I discovered that list when I was researching my book about early 20th century toxicology, The Poisoner’s Handbook. And I remember being surprised because I had believed that it wasn’t until the mid-20th century, maybe a little before the famed 1964 U.S. Surgeon General report on the dangers of smoking – that we really knew anything about the health risks of smoking.

Of course, that 1920s list turns out to only be the bare start of the one we’ve assembled today. By some counts, there are a good 4,000 chemical compounds in cigarettes and, of those, the U.S.