Inorganic arsenic (i-As) is a well-established human carcinogen to which millions of people are exposed worldwide. It is generally accepted that the genotoxic effects of i-As after an acute exposure are partially linked to the i-As-induced production of reactive oxygen species, but it is necessary to better determine whether chronic sub-toxic i-As doses are able to induce biologically significant levels of oxidative DNA damage (ODD). To fill in this gap, we have tested the genotoxic and oxidative effects of environmentally relevant arsenic exposures using mouse embryonic fibroblast MEF mutant Ogg1 cells and their wild-type counterparts. Effects were examined by using the comet assay complemented with the use of FPG enzyme. Our findings indicate that MEF Ogg1-/- cells are more sensitive to arsenite-induced acute toxicity, genotoxicity and ODD. Long-term exposure to sub-toxic doses of arsenite generates a detectable increase in ODD and genotoxic DNA damage only in MEF Ogg1-deficient cells. Altogether, the data presented here point out the relevance of ODD and Ogg1 genetic background on the genotoxic risk of i-As at environmentally plausible doses. The persistent accumulation of DNA 8-OH-dG lesions in Ogg1-/- cells during the complete course of the exposure suggests a relevant role in arsenic-associated carcinogenic risk in turn.