Health, Science and Economic interests in Aerotoxic Syndrome

The (medical - biochemical) problem:

It's a little bit comparable to the one associated with "alcohol": some can tolerate a lot and the alcohol breaks down quickly, in others it takes longer and the consequences are quicker and stronger.

In general, such biochemical processes in the human organism are called metabolism. Meaning: substances are metabolized or broken down by the body's own enzymes. In the end other substances  have been formed  and/or have been excreted.

We now know that people who are exposed to a fume event situation, can react differently:

  • To about 60% of people who fly, whether as passengers, flight attendants or pilots, a single, or a few such incidents’ apparently cause no harm. According to the previous (provisional) knowledge, because empirically valid data does not yet exist. No one has to date investigated this extensively in connection with contaminated cabin air.
  • About 35% of people who fly and have a one-off event, have a reaction but not overly bad and above all not with long-term effects. If this scenario happens on a vacation flight and one can then relax for two or three weeks at the beach, the body has enough strength to get rid of toxins.
  • For 3% to 5% however, according to the estimates of physicians who deal with such problems, fume events are a serious problem: they respond quickly to such toxic substances and most of the consequences will remain. Medically speaking, the endogenous enzyme acetylcholinesterase (AChE) is rendered inactive by, for example, organophosphates or other substances that enter the aircraft via the bleed air. And that’s when the problems begin.

And exactly these problems are discussed here.

The physical findings:

They are distinct. In contrast to the exact causes or the triggering chemical substances, of which there are obviously several.

The diagnostic findings that have emerged at the Institute for Occupational, Social and Environmental Medicine at the University Hospital Göttingen, which has the only "Fume Event Consultation Clinic" in Europe since 2014, speak a clear language. The clients - or patients - around 350 in number since they started,  complain about a variety of different symptoms. But they are always the same. Whether they are cabin crew (70%), pilots (25%) or frequent flyers (5%).

Fig. 1 shows the spectrum of symptoms, as they have been found in 27 patients in the so-called ‚D-doctors’ at a hospital. (‚D-Doctors’ means "transit physicians who are responsible for accidents at work.") Consequences of a fume event, as far as pilots and crew members are concerned are workplace accidents.

The graphic is part of a publication by BORNEMANN, SEECKTS, MÜLLER, HEUTELBECK with the title "Symptomatic crew members after inhalative intoxication by contaminated cabin air. (Work accident: fume event): Clinic and state of the early diagnosis".

The yellow-marked bars indicate "peripheral-nervous complaints", as explained in figure 2c. They sound comparaturn in to a 'falling asleep' and even convulsions. These are symptoms that can develop immediately after a fume event. And do not just stop after that for a while. Or longer.

Unfortunately, they have the peculiarity of being accompanied by other symptoms that are far more threatening: cognitive limitations. These effects also appear fast. And can last. A long time. Or for an even longer time. In the worst case, a very long time.

Figure 2b explains the cognitive-disorder symptoms shown by the brown bars. Specifically:

  • Difficulty concentrating,
  • Problems in articulating what you want to communicate
  • Coordination problems
  • and other ...

This is how it reads in the specialist publication.

And this is how it reads in a captain’s flight report. On 19 December 2010 he was approaching the airport Cologne/Bonn - about 20 km before touchdown (landing) a smell/fume event occurred (Note: FO = First Officer or Copilot ):

"During the ‚Localizer Intercept’, the FO suddenly said he was ' feeling deathly sick' and he had to don the mask. The tone of his voice frightened me more than the announcement, as he sounded highly alarmed and downright shocked.  At the same time, I realized how my senses were literally dwindling away, my field of vision narrowed almost instantly and I felt a strong dizziness. In this moment fear of losing control over my body and my actions before I could do anything about it, gripped me. "

In short: all went well (this time). Although the touchdown on the runway was very hard. But these are  situations that you have to expect when flying. Even if they are rare. To make flying safe, to think and act preventively means to take even the rare incidents seriously, to learn from them and to install preventive measures. This is what is taught in the science of risk management.

