[Retric]

I have seen a few definitions of casual smoking, I meant (one cigarette per week). I have seen not smoking every day, averaging less than one cigarette per day used.

"Pack year" is often used as a risk assessment: https://en.wikipedia.org/wiki/Pack-year 1 pack year in a lifetime is not safe, but it is a vastly lower risk profile than a pack+ per day smoker.