The majority of carcinogens from smoking tobacco are created by burning the plant fibers. Quitting smoking is the number thing someone who smokes can do to improve their health. Vaping exposes individuals to fewer carcinogens than smoking, but still has the negative health impacts of nicotine alone on heart and mental health and still some carcinogen exposure.
SmokeFree.gov has free evidence-based resources to help quit!
The copious amounts of sugar in our diets, antibiotics for livestock (or just factory farming in general), single-use plastics, and new pesticides/herbicides are today’s things that are “perfectly safe”…but not really.
With the exception of medicine, a big issue in the U.S. at least is that companies don’t have to proactively prove a new chemical/product is safe for the environment or public health before selling it. The EPA really only has the authority and staffing capabilities to step in once issues arise years or decades later. Just look at PFAS which are finally getting regulated decades too late.