Fig. 3.

Hypothetical mechanism of possible human diseases caused by endogenous formaldehyde in individuals with the ALDH2*2 allele. GSH depletion occurs due to systemic or local oxidative/glycation stress, leading to the failure of the main formaldehyde detoxification pathway via ADH5. Under such conditions, individuals with the ALDH2*2 allele, which normally oxidizes formaldehyde at lower levels, accumulate intracellular formaldehyde. The increased endogenous formaldehyde may induce various human health problems