Are you sure it was "hours"? (how many hours?)
I read it a long time ago so I can't remember specifics, but it was an absurdly long time. My feeling at the time after reading about the research methods were that they were completely unrealistic.
It's the same reaction I'd have to an anti-smoking group telling you you'll get X tar and Y nicotine off a cigarette, and their tests hook a vacuum to the back of a cigarette from light time to finish, including what you get from the burning butt. Just not real-world.