Toxic Cabin air, the cause of neurological problems

On 2nd Feb 2012, an aircraft took off from Stockholm/Bromma airport for a scheduled flight to Malmö/Sturup. After approximately five minutes the commander was affected by dizziness and nausea and therefore handed over the controls to the co-pilot. The flight was discontinued and the aircraft diverted back towards Bromma. 

Captain Andrew Myers, worked for JetBlue for 15 years but then in 2017 he became ill with a number of alarming health conditions, including toxic encephalopathy, which is a neurologic disorder, and neurocognitive disorder as well as visual difficulties, which could be permanent.The State of Oregon Workers’ Compensation Board in August 2020, ruled in favour of Myers, which in essence establishes the fact that Myers did indeed fall ill from toxic cabin air. This decision is significant because for years, the airline industry has denied the existence of what is known as aero-toxic syndrome, or exposure to toxic cabin air.

Myers will now be paid several years of compensation for loss of earnings and will also have his medical bills paid for. “It’s the first case in the US to establish that the fumes that injured Myers are dangerous, though Myers is far from alone in his injuries,” Glen Lasken, Myers’ attorney, told the Independent.

While the regulators and the manufacturers continue to defend their stand that the air quality was being maintained within the safety standards, there have been numerous crew and passengers reports of developing sickness inflight or after completion of the flight. That Boeing is well-aware of the toxicity of bleed air is indisputable. It was sued in court in the USA by a flight attendant, Terry Williams, and settled out of court in 2010.

Cabin air quality

The day before the incident, flight attendants and customers on the airplane Captain Myers was scheduled to fly, reported a strong foul odor in the cabin while descending for landing. A fume event was written up for maintenance to resolve.

The next day before take-off, Captain Myers and his First Officer, Dirk Murray, attempted to isolate the source of the fumes by performing three engine runs. During the first run, Captain Myers smelled the foul odor throughout the plane, but the First Officer, who remained in the cockpit, did not. During the second engine run, both smelled a very apparent, choking, burning odor like dirty socks or an oily smell.

Both immediately developed headaches, began coughing and had to leave the airplane to get fresh air. Captain Myers fell down on the jetway and a mechanic ran up the stairs to the plane saying, “Oh my God. There’s a haze in here.”

Captain Myers and the First Officer re-entered the plane for the third engine run with the odor still strong. Captain Myers was coughing, his eyes stung and watered, the right side of his body shook with tremors, and he had mild shortness of breath, headache and congestion. He also had some numbness in his forearm and hand that resolved after a couple of days.

Aero-Toxic Syndrome

Aerotoxic syndrome is the organophosphate poisoning resulting from exposure to bleed air. The most common but debilitating symptoms include chronic fatigue, severe headaches, cognitive dysfunction, paraesthesia, ataxia and mood-swings (Winder, C. and Balouet, J.-C. Aerotoxic syndrome). These are all, individually or collectively, enough to ground a pilot on the spot, and render cabin crew unfit for further duty.

Long-term–low-level (LTLL) contamination, such as that to which aircrew are exposed, has been shown to be more injurious than short-term acute exposure. Aircrew breathe the low-level toxicity every minute of their working days. When an aircraft lands the passengers disembark, but the crew turn around and do it all over again, time and time again. Perhaps there has too much emphasis on fume events, while the real damage is being done by LTLL.

Remedial treatment starts with removal from the toxic environment. For aircrew, this involves cessation of employment. The longer this is delayed the more intense the affliction and the more difficult the recovery. In a lot of cases, where brain damage has been allowed to go too far, full recovery is impossible. A striking observation is the connexion between exposure and symptom onset (Winder, C. and Balouet, J.-C. Aerotoxic syndrome). The reverse is also striking, namely that recovery, sometimes only partial, is possible only in the absence of further exposure. This should not have come as a surprise to the industry. The bleed air system for passenger airliners was taken from the military aviation industry. In the 1950s United States Air Force, pilots were complaining of a mysterious illness, which was traced to their exposure to the oil contamination of the bleed air that heated and pressurized their fighters, bombers and transport aircraft.

