single-strand breaks and spontaneous base losses ≤10^4: with other types of damage ~10^5 DNA damages/cell/day
||Hoeijmakers JH. DNA damage, aging, and cancer. N Engl J Med. 2009 Oct 8 361(15):1475-85. doi: 10.1056/NEJMra0804615. p.1476 right column 2nd paragraphPubMed ID19812404
|| Lindahl T. Instability and decay of the primary structure of DNA. Nature 1993 362: 709-715 DOI: 10.1038/362709a0  Sander M, Cadet J, Casciano DA, et al. Proceedings of a workshop on DNA adducts: biological significance and applications to risk assessment Washington, DC, April 13-14, 2004. Toxicol Appl Pharmacol 2005 208: 1-20 DOI: 10.1016/j.taap.2004.12.012PubMed ID8469282, 16164957
||P.1476 right column 2nd paragraph: "DNA integrity is threatened from three sides. First, spontaneous reactions (mostly hydrolysis) intrinsic to the chemical nature of DNA in an aqueous solution create abasic sites and cause deamination [primary sources 12,13]. Second, our own metabolism generates reactive oxygen and nitrogen species, lipid peroxidation products, endogenous alkylating agents, estrogen and cholesterol metabolites, and reactive carbonyl species [ref 14], all of which damage DNA. Reactive oxygen and nitrogen species alone generate several kinds of single-strand breaks and more than 70 oxidative base and sugar products in DNA [primary source 13]. Third, DNA is damaged by exogenous physical and chemical agents, but this damage is to some extent avoidable. The estimated numbers of single-strand breaks and spontaneous base losses in nuclear DNA are as high as 10^4 per cell per day [primary sources 12, 13]. Together with other types of spontaneous damage, the total may be close to 10^5 lesions per cell per day [primary source 12]. A single day in the sun can induce up to 10^5 UV photoproducts in each exposed keratinocyte, and inflammation can cause high levels of oxidative damage locally."