What's in a Cigarette: 70+ Chemicals You're Actually Inhaling
Quick answer: A burning cigarette generates smoke containing over 7,000 chemical compounds. Of these, at least 70 are known or probable human carcinogens. The most harmful include tar (a complex carcinogen mixture), carbon monoxide (blocks oxygen), formaldehyde, benzene, polycyclic aromatic hydrocarbons, and tobacco-specific nitrosamines — plus nicotine driving addiction.
People know cigarettes are "bad," but the specific chemistry is often vague. Making the abstract concrete — knowing that you're inhaling the same chemical used for embalming fluid, or the same compound found in gasoline — changes the relationship with the habit.
How Cigarette Smoke Is Created
When tobacco burns at temperatures of 900°C at the tip (and cooler in the smoke column), it undergoes combustion, pyrolysis, and distillation simultaneously. This creates two phases:
Gas phase: Carbon monoxide, nitrogen oxides, hydrogen cyanide, volatile organic compounds, ammonia
Particle phase (tar): Nicotine, polycyclic aromatic hydrocarbons (PAHs), tobacco-specific nitrosamines, phenols, catechols, heavy metals
Total cigarette smoke contains approximately 7,357 compounds, according to a 2012 analysis in Chemical Research in Toxicology. The following covers the major toxicological categories.
The Carcinogens
Tobacco-Specific Nitrosamines (TSNAs)
- NNK (4-methylnitrosamino-1-3-pyridyl-1-butanone)
- NNN (N-nitrosonornicotine)
- TSNAs are formed from nicotine during tobacco curing and combustion
- Potent lung, oral, and esophageal carcinogens
- Found only in tobacco products — not naturally occurring in food or environment
Polycyclic Aromatic Hydrocarbons (PAHs)
- Benzopyrene (most studied; potent lung carcinogen)
- Chrysene, anthracene, fluoranthene
- Formed from incomplete combustion of organic material
- Same compounds found in charred meat, vehicle exhaust, and industrial smoke
- PAHs form DNA adducts that trigger mutations in tumor suppressor genes like TP53 — a key driver of smoking-related cancer risk
Benzene
- Known human carcinogen (causes leukemia)
- Present at 50–80 μg per cigarette
- Also found in gasoline vapors and vehicle exhaust
- No safe exposure level established
Formaldehyde
- Group 1 carcinogen (IARC)
- Causes nasopharyngeal cancer and leukemia
- The same chemical used in embalming and industrial resins
- Produced from combustion of filter and tobacco materials
Acetaldehyde
- Group 1 carcinogen
- Second most abundant carbonyl compound in cigarette smoke
- Also produced when the body metabolizes alcohol
- Synergistically carcinogenic with other tobacco compounds
1,3-Butadiene
- Potent carcinogen linked to leukemia
- Present in cigarette smoke at concentrations higher than most industrial exposures
- Also found in vehicle exhaust and rubber manufacturing
Arsenic, cadmium, chromium, lead, nickel
- Heavy metals absorbed from soil into tobacco leaves
- Several are Group 1 carcinogens (arsenic, cadmium, chromium VI)
- Cadmium in cigarettes is a primary cause of smokers' kidney damage and contributes to bone loss
The Respiratory Toxins
Carbon Monoxide
- Binds hemoglobin 200x more tightly than oxygen
- Heavy smokers have 5–15% of hemoglobin saturated with CO
- Directly impairs cardiac and muscular oxygen delivery
- Detailed mechanism: Carbon Monoxide and Smoking
Hydrogen Cyanide
- Inhibits cellular respiration by blocking cytochrome oxidase
- Directly damages lung cilia (the hair-like structures that clear mucus)
- Present at 400–500 μg per cigarette
- Major contributor to smokers' susceptibility to respiratory infections
Ammonia
- Added to tobacco (and generated during combustion) to enhance nicotine absorption
- Converts nicotine from bound to freebase form, making inhalation more efficient and increasing addiction potential
- Irritant that damages airway mucosa
Acrolein
- Extremely reactive aldehyde
- Disables the cilia-mediated lung clearance system
- Forms DNA adducts
- Present at 60–140 μg per cigarette
Tar: The Mixture
"Tar" is not a single compound — it's the collective term for the particulate matter in cigarette smoke after water and nicotine are excluded. Tar is a complex mixture of PAHs, nitrosamines, phenols, catechols, and other compounds.
Beyond direct chemical toxicity, many of these compounds also cause epigenetic changes to DNA, silencing tumor-suppressor genes without altering the genetic code itself. When deposited in the lungs, tar accumulates because smokers have impaired cilia function. A pack-a-day smoker deposits approximately 1 cup (250mL) of tar in their lungs per year. See more: What Tar Does to Your Lungs
Nicotine: The Addictive Agent
Nicotine itself is not a primary carcinogen, though it has tumor-promoting effects and promotes angiogenesis (blood vessel growth that tumors need). Its role in the disease burden of smoking is primarily through addiction — it binds to acetylcholine receptors in the brain, triggering dopamine release that keeps people smoking long enough for the carcinogens to cause cancer.
The Additive Question
Cigarette manufacturers add hundreds of compounds to tobacco — sugars, flavorings, humectants, and chemicals like menthol and ammonia. Some additives have direct health effects; others modulate the burn characteristics or make smoking more palatable for new users.
Menthol deserves specific mention: it provides a cooling sensation that reduces the harshness of smoke inhalation, makes inhaling more comfortable, and suppresses the cough reflex — resulting in deeper inhalation and greater carcinogen delivery to the lungs. Menthol cigarettes are not safer.
The Comparative Perspective
It's worth noting: no other consumer product is legally sold that is known to kill more than half of its long-term users when used as directed. Cigarettes occupy a unique regulatory exception — they remain legal partly due to historical economics and political history rather than any assessment of acceptable risk.
References
- Counts ME et al. "Smoke composition and predicting relationships for international commercial cigarettes." Regulatory Toxicology and Pharmacology, 2005.
- Rodgman A, Perfetti TA. The Chemical Components of Tobacco and Tobacco Smoke. 2009. CRC Press.
- Hecht SS. "Cigarette smoking: cancer risks, carcinogens, and mechanisms." Langenbeck's Archives of Surgery, 2006.
- International Agency for Research on Cancer. IARC Monographs, Volume 83: Tobacco Smoke and Involuntary Smoking. 2004.
Frequently Asked Questions
How many chemicals in cigarettes are carcinogenic?
At least 70 compounds in cigarette smoke are classified as known or probable human carcinogens by IARC. This includes 15+ specific PAHs, 10+ nitrosamines, and several heavy metals.
Are organic or "natural" cigarettes safer?
No. Organic tobacco still produces the same combustion products when burned. The carcinogens in cigarette smoke are primarily created by combustion, not by pesticides or additives. Organic cigarettes are not meaningfully safer.
Does filtering cigarettes remove the toxic chemicals?
Cellulose acetate filters reduce some particulate matter, but ineffectively filter gases like carbon monoxide, hydrogen cyanide, and volatile organics. Filtered cigarettes may actually be smoked more intensely (deeper inhalation, more puffs) to compensate, negating filtration benefits.
Are e-cigarettes free of these chemicals?
E-cigarettes don't involve combustion, so they don't produce PAHs or carbon monoxide at meaningful levels. But they are not chemical-free — e-cigarette aerosol contains propylene glycol, vegetable glycerin combustion products, flavoring chemicals (some carcinogenic), and nicotine. The long-term health effects are not yet fully established.