A dirty little secret of the airline industry has again popped up its toxic head after four Jetstar cabin crew members were taken to hospital in Cairns on Thursday, having become overcome with fumes on a Queensland flight.
That secret is poor air quality, which crew and passengers are often exposed to in airliners. This can include inhaling organophosphates, a highly toxic byproduct of heated engine oil that is present in small quantities in most aircraft cabins, and tricresyl phosphate (TCP), which is neurotoxic to humans. Carbon monoxide can also occasionally escape into cabins from faulty engine exhaust systems or cabin heaters.
Bleed air
At the centre of the problem is “bleed air”, which is used for various purposes such as starting engines, cabin pressurisation and anti-icing. When air enters a turbine engine, it goes through a series of compressors that increase the air temperature and pressure before mixing that air with fuel and igniting it. But a small amount of that air does not enter the combustion chamber and is redirected from the engine to other systems, including the cabin where it is combined with other air.
Organophosphates are deliberately used as key ingredients in herbicides, pesticides and insecticides — precisely because they are toxic — and also have extensive applications in the manufacturing of plastics and solvents. Organophosphates are also the primary constituents of nerve gas, and studies have shown that exposure, whether acute or chronic, can lead to toxicity in humans, animals, plants and insects. There is also growing evidence of potentially damaging long-term effects of exposure to tricresyl phosphate.
Former Qantas National Jet Systems pilot Susan Michaelis is one of the world’s leading advocates for understanding the long-term effects of tricresyl phosphate. Now a lead researcher at lobby group Global Air Quality Executive, she told Crikey that she and her doctors believe that her stage four breast cancer stemmed from years of exposure to toxic cabin fumes.
Fume events
“Fume events” — when abnormal air arises in the cabin from various internal or external sources — are rather euphemistically known as cabin air quality events (CAQE).
Unions and pilots who spoke to Crikey said they are underreported, with a spokesperson for the Australian Federation of Airlines Pilots (AFAP) explaining that dangerous and potentially deadly fumes on aircraft, especially older planes, are a much bigger problem than anyone realises.
“The AFAP would like to see the Civil Aviation Safety Authority take this issue more seriously, including insisting that high-grade air filters be made mandatory for all commercial airliners flying in Australia, and that bleed air systems are redesigned in future aircraft. We should also see appropriate and accurate testing of fumes in aircraft cabins,” the AFAP spokesperson said.
Fume events are the result of the long-term design flaw that sees bleed air mixed into cabin air across most aircraft makers, including Boeing and Airbus. That has only been addressed with the very latest Boeing 787 planes that do not use bleed air in cabins. Now in its earliest stages, Qantas’ fleet-wide upgrade of Airbus aircraft A350, A321 and A220s all continue to use bleed air. CAQEs have been reported in all these aircraft. Aircraft also do not have air quality sensors, although they are being pushed for by unions.
After a fume event on a Qantas National Jet Systems B717 last year, the Australian Air Transport Safety Bureau found that airborne contaminants “may result in the rapid onset of incapacitation, which although possibly subtle, can significantly affect the safety of flight”.
An AFAP spokesperson told Crikey: “Contaminants from bleed air may be being inhaled unknowingly. It’s in the interest of aircrews and passengers that operators take this issue seriously and look for ways of mitigation — but that means spending money.”
“The union is calling for aircraft to be refitted with total air filtration and stop using bleed air that is run over engines.”
Pattern of harm
This week’s Jetstar fume event comes after a similar issue on a Bonza flight in April, and other examples appear regularly on aircraft around the globe. Last year, a Virgin Australia plane was forced to land as a “precaution” after a fume event; five passengers were assessed by medics. Qantas’s ageing B717 and Fokker aircraft are particularly susceptible to the fumes, pilots at regional airlines told Crikey.
“It seems to be occurring because as the aircraft age, the seals around the bearings in the engine wear out,” one Qantas pilot said to Crikey.
Jetstar’s management was keen, as other airlines have been in the past, to minimise the incident.
“Four of our cabin crew reported an unusual smell and started feeling unwell after the flight,” a Jetstar spokesperson told Crikey.
“The four crew members were assessed by paramedics and taken to hospital for observation. There were no passenger reports of the smell and the aircraft landed normally in Cairns. The aircraft will be thoroughly checked by our engineers.”
Causal links
As with asbestos and tobacco, it will take many years of scientific study to prove a causal relationship between organophosphates and serious diseases such as cancer.
“Some crew who have been involved in CAQEs do subsequently experience ongoing ill health and may link their symptoms to the exposure, however, the research to date has not established any causative link,” the International Aviation Transport Association has said.
But while the industry doesn’t like to say so, it is critically aware of the problem.
In the US, there have been multiple lawsuits over at least a decade for aerotoxic syndrome. Pilot unions around the world, including the AFAP, have funded the development of a blood test to detect organophosphate derivatives in a pilot’s bloodstream. Final international certification and blood spot detection is being finalised by Dr Clem Furlong’s team at the University of Washington in Seattle.
Aviation lubricant manufacturer NYCO markets an engine oil that has no organophosphate additives used by some airlines in Embraer jets. And following Boeing’s advances on the 787, a new total air filtration system is being trialled by Airbus.
In the meantime, settle back, relax and enjoy the flight, but try not to think about the air you might be breathing.
