Ok, this information is a little old, but for some reason I was thinking about this again today. Maybe it's because I was puttering a little too much today while at work. Dunno, but here's some links on the issue for your parousal:
An article from National Geographic
An article from Science World (sort of, copied on to findarticles.com)
I never realized that my puttering was so dangerous. Well, I'm sure that my family knows, but I just wasn't listenening before now. Maybe I should start to listen?