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AEROTOXIC SYDROME: ADVERSE HEALTH EFFECTS FOLLOWING EXPOSURE TO JET OIL MIST DURING COMMERCIAL FLIGHTS

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Abstract

Materials used in the operation of aircraft may contain hazardous ingredients, some with significant toxicities, and need care in handling and use. Some maintenance or operational activities, such as leaks or poorly controlled maintenance procedures, can, through contamination of aircraft cabin air, produce unwanted exposures to personnel and passengers. Occasionally, such exposures (either short term intense or long term low level) may be of a magnitude to induce symptoms of toxicity. The symptoms reported by exposed individuals are sufficiently consistent to indicate the possibility of a discrete occupational health condition, termed aerotoxic syndrome. Features of this syndrome are that it is associated with air crew exposure at altitude to atmospheric contaminants from engine oil or other aircraft fluids, chronologically juxtaposed by the development of a consistent symptomology of irritancy, sensitivity and neurotoxicity. This syndrome may be reversible following brief exposures, but features are emerging of a chronic syndrome following moderate to substantial exposures.
From: Eddington, I, editor. Towards a safe and Civil Society. Proceedings of the International Congress on
Occupational Health Conference, held in Brisbane, Australuia, 4-6 September 2000. ISBN 0 646 401546
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AEROTOXIC SYDROME: ADVERSE HEALTH EFFECTS FOLLOWING EXPOSURE TO JET
OIL MIST DURING COMMERCIAL FLIGHTS
Chris Winder Jean-Christophe Balouet
School of Safety Science Environment International
University of New South Wales 31 Rue du Geéneéral Chanzy
Sydney NSW 2052, 94130 Nogent sur Marne
Australia France
Abstract
Materials used in the operation of aircraft may contain hazardous ingredients, some with significant toxicities, and
need care in handling and use. Some maintenance or operational activities, such as leaks or poorly controlled
maintenance procedures, can, through contamination of aircraft cabin air, produce unwanted exposures to
personnel and passengers. Occasionally, such exposures (either short term intense or long term low level) may
be of a magnitude to induce symptoms of toxicity. The symptoms reported by exposed individuals are sufficiently
consistent to indicate the possibility of a discrete occupational health condition, termed aerotoxic syndrome.
Features of this syndrome are that it is associated with air crew exposure at altitude to atmospheric contaminants
from engine oil or other aircraft fluids, chronologically juxtaposed by the development of a consistent
symptomology of irritancy, sensitivity and neurotoxicity. This syndrome may be reversible following brief
exposures, but features are emerging of a chronic syndrome following moderate to substantial exposures.
Introduction
Aircraft materials such as jet-fuel, de-icing fluids, engine oil, hydraulic fluids, and so on, contain a range of
ingredients, some of which can be toxic. Although these chemicals are usually retained in engines and equipment
into which they have been added, they can sometimes find their way into cabin air where crew and passengers
are located, through incidents such as engine oil leaks, seal failures and fluid ingestion by APU/engines. Further,
operational activities, such as APU “pack” burn outs, can give rise to significant contamination.
Dozens of in-cabin leak/smoke events are documented annually, often correlated to aircraft fluid leak events.
Fume events are much more frequent, correlated to less important aircraft fluid leaks (hundreds per year), or to
other independent sources. In total, aircraft fluid leak/fume/smoke events are estimated to impact over 300 flights
per year worldwide, resulting in exposures to an estimated 40,000 or more crew and passengers. Some models
of airplanes appear to be particularly prone to leaks.
The range of bleed air contaminants and their concentrations, which may be found during in-cabin contamination
events during flight, can be extensive. Significant contaminants include: carbon monoxide, aldehydes; aromatic
hydrocarbons; aliphatic hydrocarbons; chlorinated, fluorinated, methylated, phosphate, nitrogen compounds;
esters; and oxides. One additional problem is the lower oxygen concentration operating in the cabins of planes
flying at altitude.
Inhalation is an important route of exposure, with exposure to uncovered skin being a second, less significant
route (for example, following exposure to oil mists) and ingestion improbable.
In terms of toxicity, a growing number of crew are developing symptoms following both short term and long term
repeated exposures. Neurotoxicity is a major flight safety concern, especially where exposures are intense.
Symptoms
Symptoms have been collected from ten cases of pilots, first officers, pursers and flight attendants, flying in five
airlines, three models of airplane and in four countries. The only common feature is that at some stage, they were
involved in an incident where a leak of oil mist to the flight deck or passenger cabin occurred.
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Symptoms were reported from single exposures to elevated exposures, and from long term low level exposures to
low level oil leaks or residual problems from previous contamination. Combined exposures (that is, short term
intense exposures combined with low level long term exposures) were also prevalent.
