Has anyone had a successful claim for JP4 exposure?

That is 100% incorrect information. JP4 was replaced because of its low-flash point and vulnerability to fires while transporting through pipes. JP4 was notorious for conducting static electricity in pipes which caused numerous fires and explosions. JP-8 was introduced with a higher flashpoint and lower freeze point making it ideal for both military and commercial use. The effects of JP8 are the same or similar to that of JP4. The CDC put out a 150 page report that states numerous times that the effects of JP4/JP8 on human health were minimal and caused no long term health effects. There is also no evidence to prove that the chemicals associated with JP4/JP8 cause cancer or any long term health conditions.

https://www.atsdr.cdc.gov/ToxProfiles/tp76.pdf#:~:text=Exposure%20to%20some%20components%20might%20occur%20from%20air,They%20might%20also%20spill%20some%20on%20their%20skin.