CONCERNS about the air quality on planes are nothing new, but a recent lawsuit reignites a debate over whether it could potentially be harmful. British Airways (BA) defended its safety protocols after a posthumous court case was filed on behalf of one of two former pilots who claimed that they had been poisoned by toxic cabin fumes.

The BA pilots, Karen Lysakowska and Richard Westgate, believed they had fallen victim to “aerotoxic syndrome” towards the end of their lives. They accused BA of breaching health and safety guidelines for monitoring cabin air quality—a claim that the airline strenuously rejects. Aerotoxic syndrome is the name given to a mixture of physical and neurological symptoms that some experts believe could arise from exposure to toxic fumes on passenger jets. This could happen, it is alleged, if there is a malfunction in the aircraft’s bleed air supply, which compresses air from the engines and uses it to pressurise the cabin. Almost all commercial aircraft use these systems, with the notable exception of the Boeing 787 Dreamliner.

The alleged risk comes from “fume events”, whereby faulty seals allow oil particles to enter the bleed pipe. When the air is subsequently compressed and heated, additives present in the fuel allegedly form neurotoxic aerosol particles. The British Civil Aviation Authority says flight crews have to don oxygen masks around five times a week in response to such fume events. So far, efforts to establish whether these incidents pose a threat to aircraft operations or long-term health have proven inconclusive.

Westgate’s lawyers are suing the airline. His doctor told the British Sunday Express: “Some of the symptoms are like the early onset of Parkinson’s Disease or MS. There needs to be an understanding of this, but it’s wilfully not recognised. The airline industry knows how huge the implications would be.”

BA cites independent studies commissioned by Britain’s Department for Transport which found “no evidence that pollutants occur in the cabin air at levels exceeding available health and safety standards”. It added that numerous peer-reviewed research papers found “no increase in overall cancer or mortality rates amongst cabin and flight crew”. The British government concurs, saying “concerns about significant risk to the health of airline passengers and crew are not substantiated”.

There have been other instances of pilots claiming ill effects from fumes. In December 2010, for instance, two Germanwings pilots became disorientated after smelling fumes while on approach to Cologne. Germany’s air accident authority later confirmed that the pilots, who described their own mental state “as surreal, and as within a dream”, had abnormally low blood oxygen levels. Whatever the current thinking, further research into this condition would be welcome.