Public Health Messages Associated with Low UV Index Values Need Reconsideration

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.

Environmental effects of stratospheric ozone depletion, UV radiation, and interactions with climate change: UNEP Environmental Effects Assessment Panel, Update 2020

“…The World Health Organization and many other government and non-government organisations advise that sun protection is not required when the UV index is below 3. This advice has been challenged previously based on UV radiation data from New Zealand [ 124 ] and is supported by a new study from Germany [ 125 ]. Using data from nine ground-based monitoring stations from 2007 to 2016, Lehmann and colleagues found that when the UV index is 2, people with Fitzpatrick skin types I and II can receive a minimal erythemal dose of UV radiation in 1.5 h [ 125 ].…”

“I’ve Heard of It, Yes, but I Can’t Remember What Exactly It Was”—A Qualitative Study on Awareness, Knowledge, and Use of the UV Index

“…Therefor the unitless UVI, always given as an integer value, is divided into five categories: low (values 0-2), moderate (3-5), high (6-7), very high (8)(9)(10), and extreme (11+). A low value means that sun protection is only needed for individuals with very light skin during an extended outdoor stay [28]. Starting from moderate values, sun protection measures including sunscreen use (and re-application), sunglasses, protective clothing, and staying in the shade (especially around solar noon) are recommended [25].…”

Solar Ultraviolet Exposure in Individuals Who Perform Outdoor Sport Activities

“…(Supplementary Table 3) Despite overwhelming scrutiny, the UVI has been adopted by many governments as the standard platform for public communication of UV exposure risk since its inception by the WHO 1994 [37]. Many of the research efforts detailing UVI knowledge have shown there is a minimal understanding of the UVI by the public [51,54,[85][86][87][88][89][90] and that lower UVI value recommendations underpredict erythemal risk [91][92][93]. Medical professionals have similarly displayed limited knowledge or use of the UVI [94][95][96].…”