Unfortunately this problem is all too real. I’ve flown for several years and never experienced any major fume events, just whiffs of oil at various phases of flight, and most probably constant background levels of contaminated air that one can’t smell. By the nature of their design, engine oil seals can’t be 100% effective, so inevitably an amount of oil will enter the bleed air supply.
To start with, I had no real problems except worsening fatigue and short-term memory problems, and like many others, assumed it was part of the job or of getting older. But in the last year the symptoms quickly worsened, together with a host of new neurological problems, until the point I had to stop flying.
With low doses of toxic poisoning, initially the symptoms may subside quite quickly, but with more exposures, they get worse and take longer to go away until they become constant. Due to people’s different genetic make-up, some can detoxify better than others, so everyone has a different dose threshold.
This is a huge problem, and one the airlines and authorities just don’t want to know about.