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A survey of health symptoms in BAe 146 aircrew


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The concerns that were brought to the Australian Federation of Air Pilots regarding air quality problems revealed a number of operational and OHS issues. This prompted the design and conduct of a survey of symptoms in members who fly BAe 146 aircraft in Australia. A total of 19 pilots and two flight attendants responded. Survey respondents showed high rates of symptoms which included headaches, eye, skin and upper airway irritation, neuropsychological impairment, respiratory problems, food/alcohol intolerances, muscle/joint pain, diarrhoea, and so on. While the results of this survey cannot be considered representative, they do provide self-reported data from a small number of pilots about health problems on the BAe 146, and suggest that the denials by the airlines should be re-examined.
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J Occup Health Safety
Aust NZ 2002, 18(4): 305-312
A survey of
symptoms in
BAe 146
Lawrie Cox is Senior Industrial Officer with
the Australian Federation of Air Pilots.
Susan Michaelis is a former BAe 146 First
Officer, now Research Associate with the
School of Safety Science, The University of
New South Wales.
Address for correspondence: Ms S
Michaelis, Research Associate, School of
Safety Science, The University of New South
Wales, Sydney, NSW 2052, Australia.
The concerns that were brought to the
Australian Federation of Air Pilots
regarding air quality problems revealed
a number of operational and OHS
issues. This prompted the design and
conduct of a survey of symptoms in
members who fly BAe 146 aircraft in
Australia. A total of 19 pilots and two
flight attendants responded. Survey
respondents showed high rates of
symptoms which included headaches,
eye, skin and upper airway irritation,
neuropsychological impairment,
respiratory problems, food/alcohol
intolerances, muscle/joint pain,
diarrhoea, and so on. While the results
of this survey cannot be considered
representative, they do provide self-
reported data from a small number of
pilots about health problems on the BAe
146, and suggest that the denials by
the airlines should be re-examined.
• BAe 146
Parts of this article were presented at the Aviation Air
Quality Symposium, Australian Defence Force
Academy, The University of New South Wales, held in
Canberra, Australia, 7 December 2000.
Health symptoms in BAe 146 aircrew
306 J Occup Health Safety
Aust NZ 2002, 18(4): 305-312
The Australian Federation of Air Pilots (AFAP) is the
trade union which covers pilots within Australia
(with the exception of the major airlines). During the
early 1990s, the union was aware of concerns that
were being expressed by some members, but the
matter seemed to disappear for a significant period.
This may have been due to the significant disruptions
to the industry which occurred at this time.
The issue regained some momentum in the mid- to
late-1990s, as the number of complaints began to rise
from members who crewed BAe 146 aircraft and who
had experienced smells inside the cabin and cockpit.
In some cases, these experiences led to nausea and
headaches, while in others they led to loss of balance.
Further, the number of cabin crew who were
medically released from duty on the BAe 146 was
increasing, and in 1997 there was a serious incident
on a freighter aircraft.
The major airlines had started an investigation into
the complaints and Ansett Australia had established
an “odour committee” to address the concerns that
were being raised by employees. This committee
included members of the Ansett Pilots’ Association
and Flight Attendants’ Association of Australia, as
well as a number of “experts”. While material was
being gathered and many of the affected crew were
transferred to other models of aircraft, no real
solutions emerged. Because the committee was
developed from within Ansett Australia only and
there were no equivalents at other operators, it took
some time for a wider debate to develop — although
the industry as a whole was aware of the problem.
As a result of the 1997 air freighter incident, the then
Bureau of Air Safety Investigation took a direct interest
in the issue and looked into the causes of fumes,
design of the aircraft, and so on. It was at this time that
AFAP took a more active interest in the issue because
it considered a pilot becoming incapacitated during a
flight to be a serious safety concern.
In responding to this issue, the union did not claim to
be a medical or engineering expert; however, a
significant amount of material related to the problem
was readily acquired from a number of organisations,
individuals, researchers, medical professionals, the
airlines and the Internet.
On the other hand, it seemed from the outset that the
Ansett Australia committee was relying totally on the
accepted wisdom of the medical experts involved,
rather than investigating other possible alternatives.
This point should be emphasised because, during the
later public submissions to the Senate Inquiry,
accusations were still being made by the airlines that
the complaints were simply related to stress,
hyperventilation or hormone imbalance. However,
this apparent process of denial and marginalisation
was clearly questionable, for example, the pilot
involved in the 1997 incident was a 50-year-old male
who believed himself to be a relaxed person.
