21BU14A
________________________________________________________________________________________________________
Respiratory symptoms and lung injury after inhaling fumes on aircraft: toxic fumes
or hyperventilation?
Jonathan Burdon, MD*
Consultant Respiratory Physician, 166 Gipps St, East Melbourne, Australia 3002
Anatomical considerations relevant to inhalation of toxic fumes in aircraft cabins are
summarized in the difficult clinical aspects highlighted. Hyperventilation has been proposed as a
diagnosis of the symptoms reported by affected aircrew but the evidence supporting it is weak.
Discussion of the issue appears to have lost objectivity, having become polarized between
individual sufferers seeking to honestly report their symptoms and employers with occupational
responsibilities seeking to disavow them. This polarization has the consequence of putting
exposed individuals at the risk of ill health and may, in extreme cases, constitute a safety risk.
Keywords: hyperventilation, inhalation toxicity
1. INTRODUCTION
Despite improvements in occupational hygiene, health
and safety in recent years, occupational lung disease
continues to be an important problem worldwide; it is
certain that the occupational nature of some pulmonary
conditions is yet to be recognized. The reasons for this
are unclear but include lack of knowledge, insight,
awareness and training. In some cases, known risks have
been ignored or alternative viewpoints or theories
promulgated to explain the observations and/or illness.
The respiratory tract achieves importance in the
occupational health setting because approximately 14,000
litres of air are inspired during the course of a forty-hour
working week, increasing with escalating physical
activity. Thus, the potential for airborne substances to
cause injury to the respiratory tract is a real and
important issue. Obviously, inhaled substances vary in
their potential to cause lung disease. Some compounds
rapidly cause significant airway irritation and are quickly
recognized. Conversely, those with neither irritant effects
nor odour may continue to be inhaled, often for prolonged
periods, without being recognized (e.g., carbon monoxide).
Given that each year hundreds of new chemicals are
introduced into commerce, it is, therefore, incumbent on
those individuals and organizations involved with
occupational health and safety to be sensitive to emerging
risks in the workplace, and to appreciate that early
recognition of hazards to health is of paramount importance,
that prevention is better than cure, and that lung injury
may be permanent.
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 [3–10]. In these individuals, some combination
of significant respiratory, cardiac, neurological and
neurocognitive injury has been reported [3–5, 7].
2. ANATOMICAL CONSIDERATIONS
Occupational lung diseases may involve any part of the
respiratory system, which extends from the nostrils and
nasal passages to the alveoli or air sacs deep in the lungs.
In the alveoli, air is separated from the pulmonary
capillaries by an extremely thin alveolar capillary
membrane, which allows for the rapid exchange of
oxygen and carbon dioxide between the blood stream and
the inspired air. Whilst the lung is particularly well suited
for the exchange of gases, it is also prone to the
development of disease or injury as a result of deposition
of inspired particulates and absorption of volatile
compounds, all of which vary in their potential to cause
lung irritation or actual physical injury. Broadly speaking,
lung diseases can be regarded as those affecting the
airways, those affecting the interstitial tissue (the
substance of the lung excluding the airways), and those
affecting both.
Thus, the importance of inhalation as a route of
exposure to noxious substances cannot be overemphasized.
Inspired material may take the form of solid aerosols
(powders, dusts, smoke), liquid aerosols (mists, fogs,
fumes) and gases or vapours. Their chemical and
physical properties (e.g., size, morphology) determines
how and where injury may take place.
E-mail: [email protected]
Journal of Biological Physics and Chemistry 14 (2014) 103–106
Received 6 June 2014; accepted 8 December 2014
103
© 2014 Collegium Basilea & AMSI
doi: 10.4024/21BU14A.jbpc.14.04
104
J. Burdon Respiratory symptoms and lung injury: toxic fumes or hyperventilation?
______________________________________________________________________________________________________
3. CLINICAL ASPECTS
Persons who seek medical consultation following the
inhalation of pyrolysed aircraft engine oil fumes describe
a variety of different symptoms [3–5, 7–9]. In some, the
problem is very clearly related to one organ system,
while others present with symptoms affecting multiple
organ systems.
