Can smoking permanently damage your DNA?
Smoking damages your DNA in multiple ways simultaneously and leaves recognisable mutation patterns in at least 17 types of cancer. Quitting smoking demonstrably reduces the risk, as no association between smoking-related DNA damage and cancer has been found in former smokers.
Tobacco smoke contains more than 70 carcinogenic substances. The main culprits behind DNA damage are aldehydes, such as acrolein and formaldehyde. These attach themselves to DNA like chemical 'clamps', so-called adducts. This makes the DNA difficult to read and increases the chance of errors when the cell divides. On top of that, those same aldehydes inhibit the cell's repair mechanism, meaning the damage is less effectively cleared away.
This damage leaves a recognisable trail in the DNA. In smokers with lung cancer, 30% of the mutations in a crucial tumour-suppressor gene are of a specific type that occurs in only 12% of non-smokers. Analysis of more than 5,000 tumours confirms that smoking leads to a higher number of DNA mutations with several distinct signatures in at least 17 types of cancer. These patterns correspond precisely to where smoking substances attach to DNA.
Smoking substances are not confined to the lungs. Via the bloodstream they reach the liver, kidneys and bladder, and elevated adduct levels have been demonstrated in all of these organs. This explains why smoking raises the risk of so many different types of cancer, not just lung cancer. In bladder cells it has been shown that even a minute amount of smoking-related substance already causes measurable DNA damage.
There is also good news: in former smokers, no association was found between DNA adducts and cancer. This suggests that the body has repair capacity and that quitting smoking genuinely reduces the risk. Genetic predisposition partly determines how extensive the damage turns out to be. Passive smokers are also at risk: elevated levels of smoking-related damage have likewise been found in their blood.
The findings on mutation signatures and adducts in human tissues are based on large observational and molecular studies in humans (PMID 27811275, 12379884, 19440419, 12507921). The mechanism via aldehydes has been partly demonstrated in laboratory and animal research (PMID 35690412, 26556381, 12673355). The bladder cell data come from cultured cell tissue (PMID 35877975), not from experiments in a living body.