Estimations of the human ‘vitamin D’ UV exposure in the USA

Human exposure to sunlight promotes the formation of pre-vitamin D in the skin. Low or marginal levels of vitamin D has been linked to a wide range of human health outcomes, including the development of various types of cancer. However, few data exist on the actual exposure to human due to vitamin D producing ultraviolet radiation. Most studies of human disease and vitamin D have linked latitude and location of residence to expected exposure form the available ambient UV radiation. Human UV exposure for the development of vitamin D depends on a variety of factors such as time spent outdoors, percent available skin, skin type, UV protective devices used and distribution of UV over the human form. In this paper, we investigate how latitude impacts not only on the amount of UV available for vitamin D synthesis, but also the distribution of UV over the human form.