UVA tanning devices interact with solar-simulated UV radiation in skin tumor development in hairless mice

Abstract

The carcinogenic effect of three UVA tanning sources was studied in lightly pigmented hairless mice. The three tanning sources (Bellarium-S SA-1-12, Philips TL 09R and Philips TL 10R) have different emission spectra, and emit different amounts of UVB. Radiation from the tanning sources was administered for 20 min/day, 5 day/week in daily doses equivalent to those used in suntan salons. The radiation was given alone or after 12 weeks of exposure to solar-simulated UV radiation (SOLAR UV) (10 min/day, 4 day/week; daily dose, 19.5 kJ/m2 UVA and 3.9 kJ/m2 UVB). Irradiation with Bellarium-S SA-1-12 for 47 weeks and Philips TL 09R for 74 weeks induced skin tumours in 20/20 and 13/20 of the animals, respectively. When irradiation with Bellarium-S SA-1-12 and PHilips TL 09R was administered after 12 weeks of SOLAR-UV exposure, a strong enhancement of SOLAR-UV-induced photocarcinogenesis was observed (p < 0.001). Irradiation with Philips TL 10R was only slightly carcinogenic, and during 85 weeks of irradiation only one skin tumor appeared in a group of 20 mice. However, when irradiation with Philips TL 10R was administered after 12 weeks of exposure to SOLAR UV, an enhancement of SOLAR-UV-induced carcinogenesis was observed (p < 0.001). Our results suggest that the hazards of exposure to commercial tanning devices are increased when they are used after a period of natural sun exposure. Even tanning sources with a low carcinogenic potential are able to increase SOLAR-UV-induced carcinogenesis significantly.