Again, it needs to be stressed that the AFAP officers
were not medical experts; they were simply looking for
an explanation as to what was affecting crew members.
As a result of some basic research by an AFAP
member, several descriptions of the oil used in the
aircraft were tracked down and subsequently
identified as the source of the fumes (after bearing
seal failure). Also, while seeking out what effect the
burnt oil fume could have, the material safety data
sheet was found. This document stated that the oil
was safe during tests under laboratory conditions but
the inhalation of mist or fume may cause nervous
system disorders through long-term exposure.
Many of the reports received from crew members
were comparable with nervous system disorders, with
symptoms appearing after an exposure of several
years flying on the BAe 146.
When this material came to light, the commercial
pressures began, for example:
the aircraft manufacturer denied that there was a
the airlines believed that modifications had fixed
the problem;
the regulator did not believe that the matter was
an air safety problem; and
Cox & Michaelis
J Occup Health Safety
Aust NZ 2002, 18(4): 305-312
the oil manufacturer said that there was only a
small risk and that it was working on a substitute
oil in any case.
Unfortunately for the vested interests of those
involved and for AFAP members, reports of fume
incidents occurring are still being made today.
However, as a result of consistent lobbying —
particularly from AFAP members — a Senate
Committee for Rural and Regional Affairs and
Transport has added a specific reference to air safety
and cabin air quality in BAe 146 aircraft to an existing
aviation inquiry on airspace.
The material put to the inquiry and the conclusions
of the Committee in the Senate Report are a matter of
public record, so they will not be repeated here.1
However, the Senate Inquiry clearly demonstrated the
narrow definition of air safety which is so cherished
by the regulators and airlines, and quite correctly
identified that their responsibility was to a much
wider concept of health and safety.
BAe 146 flight crew survey
In 1999, a survey of the health symptoms of BAe 146
pilots was conducted. Anonymity was guaranteed so
as to gain a more frank response to the survey
questionnaire by participants.
The response rate was low — only 21 questionnaires
were returned. Subsequently, it was discovered that in
one company the letter and questionnaire had been
removed from individual flight crew mailboxes. The
reason for this was to ensure that fewer
questionnaires would be completed and returned —
and none from that particular company.
While the questionnaire was primarily sent to pilots,
some flight attendants also replied.
Due to the removal of questionnaires from personal
mailboxes by one airline, the responses received
cannot be considered to be representative.
Nevertheless, analysis of the questionnaires that were
received showed a number of interesting trends,
which are explored below.
Respondent demographics
Most pilots in commercial aviation are male. This was
reflected in the results of the survey, in that the
majority of crew who responded were male (Figure
1). Similarly, most respondents were in the 30–50
years age group (Figure 2).
Male Female
Respondents (%)
Health symptoms in BAe 146 aircrew
308 J Occup Health Safety
Aust NZ 2002, 18(4): 305-312
Flying history
While the survey was targeted at flight crew, 90% of
the respondents were pilots, and 10% were flight
attendants. Of the respondents whose primary role
was flying, the number of years spent flying is shown
in Figure 3. All pilots were currently flying the BAe
146 full time (that is, they did not fly other models).
The respondents had substantial flying experience,
although flying experience on the BAe 146 was less
than the total years flying. Further, all pilots noted
that they flew more than 500 flight hours per year in
their current positions.
Health survey
The questionnaire contained a number of questions
about health problems, including a list of symptoms,
duration of symptoms, and so on.
Respondents were very positive about the quality of
their health before flying (particularly before flying
on the BAe 146 (Table 1)).
Respondents were less positive about whether their
health had suffered while flying on the BAe 146. Most
considered that the number of symptoms had
increased, that they were specific to flying on the BAe
146, and that the symptoms improved away from the
plane (Table 2).
Just under half of the respondents considered that the
symptoms were associated with specific exposure
situations, such as an engine oil leak. However, 37%
did not — suggesting that they considered that
symptoms were part of the normal processes of
working on the plane. This finding is quite revealing
as it indicates a fairly widespread belief in the
industry that, in addition to the BAe 146 being a
plane which is prone to engine oil leaks, there is a
persisting residual problem which is not directly
associated with the leaks but which has the potential
to continue to cause symptoms or affect health.
