Three friends of mine flew abroad over Christmas, two to the States and one to France, and all three fell ill after the plane journey. Coincidence? The first was so smitten with bronchitis that she coughed her way through her sister’s wedding, her father’s 70th birthday and Christmas dinner. The other two had set off in good health, and been taken ill the day after flying – both with flu symptoms.

It was only when Stephen Fry suggested on the Christmas edition of QI that, since the smoking ban was introduced on aircraft, passengers were subjected to less fresh and more recycled air than before, that I began to wonder whether more joined up thinking was needed over cabin air quality. There are plenty of airline regulations, but the measurement of clean air in a cabin as a standard daily tick on the hygiene chart is long overdue.

The Telegraph reported on a Department for Transport commitment to carry out tests on cabin air quality, which “are expected to begin around Christmas”, but in the meantime the DfT’s figures are slow to be published. In 2006 DfT figures show 109 flights were polluted with contaminated air – a rise on the previous year’s total of 78. But we only know that for the first six months of 2007, 72 incidents were recorded, an upward trend nevertheless.

First things first, “contaminated” air is a lot more serious than just recycling everyone’s bugs. Contaminated air is about fuel vapours and other toxins leaking into the aircraft, an issue serious enough to warrant two current campaigns from ex-Airline Pilots – the Campaign Global Campaign Air Quality Executive, and the Aerotoxic Organisation.

As well as videos, books, and complaints from the public, these campaigners suggest that 200,000 passengers a year are exposed to air contaminated with fuel vapours, with the Boeing 757, the transatlantic workhorse, suffering 43 cases alone.

My friends were not suffering the serious side-effects of toxic overload, however, their respiratory-based illnesses are more difficult to connect to the aircraft.

The CAA, responsible now for monitoring cabin air says on its website that “proportions of 50% outside air and 50% recycled are typical of modern airliners” and that “although not required for aircraft certification, the high efficiency filters used for filtering recirculated air on modern airliners will filter out most bacteria and viruses”.

There is no proof that my friends were made ill by their environment. However, there are plenty of “experts” suggesting that such subtle illnesses cannot be explained away as coincidence, and even that the modern passengers’ attack of air rage might be caused by poor air quality.

Vincent Mark, an environmental physician in Santa Cruz is quoted on Flyana as saying: "Curtailment of fresh air in airplanes can be causing deficient oxygen in the brains of passengers, and this often makes people act belligerent, even crazy…and it can be proven with a simple blood test."

The same website hosted by Diana Fairechild, a former flight attendant, confirms that it is the captain who controls the amount of fresh air in the cabin (saving on fuel by limiting the amount of fresh air supplied) and they often enjoy ten times the amount of oxygen in the cockpit. Her comments have sparked quite a debate over the past ten years but she continues to campaign regardless of criticism.

An outbreak of Mumps was reportedly spread by recycled air, and the American Center for Disease Control and Prevention has admitted that passengers are at risk from an infected passenger with TB, Sars and other airborne viruses, but the common belief that most threats come from the proximity of other infected passengers – rather than the air – is still the current thinking.

And those recovering from the hysteria over the Norovirus scare should remember that this group of infections are not airborne at all, but are more likely to come from germs found on seatbacks and tables so memorise the tips for keeping well.

For my own part, I am beginning the New Year with a firm resolve to travel in Europe by train from now on. Then, if overcome with nausea, I can always lean my head out of the window at the next station, and sniff the fresh air. Music to my nostrils.

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