Lawn bowls and solar ultraviolet radiation in Australia: exposures, risks and potential benefits for the production of vitamin D

As a popular leisure activity, particularly among the senior population, lawn bowls has the potential to sustain the vitamin D needs of individuals required for bone health. Vitamin D synthesis initiated by the photolysis of 7-dehydrochlorestrol in human skin into pre-vitamin D3 influences calcium metabolism and acts as a preventative agent deterring diseases including osteoporosis, multiple sclerosis and potentially some forms of cancer. In an Australian setting there is a substantial level of ultraviolet-B (UVB) in sunlight due to the generally high altitude of the sun and the large number of low to cloud free days. In this environment the effective photolysis of pre-vitamin D3 can be reached in several minutes according to current guidelines. These guidelines recommend a solar exposure of approximately 1/6 to 1/3 of a minimal erythemal dose (MED), with the effective production of vitamin D3 also being influenced by the age and skin type of the individual. However, excessive exposure to UVB comes at a cost. High exposures to UVB that accumulate over a lifetime or those that are received as acute sunburning episodes may lead to the development of skin cancer. Excessive exposure can also damage the effective production of dermal vitamin D3 photoproducts. This research presents measured erythemally effective UVB exposure data recorded by miniaturised polysulphone dosimeters. Exposures were measured to the exposed skin sites of two lawn bowlers on the forearm, thigh, back of the neck and eye under low and high solar elevations. These measurements were expressed relative to the ambient horizontal plane and include measurements made with and without hat protection. From this a model was developed to provide pre-vitamin D3 and erythemal exposure data estimates for each Australian capital city. Variations in the effective pre-vitamin D3 and MED exposure time show a clear variation depending largely upon latitude