Mechanisms for the production of DNA damage in cultured human and hamster cells irradiated with light from fluorescent lamps, sunlamps, and the sun.

Light from fluorescent lamps has recently been shown to be toxic and mutagenic to V-79 hamster cells. In this report it is shown that visible light (> 295 nm) from fluorescent lamps, sunlamps and the sun produces DNA single-strand breaks in hamster or human cells irradiated with these sources. Some of the DNA breaks and the mutagenic action of the light can be averted by filtering the light through para-aminobenzoic acid, which filters out wavelengths below 345 nm. The radical scavengers dimethyl sulfoxide, glycerol, and potassium iodide can also protect the cells from some of the DNA breaks, but the scavengers do not protect V-79 cells from the mutagenic action of the light sources. Hydrogen peroxide and riboflavin and tryptophan photoproducts also are shown to produce DNA breaks in V-79 cells; however, these treatments are not mutagenic to V-79 cells. These data suggest that several types of lesions may be produced in the DNA of irradiated cells by several different mechanisms, and that some of the lesions may be related to toxicity and mutagenicity of the light sources, and others may not.