Probably living in a forest, breathing fresh air, eating natural food and drinking source water is less carcinogenic?
Trees pump out all sorts of carcinogenic crap. The Great Smokey Mountains aren't smokey from man-made pollution or fire, after all. If the canopy isn't too heavy, living outdoors means susceptibility to skin cancer. Natural food, especially plants also contains all sorts of toxins. And water in nature can contain lead and arsenic and kill you too. But if you live like that, your chance of cancer might be cut down by getting bitten by a snake or attacked by a wolf or a bear or something, or just hypothermia.