The Sensitization of Near-Ultraviolet Radiation Killing of Mammalian Cells by the Sunscreen Agent Para-aminobenzoic Acid

The wavelengths of sunlight considered to be responsible for erythema and skin cancer formation are in the range 290–340 nm. Formulated sunscreens usually contain an agent that absorbs in this wavelength region, and one of the most widely used is para-aminobenzoic acid (PABA). Previous work has demonstrated the sensitization by PABA of the lethal and mutagenic effects of near-ultraviolet (UV) radiation in a model bacterial system.

Experiments with the mouse lymphoma L5178Y cell line have now demonstrated sensitization by PABA of the lethal effect of near-UV radiation, the extent of which, after correction for absorption of UV radiation by PABA, bears a direct relationship to PABA concentration.

The limitations of these results in predicting the response of human skin to the presence of PABA during exposure to UV radiation is emphasized.