Note to self: Quit Smoking Bacon.
I don't know. There's something about hickory smoke that's almost irresistible. I figure the the Almighty gave his critters (including man) the ability to adapt to his surroundings. And man has been eating smoked meats over fire for thousands and thousands of years.
Nitrates and other preservatives are a recent developments, and perhaps our bodies have a hard time dealing with those, however there are other methods of preserving meats/food our ancestors have used for eons, such as salt curing, drying, acidic, sugar (honey), enzymes (fermentation) and smoking.