The nitrosamines are considered a danger and are formed during the growing, curing, fermenting, and aging of tobacco. The others are polonium–210 (a radioactive element found in tobacco fertilizer) and polynuclear aromatic hydrocarbons (also known as polycyclic aromatic hydrocarbons). This is coming from Cancer.gov, bullet #2.
Smokeless Tobacco and Cancer - National Cancer Institute
From your link:
"7. Should smokeless tobacco be used to help a person quit smoking?
No. There is no scientific evidence that using smokeless tobacco can help a person quit smoking (7). Because all tobacco products are harmful and cause cancer, the use of all tobacco products is strongly discouraged. There is no safe level of tobacco use. People who use any type of tobacco product should be urged to quit. For help with quitting, ask your doctor about individual or group counseling, telephone quitlines, or other methods."
I've been around long enough to know when I read "all tobacco products are harmful and cause cancer" and "there is no safe level of tobacco use", I can eliminate the source as factual data. This works for me but of course YMMV.
From
Smokefree Health Effects:
"One set of chemicals that are talked about a lot in the science are nitrosamines, or tobacco-specific nitrosamines (TSNAs). Nitrosamines are a class of chemicals that we are exposed to in food and through other pathways. Some of these are known to be carcinogens in some quantities. Whether the TSNAs might be carcinogens is the subject of debate. Fortunately, it does not matter whether these chemicals might cause cancer since we have evidence about whether smokefree tobacco itself causes cancer. The evidence shows that people who use ST do not have measurable increases in cancer rates or mortality. So it does not really matter what chemicals are there."
A link from that page helped me put it into better perspective with some hard data:
Lee and Hamling 2009;
"Results
Eighty-nine studies were identified; 62 US and 18 Scandinavian. Forty-six (52%) controlled for smoking. Random-effects meta-analysis estimates for most sites showed little association. Smoking-adjusted estimates were only significant for oropharyngeal cancer (1.36, CI 1.04–1.77, n = 19) and prostate cancer (1.29, 1.07–1.55, n = 4). The oropharyngeal association disappeared for estimates published since 1990 (1.00, 0.83–1.20, n = 14), for Scandinavia (0.97, 0.68–1.37, n = 7), and for alcohol-adjusted estimates (1.07, 0.84–1.37, n = 10). Any effect of current US products or Scandinavian snuff seems very limited. The prostate cancer data are inadequate for a clear conclusion.
Some meta-analyses suggest a possible effect for oesophagus, pancreas, larynx and kidney cancer, but other cancers show no effect of smokeless tobacco. Any possible effects are not evident in Scandinavia. Of 142,205 smoking-related male US cancer deaths in 2005, 104,737 are smoking-attributable. Smokeless tobacco-attributable deaths would be 1,102 (1.1%) if as many used smokeless tobacco as had smoked, and 2,081 (2.0%) if everyone used smokeless tobacco."
It has been a while since I have read about ST. I remembered it being pretty safe, but forgot the details. It's good to look this stuff up once in a while