The above incident is described in more detail under: Incidents that usually do not appear in official statistics

As was the case of this incident. Only when the  nearly-incident was discussed in a committee meeting at the German Bundestag, the - actually - competent authority, the Federal Agency for Aircraft Accident Investigation (BFU) felt urged to investigate this case.

So much for the physical symptoms. The medical-biological-chemical ones do not sound much better.

The medical-biological-chemical findings (bio-monitoring):

The results documented in the graphic below which are from a publication resp. a lecture "Health disorders after 'fume events' of aircraft crew members: facts and fiction",  presented by Astrid HEUTELBECK (UMG Göttingen), Lygia BUDNIK (University of Hamburg) and Xaver BAUR ( UKE Hamburg), and presented at the so-called ‚Ramazzini-Days’. Bernardino RAMAZZINI (1633 - 1714) was one of the first to deal with health issues and medical precautionary measures in the workplace. And that at such an early stage in time. More than 180 globally active occupational and environmental physicians meet nowadays at the ‚Ramazzini Days’.

For your information: the findings from 9 fume event patients show how short the half-life of the chemical cocktail in human blood is after a fume event. Actually, the blood would have to be examined within the first 4 hours by specialists who are capable of proving these substances, which are otherwise uncommon (because they are forbidden) in workplaces. This can usually only be done by a specialist laboratory or the Institute of Occupational Medicine in Göttingen.

For example, n-hexane is metabolized in the human body to 2,5-hexandione and causes nerve damage. The quantitative effects on human health have only been investigated since 2012 under the EU Regulation REACH (Registration, Evaluation, Authorization and Restriction of Chemicals). Results do not exist yet. N-heptane is classified as "hazardous to health" and "environmentally hazardous" according to the EU Hazardous Substances Regulation. And so on ...

Here are the findings:

These findings are confirmed by other findings, for example by Sarah Mackenzie ROSS of the University College London, in 2008. She studied 27 pilots: Cognitive function following exposure to contaminated air on commercial aircraft.

Important to understand is that: both clinical studies (HEUTELBECK, ROSS) document symptoms in those who have them. This is done using a type of monitoring, which is stipulated in Germany i.e. for illnesses and accidents that are related to the workplace (= prohibition of hazards in the workplace). The surveys did not claim to prove a causal connection across the board. Although plausible, it is not empirically secured, because this would have required a so-called control group. That is why both surveys call for further systematic research.

Regardless of this, as far as the distinction between immediate and long-term consequences of those who are negatively affected is concerned, Charles WINDER (Australia) and Jean-Christophe BALOUET (France)  who coined the term Aerotoxic Syndrome, already spoke in 2000 at the International Occupational Medicine Congress : Aerotoxic Syndrome: adverse health Effects following exposure to jet oil during commercial flights:

So the facts are - actually - obvious. But: they are not in line with the economic interests of the aviation business. The airlines would have to convert their entire fleet or even exchange it .  Switching from bleed air to ram air which in the mean time has been done in the Dreamliner (Boeing 787) (air intake at the rear) is not that easy. For Lufthansa, for example, that would involve more than 700 aircraft.

And, as long as there is no pressure from the customers, the passengers (in the parlance of the industry: "pax"), because they are unaware of the problem and the connection of a possible health problem to a particular flight or flight event is even less clear, the industry can rely on the imperceptibility (non-perceptibility) of this connection.

Only their own employees, the cabin crew and the pilots are those who are becoming increasingly sensitized by the incidents. We hear that the airlines, especially Lufthansa, or BG Verkehr are increasing pressure on the "employees" against this awareness. In future, we will focus on these subtle (oppressive) methods.

Unfortunately it is nothing new that it takes a very long time to get such a serious health problem

  • recognized (phase 1),
  • then accepted as a problem (Phase 2)
  • and then addressed in a solution-oriented manner (Phase 3)

The health consequences of the aerotoxic Syndrome, respectively from smell and fume events, have just passed from phase 1 to phase 2. Not officially, though. If the aviation industry admitted it publicly, the pressure to act would be enormous and the costs high.

