“…The normal endogenous concentration of formaldehyde in blood is approximately 0.1 mM in rats, monkeys, and humans, and it is two-to four-fold higher in liver and nasal mucosa of rats. In extreme cases some frozen fishes, especially of gadoid species, can accumulate up to 200 mg of formaldehyde per 1 kg of moist weight due to the enzymatic degradation of a natural fish component-trimethylamine oxide (Rehbein, 1995;Pavlishko et al, 2003). Formaldehyde is classified as a mutagen and possible human carcinogen (Feron et al, 1991), one of the chemical mediators of apoptosis, i.e.…”