Study: E-Cigarettes, Tobacco Linked to Increased Risk of Oral Cancer
An analysis shows that tobacco use increases the risk of oral cancer (duh). But e-cigarettes, too, were linked to an increased risk of oral cancer, particularly if people used the nicotine-delivery devices alongside tobacco products. 
Oral cancer includes cancers of the lips, tongue, cheeks, the floor of the mouth, the hard and soft palate, sinuses, and the throat.
For the study, Benjamin Chaffee and co-author Neal Benowitz of the University of California evaluated exposure to known carcinogens based on recent use of different nicotine and tobacco product types, and whether they were used individually or together.
Data for the analysis was gathered from the Population Assessment of Tobacco and Health, in which a population of U.S. adults gave urine samples to be analyzed for tobacco-specific nitrosamines (TSNAs) N’-nitrosonornicotine (NNN), a known oral and esophageal carcinogen, 4-(methynitrosamino)-1-(3)- pyridyl-1-butanol (NNAL), a metabolite of lung carcinogen (NNK), and total nicotine equivalents. 
Chaffee and Benowitz categorized participants based on their method of nicotine intake. 
- Combustibles (cigarettes, cigars, water pipe, pipes, blunts (cigars containing cannabis)
- Smokeless (moist snuff, chewing tobacco, snus)
- Nicotine replacement products
Recent use was defined as use within the prior 3 days, and non-use was defined as no use within the previous 30 days.
In all categories of use, participants showed elevated levels of nicotine and TSNA concentrations relative to non-users. 
Smokeless tobacco users had the highest TSNA exposures, regardless of whether they used products individually or together with other products.
Participants who used only e-cigarettes were exposed to lower levels of NNN and NNAL than other product users, though they had a similar amount of nicotine exposure.
But a majority of people who used e-cigarettes also used combustible tobacco products, and this raised their TSNA levels to that of exclusively cigarette-smokers. In turn, most non-cigarette tobacco users were found to be exposed to carcinogen levels comparable to or higher than those who used only cigarettes.
The results of the analysis were presented at the General Session of the International Association for Dental Research (IADR), which was held in conjunction with the IADR Pan European Regional (PER) Congress at the ExCeL London Convention Center from July 25 to 28, 2018.
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