Two examples will briefly show how long such a process can take and to what extent  politics which should  "avert damage from the people" and is therefore equipped with powers of action, regularly fails.

Asbestos and wood preservative syndrome

1) Asbestos: 40 - 80 - 90 years

As practical and versatile as the material is (high strength, heat- and acid-resistant, fireproof - hardly inflammable, high insulation value, and due to the fiber structure easy to process), as harmful it is to health.. Everyone knows about that fact nowadays.

As it has – actually - been known since 1900. At that time, the industrial boom of asbestos began. For example, it was patented under the name "Eternit". Years later, first people fell ill - the latency period can be several years, sometimes decades. For that reason no-one wanted to see the connection. Least those who benefited economically - e.g. the construction and cement industry. "Asbestosis" - as today's "aerotoxic syndrome" - was considered a ‚fata morgana’,  a"nocebo" as many nowadays say.

Although the disease was soon pretty clear, the connection was denied. Just as today the fume events and aerotoxic syndrome are.

In 1936, asbestosis was first recognized as an occupational disease.

In 1943 the asbestos-related lung cancer. The fact that asbestos is clearly carcinogenic in humans was only officially and politically recognized in Germany in 1973. A first prohibition for the dangerous material  and for the first time it is recognized as an occupational disease. One would think that this would have included a ban.
But, it was not like that. Only six years later, in 1979, the first ban for one (single) asbestos product: spray asbestos, was put in place. But this mineral was already contained in over 3,000 other products.

It was not until 1993 that asbestos was banned in Germany. EU-wide, this ban has only been in effect since 2005.

In other words:

Until the first restriction by the policy was in place, around 80 years had gone by, and  over 90 until the general ban came in to effect.  To this day, it is a huge undertaking for  asbestos patients wanting to receive acknowledgment for their suffering as an occupational disease: those who want help, ‚must go through a hell of bureaucracy’, as the weekly newspaper DIE ZEIT commented in 2014.

If one takes the time frames between the first appearance of a problem and the (tentative) recognition of this problem, e.g. as an occupational disease, and the time it takes for politics to take action, the simplified formula for asbestos is: 40 - 80 - 90 years. This amounts to 3 generations. That’s how well politics works in such matters, when it comes to balancing the health of the population and economic interests.

One must complete this result with the remark that the time period includes two world wars. But: it was also due to the delayed adaptation of the recognition of occupational diseases by the governing body of scientific knowledge, by politicians, especially the Federal Ministry of Labor and Social Affairs in the 60s and 70s. And, by the subtle methods of the asbestos industry, to regularly down-play this problem as for example Xaver BAUR, Professor of Occupational Medicine and longtime professor at various universities, states.

2) Wood preservative syndrome: 1 - 26 - 33 - 40 years

The toxic chloroprotective wood preservatives (PCP - pentachlorophenols) and their related essences (eg TCDD such as dioxin or Agent Orange) were slightly quicker.

Found to be toxic in 1956, Prof. SANDERMANN was not allowed to publish anything about it at the express request of his highest employer, the Federal Minister of Food, Agriculture and Forestry, Heinrich LÜBKE (CDU). Meanwhile, the huge chemical industry was looking for consumer-friendly products in order to be able to use the waste from toxic chlorine chemistry economically: wood preservatives, because wood was 'in'. That the products were toxic did not bother the chemical industry managers.

The people fell ill by the thousands. The connections were obvious. However, the Federal Health Office, under direction of Federal Minister of Health, Heiner GEISSLER (CDU), published in its brochure in 1982 - 26 years after the discovery of toxic substances - under the title "About the handling of wood preservatives" on page 16: "Do not prematurely associate certain general health conditions with the use of wood preservatives."

By now the Republic had become more democratic and mature. A large article in the magazine ‚Stern’ : ‚Gefahr im Gebälk’ published ‚in the year 26’ (1982) shakes up the population, allows victims and the sick to found an initiative: IHG – (Interessengemeinschaft der Holzschutz-Geschädigten) an organisation of wood preserve victims . They go to the prosecutor. Not where the SPD has ruled for decades and home of the BAYER group, but in Hesse, where the SPD, tolerated by the Greens, is leading a minority government that will soon lead to the first red-green coalition.

