Nicotine accumulates in toenail tissue whether or not the toes belong to a smoker or a nonsmoker who had passive exposure. Researchers at UC-San Diego followed 850 men over a 12 year period, collecting their nail clippings and assaying them for nicotine.  Their study showed that men who had the highest nicotine levels were three and a half times more likely to develop lung cancer.  We might have guessed that anyway, but no one else seems to have used toenail clippings to make that determination-which, of course, might contain other useful biomarkers for chronic illnesses. MORE