Not sure why I was downvoted, look here: http://en.m.wikipedia.org/wiki/Polonium#Tobacco

Edit: I stand corrected. Thank you

It's not entirely true. Even though the vast majority of tobacco-related cancer deaths may be caused by polonium, cancer deaths are still only around a third (iirc) of total tobacco deaths.

Compare the 12,000 at the Wikipedia link to the 1.6 million here:

http://www.who.int/cancer/prevention/en/

From those numbers, the polonium is not a primary concern.