While we could find no documents explicitly stating that smokers would not be accepted, NASA does say that they support a smoke free workplace policy.
In order to qualify as an astronaut for space flight, one must be in top physical shape. A week-long process of personal interviews, medical screening, and orientation will be required for both civilian and military applicants under final consideration.
Anecdotal sources suggest that physical examination include: physical measurements of just about everything, eye examinations, dental examinations, MRIs, stringent heart and cardiovascular check-ups, and the VO2 max stress test. There is no age limit, and if you can pass you're good to go, but chances of passing do decrease with age.
There's a myth about menthol cigarettes keeping people from going into space, as it contain fiberglass (used to make car parts) or the menthol may crystalize in your lungs, and when introduced into a weightless environment the crystals could stab your lungs or cause any other health mishaps.
But there is no evidence to support it. The fact is that there are more than 7,000 known chemical compounds, as well as toxic and carcinogenic agents, in tobacco and cigarette smoke. Some of these include ammonia (used in fertilizer and household cleaning products), formaldehyde (used to preserve dead bodies), and methanol (used in antifreeze). All of these chemicals have been shown to cause cancer and other deadly diseases. - Smokefree.gov
Want to become an astronaut? Check out some insider tips on NASA's astronaut selection at Astronautforhire.com.