mine is a reebok one I got at Target, I've had it for 4 years, and it still smells like rubber. It makes my eyes burn when I use it, still! And I just realized how bad for me this likely is. Hmmmm..help!
I have the black Manduka (except mine was remarketed by Lulu so its purple) and it smelled for about a year. Just air it out. Or I think you can wash it.