Data on symptoms were collected by asking the
question: Do you experience any of the following
symptoms during your work pattern? Respondents
were asked to rate such symptoms as “occasional”,
“sometimes”, “often” and “long term”. While the
subjective nature of the ratings is acknowledged, it
does allow the respondent to answer the question
Age of respondents
Age group
20–30 30–40 40–50 50–60
Number of respondents (%)
Cox & Michaelis
J Occup Health Safety
Aust NZ 2002, 18(4): 305-312
without raising the problems that quantitative
answers may produce. Data on symptom severity are
shown in Table 3.
Of all the data collected in this survey, the symptom
severity data reveal the most about health problems
from flying on the BAe 146, namely:
a wide range of symptoms was reported, in many
body systems;
some symptoms were reported at fairly high rates
(for example, headaches, irritation and
respiratory problems);
some symptoms occurred quite frequently (for
example, skin irritations and disorientation);
some symptoms, such as coordination or memory
effects, presented significant safety problems; and
— some symptoms only occurred as long-term
effects (for example, immune system disorders).
These data show that the range of symptoms is
extensive, and frequency of symptoms cannot be
dismissed as being part of the normal health
symptom background. Other symptoms, such as
coordination or memory problems, are alarming —
given that the respondent was flying a plane at the
The questionnaire also provided respondents with
extra space to add other comments. These are noted
below. In general, they support the results of the
Flying experience of respondents
Years flying
Years flying on the
BAe 146
Years spent flying
1–2 3–5 6–15 16–25 above 25
Respondents (%)
Health status
Health status Good Moderate No answer
How was your health prior to your flying career?
How was your health prior to flying the BAe 146?
Health symptoms in BAe 146 aircrew
310 J Occup Health Safety
Aust NZ 2002, 18(4): 305-312
Symptom development
Symptoms Yes No No answer
Have your symptoms increased since flying the BAe 146?
Do symptoms increase by the same amount on other models of planes?
Do symptoms increase more while on duty?
Do symptoms increase more on the BAe 146 than elsewhere?
Do symptoms decrease a few hours after sign off?
Do symptoms improve on holidays or days off?
Did you have symptoms prior to flying the BAe 146?
Do symptoms only occur after exposure incidents?
Symptom severity
Symptom severity No answer Occasional Sometimes
Headaches, light-headedness,dizziness
Irritation of eyes, nose and throat
Memory impairment (short-term)
Concentration difficulties, confusion
Blurred vision, tunnel vision
Nausea, vomiting, gastrointestinal problems
Fatigue, weakness, decreased performance
Respiratory distress/difficulties
Numbness (head, limbs, lips, fingers)
Balance/coordination difficulties
Joint pain, muscle weakness
Intolerance to chemicals/odours
Intolerance to foods/alcohol
Skin irritations
Immune system disorders
General increase in feeling unwell
Long term
Cox & Michaelis
J Occup Health Safety
Aust NZ 2002, 18(4): 305-312
survey data shown above, and are quite revealing in
terms of the additional problems that they uncover:
increased colds, running nose, watery eyes;
increased skin irritation to eyes and neck;
on flights of four hours plus, extreme headaches
usually occur next day and last for 24 hours;
eyes become bloodshot and painful;
skin rash to hands;
violent protracted headaches;
initial experience during duty or period
immediately following has now increased to
approach to airport or similar environment;
fatigue and lack of attention to detail has been
evident for quite some time;
when PAC filters changed, odour decreases;
nausea felt whenever odour present; and
affect on liver, fatigue, chemical sensitivity and
sore eyes.
Overall, the survey provides limited results about the
health issues for pilots flying on the BAe 146. It could
be argued that the results of the survey should be
dismissed as they are not representative, cover only a
small sample size and — because of the action taken
by one company to stop its staff from filling out the
questionnaire — do not even represent one part of the
union’s constituency of interest.
However, the survey does provide self-reported data
from a number of pilots about the health problems as
a result of flying on the BAe 146. Therefore, the
results of this survey are not airline or union rhetoric
about what is or might be the real situation and, as
such, they should be heeded.
Further, the findings of such a small survey are
interesting because they provide data that support
what is already known. The BAe 146 is a plane which
is prone to engine oil leaks, the contaminants in the
oil are known to cause health problems when present
in the plane’s cabin, and the range of health problems
reported in previous studies is entirely consistent
with the findings of this study.
