Heavy drinking of alcohol, especially spirits (gin, whisky, vodka, rum etc), increases the risk of getting cancer of the mouth or throat.  This risk is increased more if the drinking is also linked to cigarette smoking. 

How the alcohol causes cancer is poorly understood. It has been suggested that a substance called acetaldehyde is responsible. Pure alcohol is broken down to make acetaldehyde. Acetaldehyde damages cells and may make them more likely to become cancerous. Studies have shown that the saliva of heavy drinkers contains acetaldehyde, so this could be the cause of damage to the cells lining their mouth and throat.