Between all the watercooler conversations, Google rants, scientific studies and litigious claims, the question of whether poor aircraft cabin air can lead to illness is one full of misinformation and differing opinions.
At the heart of more contentious debates is whether long-term exposure to aircraft cabin air can cause Aerotoxic Syndrome. More specifically, the question of whether harmful VOC's from engine bleed events are at fault.
Aerotoxic Syndrome is not recognized in medicine, but that has not stopped it from becoming more prominent in both the media and the industry. This article aims to take a more in-depth look at both sides of the debate and cast some light on what airlines can do to avoid becoming associated with it.
Aerotoxic Syndrome (AS) is an excellent example of how media coverage, contradicting scientific research, and internet misinformation can spark fear and anger about passenger and crew inflight safety.
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The term was coined in 2000 to describe any number of short-term and long-term effects brought on by breathing cabin air with high levels of bleed-air contamination. The lack of specificity in regard to exact symptoms has been one of the contributing factors to why Aerotoxic Syndrome is still hotly disputed.
Since 2000, numerous industry studies have reported that there is no scientific and medical evidence, supporting the validity of Aerotoxic Syndrome– IATA, ASMA, EASA, to name a few.
On the other hand, a study held by the World Health Organisation in 2017 concluded that there substantial evidence to establish causation between aircraft bleed-air and "acute and chronic symptoms, findings and diagnoses."
So what research is to be believed?
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Stepping away from the debate regarding whether Aerotoxic Syndrome is a legitimate medical issue, let's look are what could cause illness. We should look at the usual suspects associated with Aerotoxic Syndrome–tricresyl phosphate (TCP) and tri-ortho-cresyl phosphate, (TOCP).
TCP and TOCP can be introduced into the aircraft cabin air through fume events. Where leaking hydraulic fluid, de-icing agent or oil is vaporized in the bleed air intake. There is little debate to whether TCP and TOCP are hazardous. Instead, the discussion revolves around the volume and frequency these compounds are dangerously present in cabin air.
There is also contention regarding how often fume events occur. Advocates for the legitimacy of "aerotoxicity" claim that fume events happen an estimated 2.6 times a day.
Whereas, industry studies conducted by the FAA and EASA claim that fume events are extremely rare.
Because of the lack of consistency regarding fume event frequency and illness symptomology, the CAA reported that "there may be a psychologically mediated nocebo response which is being triggered by an awareness of irritation or an odour."
Regardless of what side of the aisle that you're on in regards to the research around Aerotoxic Syndrome, airlines can avoid the problem through a little awareness and early adoption of upcoming technologies.
HEPA filters have been the industry standard since the 1980s, and are exceptionally good at filtering out contaminants that originate in the recirculated air–such as bacteria, fungi, viruses, etc. But for removing odours and the potential for VOCs, such as TCP and TOCP, which often elicit concern for safety, you need more robust filters.
HPAC (High-Performance Activated Carbon) filters–and Pall's newest line of A-CAF (Advanced Carbon Air Filter) which combine HEPA and HPAC–offer a higher filtration percentage, including many other positive features.
To date, Boeing's 787 is the only aircraft that operates on a "bleed-free" cabin air circulation system. It does this through a separate system that pulls air in from outside the fuselage, thus removing any possibility of fume events.
Details are still under wraps as the technology is perfected, but Pall is in development of a pre-cabin filtration system which aims to mitigate bleed air "fume" events before they even reach the cabin air mixture unit.
They are also developing a Cabin Air Quality Sensor, which will help pinpoint the specific origins of cabin air odours and contaminates.
