David Newnham
Runny nose, annoying cough and a sore throat that won’t go away? Time was when your doctor would recommend a good holiday. But today, the question “When were you last on an aeroplane?” is more likely to pinpoint the source of an infection than suggest a cure.
The practice of recirculating cabin air to cut fuel costs is being increasingly blamed for spreading diseases among airline passengers and crew – diseases ranging from severe gastro-intestinal infections that have struck down 200 at a time to drug-resistant strains of tuberculosis that only respond to the most prolonged and unpleasant courses of treatment.
Yet despite a growing awareness among passengers, flight attendants and health professionals that inadequate ventilation can damage the health of anyone who spends more than a few hours in a plane, airlines and their regulators worldwide seem reluctant to grant air quality higher status on their safety agenda.
So great is the concern with lack of regulation and what many see as a culture of secretiveness within the industry that a British charity organisation now proposes to challenge airlines to adopt a common set of standards and to open themselves up to independent scrutiny.
The Oxford-based Aviation Health Institute hopes to persuade companies to use top- quality air as a selling point, much as they now boast about leg-room, fine wines or metal cutlery. The aim is to harness the competitive forces that many believe have been responsible for driving down the quality of cabin air since the oil crisis of the late 1970s.
It is a paradox of air travel that the older the aircraft, the fresher the air. Planes such as the Concorde and the Boeing 737-200 rely for their ventilation entirely on fresh air drawn through the engines, ducted into the front of the cabin and expelled at the rear end. This air is extremely dry -which has its own health implications – but at least it enters the aircraft free of micro-organisms, and passengers can counteract the dryness by drinking water. What’s more, in these older planes, the cabin air is completely replaced every three minutes.
Diverting air in this way, however, reduces the efficiency of the jet engines by up to 2%, and for this reason, airlines reacted to the threat of dearer fuel 20 years ago by ordering aircraft with a ventilation system in which half the air in the cabin is simply filtered, mixed with fresh air and recirculated. The result is a 50/50 blend of fresh and used air -the latter containing less oxygen and more carbon dioxide, in addition to any particles and organisms that may not have been trapped by the filters.
It is the commercial pressure on airlines to stretch this 50/50 ratio of fresh and recirculated air even further, and the limitations of official controls, that worries Farrol Kahn, director of the Aviation Health Institute.
At present, only the concentration of carbon dioxide in cabin air is controlled by law, and Kahn believes the temptation to move from 50% to 55% or even 60% recirculated air is enormous.
Kahn believes airline pilots – whose air supply is of a much higher quality, partly for the benefit of the electronic equipment in the cockpit – can be under indirect pressure to decrease the level of air-conditioning in the cabin during a flight. In an aeroplane every piece of onboard equipment ultimately takes its power from the engines. On many aircraft, says Kahn, individual air conditioning units can be switched off, or run at lower settings. “If you switch off one or two units, particularly after the meal when people are sleeping, then you are saving in total maybe 2% of fuel costs over a year.”
Paradoxically, Kahn says, the introduction of non-smoking flights may make it easier for airlines to reduce airflow, because the presence of tobacco smoke indicated the air was not being changed quickly. He would like to see airlines commit themselves publicly to providing maximum airflow through cabins at all times.
The Centres for Disease Control and Prevention in Atlanta has documented a number of cases of transmission of TB on airliners, and says long-haul flights in particular place passengers and crew in a hazardous environment.
Crew members, they say, complain of symptoms normally associated with so-called “sick building syndrome” – “recurring or constant lethargy and headaches and a range of influenza/cold-type eye, nose and throat complaints”.