In his recent commentary, Robins (2009) disputed the role played by ultraviolet radiation (UVR), namely, the vitamin-D-producing wavelengths of ultraviolet B (UVB), in the evolution of human skin. He questioned the theory that reduced levels of pigmentation in human skin were selected to facilitate absorption of UVB. He provided evidence to support his idea that people can produce enough vitamin D in their skin, regardless of pigmentation, if they are not pursuing a modern lifestyle. He asserted that, within his framework, rickets was the only selective force that could have influenced the evolution of light pigmentation because other detrimental effects of vitamin D deficiency are unproven. As rickets is increased by industrialization, Robins concluded that ‘‘. . . vitamin D status could not have constituted the fitness differential between lightly pigmented and darkly pigmented individuals at high latitudes that favored the evolutionary selection of the former’’ (Robins, 2009). In this article, we examine the current evidence for what has been termed the ‘‘vitamin D theory,’’ and highlight the importance of UVB penetration in the evolution of human skin. We begin with an overview of the solar processes involved in cutaneous vitamin D synthesis, followed by a discussion of causal arguments and causation in the context of the vitamin D theory, and conclude with a review of physiological mechanisms and their evolutionary significance.

/pdf/news-and-views-vitamin-d-and-the-evolution-of-human-3unihq8hij.pdf

News and Views Vitamin D and the Evolution of Human Depigmentation

Vitamin D and the evolution of human depigmentation

Recent Advances and a Roadmap to Wearable UV Sensor Technologies

The performance of photovoltaic (PV) modules and their component materials under the stresses in the outdoor environment is the most important indicator of reliability, durability, and safety of PV modules throughout their service life. Tedlar polyvinyl fluoride films have been a key component in backsheet component structures and used in PV modules that have been in the service environment for over 25 years. The performance of fielded modules and components can be compared with the performance in durability tests using other backsheet materials including polyethylene terephthalate. Accelerated testing protocols are described including UV exposure based on solar irradiance in different climates and relevant albedo levels for exposure of the back of PV modules. The change in critical performance properties in durability tests including damp heat and UV is compared with backsheets that are extracted from fielded modules. Analysis of mechanical and chemical properties of the inner and outer layers of backsheets that are removed from fielded modules is examined. Area-specific coring techniques that are followed by layer composition analysis were also used to understand fielded module failure mechanisms/defects. The impact of extended damp heat and UV on backsheet properties and module performance that is observed in the field is further quantified through measurement of mechanical, optical, electrical, and permeability properties of the backsheet and power, electrical insulation, and physical properties of the modules. Correlations between field performance and accelerated testing are demonstrated. The first results for sequential and combined stress testing are described and compared with the field performance. A comparison of two large and diverse sets of modules from two different locations (EU and Japan) is discussed, and the power loss with field exposure period and the impact of backsheet is described.

A Comparison of Key PV Backsheet and Module Performance from Fielded Module Exposures and Accelerated Tests

Minimizing exposure to ultraviolet (UV) radiation is an essential component of skin cancer prevention Providing and using natural and built shade is an effective protection measure against harmful UV This article describes the factors that must be addressed to ensure quality, effective, well-designed shade and recommends best practice approaches to improving the protection factor (PF) of shade structures It identifies examples of interventions to increase shade availability and use, and examples of effective shade based on measured protection factors or measured reductions in UV exposures Finally, this article considers examples of best practice for undertaking shade audits The article is based on refereed articles and reviews, reports, conference papers and shade practice and policies from reports and on web sites Articles for the Australian setting are considered first, followed by those in an international setting

Shade provision for UV minimization: a review

This article presents measurement results of intensity of solar UVA and UVB radiation, as well as UV radiation albedo from various surfaces. The intensity of albedo was measured from natural surfaces, such as: sand, grass, water, and snow. The paper also presents measurements of solar emitted UVA and UVB radiation intensity in the shadow. Ultraviolet radiation intensity and surface albedo was measured using a handy UVA radiation radiometer UVA ‐ 365HA, with spectral response of 320–390 nm and a handy UVB radiation radiometer PMA2201, with spectral response of 280–320 nm. The results of measurements show that snow has the maximum albedo ‐ from 50 to 60 per cent, sand ‐ 10 per cent, and the minimum albedo is for grass ‐ 2 or 3 per cent. The data of experimental measurements of UVA and UVB radiation in the shadow show that maximum reduction of intensity of UVA radiation up to 80%, was at 1 p.m. in comparison with reduction of intensity of UVB radiation to 70% at 2 p.m.

/pdf/ultraviolet-radiation-albedo-of-natural-surfaces-1l8ofbi06h.pdf

Ultraviolet radiation albedo of natural surfaces

Preliminary analysis of the data of ultraviolet (UV) radiation and ground‐level ozone concentration measurements from Rugsteliskes Monitoring Station over the years 2002–2003 is presented. Observations showed that an average UV radiation value in January and July of 2002 differed about 10 times. Maximum intensity of UVA radiation was observed in July (about 2,4 W/m2), and minimal one ‐ in December (0,1 W/m2), the highest UVB radiation intensity was in May (0,09 W/m2), while a minimal UVB radiation value as well as that of UVA was registered in December (0,07 W/m2). Relationship between the highest ozone concentration and UVB radiation values during the summer of the investigation period was found to be linear.

Renata Chadyšiene

Papers

Ultraviolet radiation albedo of natural surfaces

Ultraviolet radiation and ground-level ozone variation in Lithuania