OK, I am not in the aviation industry and not sure where you are coming from but ... there is evidence that suggests jet fuel may cause PD. Folks exposed to jet fuel on aircraft carriers have a significantly higher rate of PD.
The Department of Defense (DOD) has, and continues (with Senate/House annual approval) to support funding a study on this and other related issues included in the NETPR (I knew you would ask ... Neurotoxin Exposure Treatment Parkinson's Research ... or something very close). Here is one site with info from Parkinsons Action Network, THE advocacy organization for people with Parkinsons. I'm sure there are others: