For most of us, there's a clear correlation between bad breath and smoking: if you smoke, you will have an offensive tobacco odor on your breath that all non-smokers will detect if they are close enough. Of course, a tobacco odor also tends to linger on the clothes and hair of a smoker, so tobacco on the breath is probably not a very large issue. Surprisingly, however, there are more pieces of the puzzle that tie bad breath to smoking in other ways.
Smoking apparently inhibits saliva production. This is a problem because saliva plays an important role in inhibiting the multiplication of anaerobic bacteria, which live at the back of the tongue, and sometimes in spaces between teeth and gums, and between the teeth. These anaerobic bacteria (bacteria which live where there is no oxygen) produce volatile sulfur compounds (VSC) when they digest proteins for nutrients. So bad breath and smoking go hand in hand because smoking decreases saliva and a decrease in saliva results in an increase in VSC producing anaerobes in the mouth.
Smoking also increases the risk of gum disease and tooth decay. Smokers apparently have more cavities that non-smokers. They also have gums that tend to detach from the teeth and recede, leaving exposed roots and spaces between gums and teeth where those VSC producing bacteria can flourish. The roots of the teeth, which are supposed to be protected by healthy gums, are not covered with enamel, so they are more subject to tooth decay. In this scenario, bad breath and smoking result from an unhealthy mouth full of tooth decay, periodontal disease, and proliferating VSC producing bacteria.
It's not just bad breath and smoking that you need to worry about: other tobacco products carry similar risks. Pipe smoking and cigar smoking cause all the same problems as cigarette smoking, and chewing tobacco has all these and more. Smokeless tobacco frequently has sugar added to it, and may contain particles of grit, both of which have implications for oral health. The association between sugar and dental cavities is well known, and chewing on sand will put wear and tear on tooth enamel, also contributing to tooth decay.
So it's not just the odor of cigarette smoke on the breath and that brownish yellow stain on the teeth that you need to think about when you get close to someone else. The best solution is, of course, to quit smoking, but if you can't do that, use a good breath product that will help control the VSC producing bacteria that link bad breath and smoking. That will help a bit.
R. Drysdale is a freelance writer with more than 25 years experience as a health care professional. She is a contributing editor to Bad Breath and Smoking, a blog dedicated to the treatment of bad breath.