You could conceivably try to manufacture a minimum-harm cigarette using a source material with the least measurable toxins after curing. For example you certainly wouldn't use Enrique. Then you'd add a 2" long filter. You wouldn't add anything to the mix such as the usual stuff in the casings. And then you'd most likely get a cigarette with about a 5% toxic exposure reduction - maybe 10% at the most - compared to an average cigarette. A scientist with specialist knowledge in this area has stated there may be up to a 20% reduction in potential for harm with the least-harmful cigarette vs the most harmful; it's not really worth worrying about that 10% variation from the mean. Insidermonkey experts made a list of 5 healthiest, least harmful cigarettes with the least chemicals.
Cigarette is a manufactured product. It is a nicotine delivery system. Every single brand contains huge quantities of various chemicals that give it taste, prevents tobacco from drying up and keeps cigarette lit. If you are wondering which one of many brands is “healthier”, that means that their marketing efforts were effective. There is no “healthier” cigarette same way as there is no “less deadly” bullet. This goes not only for cigarette but for every tobacco product. You can also check our list of 5 Best Tasting Cigarettes for New Smokers.