Symptoms from single or short term exposures are shown in Table 1 below and include: blurred or tunnel vision,
disorientation, memory impairment, shaking and tremors, nausea/vomiting, parasthesias, loss of balance and
vertigo, seizures, loss of consciousness, headache, lightheadedness, dizziness, confusion and feeling intoxicated,
breathing difficulties (shortness of breath, tightness in chest, respiratory failure), increased heart rate and
palpitations, nystagmus, irritation (eyes, nose and upper airways).
Table 1: Aerotoxic Syndrome – Symptoms, Intensity and Chronological Sequence
Symptom Imme-
diate Post-
flight Short
term Medium
term Long
term
Seizures, “gray outs”, unconsciousness 99 9
Disorientation 99 99 9
Loss of balance 99 99 9 9
Problems with coordination 99 99 99 9
Headache, lightheaded, dizziness 99 99 99 99 99
Weakness, fatigue, exhaustion 99 9 9 9 9
Chronic fatigue
9 99 99
Cognitive problems 9 9 99 99 99
Numbness, hot flashes 99 99 9 9
Shaking/tremors, fasciculations, nystagmus 99 99 9 9 9
Irritation of eyes, nose and throat 99 9
Nausea, vomiting 99 99
Blurred vision, tunnel vision 99 9 9
Respiratory problems 99 9
Chest pain 99 9
Increased heart rate, palpitations 9 9
Joint pain, muscle weakness, salivation 9 9
Rashes, blisters (uncovered body parts) 9 99 9
Loosing hair (2 cases of severe exposure) 9 9
Immunodepression
9 9
Acquired Multiple Chemical Sensitivity
9 99
Key to Exposure Intensity: 9 Mild intensity and/or symptoms occur occasionally
99 Severe intensity and/or symptoms present continuously
Key to Column headings:
Immediate: minutes to hour, during or soon after exposure
Post-flight: hours to days Short term: days to weeks
Medium term: weeks to months Long term: months to years
Symptoms from long term low level exposure or residual symptoms from short term exposures include: memory
impairment, forgetfulness, lack of coordination, nausea/vomiting, diarrhoea, respiratory problems, chest pain,
severe headaches, dizziness and feeling intoxicated, weakness and fatigue (leading to chronic fatigue),
exhaustion, increased heart rate and palpitations, numbness (fingers, lips, limbs), hot flashes, joint pain, muscle
weakness and pain, salivation, irritation (eyes, nose and upper airways), skin itching and rashes, skin blisters (on
uncovered body parts), signs of immunosupression, hair loss, chemical sensitivity leading to acquired or multiple
chemical sensitivity (see Table 1).
It is also apparent that some symptoms occur immediately or soon after exposure, for example, many of the
irritant, gastric, nervous and respiratory effects. However, others, such as nervous system impairment,
immunodepression and chemical sensitivity, develop later, perhaps months after exposures may have ceased.
Further, while some of these symptoms are fully reversible, others appear to persist for longer (see Table 1).
Debate is also continuing about the links between exposure and some of longer term symptoms (such as chemical
sensitivity).
Symptom severity depends on a number of factors, including the range of contaminants present, the intensity,
duration and frequency of exposure, toxicity of compounds (expectedly influenced by cabin environment factors
such as humidity, decreased oxygen concentration and contaminants such as carbon monoxide), and individual
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susceptibility.
While single/long term exposure to aircraft engine lubricants and hydraulics (basically due to their chemical
content and possible thermal decomposition products) is diagnosed as responsible for the aerotoxic syndrome, air
crew or passengers exposed to same events or similar doses do not necessarily develop same symptom severity.
The variation in symptoms severity is attributed to individual susceptibility, including anaphylactic response, may
also depend on other potentiation factors, including prior exposure events.
Aerotoxic Syndrome
The symptoms reported by exposed individuals as shown in Table 1 are sufficiently consistent to indicate the
development of a discrete occupational health condition, and the term aerotoxic syndrome is introduced to
describe it. Features of this syndrome are that it is associated with air crew exposure at altitude to atmospheric
contaminants from engine oil or other aircraft fluids, chronologically juxtaposed by the development of a consistent
symptomology of irritancy, sensitivity and neurotoxicity. This syndrome may be reversible following brief
exposures, but features are emerging of a chronic syndrome following significant exposures.
Management of Occupational Health and safety in the Aviation Industry
It has become apparent that the primary safety consideration of the airlines is to keep airplanes flying - the safety
of workers appears to have a very low priority to operational safety. Further, the regulatory agency involved in
aviation safety (the Civil Aviation Safety Authority) admitted in evidence to the Senate Aviation Inquiry that its area
of responsibility is airplane safety, not occupational health and safety.
