I have heard that with car interiors as they get older that they break down and give off fumes which are what is causing the issue.
I have also been watching the cars general apholstory (spelling) and see, of all things, the interior door opening handle surround is breaking down at a great rate of knots on, mainly, the front LH side.
The car is not in constant use and people rarely sit or use any of the passenger doors/seats.
Front passenger side
Front drivers door
Has anyone found any way to slow this process down, maybe layers of Armour all or some other product can help ?