What is this??

This has been happening for awhile now and I cannot for the life in me figure out what it is! At first I thought it was coal dust because my hubby started the coal mines and I would be like “oh he touched something” and never really paid much mind to it but it’s been months since he’s worked in the coal mines, and I can washed these things a thousand times and it always comes back!

It’s like a thin black layer that is so hard to get off! It only gets on plastic or my paper products. I also do not use candles! Help? Lol

( I’ve only seen it happen in the kitchen so far!)