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Air pollution impacts on ozone
Published in Abhishek Tiwary, Ian Williams, Air Pollution, 2018
The melanin pigment molecules that characterise naturally dark skin absorb UV and prevent its penetration into the skin (Figure 12.22). Fair skin, on the other hand, transmits effectively in the visible and UVA regions, and retains a higher transmissivity well into the UVB region, before cutting off sharply below 290 nm. The total sunburning potential of a given radiation environment can be summarised by the erythemally effective radiation (EER, with units of mW m−2), which is the integral of the energy in the solar spectrum at each wavelength weighted by the erythemal action spectrum. When skin is exposed to EER, a dose accumulates which eventually causes just-perceptible reddening of the skin. This standard erythemal dose (SED) has been set at 200 J m−2 for the most sensitive skins, based on exposure to monochromatic radiation at the maximum spectral efficiency for erythema (around 300 nm). Maximum daily UV doses under clear summer skies are about 70 SED in the tropics, 60 SED at mid-latitudes and 45 SED at temperate (UK) latitudes.
Ozone depletion and ultraviolet radiation
Published in Abhishek Tiwary, Jeremy Colls, Air Pollution, 2017
The melanin pigment molecules that characterise naturally dark skin absorb UV and prevent its penetration into the skin (Figure 13.22). Fair skin, on the other hand, transmits effectively in the visible and UVA regions, and retains a higher transmissivity well into the UVB region, before cutting off sharply below 290 nm. The total sunburning potential of a given radiation environment can be summarised by the erythemally effective radiation (EER, with units of mW m–2), which is the integral of the energy in the solar spectrum at each wavelength weighted by the erythemal action spectrum. When skin is exposed to EER, a dose accumulates which eventually causes just-perceptible reddening of the skin. This standard erythemal dose (SED) has been set at 200 J m–2 for the most sensitive skins, based on exposure to monochromatic radiation at the maximum spectral efficiency for erythema (around 300 nm). Maximum daily UV doses under clear summer skies are about 70 SED in the tropics, 60 SED at mid-latitudes and 45 SED at temperate (UK) latitudes.
Flavonoids from Quercus Genus: Applications in Melasma and Psoriasis
Published in Tatjana Stevanovic, Chemistry of Lignocellulosics: Current Trends, 2018
Esquivel-García Roberto, Velázquez-Hernández María-Elena, Valentín-Escalera Josué, Valencia-Avilés Eréndira, Rodríguez-Orozco Alain-Raimundo, Martha-Estrella García-Pérez
Melasma prevalence varies per sex, ethnic composition, skin phototype, and intensity of sun exposure. This pathology is common in women of reproductive age, particularly in their thirties and forties, though the onset of the disease is earlier in light skin types than in dark skin types. Epidemiological studies have reported higher prevalence among more pigmented phenotypes, such as East Asians, Indian, Pakistani and African, and it is also common among Americans and Brazilians who live in intertropical areas. Besides, a genetic predisposition has been observed, since almost half of the patients have relatives affected with the disease (Passeron 2013, Handel et al. 2014).
Temperature stability of vitamin D2 and color changes during drying of UVB-treated mushrooms
Published in Drying Technology, 2018
Nils Nölle, Dimitrios Argyropoulos, Joachim Müller, Hans Konrad Biesalski
Vitamin D belongs to the fat-soluble vitamins and could be identified in some of the oldest, still living phytoplankton species.[1] Not only it is mainly known for its role in the calcium and phosphate metabolism but also induces cell differentiation and modulates the immune system.[2] Owing to different reasons, vitamin D deficiency can be found in both developed and developing countries.[3,4] To maintain a vitamin D status necessary for good health, a daily intake of 400 IU for infants and 800 IU for children and adults (1 IU equals 25 ng vitamin D) is recommended.[5] Endogenous synthesis of vitamin D through exposure of 7-dehydrocholesterol to UV light covers most of the daily requirements but can be diminished by factors like dark skin, clothing habits, and age.[6] Therefore, dietary sources are important for supplying vitamin D, but only few foods are naturally rich in vitamin D such as fatty sea fish and dairy products.[7] Mushrooms represent the only nonanimal food source of vitamin D. The explanation for this is that their cell membranes are composed of ergosterol, which is converted by UV light into vitamin D2.