Usually, the afflicted persons who report their
symptoms to physicians are flight crew, but passengers
and aircraft maintenance engineers have also reported
symptoms after exposure to oil fumes on aircraft. The
most commonly reported immediate effects of the
inhalation of fumes include blurring of vision and
respiratory symptoms, such as cough and breathlessness,
but also including headache, nausea, dizziness, vertigo,
loss of balance, a feeling of fatigue and neurocognitive
impairment. The last-named typically includes degradation
of multitasking and problem solving abilities, disorientation, memory impairment and confusion.
Whilst acute symptoms may resolve within a short
interval, some affected persons experience chronic ill
health that may last for months or years and, sometimes,
the condition is permanent.
4. RESPIRATORY SYMPTOMS
The focus of this paper is the reported respiratory
symptoms. Respiratory complaints among aircrew are
prominent. Published studies [7, 16–22] have drawn
attention to respiratory abnormalities in previously
healthy, predominantly nonsmoking aircrew who have
experienced symptoms following an aircraft cabin fume
event. These complaints are consistent with lung injury
secondary to hydrocarbon inhalation and, in many cases,
the abnormalities are irreversible. Breathlessness, cough
and chest pain or tightness are reported in most subjects.
Other presenting symptoms have been those of wheezing,
occasionally coughing blood and complaints of upper
respiratory tract and sinus irritation. Sinusitis and nasal
bleeding are also common.
Physiologically, there is usually little to find on routine
clinical testing and this is likely to relate to delays in
undertaking appropriate testing. Routine lung function
testing often yields normal results, but analysis of blood
gas measurements has suggested subtle changes in gas
exchange (widened alveolar–arterial oxygen gradient) in
some individuals [11].
Assessments of gas exchange, as measured at the
time of the incident, have rarely been reported. But as one
example, following a documented incident on 19
December 2010 in Germany [23], both the pilot’s and copilot’s blood oxygen levels were measured immediately
JBPC Vol. 14 (2014)
after the event and reported to have been “substantially
below 80%”. Whilst this observation may have been
spurious and related to vasoconstriction secondary to
extreme hyperventilation, there is no comment in the
report that the latter was observed.
Recurrence of symptoms with return to duty are
frequent. A variety of diagnoses have been applied to
affected individuals, including asthma, reactive airways
dysfunction syndrome and reduced tolerance to multiple
chemicals. Sometimes an interstitial lung disease (lung
scarring process) has been suspected.
5. HYPERVENTILATION
More recently, the notion that hyperventilation is the
cause of the symptoms reported by affected aircrew has
been put forward and given credence, at least in some
quarters. This approach is based on the contention that
stressful events prompt an increase in the volume of air
inhaled per minute and that the symptoms described
following a fume event are consistent with this condition.
That hyperventilation may occur in stressful situations is
unquestioned and has been described [24]; the authors
attempted to document the occurrence of symptomatic
hyperventilation in airline pilots by publishing a validated
questionnaire in a pilot newsletter distributed to 6000
subscribers. Of those, fifty-five pilots responded, and 22
reported symptoms of moderate (19) to severe (3)
hyperventilation. That study indicates that pilots may
occasionally report hyperventilation. However, a response
rate of less than 1% significantly limits the ability to draw
any conclusions from these data.
Hyperventilation syndrome is easily recognized by
experienced clinicians and, whilst it usually resolves
promptly, it may occasionally cause chronic symptoms of
dizziness, light headedness and breathlessness or a
sensation of dissatisfied breathing. It does not, however,
lead to long term neurocognitive disability, respiratory or
cardiac abnormalities as have been documented following
fume events. To argue that fume-affected aircrew suffer
from the hyperventilation syndrome because the symptoms
exhibited by them are those seen in that condition is to
close the diagnostic mind to other possibilities; it is a
logical fallacy. It is akin to saying that the breathless
patient suffers from lung disease when, in fact, there are
many possible diagnoses including anaemia, cardiac
disease and neuromuscular disease. In short, a diagnosis
cannot be made by forcing all the jigsaw puzzle pieces
together to make a picture. A broader view that takes
into account the pattern of illness and the natural history
is required.
