Internal hazards: baseline DNA damage by endogenous products of normal metabolism

Recent improvements in the ability to detect chemically modified bases in D NA have revealed that not only does the genetic material incur damage by fo reign chemicals, but that it also sustains injury by reactive products of n ormal physiological processes. This review summarises current understanding of the DNA-damaging potential of various substances of endogenous origin, including oxidants, Lipid peroxidation products, alkylating agents, estroge ns, chlorinating agents, reactive nitrogen species, and certain intermediat es of various metabolic pathways. The strengths and weaknesses of the exist ing database for DNA damage by each class of substance are discussed, as ar e future strategies for resolving the difficult question of whether endogen ous chemicals are significant contributors to spontaneous mutagenesis and c ancer development in vivo. (C) 1999 Elsevier Science B.V. All rights reserv ed.