Monitoring studies conducted by aircraft manufacturers and the airlines have failed to detect any major
contaminants, although to date most monitoring studies have used inappropriate sampling techniques (such as air
collection of poorly volatile contaminants) or inadequate methodologies (such as sample collection time, sample
volume, storage of samples, not taking account of altitude). No monitoring has been conducted during a leak
incident
Attempts by airlines to address this problem through design, maintenance and operational improvements and
through staff support and medical care have not been successful, and in the main, continue to be reactive and
piecemeal. Obviously, in some cases, options such as improving engine design are not within the sphere of
activity of the operators. The efficacy of recent modifications to the aircraft remains unknown, and leaks are still
occurring, albeit at a reduced rate.
An admission was grudgingly made by one airline in 1998 that adverse exposures had been occurring, and that
such exposures might cause irritation and transient effects. However, the development of long term symptoms is
vigorously denied.
Civil aviation regulations clearly state that "the ventilation system must be designed to provide a sufficient amount
of uncontaminated air to enable the crew members to perform their duties without undue discomfort or fatigue and
to provide reasonable passenger comfort." The admission that irritation and transient symptoms can occur
demonstrates non-compliance with the above rules.
Further, the adversarial and acrimonious manner in which some airlines have pursued workers compensation
cases brought by staff with aerotoxic syndrome indicates a confrontational approach which is unlikely to be
beneficial to all parties in the long term.
Conclusions
Direct exposure to hydraulics and lubricants are known to be toxic, causing effects such as blurred vision,
disorientation, memory loss, lack of coordination, nausea, that if they occurred in flight crew, are direct threats to
flight safety. Further, there is factual evidence that flight deck, cabin crew and passengers can be directly
exposed to trace chemicals on aircraft in sufficient concentrations to cause acute, immediate to long term
symptoms.
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These exposures can produce symptoms of toxicity. Symptoms associated to the aerotoxic syndrome clearly
include neurotoxicity as neuropsychological effects, as well as other symptoms typically correlated to chemical
intoxication. Links between neurotoxic effects and certain contaminants known to be neurotoxic (such as the
phosphate esters) are suspected.
Aerotoxic syndrome presents significant issues with regard to the health of pilots, cabin crew and passengers, but
most notably with regard to air safety if pilots are incapacitated and cabin crew cannot supervise cabin
evacuations during emergencies. Health effects include short term irritant, skin, gastrointestinal, respiratory and
nervous system effects, and long term central nervous and immunological effects. Some of these effects are
transient, others appear more permanent. The exacerbation of pre-existing health problems by toxic exposures is
also highly probable.
This is a hidden issue. Staff of the airlines are worried about job security and what might happen to them if they
complain about working conditions and make their symptoms public. At present, with only a few cases proceeding
in the courts, little compensation has been awarded to airline workers affected by toxic fumes. Therefore, staff are
reluctant to come forward until their health in jeopardised sufficiently that they can no longer fly without
compromising their health and safety.
... Cardiological symptoms and signs mentioned in aircrew are increased heart rate, palpitations and dysrhythmias (Winder and Balouet, 2000). There are no systematic studies on cardiotoxicity in aircrew after fume events. ...
... Furthermore, pilots exposed to fume events have been found to have raised carboxyhemoglobin levels, reflecting exposure to carbon monoxide 1950; Start of the jet era, air supply in pressure cabins in airplanes is provided by bleed air systems 1950-1999 2000-2004 2005-2009 2010-2014 2015-2019 2020-2022 First report of fume events and cabin air contaminaƟon (Kitzes, 1956) First report of health effects of contaminated air (Montgomery et al., 1977) Increased suscepƟbility to OP-exposure by serum PON-1 acƟvity.(1993) Smoking prohibited onboard all flights (1997) Symptoms aŌer exposure to contaminated air: "Aerotoxic Syndrome" (Winder and Balouet, 2000) Increased suscepƟbility to toxic compounds due to Cytochrome P450 enzymes (Hedlund et al., 2001) Neuropsychological abnormaliƟes in aircrew (Coxon, 2002) Health surveys of aircrew (Cox andMichaelis, 2002, Michaelis, 2003) Important paper on air quality and health effects of BAe aircrew (van NeƩen, 1998) TCP/ToCP or carbonmonoxide as the main cause of symptoms? (van NeƩen, 2005) PET-scan abnormaliƟes in flight aƩendants aŌer a fume event ( Heuser et al., 2005) Lung injury in BAe 146 aircrew (Burdon and Glanville, 2005) Guide for healthcare providers; exposure to aircraŌ bleed air contaminants (Harrison et al., 2009) Important paper on neuropsychological assessment of cabin crew (MackenzieRoss, 2008) Health surveys of aircrew (Harper, 2005;Somers, 2005) Large aircraŌ sampling studies (Denola et al., 2011) Urine sampling of cabin crew (Schindler et al., 2013) Elevated auto-anƟbodies against brain specific proteins (Abou-Donia et al., 2013) TCP/ToCP is not likely to be responsible for health problems of pilots and cabin crew (de Boer et al., 2015) Abnormal fMRI and DTI-MRI in aircrew (Reneman et al., 2016) Frequency of fume events (Shehadi et al., 2016) Aerosol of ultrafine parƟcles in cabin air (Cao et al., 2017;Howard et al., 2018) Large air sampling study (Schuchardt et al., 2019 UFP measurements onboard aircraŌ Experimental evidence of lung toxicity of bleed air contaminaƟon (He et al., 2021) Large study, funded by the European Union, of the quality of the air inside the cabin of aeroplanes and its health implicaƟons, "FACTS" study, report in 2022? ...
