I bought a mouse mat a week or so ago. It's one of the ones with the gel wrist support. The thing FUCKING REEKS. I can't quite tell if it's a burning plastic smell (like if it's reboxed stock from a warehouse fire) or if it's just a very strange smelling plastic material they've used, but it's noxious, really unpleasant. I figured the smell would go away after a few days but it hasn't. I tried bathing it in detergent for an hour or two, that was a few days ago now and it seems to have done nothing. My hand comes away smelling of it whenever I use it. I'm basically ready to throw the fucking thing away but I know people around here have peculiarly strong materials science knowledge so I thought it couldn't hurt to ask.
Ha! I have bought two of those in the last 2-3 years, and can attest to that. They stink so bad but the smell went away after a short while.
Soaking it in a 50/50 mix of vinegar & water works with some things. If that doesn't work, covering it in bicarbonate of soda and leaving it for a day or two could help absorb some of the fumes.
I don't have any vinegar or bicarb of soda. Maybe I'll put it out on the patio. Expose it to the elements for a week or so. I'd swear it's starting to stink out the room, but that's probably my imagination. It's definitely rubbed off onto the desk, though. Ironically it's a "Trust" brand mousepad, I'll be trusting them with fuck all in the future.