Chewing tobacco, a form of smokeless tobacco, is a product that is not burned but rather placed between the cheek and gum, where nicotine and other chemicals are absorbed through the lining of the mouth. While highly dangerous and linked to numerous fatal diseases, this product is generally not the direct cause of the vast majority of lung cancer cases. Lung cancer is overwhelmingly a disease of smoke inhalation, where the toxic byproducts of combustion are deposited directly into the respiratory system. However, this distinction does not make chewing tobacco a safer option, as it contains at least 28 known carcinogens that pose other immediate and long-term health hazards.
Why the Risk Differs
The fundamental difference in risk lies in the method of delivery, which determines where the toxic agents concentrate within the body. When tobacco is smoked, the high heat of combustion generates thousands of chemicals, with at least 70 of these being confirmed carcinogens. These substances are inhaled as smoke and directly coat the lung tissue, which is the mechanism responsible for about 90% of lung cancer diagnoses.
Chewing tobacco, by contrast, is absorbed through the oral mucosa, bypassing the lungs entirely in the initial process. The cancer-causing compounds, such as tobacco-specific nitrosamines (TSNAs), enter the bloodstream through the mouth’s lining and are then distributed throughout the body. This systemic absorption means that while the lungs are spared the direct assault of smoke, the carcinogens can still reach and impact other organs.
Some epidemiological studies suggest that smokeless tobacco users who have never smoked may still face an increased risk of lung cancer compared to non-users. This secondary risk is thought to be a result of the systematic distribution of carcinogens like NNN and NNK. However, the most significant danger from chewing tobacco remains localized to the areas of direct contact and the organs that process the absorbed toxins.
Primary Cancer Risks Associated with Chewing Tobacco
The most pronounced cancer threat is to the oral cavity, which includes the lips, tongue, cheeks, and gums, due to the prolonged, direct contact with the product. The tobacco is held against the delicate squamous cells that line the mouth, where its high concentration of carcinogens causes genetic damage. This cellular change can lead to the development of squamous cell carcinoma, the most common form of oral cancer linked to chewing tobacco use.
The potent cancer-causing agents in chewing tobacco are Tobacco-Specific Nitrosamines (TSNAs), which are formed during the curing and fermentation of the tobacco leaf. The levels of TSNAs in smokeless tobacco products can be significantly higher than in cigarettes, making them particularly dangerous. These carcinogens are directly absorbed into the tissue where the tobacco rests, explaining why cancer often develops specifically at the site of placement.
Swallowing tobacco juices exposes the digestive tract to these concentrated TSNAs. This exposure significantly increases the risk for cancer of the pharynx (throat) and the esophagus. Furthermore, smokeless tobacco use is associated with an elevated risk of pancreatic cancer, suggesting that the absorbed carcinogens circulate and affect organs far from the initial point of contact.
Non-Cancer Health Effects
Chewing tobacco causes severe and irreversible damage to the oral structure. The constant abrasion from the tobacco particles, combined with the chemical irritants, causes the gum tissue to recede, exposing the tooth roots. This gum recession does not naturally reverse and can lead to bone loss around the teeth, eventually causing tooth loss.
Many chewing tobacco products contain added sugars, which combines with reduced saliva flow to rapidly accelerate tooth decay and cavity formation. A common sign of damage is the development of leukoplakia, which are leathery, white or gray patches that form where the tobacco is held. These patches are considered pre-cancerous lesions that frequently progress into oral cancer.
The high nicotine content also exerts an immediate effect on the cardiovascular system. Nicotine is readily absorbed through the oral lining, and a single period of chewing can deliver as much nicotine into the bloodstream as smoking three cigarettes. This influx of nicotine acts as a stimulant, causing an increase in both heart rate and blood pressure, which places undue strain on the heart over time. The rapid, high dose of nicotine makes smokeless tobacco intensely addictive, often more difficult to quit than cigarettes.