Utilising shade to optimize UV exposure for vitamin D

Abstract

Abstract. Numerous studies have stated that humans need to utilise full sun radiation, at certain times of the day, to assist the body in synthesising the required levels of vitamin D 3 . The time needed to be spent in the full sun depends on a number of factors, for example, age, skin type, latitude, solar zenith angle. Current Australian guidelines suggest exposure to approximately 1/6 to 1/3 of a minimum erythemal dose (MED), depending on age, would be appropriate to provide adequate vitamin D 3 levels. The aim of the study was to determine the exposure times to diffuse solar UV to receive exposures of 1/6 and 1/3 MED for a changing solar zenith angle in order to assess the possible role that diffuse UV (scattered radiation) may play in vitamin D 3 effective UV exposures (UV D 3 ). Diffuse and global erythemal UV measurements were conducted at five minute intervals over a twelve month period for a solar zenith angle range of 4 • to 80 • at a latitude of 27.6 • S. For a diffuse UV exposure of 1/3 MED, solar zenith angles smaller than approximately 50 • can be utilised for exposure times of less than 10 min. Spectral measurements showed that, for a solar zenith angle of 40 • , the UVA (315-400 nm) in the diffuse component of the solar UV is reduced by approximately 62% compared to the UVA in the global UV, whereas UV D 3 wavelengths are only reduced by approximately 43%. At certain latitudes, diffuse UV under shade may play an important role in providing the human body with adequate levels of UV D 3 (290-315 nm) radiation without experiencing the high levels of UVA observed in full sun.

User-centered development of a smart phone mobile application delivering personalized real-time advice on sun protection

“…Advice is corrected for shade use (based on solar zenith angle: <50°=50 % reduction in vitamin D; 50°–60°=25 %; >60°=12 %) [61], but not for sunscreen use because studies of sunscreen in practice have indicated it does not affect vitamin D levels [62–64]. While there is controversy over vitamin D [65–73], this advice shows users that a short sun exposure during the mid- and low-latitude summers would produce adequate vitamin D without risking sunburn [57, 74] and encourages them to balance vitamin D synthesis with the risks of skin damage.…”

Sun exposure as a strategy for acquiring vitamin D in developing countries of tropical region: Challenges & way forward

“…Utilizing shade: Shaded environments may also be utilized for sun exposure without experiencing the high levels of UVA of full sun 75 76 . At 27.6° S (Australia), diffuse UV under shade has been proved to be capable of providing the human body with adequate levels of UVD3 (290-315 nm) radiation 77 78 .…”

Shadow‐band correction for diffuse ultraviolet radiation measurements

“…Although global solar UV radiation is frequently registered at many radiometric stations worldwide, its diffuse fraction is scarcely measured, and therefore, information about the direct‐to‐diffuse partitioning is usually unavailable. To our knowledge, only few studies have reported experimental solar UV diffuse measurements [ Parisi et al ., , ; Grant and Gao , ; Utrillas et al ., , ; Utrillas , ; Turnbull et al ., ; Turnbull and Parisi , ; Nuñez et al ., ].…”