An Analysis of UVA Emissions from Sunlamps and the Potential Importance for Melanoma

Abstract

Exposure to solar UV radiation is a risk factor for cutaneous malignant melanoma (CMM). Epidemiologic studies have also considered the use of sunlamps as a possible contributor to CMM. We measured and analyzed the emission spectra of six different currently marketed sunlamps and a historical sunlamp, the UVB-emitting FS lamp, and compared the results to solar exposure. For a typical tanner (20 sessions @ 2 minimal erythema doses (MED)/session), the annual UVA doses from commonly used fluorescent sunlamps were 0.3-1.2 times that received from the sun. For a frequent tanner (100 sessions @ 4 MED/session), the annual UVA doses from fluorescent sunlamps were 1.2-4.7 times that received from the sun and 12 times for recently available, high-pressure sunlamps. To determine biologically effective doses, action spectra for squamous cell carcinoma (SCC) in humans and for melanoma in the Xiphophorus fish (XFM) were applied to the sunlamps' emission spectra. The results for the effective doses using the SCC action spectrum tracked the UVB doses, while the results using the XFM action spectrum tracked the UVA doses. When combined with UV exposure received from the sun, typical sunlamp use results in an approximate doubling of annual effective dose, if the XFM action spectrum is applied. Frequent use, however, can increase the annual effective XFM dose by as much as 6 times what would be received from the sun alone for fluorescent sunlamps and as much as 12 times for newer, high-pressure sunlamps.

Epidemiologic Evidence for Different Roles of Ultraviolet A and B Radiation in Melanoma Mortality Rates

“…Most of the energy received from the sun at ground level is in the visible and infrared and only a small proportion is in the ultraviolet (23). Historically, it was estimated that 5% of solar UV irradiation was UVB (24). However, more recent spectrophotometric measurements suggest that UVB is approximately 3% of total UV energy at noon in midsummer.…”

True

“…Lastly, the only existing animal model of melanoma for which an action spectrum has been estimated, the platyfish-swordtail hybrid model, shows that UV-A exposure may be more important than UV-B (Setlow et al, 1993). Indeed, in terms of biologically effective doses (applying action spectra for the platyfish-swordtail hybrid model), frequent sunbed use can increase the annual effective dose as much as six times what would be received from the sun alone (Miller et al, 1998). When considering all these data together, it may be tempting to suggest that primarily UV-A and not UV-B is associated with the development of melanoma.…”

Effects of Ultraviolet Exposure Behaviors on Skin Pigmentation and Melanoma

“…Frequent tanners, defined as those with 100 or more sessions total in their lifetime, using modern highpressure sunlamps, were found to have up to 10-times greater annual UV exposure compared to other tanners [4].…”