Carcinogenicity
Acetaldehyde is a probable or possible carcinogen in humans. In 1988 the International Agency for Research on Cancer stated, "There is sufficient evidence for the carcinogenicity of acetaldehyde (the major metabolite of ethanol) in experimental animals." In October 2009 the International Agency for Research on Cancer updated the classification of acetaldehyde stating that acetaldehyde included in and generated endogenously from alcoholic beverages is a Group I human carcinogen. In addition, acetaldehyde is damaging to DNA and causes abnormal muscle development as it binds to proteins.
A study of 818 heavy drinkers found that those who are exposed to more acetaldehyde than normal through a defect in the gene for acetaldehyde dehydrogenase are at greater risk of developing cancers of the upper gastrointestinal tract and liver.
Many microbes produce acetaldehyde from ethanol, but they have a lower capacity to eliminate the acetaldehyde which will then lead to the accumulation of acetaldehyde in saliva during heavy alcohol drinking. Acetaldehyde is also the most abundant carcinogen in tobacco smoke; it is dissolved into the saliva while smoking. Fermented food and many alcoholic beverages will also contain significant amounts of acetaldehyde. Acetaldehyde, derived from mucosal or microbial oxidation of ethanol, tobacco smoke, and diet, appears to act as a cumulative carcinogen in the upper digestive tract of humans.
Read more about this topic: Acetaldehyde, Safety