Sunbeds have become an important source of UV-A exposure; up to 95–100% of the body is exposed in a sunbed compared to 15–50% during outdoor activities (Berwick, 2008). Recent publications in this journal have studied the effects of both UV-A (315–400 nm) and UV-B (290–315 nm) exposure on skin mutagenesis and carcinogenesis (e.g., Bennett, 2008), and this is further supported by Noonan et al. (2012). Fisher (2011) and Fears et al. (2011) emphasized that the use of sunbeds for indoor tanning is common and increases melanoma risk. Coelho and Hearing (2010) and Miyamura et al. (2011) described how UV-A exposure does not increase melanin production and confers little or no protection against subsequent UV exposure. However, as recently pointed out by authors such as Autier et al. (2011), it is important to understand which UV wavelengths actually increase melanoma risk, and at present, UV wavelengths from sunbeds have only rarely been measured in epidemiological studies.
In an effort to try and fill this knowledge gap, we compare herein our recent findings on UV-A and UV-B exposure from sunbeds and natural sun. Spectral (unweighted) UV irradiance was measured in 191 sunbeds in 78 tanning facilities throughout Norway using a mini spectroradiometer (Nilsen et al., 2011). Mean unweighted UV-A and UV-B irradiances and erythema weighted UV irradiance (W/m2) were presented for the bench, canopy and facial position of the sunbed. The erythema weighted UV irradiance was found by multiplying the unweighted total UV irradiance by the reference action spectrum for UV-induced erythema in human skin (Commission Internationale de L’Eclairage, 1999). UV irradiances from natural sun at 35°N (Crete, Greece) and 60°N (Oslo, Norway) were also estimated for a clear day in summer at noon (when the sun’s intensity is at its maximum). Figure 1 shows these values normalized to values from natural sun at 35°N. Normalized values were calculated for 10 min of sunbed exposure and 10 min of natural sun exposure, that is, the typical duration of a sunbed session. However, these normalized values would have been the same if we had used somewhat longer exposure times or if we had used UV irradiances alone (i.e., measured intensity without considering exposure time). Compared to natural sun, UV-A exposure from sunbeds was highest at the facial position (five times higher), although it was also higher at the bench and canopy (3.2 and 3.4 times higher, respectively). UV-B exposure from sunbeds was lower at all sunbed positions compared to that from natural sun (0.7–0.8 times), whereas the erythema weighted UV exposure was about the same from sunbeds and natural sun at 35°N. The 10-min UV exposure values (in kJ/m2) above each bar in Figure 1 show the higher UV-A exposure compared to UV-B and erythema weighted UV exposure. It is important to note that these estimates are based on mean values and that large variations were observed between the different sunbeds. Indeed, UV-B and UV-A irradiances from the measured sunbeds were 0.05–2 and 1.5–19 times, respectively, higher than those from the summer sun at 35°N. Mean erythema weighted UV exposure from sunbeds was similar to that from natural sun at 35°N (Figure 1C).
Sunbed regulations have focused on minimizing erythema with little emphasis on whether harmful effects are caused by UV-A or UV-B radiation (European Commission Health and Consumer Protection Directorate General Scientific Committee on Consumer Products, 2006; European Committee for Electrotechnical Standardization, 2010). The high values of UV-A exposure from modern sunbeds are alarming in light of the increased focus on UV-A irradiance as a carcinogen (El Ghissassi et al., 2009; Noonan et al., 2012).