crablab
The air cycle machines on the 787 use oil for lubrication, and can also fail in such a way as to introduce oil fumes into the cabin air.
After one of the previous aero-toxic shouting matches on PPRuNe, I started watching the Boeing incoming 21.3 reports for fume events (so all Boeing and Douglas/MacDac commercial aircraft) and continued to do so for over a year (I recently retired so I no longer have access).
What I noticed was, by a wide margin, most reported fume events were galley related - either burned/overcooked food, or electrical smoke from a galley appliance. Most of the rest were also some sort of electrical overheat. Less than ten percent were related to the cabin air system in some way. A few were reported right after an engine water wash (if the people doing the water wash don't do all the correct steps, some of the wash fluid can get into the engine bleed system). A couple others were failures of the ECS packs, and one was the failure of an air cycle machine on a 787. I saw two that were traced to the engine - both Rolls powered 757s. Naturally there were several where no fault was found.
If someone was really serious about investigating aero-toxicity, the first thing they should do is go start sampling the air around the major airports - it's far more polluted than the stuff you're breathing at cruise. Not only is there the exhaust from all those airplanes, turbine engines use differential air pressure to keep the oil where it belongs and consume far more oil at/near idle than they do at power. So all those aircraft with their engines idling are spewing oil fumes out the exhaust.