The Australian Federation of Air Pilots considers that
the presence of contaminants in flight decks and
passenger cabins of commercial jet aircraft constitutes
an air safety, occupational health and passenger
health problem and the following observations have
been made:
1. Incidents involving leaks of engine oil and other
aircraft materials into the passenger cabin of aircraft
occur and are recognised through service bulletins,
defect statistics reports and other sources. The rates of
incident occurrence are higher than the aviation
industry admits, and for the BAe 146 are significant.
The Australian Federation of Air Pilots supports full
reporting and follow-up investigations in accordance
with all regulatory requirements, as well as medical
investigations for those exposed.
2. As indicated by manufacturer information and
industry documentation, aviation materials such as
jet oils and hydraulic fluids are hazardous and
contain toxic ingredients. If such fluids leak into the
air supply, cabin and flight deck, toxic exposures are
possible. The Australian Federation of Air Pilots is
concerned about such exposure events, and supports
industry, government and inter-government
initiatives to reduce such incidents.
3. Leaks of oil and other fluids into aircraft may be
considered as a “nuisance” by some, but where such
leaks affect the health and performance of crew, or the
health of passengers, they should be considered as a
flight safety and health issue which breaches
airworthiness standards and other regulations.
4. Attempts by the industry to minimise this issue
(such as acceptance of under-reporting of incidents,
inadequate recognition of the extent of the problems,
inadequate adherence/interpretation of the
regulations, inadequate monitoring, inappropriate
use of exposure standards and care provided to crew
Health symptoms in BAe 146 aircrew
312 J Occup Health Safety
Aust NZ 2002, 18(4): 305-312
reporting problems) have made it possible for the
problem to continue.
5. The Australian Federation of Air Pilots is also
concerned that the health implications — both short
and long-term — following exposure to
contaminants reported by crew and passengers must
be properly addressed. A syndrome of symptoms is
emerging, called “aerotoxic syndrome”, suggesting
that these exposures are common and a sufficiently
large group of affected individuals exists.
6. Where contaminants impair the performance or
affect the ability of pilots to fly planes — as has been
stated in a number of reports — this is a major safety
problem. Where contaminants cause undue
discomfort or even transient health effects in staff and
passengers, this is a breach of Federal Aviation
Regulation 25.831 and other regulations.
7. Until recently, the aviation industry’s approach in
dealing with this problem has been to deny that it
exists but some limited attempts have now been made
to address this problem.
The most important message that AFAP would like to
convey to its members is, in the event of a fume
no matter where a report of fumes or odours
comes from, take it seriously;
record all relevant details related to the event,
including aircraft registration, flight crew, flight
details, time, place, who is affected and any
underlying issues;
get the aircraft to the nearest alternate destination
or return to departure point;
clear the aircraft;
have engineering look at the aircraft;
where possible, affected crew should seek medical
assistance as soon as possible;
ensure that the company records the event; and
report the event to the Australian Transport Safety
All of the above recommendations are critical and,
although they may seem obvious, there are a number
of well-publicised incidents when such information
was not recorded or details reported.
The issue of cabin air quality needs to be treated with
an open mind, that is, we may not be able to rely on
an existing medical solution to fix the problem. The
approach of AFAP has been to take in all possible
solutions and work for the best possible result for
those directly affected. As such, it is critical that the
answers to the following questions are fully
What effects do the fumes have on the body?
What are the long-term health implications for an
Ultimately, a regulatory authority is needed which
will protect the interests of employees and the
travelling public without being influenced by
commercial interests. From the evidence that was
presented to the Senate Inquiry, it is apparent that
AFAP lacks confidence in the Civil Aviation Safety
Authority (CASA) to perform such a role.
In AFAP’s view, CASA’s role in dealing with the
problem of oil leaks on the BAe 146 has been
inadequate, and in some cases, because of its
reluctance to get involved, has made the problem
In concluding this article, it should be stated that it
has taken the last five years to get to this point. The
first reports of fume problems began in the late 1980s
and the effects of the fumes are now starting to take
their toll on current employees. There is no doubt
that many more problems will start to appear in the
near future.
1. Senate Rural and Regional Affairs and Transport
References Committee. Air safety and cabin air quality in
the BAe 146 aircraft. Canberra: Parliament of Australia,
October 2000. Website at
... The authors coined the term 'aerotoxic syndrome' for the association of symptoms with exposure to hydraulic fluids and to engine oil fumes mixing with cabin air. Cox and Michaelis (2002) undertook a small-scale survey of Australian aircrew who reported an increase in health complaints (most notably headaches, respiratory difficulties, eye and skin irritation, fatigue and cognitive impairment) since flying the BAe-146 aircraft type. Almost half of the respondents mentioned an association with exposure to engine oil fumes. ...
