How bout the National Cancer Institute?
https://progressreport.cancer.gov/prevention/red_meat
It's not entirely clear exactly what produces the increased risk of bowel and/or brain cancer but they are looking into it.
"more research is needed to understand how red meat and processed meats influence cancer risk. The increased risk may be explained by the iron and fat content in red meat, and/or the salt and nitrates/nitrites in processed meat. Additionally, when meat is cooked at high temperatures, substances are formed that may cause cancer."
I also usually imagine overconsumption is the problem but according to some - it's not like you're entirely safe as long as you stay below a certain limit.
" the risk of developing bowel cancer goes up 1.18 times for every 50 grams of processed meat eaten per day"
https://www.cancercouncil.com.au/1i...nd-cancer/red-meat-processed-meat-and-cancer/
That's ..also misleading.
To a large extent - inhaling smoke from anything is dangerous. Carbon monoxide being one of the culprits.
With burning tobacco, tar is also a main concern.
Tar is the name for the resinous, partially combusted particulate matter made by the burning of tobacco and other plant material in the act of smoking.
You don't necessarily need to add stuff in a lab to make tobacco dangerous - if you burn it, you get tar.