Respiratory symptoms and lung injury: toxic fumes or hyperventilation? J. Burdon 105
______________________________________________________________________________________________________
6. DISCUSSION
Based on the author’s medical assessment of aircrew
and others who report exposure to toxic fumes on
aircraft, there is an obvious symptom complex caused by
the inhalation of toxic fumes that contain pyrolysed
volatile hydrocarbons in aircraft cabins. It is a condition
with a variety of symptoms, many of which are common
to most affected persons. In many, the symptoms are
temporary, but in others the illness is more prolonged and
may result in permanent injury. This observation raises
serious concerns about the occupational health and safety
of aircrew, passengers and other potentially exposed
individuals. The fact that not all those exposed develop
symptoms is not surprising. There is a recognized
differential sensitivity to the effects of the chemical
constituents of the fumes, which may be due to a number
of factors, including the concentration and duration of
exposure, individual sensitivity, and genetic predisposition. There are parallels to this experience with those
affected by chemicals in the general community. For
example, occupational asthma is clearly recognized, in
some cases, to occur after exposure to chemical concentrations well below industry-accepted standards, which are,
of course, set to protect most persons—complete
protection of everyone can only be made by exclusion.
The contentious issue at present is whether the
symptoms reported after exposure to fumes are real or
imagined. Examination of the literature shows that a
myriad of explanations and diagnoses have been
suggested, and some august bodies have concluded that the
broad range of reported symptoms fails to warrant a
specific diagnosis. This has led to the ongoing debate, with
the afflicted on the one hand, and the air transport industry
and its regulators on the other, with the latter seeming to
either ignore the problem or find other more apparently
attractive explanations [8]. In large part, these are tied to
the notion that the symptoms are not related to fume
events, that psychological problems are the explanation,
and that hyperventilation is the cause of the symptoms.
7. CONCLUSION
With current knowledge and data, the hypothesis that
reported symptoms have a psychological basis can no
longer be sustained [2, 25]. Regulatory bodies should
require systematic and detailed data collection and
reporting to better characterize the extent of these
incidents. Ignoring or providing poorly thought-out
alternative explanations for the facts is, at best, unhelpful
1
and, at worst, puts exposed individuals at risk of ill health
that may be irreversible.1
REFERENCES
1. Kitzes, G. Cabin air contamination problems in jet aircraft.
Aviation Med. 2 (1956) 53–58.
2. Michaelis, S. Health and Flight safety Implications from
Exposure to Contaminated Air in Aircraft ( PhD thesis).
Sydney: University of New South Wales (2011).
3. Cox, L. and Michaelis, S. A survey of health symptoms in
BAe 146 aircrew. J. Occupational Health Safety (Aust. NZ)
18 (2002) 302–312.
4. Harper, A. A survey of health effects in aircrew exposed to
airborne contaminants. J. Occupational Health Safety
(Aust. NZ) 21 (2005) 433–439.
5. Somers, M. Aircrew exposed to fumes on the BAe 146: an
assessment of symptoms. J. Occupational Health Safety
(Aust. NZ) 21 (2005) 440–449.
6. Air Safety and Cabin Air Quality in the BAe 146 Aircraft.
Canberra: Senate Rural and Regional Affairs and Transport
References Committee (2000).
7. Burdon, J. and Glanville, A. Lung injury following
hydrocarbon inhalation in BAe 146 aircrew. J.
Occupational Health Safety (Aust. NZ) 21 (2002) 450–454
8. Contaminated Air Protection: Proc. Air Safety and Cabin
Air Quality Int. Aero Industry Conf. (ed. C. Winder).
London: British Airline Pilots Association (BALPA) &
Sydney: School of Safety Science, University of New
South Wales (2005).
9. Mackenzie Ross, S., Harper, A. and Burdon, J. Ill health
following exposure to contaminated aircraft air:
psychosomatic disorder or neurological injury? J.
Occupational Health Safety (Aust. NZ) 22 (2006) 521–528.
10. Balouet, J.-C. and Winder, C. Aerotoxic syndrome in air
crew as a result of exposure to airborne contaminants in
aircraft. Proc. (ASTM) Symp. on Air Quality and Comfort
in Airliner Cabins, New Orleans, 27–28 October 1999.
