ALDH2 and lung cancer: In addition, individuals with the atypical allele of the aldehyde dehydrogenase 2 (ALDH2) gene, which results in inactive ALDH2 activity, bringing about a high blood concentration of acetaldehyde, the initial metabolite of alcohol, are prevalent in the Japanese population.4 Acetaldehyde has been shown to be carcinogenic in experimental animals,5 and therefore Japanese people may have a different susceptibility to lung cancer than Westerners.