UVR exposure and vitamin D in a rural population. A study of outdoor working farmers, their spouses and children

Background: Living and working in the countryside may result in excessive UVR exposure, with increased risk of skin cancer. Some sun exposure is, however, recommended, since vitamin D production is UVB-dependent. Objectives: To examine UVR exposure and vitamin D levels in a rural population of outdoor working male farmers, their indoor working spouses and their children, expected to receive high UVR exposure. Methods: Prospective, cohort study. During the summer 2009 daily, personal UVR exposure and sun behaviour were recorded by dosimetry and diaries (17 403 days). Vitamin D was measured at the end of summer and the following winter. Results: Risk behaviour (= exposure of shoulders/upper body to the sun), beach days, sunscreen use and sunburns were infrequent. Farmers and boys had the highest daily UVR exposure (both 1.5 SED per day), likewise on work days. On non-work days the UVR exposure was even higher (up to 2.0 SED per day). Farmers, girls and boys had a higher chronic UVR exposure than the spouses, who had more intermittent high UVR exposure. Vitamin D levels did not differ between family members. At the end of summer 16% of the participants were vitamin D insufficient, the following winter, 61%. Some UVR exposure variables correlated positively, but weakly, with vitamin D levels. Conclusions: UVR exposure was generally high among this study population, however, vitamin D levels still dropped below the recommended level during winter for most participants. Differences in UVR exposure between the groups did not result in differences in vitamin D levels.