NOS Pomona Cables, gassing+split plastic how to clean?

[Vertamps]

Hello, bought these two vintage shielded Pomona cables(model 1167-60).
 There probably from the early 80's im guessing, Well i got an extra discount as each cable has a connector end that is split. Just gonna plastic epoxy them.
The cables are gassing and SMELL, and leave the smell on my hands.

*Will Soaking in isopropyl alcohol damage the cables further and cause more gassing?
-Cleaning a few times with dish soap and water seems safe option.
 
Alternative @$55 brand new from digikey, with the extra discount from the seller i figured i could save the cables and be happy.
/*edit,  a quick google mentions baking soda scrub, ill try that on one cable and dish soap on the second cable then compare.*/