Recently Hidaka et al studied damage to DNA by TiO2 and ZnO after UV exposure. The authors observed an increase in nicks on supercoiled DNA plasmids forming a relaxed and ultimately linear DNA conformation as a result of hydroxyl radicals generated by UV irradiated by TiO2 and ZnO. The mechanism of the reaction includes the hydroxyl radical attacking the ribose, deoxyadenosine, guanosine, and cytidine nucleotides within 30 minutes of irradiation. This reaction results in the rapid degeneration of DNA constituent nucleotides deoxyadenosine-‘5’-monophosphate, guanosine monophosphate, and cytidine monophosphate in the presence of UV irradiated TiO2 and ZnO.