September 2014:
‘Feature: Are aerotoxic syndrome claims in the air? – Part 1’ (Page 4 onwards) -
https://www.bc-legal.co.uk/images/pdf/BCDN64
‘Although the evidence indicates toxicity is unlikely, the COT* has nevertheless advised it would be desirable to prevent fume events. What progress has been made in this regard? As to the aircraft manufacturing industry, it has largely failed to implement any preventative measures. With respect to Airbus, it appears to believe there is no issue with air contaminants. John Leahy, Chief of Operations, referred to the possibility of air cabin contaminants as ‘absurd’; he confirmed none of Airbus’ aircraft will be bleed air free.
Indeed, its new A350 XWB aircraft, which is in the late stages of flight testing and due to be first delivered later this year, has adopted a bleed air system for cabin air.’
*Committee On Toxicity (U.K.)
As you can see from the document above there were many recommendations made by various parties & agencies which were never acted upon. Couple that with one of the worlds largest aircraft manufacturers being in complete denial to any possibility of the air onboard its aircraft being contaminated - and you have a perfectly reasonable explanation as to why there have been so many deaths of previously fit & healthy young pilots and cabin crew, along with the 1000’s (if not tens of 1000’s) of injuries caused from exposure to and inhalation of fumes from heated engine oil and hydraulic fluid within the aircraft air supply which is bled-off from the aircraft engines directly to the aircraft cabin and cockpit without any filtration.

‘Contaminated Cabin Air: A Health Problem becomes certainty. The Chronology of the socalled Aerotoxic Syndrome’
‘Passengers should never be exposed to health risks when flying! This is one of the principles of the European Aviation Safety Agency, EASA. Nevertheless, there is a health risk: in the form of contaminated cabin air. Although it is now medically provable that flying can deposit toxins in the body of passengers, pilots and flight attendants, the entire industry wraps itself in a silent cloak. Likewise the authorities.’
https://www.anstageslicht.de/themen/english/aerotoxic/contaminated-cabin-air-a-health-problem-becomes-certainty-the-chronology-of-the-socalled-aerotoxic-syndrome/

‘The entire industry wraps itself in a silent cloak; likewise the authorities’. So true.
Add to that a judicial system in the U.K. which picked up 51 individual cases (lodged with various courts in England against 5 UK registered airlines) and called them ‘a cohort’. The same judicial system which decided that only 8 cases will be heard sometime in 2022 with the other 43 cases ‘paused’ and dependent on the outcome of the eight - it’s blatantly obvious what is really going on.
But rather than work on solutions to eliminate the contaminated air in aircraft, every party involved insists on denying, ignoring, evading and dismissing the issue.

Quote from George Bates - Senior Engineer - Boeing Environmental Controls - 28th October 2007:
‘I will add the Propulsion folks do not account or certify the bleed air quality they feed to us. For the 747-S, John Klym was the most recent to try to get the Propulsion folks to step up to owning their system by-products. All he got was the run around like I got in 2000 for the 767-400.’
‘Who knows what the by-products are in hot synthetic Turbine Oil. The Material Data Sheet has warnings about skin contact and breathing the fumes of the oil, let alone the complication of partial combustion products.’
‘Bottom line is I think we are looking for a tombstone before anyone with any horsepower is going to take interest.’