Earlier quoted context omitted.
The thing is that both activities were always clearly likely to be harmful, if you took a step back from the cultural perspective that accepted them so thoroughly. Smoking tobacco is inhaling an acrid a mix of chemicals that makes you cough, kind of feel sick and lightheaded, smells awful and leaves a tan stain - it’s not hard to guess that it’s not healthy. Remember that half of people who die from tobacco die from…
"Both activities were always clearly likely to be harmful". With the benefit of 70 years of medical research this is an easy statement to make, but at the time this was far less clear - smoking was for a long time actively promoted as having health benefits [1][2] It's easy from a modern perspective to look back and apply our accumulated wisdom, but it was not self-evident that smoking was necessarily bad. Otherwise…
For example, lore is replete with stories of young people's initial experiences with smoking involving coughing, choking, turning green and feeling nauseous or vomiting. There's also the fact that nicotine has long been known to be a poison as strong as cyanide, and has been used for insect control by Europeans as far back as 1763.