economic trends in tobacco Chart: Has Smoking Lost Its Cool? Finance & Development, December 1999

(EDIT: AliceD's answer also depicts the well-known staining of teeth, which are not keratinized, showing that the staining mechanism is likely a nonspecific adsorption of greasy things onto surfaces.) The stain can be fixed through the involvement of free radicals and other reactive species in cigarette smoke, like formaldehyde

Looking southwest, 2007.

While slightly less sensitive than GC-MS, ELISA offers a reliable option for routine nicotine testing in medical contexts, especially when quick results are needed at a lower cost

The cure will pull moisture out of the pork belly and liquid will accumulate in the bag