... In surveys of health symptoms in pilots and cabin crew with probable aerotoxic syndrome sensory complaints, such as paresthesia, tingling and numbness are reported in 20-70% of cases (Cox and Michaelis, 2002;Michaelis, 2003;Michaelis et al., 2017;Somers, 2005;. These typical sensory symptoms contrast with the predominantly motor symptoms of the delayed type OP-polyneuropathy. ...
... Respiratory symptoms are common among aircrew and have been reported in various studies (Burdon, 2012;Burdon and Glanville, 2005;Cox and Michaelis, 2002;Mackenzie Ross et al., 2006;Michaelis et al., 2017;Winder and Balouet, 2001). These symptoms include nasal or throat irritation, sinus problems, tightness of chest, cough, wheezing, influenza-like symptoms during flight, and dyspnea. ...
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.
... Fumes produced by pyrolysed engine oil have been recognized to contaminate the incoming air in aircraft flight decks and cabins for more than fifty years [1,2]. However, the potential toxic effect of these fumes on the health and well-being of aircrew has only become more widely recognized over the last decade or so, as a result of a growing number of publications regarding the deleterious effects on the health and well-being of some aircrew [3][4][5][6][7][8][9][10]. In these individuals, some combination of significant respiratory, cardiac, neurological and neurocognitive injury has been reported [3][4][5]7]. ...
... Fumes produced by pyrolysed engine oil have been recognized to contaminate the incoming air in aircraft flight decks and cabins for more than fifty years [1,2]. However, the potential toxic effect of these fumes on the health and well-being of aircrew has only become more widely recognized over the last decade or so, as a result of a growing number of publications regarding the deleterious effects on the health and well-being of some aircrew [3][4][5][6][7][8][9][10]. In these individuals, some combination of significant respiratory, cardiac, neurological and neurocognitive injury has been reported [3][4][5]7]. ...
... Persons who seek medical consultation following the inhalation of pyrolysed aircraft engine oil fumes describe a variety of different symptoms [3][4][5][7][8][9]. In some, the problem is very clearly related to one organ system, while others present with symptoms affecting multiple organ systems. ...
... The Australian Federation of Air Pilots (AFAP) had previously done a survey of its members in relation to problems that they had had with fumes on the British Aerospace 146 (BAe 146). 1 Since that survey had shown a significant pattern of symptoms and that under-reporting was of concern, it was felt that a survey among BALPA members might show a similar pattern. ...
... health symptoms reported by Australian BAe 146 pilots. 1,[5][6][7] Both the BAe 146 pilots and the B757 pilots reported a similar pattern of extensive symptoms at high to moderate rates (including eye, nose and throat irritation, headaches and dizziness, fatigue, feelings of being unwell, concentration difficulties, memory impairment and nausea), although the symptoms were at a higher frequency and with more long-term effects among the BAe 146 pilots. In addition, symptoms occurred not only after specified leak events but also during "nonevent" flights, and were more prevalent on the B757 and BAe 146 than other aircraft. ...
Full-text available
A survey of health symptoms was undertaken in pilots who were members of the British Airline Pilots Association flying the Boeing 737, Boeing 757 and Airbus A320. Six hundred questionnaires were sent out to members, and 106 pilots responded. Survey respondents were predominantly male (104/106) and many had extensive flying experience. With regard to leak events (that is, leaks of engine oil and hydraulic fluids into the aircraft), 93/106 reported that they had been involved in at least one. The total number of incidents reported was estimated to be 1,674+, with all but seven occurring on the B757. Following exposure to the contaminated air, high rates of symptoms were reported by the pilots, including: irritation of the eyes, nose and throat; headaches, light-headedness and dizziness; fatigue, weakness and a decrease in performance; a general increase in feeling unwell; concentration difficulties and confusion; diarrhoea; nausea, vomiting and gastrointestinal problems; numbness (head, limbs, lips, fingers); short-term memory impairment; and joint pain/muscle weakness. These symptoms are a direct breach of US Federal Aviation Regulation 25.831, which includes a specific requirement that cabin air should not cause symptoms of discomfort, fatigue, irritation or toxicity.
