Potent Genotoxicity of halogen lamps, compared to fluorescent light and sunlight

Abstract

The light emitted by halogen lamps induced mutations in salmonella typhimurium and DNA damage in Escherichaia coli, as shown by the hypersensitivity of DNA repair-deficient strains. The mutagenicity of halogen lamps was considerably higher than that of fluorescent light and of sunlight, even at much lower ifiuminance levels. Excision mechanisms and SOS functions were involved in repairing light-induced base-pair substitutions and franieshift errors in bacterial DNA. At variance with solar irradiation, which produces mutagenic effects over a wide UV spectrum, genotoxicity of halogen lamps was almost exclusively due to far-UV wavelengths transmissible through UV-R-250 and UV-R-280 interference filters. The main mutagenic component of fluorescent light was transmitted through the UV-R-280 filter. Far-UV wave lengths (254 nm) were almost 10⁴ more mutagenic than near-UV wavelengths (365 nm). All light sources exhibited some residual mutagenicity even following filtration through various cloths. On the other hand, appropriate glass or plastic covers consistently prevented mutagenic effects. This emphasizes the urgent need for a compulsory shielding of halogen and fluorescent lamps in order to prevent unnecessay exposures to genotoxic and potentially carcinogenic UV radiations.