Smoke, “products of combustion”, aren’t good for your lungs, but seems to me there would be a big difference between inhaling some of the smudge smoke and smoking a cigarette. Also some people use a LOT of smoke when smudging, some just enough to know it happened. Your own practice can be using just a small amount. I.e. moderation is the key. Also keep in mind your own allergies. Some people would have a tough time being exposed to sage on a regular basis, some would not notice. The amount of smoke is inconsequential to the results, the effect comes from intention and your focus on the ritual.