"Aerotoxic Syndrome" is the collective name for a wide range of seemingly vague and unrelated health complaints. It is a controversial term, for a disease whose existence has been persistently denied for decades, by an very strong airline industry lobby. In 1999, Dr. Harry Hoffman (U.S.A), Prof. Chris Winder (Australie) and Jean Christophe Balouet PhD (Frankrijk) published a scientific report in which the term “Aerotoxic Syndrome” was used for the first time: "Aerotoxic Syndrome: Adverse health effects following exposure to jet oil mist during commercial flights". The report describes the results of exposure to vapours of the lubricating oils used in jet engines. Even though the airline industry tries to make you believe differently, this does occur quite frequently. As a result of a.o. oil leakage from the engines, the air that is used for cabin pressurization and ventilation gets contaminated by oil particles containing a.o. Organo Phosphates.
The symptoms of Aerotoxic Syndrome are in fact the direct result of poisoning by these Organo Phosphates. These are among the most toxic chemical compounds known to man. From a chemical perspective, they are closely related to nerve gases such as Sarin. They can seriously damage the brain- and nerve system, thereby causing a wide range of (often neurological) medical complaints.
The airline industry (both aircraft manufacturers and airline companies) have persisted for decades that "there is no evidence of any causal relationship" between these matters. A parallel with the tobacco industry pops into mind here: Tobacco smoke had been known to be highly toxic for a long time. Also, the inhalation of these toxic substances was known to promote lung cancer. But even then, it remains difficult to legally prove that the lung cancer that an individual develops today, was indeed caused directly by his smoking in the past.
Incidents are underreported
The reporting by crew of so-called "Fume Events", incidents where larger quantities of toxic substances enter the cabin, have been discouraged by many airline companies for years. By reporting the (sometimes serious!) complaints about cabin smoke and/or odours in the Technical Logbook as an "odour incident" (which sounds a lot less serious than "Fume Event"), or even not reporting them at all, time consuming maintenance and high costs are avoided. For example: the A320 series of Airbus is one of the types that are frequently involved in Fume Events. Some time ago, Airbus adopted a maintenance rule, prescribing a thorough cleaning of the entire air conditioning system's interior after each Fume Event, a procedure that takes 4-5 days in a hangar. But, when such an incident is written down as an "odour incident", the aircraft can be released to service within a few hours... As consequence however, that aircraft will become more and more contaminated, with all the consequences of that for crews and passengers. On the internet these days, lists are shared of notorious "stinck planes", airplanes which are repeatedly involved in Fume Events, without proper preventative measures being taken.
Number of reported incidents is increasing
Over the last few years, an increase in the number of reported Fume Events can be noticed. Two explanations can be pointed out for this phenomenon:
1) Among crew, there is an increasing level of awareness of the dangers involved. One hears more often of colleagues having suffered (often permanent) health damage from contaminated cabin air. In the Netherlands alone, hundreds of cockpit- and cabin crew members have turned unfit for work (in a number of cases even permanently) as a result of exposure to Organo Phosphates during their normal daily work. World wide we're looking at thousands of such cases. When subsequently confronted with such a situation, chances are that the crew will take it more seriously, and take appropriate measures (such as an immediate return, diversion, or execute a precautionary/emergency landing as soon as possible). Until a few years ago, these problems were very often strongly downplayed, especially by cockpit crew, with all it's implications...
2) Until the nineties, engine manufacturers would prescribe every jet engine to undergo a Heavy Maintenance inspection every 5.000 flying hours. The engine needed to be taken off the aircraft for that and be completely disassembled in the work shop. Part of this check was the replacement of all oil seals. Obviously this was a costly operation! The later generations of jet engines however, became more and more reliable and less prone to malfunctions. As the airline companies were pressing to cut maintenance costs, maintenance was gradually shifted from flight time-based to (wear) condition-based. Not too long ago, an engine manufacturer proudly announced that one of its engines had served for 25,000 flying hours without a single shop visit! This increased reliability is obviously a great achievement, but the used oil seals have barely changed over time, and so they wear just as fast as they used to do! The result is a drastic increase in the number of oil leak- and Fume Events (that are preferably camouflaged as "odour incidents" by the airline companies)