11. Burdon, J. and Glanville, A.R. Lung injury following
hydrocarbon inhalation in BAe 146 aircrew. In:
Contaminated Air Protection: Proc. Air Safety and Cabin
Air Quality Int. Aero Industry Conf. (ed. C. Winder),
pp. 53–58. London: British Airline Pilots Association
(BALPA) & Sydney: School of Safety Science, University
of New South Wales (2005).
12. Hartman, D.E. Neuropsychological Toxicology: Identification and Assessment of Human Neurotoxic Syndromes.
Oxford: Pergamon Press (1988).
13. Harper, A. Illness related to cabin air: a survey of symptoms
and treatment among commercial pilots and cabin crew. In:
Contaminated Air Protection: Proc. Air Safety and Cabin
Air Quality Int. Aero Industry Conf. (ed. C. Winder),
pp. 43–51. London: British Airline Pilots Association
(BALPA) & Sydney: School of Safety Science, University
of New South Wales (2005).
14. Heuser, G., Aguilera, O., Heuser, S. and Gordon, R. Clinical
evaluation of flight attendants after exposure to fumes in
In acute cases the onset of ill-health may be so rapid as to constitute a safety risk, in which the pilot is unable to adequately
respond to an emergency situation or, in extremis, handle the aircraft.
JBPC Vol. 14 (2014)
106
J. Burdon Respiratory symptoms and lung injury: toxic fumes or hyperventilation?
______________________________________________________________________________________________________
cabin air. In: Contaminated Air Protection: Proc. Air
Safety and Cabin Air Quality Int. Aero Industry Conf. (ed.
C. Winder), pp. 107–112. London: British Airline Pilots
Association (BALPA) & Sydney: School of Safety Science,
University of New South Wales (2005).
15. Somers, M. Assessing over thirty flight crew who have
presented as a result of being unwell after exposure to
fumes on the BAe 146 jets. In: Contaminated Air Protection:
Proc. Air Safety and Cabin Air Quality Int. Aero Industry
Conf. (ed. C. Winder), pp. 131–145. London: British Airline
Pilots Association (BALPA) & Sydney: School of Safety
Science, University of New South Wales (2005).
16. Coxon, L. Neuropsychological assessment of a group of BAe
146 aircraft crew members exposed to jet engine oil emissions. J. Occup Health Safety (Aust. NZ) 18 (2002) 313–319.
17. Cox, L. A pilot perspective on the issue of cabin air quality.
Proc. Aircraft Air Quality Symp., Canberra, 7 December
2000. Reports in Safety and Environmental Science
(August 2001) pp. 83–118.
18. Glanville, A.R. Toxic planes: the respiratory effects of
flying. Respirology 9 (2004) A55.
19. Rayman, R.B. and McNaughton, G.B. Smoke/fumes in the
cockpit. Aviation Space Environmental Med. 54 (1983)
738–740.
JBPC Vol. 14 (2014)
20. Taskin, D.P., Coulson, A.H., Simmons, M.S. and Spivey, G.H.
Respiratory symptoms of flight attendants during high
altitude flight: Possible relation to cabin ozone exposure.
Arch. Occupational Environmental Health 52 (1983) 117–137.
21. van Netten, C. Air quality and health effects associated
with the operation of the BAe 146-200 aircraft. Appl.
Occupational Environmental Hygiene 13 (1998) 733–739.
22. Winder, C., Fonteyn, P. and Balouet, J.-C. Aerotoxic
syndrome: a descriptive epidemiological survey of aircrew
exposed to in-cabin airborne contaminants. Proc. Aircraft
Air Quality Symp., Canberra, 7 December 2000. Reports in
Safety and Environmental Science (August 2001) pp. 51–58.
23. Hradecky, S. Accident: Germanwings A319 near Cologne
on 19 December 2010, smoke in cockpit, both pilots nearly
incapacitated. http://avherald.com/h?article=434e753b/
0000&opt=0 (viewed on 17 August 2013).
24. Karavidas, K.M. and Lehrer, P.M. In-flight hyperventilation among airline pilots. Aviation Space Environmental
Med. 80 (2009) 495–496.
25. Burdon, J. The “Aerotoxic Syndrome”—real condition or
flight of fancy? J. Occupational Health Safety (Aust. NZ)
27 (2011) 201–204.