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The term aerotoxic syndrome has been proposed to describe a constellation of symptoms reported by pilots and cabin crew following exposure to possible (neuro)toxic substances in cabin air. Several organ systems are involved. Potentially toxic chemicals emanate from hydraulic fluids and engine oil and include organophosphate compounds, solvents and carbonmonoxide. Oil contamination in the compressor will result in nanoparticles in bleed air under most operating conditions. Overfilling of oil or faulty seals lead to oil leaks which permit ultrafine particles to cross oil seals. Extremely high temperatures in aircraft engines may alter the composition of the original oil and create new toxic compounds. De-icing fluids and the use of insecticides may also contaminate cabin air. Regulatory authorities estimate fume events (incidental smells, smoke or mist inside an airplane) happen on 0.2–0.5% of flights. Objective evidence of exposure is often lacking and indirect proof in the form of biomarkers is scarce. The underlying mechanisms leading to chronic symptoms, extend beyond cholinesterase inhibition. Individual genetic differences in the ability to metabolize solvents and organophosphates may explain why long-term intermittent low-level exposure causes ill health in some people. We discuss the current evidence for central nervous system injury in aerotoxic syndrome and propose diagnostic criteria to argue for its recognition as occupational disorder. Prospective studies and a proactive attitude of authorities are required. Nano-aerosols as vehicles for toxic compounds should stimulate the development of bleedless aircraft. Until then the “aircraft cabin of the future” should have continuous cabin air monitoring and filter technology to make flying safe for everyone.
... TCP, particularly the ortho-substituted isomers, are known to be neurotoxic (Petroianu, 2016). It is the suspected exposure of pilots and flight attendants to this compound, as well as an unknown aggregation of other contaminants found within the engine oil, deicing fluid, hydraulic fluids, and flame-retardant materials, followed by potentially resultant symptomology, that has led to the coining of the term "Aerotoxic Syndrome" to describe occupational illness on aircraft (Winder and Balouet, 2000). Acute onset and chronic symptoms that have been associated with occupational exposure include irritation of the eyes, nose, and throat, disorientation, headaches, dizziness, numbness, cardiovascular concerns, tremors, and cognitive problems (Winder and Balouet, 2000). ...
... It is the suspected exposure of pilots and flight attendants to this compound, as well as an unknown aggregation of other contaminants found within the engine oil, deicing fluid, hydraulic fluids, and flame-retardant materials, followed by potentially resultant symptomology, that has led to the coining of the term "Aerotoxic Syndrome" to describe occupational illness on aircraft (Winder and Balouet, 2000). Acute onset and chronic symptoms that have been associated with occupational exposure include irritation of the eyes, nose, and throat, disorientation, headaches, dizziness, numbness, cardiovascular concerns, tremors, and cognitive problems (Winder and Balouet, 2000). In response to the concern about the neurotoxicity of Triortho-Cresyl Phosphate (ToCP), concentrations have been reduced in oil formulations resulting in the absence of detectable levels of ortho isomers of TCP in new or used aircraft oil (Winder and Balouet, 2002;Megson et al., 2016Megson et al., , 2019. ...
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... We have observed that some of the most severely "TILTed" individuals were "initiated" by exposure to organophosphates (OPs) [90]. Groups exposed to OPs and at risk for TILT include agricultural workers, sheep dippers, occupants exposed to pesticides, Gulf War soldiers, and airline crew members exposed to "fume events" during which engine lubricants (OPs) bleed into cabin air [6,113]. OPs irreversibly bind acetylcholinesterase. ...
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... Yet these principles have sadly all too often been subverted by industry, governments and complicit or captured regulators as the former head of the United States Occupational Safety and Health Administration, David Michaels, has carefully and recently documented. 1 Table 1 illustrates how such approaches have either crudely or at times in a more subtle manner been adopted to air quality threats to crew linked to their possible organophosphate exposures (OPs). 2,3 This is against a backdrop of a range of aviation regulations, standards and guidance material dealing with cabin air quality affecting crew and passengers in various ways. Examples of these include CS/FAR 1309 Equipment and Systems Design -Airframe: CS E510…. ...
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ResearchGate has not been able to resolve any references for this publication.