Smoking involves the combustion of tobacco, releasing thousands of chemicals inhaled into the body. This practice introduces a complex mixture of substances, affecting various bodily systems.
How Smoking Harms the Body
The respiratory system, directly exposed to tobacco smoke, experiences immediate and chronic damage. Chemicals in smoke, such as hydrogen cyanide and tar, paralyze and destroy cilia, tiny hair-like structures lining the airways that sweep away mucus and trapped particles. This damage impairs the lungs’ cleaning mechanism, leading to mucus buildup and increased susceptibility to infections and inflammation.
Beyond the airways, smoking profoundly affects the cardiovascular system. Nicotine and other chemicals contribute to the hardening and narrowing of arteries, a process known as atherosclerosis. This occurs as substances in smoke damage the inner lining of blood vessels, promoting plaque formation and reducing blood flow. Reduced blood flow can lead to heart attacks and strokes.
Tobacco smoke contains over 7,000 chemicals, with at least 70 known to cause cancer. Carcinogens include polycyclic aromatic hydrocarbons (PAHs) and tobacco-specific nitrosamines (TSNAs). PAHs, like benzo[a]pyrene, are potent carcinogens formed during incomplete combustion of organic material. TSNAs, including NNK and NNN, are highly carcinogenic compounds derived from nicotine and other tobacco alkaloids. These substances directly damage DNA, leading to mutations that disrupt normal cell growth and division, promoting cancer development in various organs, including the lungs, mouth, throat, esophagus, and bladder.
The Science of Nicotine Addiction
Nicotine, a primary component of tobacco, drives the addictive nature of smoking through its neurobiological effects. When inhaled, nicotine rapidly reaches the brain, typically within seconds. There, it binds to specific nicotinic acetylcholine receptors (nAChRs), particularly the α4β2 subtype, widely distributed throughout the brain.
This binding triggers the release of neurotransmitters, notably dopamine, in brain regions associated with reward, such as the nucleus accumbens. The surge in dopamine produces pleasurable sensations, reinforcing the smoking behavior. Repeated nicotine exposure leads to neuroadaptations, including an increase in nAChRs, making the brain accustomed to high nicotine levels.
As nicotine levels decline between cigarettes, the brain’s accustomed state is disrupted, leading to withdrawal symptoms. These symptoms can include intense cravings, irritability, anxiety, difficulty concentrating, and depressed mood. The discomfort of withdrawal prompts individuals to smoke again, alleviating symptoms and restoring dopamine levels, perpetuating the cycle of addiction. This interplay forms the biological basis of tobacco dependence.
Exposure to Tobacco Smoke
Exposure to tobacco smoke extends beyond the direct act of smoking, encompassing both secondhand and thirdhand smoke. Secondhand smoke is a mixture of exhaled smoke and sidestream smoke from the burning end of a cigarette. This involuntary exposure contains harmful chemicals found in mainstream smoke, including carcinogens like benzene and tobacco-specific nitrosamines.
Children are vulnerable to secondhand smoke due to their developing bodies and faster breathing rates. Exposure increases their risk of respiratory infections like bronchitis and pneumonia, ear infections, and more frequent and severe asthma attacks. Secondhand smoke is linked to sudden infant death syndrome (SIDS) and impaired lung development in children.
Thirdhand smoke refers to residual chemicals from tobacco smoke that settle on surfaces, clothing, furniture, and dust, persisting long after a cigarette is extinguished. These residues can be re-emitted into the air or absorbed through skin contact or ingestion, especially by young children who touch contaminated surfaces and then their mouths. Thirdhand smoke contains carcinogens like NNK and polycyclic aromatic hydrocarbons. These compounds can react with indoor pollutants to form new, potentially more toxic substances over time.
Strategies for Cessation
Quitting smoking involves behavioral and pharmacological approaches to address physical addiction and learned behaviors. Behavioral therapies provide coping strategies and support systems. Cognitive Behavioral Therapy (CBT) helps identify smoking triggers and develops alternative responses, teaching relaxation techniques and relapse prevention skills. Counseling, including telephone quitlines, offers personalized guidance and support during cessation.
Pharmacological interventions help manage nicotine cravings and withdrawal symptoms. Nicotine Replacement Therapy (NRT) delivers nicotine without tobacco smoke’s harmful chemicals, available as patches, gum, lozenges, and nasal sprays. These products reduce withdrawal discomfort, making it easier to abstain from cigarettes.
Other prescription medications, like bupropion and varenicline, also assist in quitting. Bupropion, an antidepressant, reduces nicotine cravings and withdrawal symptoms. Varenicline works by partially stimulating nicotine receptors in the brain, reducing cravings and withdrawal, and blocking the pleasurable effects of nicotine from cigarettes. Combining behavioral support with these medications increases the likelihood of successful cessation.