Do you have more information on this? Seems interesting!

Just search for the paper on the topic, written by the Phillip Morris Unbiased Research Group. it explains how frogs breathing air got more cancer then frogs trapped in airtight boxes and only allowed to breathe exhaled tobacco smoke, who mostly died for other reasons. seems legit...

Well there is much known fact about how tabacco absords radiating material. But until now I have not found anything about how that changed during the ages. But simple logic tells me there must have been an affect on how dangerous smoking is.