UV Radiation: Balancing Risks and Benefits^†

Abstract

We use action spectra published by the International Commission on Illumination to examine diurnal, seasonal and latitudinal variations in erythemally weighted (sunburning) UV-a health risk, and vitamin D-weighted UV-a health benefit. Vitamin Dweighted UV is more strongly dependent on ozone and solar zenith angle. Consequently, its diurnal, seasonal and geographic variability is more pronounced than for erythemally weighted UV. We then investigate relationships between the two quantities. An algorithm is developed and used to relate vitamin D production to the widely used UV index, to help the public to optimize their exposure to UV radiation. In the summer at noon, there should at mid-latitudes be sufficient UV to photosynthesize optimal vitamin D in $1 min for full body exposure, whereas skin damage occurs after $15 min. Further, while it should be possible to photosynthesize vitamin D in the winter at midlatitudes, the amount of skin that must be exposed is larger than from the hands and face alone. This raises the question of whether the action spectrum for vitamin D production is correct, since studies have reported that production of vitamin D is not possible in the winter at mid-latitudes.

Biologically effective surface UV climatology at Rome and Aosta, Italy

“…Following the procedure described in [11], the recommended times (t vitD ), to produce enough vitamin D (cloudless sky) without inducing erythema (t ery ), as a function of UVI and for different exposed areas of the body (A), were determined. Table 3 reports t vitD and t ery for low (UVI=1) and high (UVI=9) sun conditions with the corresponding UV vitD /UV ery ratios, suitable for both sites and based on the similar climatologies.…”

Ultraviolet-A triggers photoaging in model nematode Caenorhabditis elegans in a DAF-16 dependent pathway

“…McKenzie et al (2009) mentioned that during summer season, there will be enough UV to photosynthesize vitamin D in 1 min in the mid-latitude regions. However, if the exposure time is further extended to 15 min, it will lead to skin damage (McKenzie et al 2009).…”

“…McKenzie et al (2009) mentioned that during summer season, there will be enough UV to photosynthesize vitamin D in 1 min in the mid-latitude regions. However, if the exposure time is further extended to 15 min, it will lead to skin damage (McKenzie et al 2009). In addition, long-term exposure of skin against UV radiations leads to premature aging or photoaging, which is characterized by wrinkle formation, hyperpigmented lesions or age spots, and decrease in the integrity of the skin (Puglia et al 2014).…”

Basal and squamous cell carcinoma risks for golfers: An assessment of the influence of tee time for latitudes in the Northern and Southern hemispheres

“…Whereas, the UV irradiance (Wm -2 ) changes rapidly with the movement of the sun, peaking at solar noon, the total UV exposure (Jm -2 ) is dependent upon the variation of the irradiance in the playing interval and the length of the playing interval itself. The rate at which the peak UV irradiance is reached and the height of the daily UV irradiance curve varies also with latitude and season (18,19). These variations will affect skin cancer distributions for golfers as is the case with other population groups which show an increase in incidence with decreasing latitude (20,21,22).…”