 acrolein, formaldehyde, acrylonitrile, 1,3-butadiene, acetaldehyde, ethylene oxide and isoprene).Endogenous (metabolically-caused) DNA damage is also very frequent, occurring on average more than 60,000 times a day in the genomes of human cells (see DNA damage (naturally occurring)).Externally and endogenously caused damages may be converted into mutations by inaccurate translesion synthesis or inaccurate DNA repair (e.g.