If someone smokes only once a year, on Purim, is one allowed to do so? To be detailed, this is an adult over the age of 20, a young working professional, and will not get addicted to the one cigar.
I assume you are asking about the health risk that smoking causes.
In general, and as documented here on MY, regular smoking is forbidden.
However smoking once a year is a different story as it is like many other low-risk activities that one engages in, e.g., driving for recreational purposes or some more dangerous sports. As I documented at length here, many low-risk activities are permitted, e.g.,
- based on what society considers reasonable (R Moshe Tendler)
- when danger is minimal and disaster rarely occurs (R Chaim Ozer Grodzinsky)
As always CYLOR for specific cases.