Abstract
Overexposure to ultraviolet (UV) radiation is the main modifiable risk factor for skin cancer. The Global Solar Ultraviolet Index (UVI) was introduced as a tool to visualize the intensity of UV radiation on a certain day, which should enable and encourage people to take appropriate protective measures. The ‘low’ exposure category of the UVI, defined by a rounded UVI value of 0, 1 or 2, was linked to the health message ‘No protection required’ by the World Health Organization and partner organizations. However, published evidence corroborating this advice is not available. To evaluate the erythemal risk of low UVI days, we analyzed 14,431 daily time series of ambient erythemal irradiance data measured at nine stations of the German solar UV monitoring network during the years 2007–2016. We analyzed the proportion of days in the sample for which ambient erythemal doses calculated for various time intervals exceed average minimal erythemal doses (MEDs) of the Fitzpatrick skin phototypes I–VI to assess the potential for erythema arising from sun exposure on days with low UVI values. Additionally, we calculated for each day the minimum exposure duration needed to receive one MED. Our results indicate that on days with a UVI value of 0, risk of erythema is indeed negligible. Conversely, the abovementioned health message appears misleading when melano-compromised individuals (skin type I and II) spend more than 1.5 hours outdoors on days with a UVI value of 2. Under rare circumstances of prolonged exposure, MEDs of the two most sensitive skin types can also be exceeded even on days with a UVI value of 1. Hence, current WHO guidance for sun protection on days with low UVI values needs reconsideration.
Highlights
IntroductionUltraviolet (UV) radiation, approaching Earth every day in the form of sunlight, has officially been classified as carcinogenic to humans by the International Agency for Research on Cancer [1]
Ultraviolet (UV) radiation, approaching Earth every day in the form of sunlight, has officially been classified as carcinogenic to humans by the International Agency for Research on Cancer [1].Overexposure to UV radiation is responsible for a substantial proportion of melanoma and nonmelanoma skin cancers [2], the incidence rates of which have been increasing for decades worldwide [3,4]
We analyzed the proportion of days in the sample for which ambient erythemal doses calculated for various time intervals exceed average minimal erythemal doses (MEDs) of the Fitzpatrick skin phototypes I–VI to assess the potential for erythema arising from sun exposure on days with low Ultraviolet Index (UVI) values
Summary
Ultraviolet (UV) radiation, approaching Earth every day in the form of sunlight, has officially been classified as carcinogenic to humans by the International Agency for Research on Cancer [1]. From a geographical latitude of 47.91°N to 54.92°N, a geographical longitude of of the7.91°E stations was chosen in such a way regions in Germany were covered: to 14.11°E, and a height above sea that level all of 4major to 1205climate m [18,19]. Rhine valley of (both of which stations suffer from polluted air), Uplands, and the Alpine foreland This way, locations the measuring provide anthropogenically polluted air), and the Alpinewhere foreland. The locations ofto thethe measuring a representative sample of places in Germany people themselves sun in their stations provide a representative sample of places in Germany where people expose themselves to working life or in their leisure time. From here, the term ‘day’ in this paper does not refer to a single specific calendar day, but rather to our unit of observation, which is one diurnal course of Eer during this calendar day at one specific station of the network
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