How harmful is 1-3 cigarettes a week?

A year back, i spent 3 months in spain and because of the smoking culture i was surrounded by there, i took up smoking. I was smoking about half a pack a day. I came home then and found it very hard to quit but within a month, i was on 2-3 a week and kept that habit. I usually have one midway through the week and then another one, only occasionally do i allow myself a third one. I haven't exceeded this in the last year so i won't but how bad is 1-3 ciggies a week?