ALDH2 and head and neck cancer: Considering the carcinogenicity of acetaldehyde and the significantly increased risk for head and neck cancer, esophageal cancer, and other cancers for ALDH2*2 variant carriers, implementation of chemopreventive strategies may be a worthwhile effort for specific high-risk groups, such as ALDH2*2 individuals who are heavy drinkers or smokers or industrial workers who have a higher acetaldehyde exposure burden.