Attached.

Cigarette smoking
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Cigarette smoking is the leading cause of lung cancer, accounting for about 85% of lung
cancers. Risk for lung cancer increases with the duration, intensity and depth of smoke
inhalation.

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Second-hand (passive) smoking also causes lung cancer, but is less strongly associated
compared to active smoking.

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Cigarettes contain multiple carcinogens (more than 60) that have been shown to induce
cancers in laboratory settings.
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Polycyclic aromatic hydrocarbons (PAH) such as benzo[α]pyrene produce
mutations in the p53 gene. G to T transversion within the p53 gene is a molecular
signature of lung tumours caused by tobacco mutagens.

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N-nitroso compounds are a major group of chemicals found in tobacco smoke,
several of which are potent animal carcinogens.

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Nicotine: causes addiction to cigarette smoking and is also a promoter for carcinogenesis.
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Sympathetic/parasympathetic activation: nicotine binds to and activates
nicotinic cholinergic receptors, which are located on both sympathetic and
parasympathetic postganglionic neurons. The endogenous ligand for this receptor
is acetylcholine (ni...