carcinogens are not found naturally in plants.
Chemical additives and chemical pestacides cause carcinogens.

I dont have the best lungs and if it was not for steriods during my early youth I would not be alive today. If I smoke a few cigs in a day I weeze at night when going to sleep. If I smoke organic bud all day long I breathe fine. I can smoke all day every day for a year and have not one problem from breathing.
Its the chemicals that do it to me. If I smoke any thing that is organic I dont have a problem and if it was bad I would know it. The chems are what get me.