HEPA filters are inadequate protection

The recirculated air is often filtered using a high efficiency particulate air filter (HEPA) which removes microorganisms and other particulate contaminants but does not remove other contaminants such as volatile organic compounds (Judith Anderson & Dr. Nlichaelis testimony; Exs. 13 9-155 & 141-4 ). Apart from noticeable fume events, pilots are chronically exposed to engine vapors that continuously leak through the oil seals in tiny amounts because the use of pressurized air to both seal the jet engine’s bearing chamber and to provide ventilation for the cabin guarantees that fugitive low-level oil emissions will enter the breathing air supply during normal engine operations (Judith Anderson & Dr. Michaelis testimony; Ex. 142, pages 3 & 5).

USA Congress concerned

“On September 19, 2019, the United States Congress expressed its ‘deep concern’ to JetBlue Airways regarding

(I) the significant number of severe fume events over the past few months, which posed a significant health risk to inflight crewmembers and passengers,

(2) a disturbing pattern of fume events on board JetBlue aircraft, and

(3) JetBlue’s attempt to skirt FAA reporting standards and workers’ compensation la\VS by reclassifying ‘fume events’ or ‘cabin air safety events” as ‘odour events.’ That last concern raised significant doubt with the United States Congress regarding JetBlue’s intention to faithfully adhere to existing health, safety, and labor laws. In light of the prevalence of flight crew members developing neurological problems following toxic gas exposures on planes, JetBlue added ‘fume events’ to its required documentation.”

The cabin air quality may have long terms detrimental effect on the airline crew health. The substance TCP, tricresyl phosphate, is used in jet engine oils. A neurotoxic isomer of TCP, triorthocresyl phosphate, ToCP, can under some conditions form an aerosol in the event of oil leakage from the engine. This aerosol can contaminate the air on board the aircraft via the air conditioning system. The required amount of ToCP to reach the threshold value is however so high that the risks may be considered negligible. 

In UK the Department for Transport Aviation Health Working Group (AHWG) commissioned Cranfield University to carry out air cabin monitoring for contaminants on 100 flights across five different aircraft types – the BAe 146, the Boeing 757 and the Airbus A319, A320 and A321.19 A series of air samples were taken at defined points during all phases of flight (climb, cruise and descent) with the objective of detecting and identifying any VOCs, semi -VOCs, particles and carbon monoxide. In the case of some of the substances tested for, the European Standard, ‘Aircraft Internal Air Quality Standards, Criteria and Determination Methods’ (BS EN 4618: 2009) set health and safety limits. In the absence of a specific cabin standard or limit, the study referred to other standards and guidelines established for domestic or occupational exposures.

The report, published in March 2011, found that no guidelines or standards were exceeded. Specifically, the Workplace Exposure Limits (WELs) established by the Health and Safety Executive (HSE) for organophosphates – including tri-orthocresyl phosphate (TOCP), the most toxic form of TCP, and tributyl phosphate (TBP) – were not breached. Indeed, it was noted that in 95% of the cabin air samples, no detectable amounts of TOCP or other TCPs were found. TBP was detected more routinely, but not in the majority of samples; TBP levels were highest during first engine start. Levels of other substances, such as carbon monoxide, toluene and xylenes, were comparable to levels of indoor pollutants seen in domestic homes.

Crew display high level of anti bodies

In a recent exploratory study, auto-antibodies in serum against a number of proteins present in the (central) nervous system were measured (Abou-Donia et al., 2013). These auto-antibodies may be formed and released into the bloodstream upon damage to the cells of the nervous system. Serum samples of 34 flight crew members with central nervous system (CNS)-related complaints and of 12 healthy age-matched controls that had no connection with the aviation industry and no neurological symptoms were analyzed. Although the auto-antibody levels of the flight crew members and the controls showed some overlap, the levels of auto-antibodies were clearly (much) higher in many air crew members. In addition, one case subject showed an increase in auto-antibodies shortly after flying, which decreased only slowly over the subsequent months of non-flying. 

mindFly analysis

Aero toxicity is an area of concern especially with the advent of pressurized cabin. There is a need for an international body like the ICAO to come up with regulations specifying the standards of cabin air quality and mitigation strategies. While ICAO has agreed and issued the Cir 344-AN/202 Guidelines on Education, Training and Reporting Practices related to Fume Events, it remains a guideline for reporting till intense research work is carried out and published for public benefit. Manufacturers and Airlines have compensated individuals possibly for the detrimental effects to their individual health due the quality of cabin air but the majority are still at large, exposed to the same toxins.

About Capt. Amit Singh

I think therefore I am Airlines Operations and Safety balance expert. A former head of operations/training and safety of successful LCC's in India. An experienced member of the startup teams of these airlines has hands-on experience in establishing airlines systems and processes.

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