In recent years, concerns have been raised about possible adverse health effects of exposure to contaminants in cabin air. Incidents are not always severe, however, when they are the incidents can be alarming and, as with any injury, it’s better to be treated sooner rather than later. Working with clinical toxicologists at Guy’s and St. Thomas’ NHS Foundation Trust, the Royal College of General Practitioners, the Civil Aviation Authority, easyJet and academia, BALPA has introduced a pathway that allows doctors to assess the severity of an incident and take appropriate action. When patients present with cabin air-related symptoms, which can include itching or soreness of the eyes, nasal discharge, sore throat or coughing, doctors now have a ‘care pathway’ in place to ensure patients receive the correct treatment as quickly as possible.

What causes contaminants in cabin air?
In almost all modern commercial jet aircraft the cabin air supply is drawn from the engines. The hot, pressurised air taken from the engines, referred to as ‘bleed air’, is cooled and conditioned in the aircraft’s air-conditioning system before being supplied to the aircraft cabin.

On occasion, the cabin air may be contaminated when an oil seal fails, allowing jet oil or hydraulic fluid to leak into the bleed air supply. This can result in an oil mist or odour in the aircraft which is sometimes described as smelling like ‘sweaty socks’. However, most odours or fumes detected within an aircraft cabin do not arise from oil contamination of the air supply. For example, they can also originate from faulty electrical equipment, galley areas and the toilets.

Concerns have been raised that contamination of aircraft cabin air with oil/hydraulic fluid may cause both short- and long-term adverse effects on health. Research in a number of countries has shown that short-term health effects can occur, but so far has not confirmed the existence of any long-term health effects. However, the research findings to date have not conclusively ruled out the possibility of long-term health effects and further work is being carried out to try and resolve this.

What are the short-term health effects?
Symptoms that have been reported at the time of contaminated air events include irritation of the eyes, nose and throat, headache, dizziness and tingling in the hands, feet and face. These symptoms, which may be caused by the irritancy of chemicals or through a ‘nocebo’ response (Illness, often with physical symptoms and signs, which is triggered through psychological processes in response to a perceived harmful exposure) normally resolve quickly, either on leaving the aircraft or once the fumes or smell disappears during the flight. There is currently no evidence that these short-term health effects can lead to long-term health problems, and therefore no further investigation or treatment is necessary if the symptoms have gone away.

What are the possible long-term health effects?
In some cases, symptoms that start at the time of exposure to a contaminated air event may persist, while in others, symptoms develop some time after an event or where there is no history of exposure to a specific contaminated air event.

Symptoms that have been reported include:

• neurological symptoms such as headaches, fatigue, weakness, problems with balance, pain, numbness, memory problems
• psychological symptoms such as depression, anxiety, poor concentration
• skin problems, respiratory or gastro-intestinal symptoms are also occasionally reported

However, it is unclear whether any form of long-term illness occurs more often in people with such exposures, and if so, whether it arises through toxic or ‘nocebo’ mechanisms. From what is currently known about the concentrations of potentially toxic chemicals in contaminated air, long-term toxic effects would not be expected, but this remains an area of scientific uncertainty.

For pilots that experience symptoms, or are concerned, we recommend they consult a doctor. For persisting symptoms or concerns the new pathway now recommends that their doctor refers them to the regional NHS Poisons Unit where the opinion of a clinical toxicologist can be obtained.

You can view the care pathway on the CAA’s website.