The problem requires a scientific approach;
I would suggest:
1. There has to be agreement there is a problem: that involves some scientific research and analysis.
2. If discovered that cabin air does have toxic ingredients they need to be identified.
3. The source needs to be identified. It has been mentioned various possibilities.
4. If the source is engines then the spotlight falls on the engine manufacturers.
5. If the source is in the fuselage, zircon' ducts, packs, etc. then the spotlight is no the aircraft manufacturers. How ever they are the seller of there final product on toto.
6. The XAA with jurisdiction in the country of manufacturer has to take responsibility for enforcing the process all the way through to solution.
Who is going to enforce that the XAA fulfils its duties? They have a duty of care to pax & crew. Perhaps their government has to hold them to account and ensure they act on their responsibilities. talking about it in the bar, or even the newspapers, will be short term effective at best. Imagine there being an air pollution event in a factory that affects workers. The union would have all the workers outside PDQ until it was solved. Is this another demonstration of the true influence of todays aircrew unions? If their is a problem why are they not protecting the health of their members?
Why do the unions not combine first with the Airline Passengers Association. They are all in the same smelly boat; so to speak.
There are some 'ifs' here, so let's find the truth soonest and so a strategy can be discussed and implemented.