Aerotoxicity, if it exists, has nothing to do with recycled air in the air-con system. It is a reaction to oil contamination in the air-con which is caused by low pressure bleed air at the labyrinth seals that keep the engine oil in the engine where it should be. The only thing keeping the oil from entering the bleed air system is the pressure of the bleed air itself. This means that oil can contaminate the system when the bleed pressure is low such as during engine start. There is no doubt that some people suffer short term effects from the exposure including hayfever type symptoms, headache, nausea, etc. It is not clear whether it causes long term effects and it won't be easy to prove because the symptoms are fairly non-specific and could be caused by a number of other things. Many people don't even suffer any short term effects. I've had a number of cabin air quality "events" and I've suffered no ill effects aside from being able to smell oil, other crew members have come off feeling worse though.