The prosecutor needs 7 years to investigate all cases watertight with the help of the Federal Criminal Police Office. He knows about the influence of industry on politics and justice, knows the expensive lawyers of large corporations and also suspects the purchasability of scientists, assessors and well-known occupational physicians who testify before the courts regularly, and in favour of the professional associations and the companies behind it – respectively against the interests of the victims.

Of course the judges do not want to, but then have to, and they waste a lot of time trying to drag it out . Public prosecutor Erich SCHÖNDORF investigates the companies and finds what he had feared: the proposed experts are on the corporations’ payroll. In particular, Germany's occupational medicine icon, Prof. Dr. Gerhard LEHNERT, who later becomes president of the "German Society for Occupational Medicine and Environmental Medicine (DGAUM)". The "independent assessor" has a consulting contract with BAYER AG, whose subsidiary DESOWAG is the largest producer of wood preservatives.

Independent of the public prosecutor's investigation, the Federal Environment Minister Klaus TÖPFER (CDU) issues a ban on pentachlorophenol (PCP-V) - 33 years after the discovery of its toxicity.

The first verdict for the victims, even if purchased experts deny any connection between the toxicity of the wood preservatives and the clinical pictures, will be collected by the BGH. Then, at the district court of Frankfurt, it ends with  the decision against a fine for those responsible. Statement by judge GEHRKE: "The public interest in prosecution has been significantly reduced  by various circumstances" - exactly 40 years after the prohibition of speech by the high politics.

This does not help the victims. Only a few can enforce claims in civil proceedings. Most have to give up due to financial reasons. Prosecutor SCHÖNDORF is more than angry:  as a criminal lawyer he coined a new term in a SPIEGEL essay: Crime in Science.

And this is the short version of the wood preservative syndrome: 1 - 25 - 33 - 40 years. A quarter of a century until the first major media report, and comparatively short until  politics draw the consequences; but 4 decades until the criminal proceedings for environmental and health crime - ultimately unsuccessful - ended (more at

The Aerotoxic Syndrome in Science

A comparison of asbestos and wood preservative syndrome with aerotoxic syndrome suggests that this problem has been going on for a very long time and is still not really recognized. It has been known since the fifties - at least.

Prof. Dr. Dietrich HENSCHLER from the Institute of Pharmacology at the University of Würzburg, was the first person to deal with tricresyl phosphates and also described the development of historical medical findings: "Tricresyl phosphate Poisoning". His result in 1958 - 12 years after the first jets were put into service for military purposes in 1943: Organophosphates, especially the forms of tricresyl phosphates, are toxic.  Poisonous. No matter where and how they appear in which products. At the time, however, only the manufacturers of engine oils and the engine builders know this.  Also the military, e.g. in the USA. Because there, pilots constantly become incapacitated on their flights.

In the 60s, 70s and 80s, flying is becoming more and more of a trend. The German peoples’ desire to travel especially to warmer countries with more sun, and the flourishing of tourism promote this development. Smell events or fume events are very rare. The speed with which popular destinations can be reached causes the customers of this new mass transport system to forget much of what may seem strange or temporarily unpleasant. Environmental and health awareness is something that gradually brings a new and colorful movement into the minds of people who call themselves the GREENS. They move into parliaments in the 1980s (1982 Hesse, 1983 Bundestag).

Flying is still relatively expensive and only cheaper on charter flights. The national airlines, mostly state-owned, are not (yet) threatened by low-cost competition or airlines from the Arab world where oil and kerosene are cheap. The cost calculations of the airlines therefore allow for regular maintenance at short intervals. Also, the maintenance of the turbines. A turbine is serviced every 15.000 hours and checked for the seals of the oil supply. Today (2017) the intervals are over 40.000 flight hours.

Iin the 90’s fume events are gaining public attention when British Aerospace launches its revised BAE 146 and BAe Avro RJ four-engine short-haul aircraft, which is widely used in Europe and Australia. The aircraft, or the 4 turbines, are vulnerable to smell and fume events.

