The results suggest that a high level of vitamin D(3) at the time of diagnosis, and thus, during cancer treatment, may improve prognosis of the three cancer types studied.

No abstract

I describe a method to derive biologically effective UV dose rates, total ozone abundances, and cloud optical depths from irradiance measurements with moderate bandwidth filter instruments that have only a few channels in the UV region. These quantities are determined when the measured irradiances are combined with radiative transfer calculations. The method was applied to a four-channel filter instrument with center wavelengths at 305, 320, 340, and 380 nm and bandwidths of 10 nm. I compared the instrument with a high-wavelength-resolution spectroradiometer during a 1-week period in San Diego, California, with variable cloudiness. The relative difference in Commission Internationale de l'Éclairage (CIE)-weighted UV dose rates for solar zenith angle's (SZA's) < 80° was 1.4 ± 3.2%. The relative difference for clear sky was 0.6 ± 1.5% for SZA's < 80°. The total ozone inferred from the irradiance measurements with the filter instrument is insensitive to clouds. The instrument was compared with a Dobson and a Brewer instrument in Oslo, Norway, 60°N, for more than 1 year. The relative difference in derived ozone abundance for the entire period, including cloudy days, was 0.3 ± 2.9%. The standard deviation was reduced to 1.9% when only clear sky and SZA's < 60° were included. By using the total ozone and the cloud optical depth derived from the filter instrument as input to a radiative transfer model, one can compute a complete spectrum from 290 to 400 nm with 1-nm resolution. Such calculated spectra are in good agreement with spectra measured simultaneously with a high-wavelength-resolution spectroradiometer for clear as well as cloudy sky conditions and can be used to determine dose rates for any desired action spectrum. Only one UV-B channel and one UV-A channel are required to compute the spectra.

Solar radiation is the main cause of skin cancers. However, it also is a main source of vitamin D for humans. Because the optimal status of vitamin D protects against internal cancers and a number of other diseases, a controversy exists: Will increased sun exposure lead to net health benefits or risks? We calculated the relative yield of vitamin D photosynthesis as a function of latitude with a radiative transfer model and cylinder geometry for the human skin surface. The annual yield of vitamin D is 3.4 and 4.8 times larger below the equator than in the U.K. and Scandinavia, respectively. In populations with similar skin types, there are clear latitude gradients of all major forms of skin cancer, indicating a northsouth gradient in real sun exposure. Surprisingly, the incidence rates of major internal cancers also increase from north to south. However, the survival prognosis also improves significantly from north to south. Reasons for these findings are discussed in view of the role of vitamin D. In Norway, melanoma rates increased by a factor of 6 from 1960 to 1990, while the prognosis improved in the same period. After 1990, melanoma rates have remained constant or even decreased in age groups <50 years, whereas the prognosis has not improved further. These data, together with those for internal cancers and the beneficial effects of an optimal vitamin D status, indicate that increased sun exposure may lead to improved cancer prognosis and, possibly, give more positive than adverse health effects.body mass index ͉ cutaneous malignant melanoma ͉ squamous cell carcinoma ͉ ultraviolet radiation T here is a controversy as to whether increased sun exposure to Western populations would prolong or shorten lifetime expectancy, result in fewer or more cancer deaths, and, in general, lead to health benefits or risks (1, 2). For years, emphasis has been placed on the increasing time trends of incidence and mortality rates of cutaneous malignant melanoma (CMM) (3, 4) and, in contrast, on the protective role of vitamin D regarding many types of internal cancer and other diseases (5-7). Too much sun exposure has been blamed for the high and increasing incidence rates of CMM. However, solar radiation is a major, if not the main, source of vitamin D in humans. Therefore, a population's increased sun exposure leads to improved vitamin D status. The observation that the incidence and mortality of several types of internal cancers decreases with decreasing latitude in the United States and other countries initiated the research on vitamin D-cancer relationships in the 1980s and 1990s. However, in some cases, there is an inverse gradient of the rates of internal cancer with latitude (1), with the rates being higher in regions with high annual UV fluences (New Zealand and Australia) than in countries with low annual UV fluences (Northern Europe, Scandinavia, and the U.K.), despite the fact that the populations of these regions are closely related genetically or, at least, have similar skin types, which is important for the photosy...

The Sun has played a major role in the development of life on Earth. In Western culture, people are warned against Sun exposure because of its adverse effects: erythema, photoimmunosuppression, photoageing, photocarcinogenesis, cataracts and photokeratitis. However, Sun exposure is also beneficial, since moderate doses give beneficial physiological effects: vitamin D synthesis, reduction of blood pressure and mental health. Shortage of Sun exposure may be even more dangerous to human health than excessive exposure. Avoiding Sun exposure leads to vitamin D deficiency which is associated not only with rickets and osteomalacia, but also with increased risk of cardiovascular disease, multiple sclerosis, rheumatoid arthritis, diabetes, influenza, many types of cancer and adverse pregnancy outcomes. Solar radiation induces nitric oxide release in tissue and immediate pigment darkening which certainly play important roles, although these are still unknown. Action spectra relevant for health are described. We will also review what is known about spectral and intensity variations of terrestrial solar radiation as well as its penetration through the atmosphere and into human skin and tissue.