... Some researchers have suggested chronic exposure to OP compounds (particularly TCP) in engine oil may be to blame (Winder & Balouet, 2002). To reflect this, in 2000 Winder and Balouet proposed the term 'Aerotoxic Syndrome' to describe the common symptoms reported by aircrew following exposure to toxic fumes in aircraft cabins, and encompasses both shortand long-term effects such as ear/nose/throat irritation, skin conditions, nausea and vomiting, respiratory problems, headaches, dizziness, weakness and fatigue, sensory changes and nerve pain, tremors, chemical sensitivity and cognitive impairment (e.g., Abou-Donia, 2003;Cox & Michaelis, 2002;Coxon, 2002;Mackenzie Ross, Harper, & Burdon, 2006;Mackenzie Ross et al., 2011;Michaelis, 2010;Montgomery et al., 1977). In addition, recent studies have reported evidence of neuropsychological impairment (Heuser, Aguilera, Heuser, & Gordon, 2005;Mackenzie Ross, 2008;Mackenzie Ross et al., 2006;Mackenzie Ross et al., 2011;Reneman et al., 2015) and neurological damage (Heuser et al., 2005); evidence of nervous system degeneration (Abou-Donia, Abou-Donia, El Masry, Monro, & Mulder, 2013; Abou-Donia, van de Goot, & Mulder, 2014); and altered white matter microstructure, cerebral perfusion and activation (Reneman et al., 2015) in aircrew and pilots. ...
... The only studies published to date that have attempted to explicitly measure and link ill-health with exposure to cabin fumes have relied solely on self-report questionnaires. In these studies, pilots and air crew were asked to report whether (and how often) they had experienced fume events or noxious smells whilst flying, as well as being given a health survey where they could report any symptoms that they believed they had experienced as a consequence (Cox & Michaelis, 2002;Harper, 2005;Michaelis, 2003). These studies found that an array of symptoms were typically reported immediately following exposure, including headache, cognitive impairment, fatigue, eye, nose, throat irritation, respiratory problems, nausea and skin irritation. ...
Full-text available
Toxicology is a new science, the complexities of which have been highlighted in the papers contained within this special section. Our understanding of the mechanisms through which various chemicals interfere with nervous system function is constantly evolving and research is unable to keep up with the speed with which new chemicals are produced and put onto the market. Thus there are often controversies surrounding the health-effects of commercially available compounds and disagreement around what constitutes safe exposure limits. This article will introduce readers to an emerging concern in this field, the potential risk to health of toxic fumes in airplane cabins. We explore the challenges and methodological issues encountered by researchers who have tried to investigate this issue and highlight the need for further research on this topic. We hope this article will promote discussion amongst academics and clinicians, and lead to the identification of creative solutions to the methodological issues encountered to date.
... In surveys of health symptoms in aircrew, sensory complaints such as paraesthesia, tingling, restless legs, muscular jerking, and numbness are reported in 20-77% of cases [17,24,26,30,32,107], consistent with a toxic sensory polyneuropathy. In some of these studies respondents reported that symptoms occurred after exposure to oil or hydraulic fluid leaks and fumes from the aircraft ventilation system and subsequently sought medical attention [17,32]. ...
Full-text available
Thermally degraded engine oil and hydraulic fluid fumes contaminating aircraft cabin air conditioning systems have been well documented since the 1950s. Whilst organophosphates have been the main subject of interest, oil and hydraulic fumes in the air supply also contain ultrafine particles, numerous volatile organic hydrocarbons and thermally degraded products. We review the literature on the effects of fume events on aircrew health. Inhalation of these potentially toxic fumes is increasingly recognised to cause acute and long-term neurological, respiratory, cardiological and other symptoms. Cumulative exposure to regular small doses of toxic fumes is potentially damaging to health and may be exacerbated by a single higher-level exposure. Assessment is complex because of the limitations of considering the toxicity of individual substances in complex heated mixtures. There is a need for a systematic and consistent approach to diagnosis and treatment of persons who have been exposed to toxic fumes in aircraft cabins. The medical protocol presented in this paper has been written by internationally recognised experts and presents a consensus approach to the recognition, investigation and management of persons suffering from the toxic effects of inhaling thermally degraded engine oil and other fluids contaminating the air conditioning systems in aircraft, and includes actions and investigations for in-flight, immediately post-flight and late subsequent follow up.