In Germany, the pilot Sandy VERMEER, is regularly raising the alarm due to his negative experiences at his employer Cityline (Lufthansa). The airline 'sold' him the reason,  that it is  the "typical operating smell" of this aircraft.

In Australia, crew members are not as patient. Chris WINDER, toxicologist at the University of New South Wales, recalls the problem in one of the first German TV-reports (WDR Markt v. 29.3.2010): "First there were two pilots and a stewardess in 1997. A little later three, from thre ethere were suddenly five, five of them turned ten, then twenty, and I realized that there was something going on;  and then a French colleague with similar numbers of people with the same symptoms appeared and I realized that we have an international problem! "

As more and more people get involved, the Australian Parliament has to respond: a commission of inquiry is set up to acknowledge the dangers and problems of health: in a detailed report that coincides with the publication in which Chris WINDER, his French colleague Jean- Christophe BALOUET (an environmental scientist and paleontologist) and the American Harry Hoffman (doctor and physician for the US Air Force) give the problem a name: aerotoxic syndrome.  

Now, at the latest, the problem is internationally known: at the manufacturers of turbines, the airlines and in the sciences. Researchers from different disciplines are addressing the topic worldwide. And since then come to a) again, and b) more or less the same result: aerotoxic syndrome exists. But, too little is known about the many different substances: the chemical cocktail when a fume event occurs is made up of more than 200 individual substances. Substances with little known impact on health and the environment.

The names of the most important experts who have since been involved, are listed here: The scientists and experts: an ABC.

Also described in that text: those scientists and experts who, on behalf of the aviation-industry have been concluding in their comments, statements and opinions a) regularly , and b)  more or less with same results in their findings.  The results cannot be ignored. But the proof of a causal link can. It is not given. One of the best known, Professor Michael Bagshaw. His key message: "Much of the scientific data presented in support of the hypothesis that contaminated cabin air causes the alleged" aerotoxic syndrome "is not up to scientific consideration." BAGSHAW, formerly chief medical officer of British Airways, then professor of Aeronautical Medicine at King's College, London, is now a medical advisor at Airbus.

The slow Diffusion of Knowledge

Everybody knows the principle "in dubio pro reo." Meaning: before you make a (possibly irreversible) mistake, you decide to acquit someone who has (allegedly) done something.

There are analogous principles in science. Because science is designed for expansion, that is to say, progress in knowledge. As long as something has not yet been proven, it is theoretical, that is: it remains theory. Only when there is valid and sustainable evidence, theory becomes empirically based knowledge.

However, and vice versa: if, for example, there is a risk in the medical world that can be at the expense of people, then you adapt to it and act accordingly. Even if it has not yet been definitively proven: in doubt for life and health.

Applied to the aerotoxic syndrome, which reflects a wide range of symptoms, this means that it is assumed that the suspected causal relationships are present, at least as long as they can not be clearly refuted (falsified). Meaning: one must get to the bottom of the suspected connections. Open minded.

The latter can, strictly speaking, only be provided by independent scientists. Those who do not research on behalf of specific interests, and who are not on any pay-roll whatsoever. This must be taken into account when evaluating scientific statements and opinions. Prejudiced opinions and scientific crime are more widespread than one would expect.

So the short formula, regarding problem acceptance and solution options, looks like this from today's point of view:

It took just over 10 years to prove the engine oil’s toxicity after the first jets were introduced. Another 50 years until the problem was addressed in Germany within Lufthansa. Until  the subject made it’s way into (public) television (in 2009), it took around 60 years to this day, while the problems, of those who benefit from it are still being officially denied, and politicians refusing to acknowledge this unsatisfactory condition,  around 70 years have passed.One might think that the aerotoxic syndrome problem took place one hundred years earlier, in the era of the painful asbestos conflicts.

But we do not want to accept that. Now, we try to disclose the diverse influencial structures behind the scenes. And we will call a spade a spade and name names when it comes to the down playing  of the still existing problems.

(JL / translated by BB)