering issue can be further expanded so that the fuel use for each flight could be under question. Dirty filters use more fuel as the engines have to work harder to push the air through the filtration system. Therefore ensuring that filters are always clean results in a fuel saving, allowing less fuel to be carried with a corresponding increase in revenue-generating passengers or cargo which could be allowed for. This assumes that one of the potential issues here may be filters which need more frequent maintenance: however, that will not necessarily be an outcome of any research.

In my view there is sufficient anecdotal evidence of there being problems with the air quality of aircraft cabins. What progress has been made in that regard? Some related websites are:

http://projects.bre.co.uk/envdiv/cabinair/
http://www.bre.co.uk/page.jsp?id=231
http://www.aivc.org/medias/pdf/Air/air0309_web_ed.pdf
http://ec.europa.eu/research/growth/aeronautics-days/pdf/session-e/perera.pdf
http://www.sae.org/aeromag/techupdate/11-2002/
http://www.parliament.uk/documents/upload/stathAirbus.pdf