... A number of crew members reported a wide spectrum of neurological symptoms, often referred to as "Aerotoxic Syndrome" (Winder, 2002;de Boer et al., 2015;Harrison and Mackenzie Ross, 2016;Michaelis et al., 2017;Hageman et al., 2022), including cognitive and neuropsychological impairments (Cox and Michaelis, 2002;Heuser et al., 2005;Ross, 2009;Reneman et al., 2016). Other adverse effects associated with this alleged syndrome are neurological damage (Heuser et al., 2005), nervous system degeneration (Abou-Donia et al., 2014, reduced brain activation, and alteration of white matter microstructure and cerebral perfusion (Reneman et al., 2016). ...
In most airplanes, cabin air is extracted from the turbine compressors, so-called bleed air. Bleed air can become contaminated by leakage of engine oil or hydraulic fluid and possible neurotoxic constituents, like triphenyl phosphate (TPhP) and tributyl phosphate (TBP). The aim of this study was to characterize the neurotoxic hazard of TBP and TPhP, and to compare this with the possible hazard of fumes originating from engine oils and hydraulic fluids in vitro. Effects on spontaneous neuronal activity were recorded in rat primary cortical cultures grown on microelectrode arrays following exposure for 0.5h (acute), and 24h and 48h (prolonged) to TBP and TPhP (0.01 - 100µM) or fume extracts (1 - 100µg/mL) prepared from four selected engine oils and two hydraulic fluids by a laboratory bleed air simulator. TPhP and TBP concentration-dependently reduced neuronal activity with equal potency, particularly during acute exposure (TPhP IC50: 10 - 12µM; TBP IC50: 15 - 18µM). Engine oil-derived fume extracts persistently reduced neuronal activity. Hydraulic fluid-derived fume extracts showed a stronger inhibition during 0.5h exposure, but the degree of inhibition attenuates during 48h. Overall, fume extracts from hydraulic fluids were more potent than those from engine oils, in particular during 0.5h exposure, although the higher toxicity is unlikely to be due only to higher levels of TBP and TPhP in hydraulic fluids. Our combined data show that bleed air contaminants originating from selected engine oils or hydraulic fluids exhibit neurotoxic hazard in vitro, with fumes derived from the selected hydraulic fluids being most potent.
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Cabin air on commercial aircraft is sometimes contaminated with hydraulic fluids, synthetic jet engine oils and combusted or pyrolised materials, and aircrew have been reporting ill health following fume events for many years. The purpose of this article is to raise awareness among physicians of the short- and long-term health effects that may develop after exposure to pyrolised engine oil, and to discuss issues regarding causation and diagnosis. Symptoms reported by aircrew are often referred to as "non-specific", and some physicians reject the concept of chemical poisoning and attribute symptoms to other factors, such as psychosomatic disorder. A single case study is presented to highlight the issues of differential diagnosis, and published reports regarding the nature of ill health reported by aircrew following contaminated air events are reviewed. Scientific uncertainty regarding the potential hazards of inhalation of pyrolised engine oil is not evidence for psychological causation.
Pyrolysed engine oil sometimes contaminates the ventilation supply air on commercial aircraft, exposing crew members and passengers to oil fumes. Aircraft occupants have documented both acute and chronic symptoms, largely neurological and respiratory, during and after such exposures. However, aviation regulators do not require airlines to either clean or monitor the ventilation supply air for oil-based contaminants and there is no central reporting system for either crew members or passengers. This paper presents the debate over whether existing evidence of ill health and compromised flight safety warrants engineering and administrative controls to protect crew members in particular. It also describes the regulatory frameworks for aviation workplace safety/health and air supply system design/maintenance in the US. The authors recommend a combination of engineering and administrative controls to prevent exposure to oil fumes on aircraft.
Pilots and flight attendants are concerned about the perceived failure of the aviation industry and its regulators to address the problem of cabin air contamination and the health effects among aircrew following exposure to these contaminants. The aim of this paper was to survey a self-selected group of affected commercial aircrew (including 39 pilots) and document their symptoms and treatment. Various symptoms were reported by the aircrew, but neurological symptoms were present in nearly all cases. The symptoms affected the performance of the aircrew during flight, and there was a reluctance to report the fume events and symptoms. The problem of fume events represents a threat to the safety of those on board the aircraft and unacceptable health issues among aircrew. Although the problem is continuing to occur, it is not being systematically addressed.
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