Why is my windscreen constantly dirty ????

[matjk]

The inside windscreen of my 2012 Elise SC is constantly dirty , covered in a film that looks like condensation but is not , it smears of ok with a wipe but it’s a ball ache , much worse in hot weather , winter it doest so it ! It’s like the dashboard is outgassing but it’s 6 years old FFS and there is no smell ! Any suggestions to stop it ??

[matjk]

I don’t think it’s my shoes or the heater , I can clean it, leave the car without getting in it or starting it then return 3 days later and it’s back, it can just be mine ? Or maybe it is