What harmful substances are present in tobacco smoke? 

There are over 7,000 chemical substances in tobacco smoke, and at least hundreds of harmful substances are currently known, with at least 70 carcinogenic substances. The main harmful substances include the following:

(1) Nicotine (alkaloid): It is the primary addictive substance in tobacco smoke. After entering the brain, it induces a sense of pleasure.

(2) Volatile substances: The main harmful ones include carbon dioxide, carbon monoxide, nitrogen oxides, sulfur-containing gases, and various volatile organic compounds.

(3) N-nitrosamines: Multiple types of N-nitrosamine substances are present in tobacco smoke, mainly generated during the processing, curing, and storage of tobacco. They are carcinogenic.

(4) Polycyclic aromatic hydrocarbons (PAHs): PAHs are products of incomplete combustion of organic matter. Tobacco smoke contains over 500 types of PAHs, among which acenaphthene, acenaphthylene, anthracene, benz[a]anthracene, and benzo[a]pyrene are carcinogenic.

(5) Aromatic amines: Aromatic amines and their derivatives are primarily used as antioxidants in fuels, pharmaceuticals, pesticides, plastics, and rubber products. Studies have shown that tobacco smoke contains aromatic amines, with 2-naphthylamine and 4-aminobiphenyl being carcinogenic.

(6) Heterocyclic amines: Heterocyclic amines are compounds containing at least one cyclic hydrocarbon and one amine-substituted ring. In addition to tobacco smoke, they are also present in certain foods (such as grilled meats).

(7) Free radicals: Tobacco combustion generates a large number of free radicals, which are distributed in both the gas and particulate phases of tobacco smoke. The main free radicals in the gas phase of tobacco smoke are alkyl, alkoxy, and nitrogen oxide (NOx) radicals. Free radicals have strong oxidizing properties and can trigger oxidative stress in the human body.

Research results indicate that oxidative stress plays a role in pathological processes such as inflammation, endothelial dysfunction, lipid abnormalities, and platelet activation.

(8) Metals and radioactive substances: Studies have shown that the metals in tobacco and tobacco smoke are mainly absorbed from the soil. Therefore, factors that can alter soil composition (such as sediments, fertilizers, and sewage irrigation) can affect the metal content in tobacco smoke.

When tobacco is smoked, the temperature at the combustion center can reach as high as 900°C, causing many metals to volatilize and enter tobacco smoke, where they can be inhaled by humans. The concentration of metal substances in tobacco smoke is related to tobacco processing, ventilation, additives, and their concentration in tobacco leaves.

Metals found in tobacco smoke include cadmium, lead, cobalt, chromium, antimony, thallium, and mercury. Many of these metals in tobacco smoke are carcinogenic and can also cause DNA damage. Radioactive substances such as lead-210 and polonium-210 can also be detected in tobacco.