The costs of excessive solar UV exposures are high with over 1 million non-melanoma cases and 59,940 melanoma cases in the USA during 2007 (American
Cancer Society, 2008). In 2007, there were 2,740 deaths from nonmelanoma and 8,110 deaths from melanoma in the USA. Additionally, there is the incalculable cost of the associated human suffering and disfigurement. The risk of the detrimental sun-related effects can be lowered by the reduction of human exposures to solar UV radiation. On the positive side, exposures to UVB wavelengths (280 nm -320 nm) are required for the production of vitamin D (Holick, 2004a). The solar UVB waveband acts as an initiator of the synthesis of vitamin D3 by the photolysis of 7-dehydrocholesterol in the human skin, to pre-vitamin D3. This vitamin plays an important role in calcium metabolism and is essential for good bone development, prevention of rickets in children, and prevention of osteoporosis, osteomalacia, and fractures in the elderly (Holick, 2004b). Vitamin D can also be obtained through vitamin D supplements and a small number of foods; however, the simplest way to obtain vitamin D is from moderate exposure to sunlight (Holick, 2004a). Exposures of 1 MED (minimum erythemal dose) to the entire body produce serum vitamin D that is equivalent to 10,000 IU to 25,000 IU of vitamin D (Holick, 2004b). Furthermore, optimisation of adequate sun exposure to maintain adequate serum vitamin D levels, while avoiding excessive exposures that increase the risk of skin cancer, is also the most cost effective way of maintaining adequate vitamin D levels without the additional burden of vitamin D supplements. Adequate levels of vitamin D can be maintained by exposures of 1/6 to 1/3 MED to 15% of the body (Samanek et al., 2006). It is estimated that 90% - 95% of the vitamin D levels required in the human body are obtained from exposure to sunlight (Holick, 2004a).
Agricultural production and natural vegetation can be influenced by changed levels of solar UV and visible radiation due to atmospheric change. The UVB has been shown to produce biological damage in higher plants (Caldwell, 1971). The wavelengths extending into the UVA (320 nm - 400 nm) waveband have also been found to produce a response in plants with an action spectrum for plant growth inhibition in higher plants that extends to 366 nm being recently developed (Flint and Caldwell, 2003). The action spectrum for a biological reaction provides the effectiveness of each wavelength for producing that reaction (Ambach and Blumthaler, 1993).
In order to optimize the UV exposure of humans and to reduce the influence of UV exposures on both agricultural crops and natural vegetation, a complete understanding of the solar radiation environment is necessary. As recommended by the World Health Organization (WHO, 1994), monitoring of personal UV exposures is important in order to establish the percentage of the ambient solar UV received by the population. Solar UV dosimeters are an important tool in this research. Dosimeters that have been developed for UV research fall into two categories; namely, the thin film type and the spore or biofilm type. The latter types are based on spores or biological specimens that are UV sensitive (e.g., Quintern et al., 1992; Quintern et al., 1997; Munakata et al., 1998). For the thin film type, dosimeters fabricated from a polysulphone thickness of 30 ^m-45 ^m possess a spectral response that approximates the erythemal action spectrum (CIE, 1992). This chapter reports on the use of thin film dosimeters in different environments in order to provide an improved characterization of the solar radiation environment for humans and plants.
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Complete Guide to Preventing Skin Cancer. We all know enough to fear the name, just as we do the words tumor and malignant. But apart from that, most of us know very little at all about cancer, especially skin cancer in itself. If I were to ask you to tell me about skin cancer right now, what would you say? Apart from the fact that its a cancer on the skin, that is.