Really this is one of the more useless statistics. It's pretty much impossible to OD unless you're a toddler and you accidentally drink juice.

What matters is the affects small amounts of nicotine, repeatedly, have over time. Nicotine increases blood pressure and so it slowly destroys your cardiovascular system. Smoking is, of course, bad for your lungs.

The combination of lung damage and heart damage is deadly. Typically heart failure will require more oxygen in your blood to make up for the fact your heart doesn't work. But the lungs are bad at extracting oxygen when they have pulmonary damage.

Maybe not a useful statistic, but it's definitely 100% not harmless in the correct dosage. It has been successfully used for both murder and suicide. Being water-soluble, just soak tobacco leaves in water and you'll eventually be able to extract a useful amount.

I smoked for >20 years, quit for 10, then started again when dealing with grief after my partner passed away, and smoked for another 10. I get it, literally: high-blood pressure, etc. Although, when quitting, it was always the tar that really drove me crazy.

Another thing I've realized, is that smoking is a double-whammy vector towards heart disease: smoking promotes heart disease directly, but smoking also promotes gum disease, and gum disease promotes heart disease.