The total annual exposure to erythemally effective UVR was estimated for average work situations in a high exposure environment, viz, farm workers in Southeast Queensland (27.5° S), and the effect of hat usage was examined. If no sun protection is used, the annual erythema exposures for this group of workers at three facial sites: forehead, nose and cheek are 40, 57 and 34 J ṁ cm−2 respectively. If a hat is worn throughout the year, the exposures are reduced to 6, 19 and 20 J ṁ cm−2, respectively. The mean ratio of exposure without the hat to that with the hat (mean protection factor, MPF) was found to be 6 for the forehead, 3 for the nose and 2 for the cheek. The risk of non-melanoma skin cancers without the protection of the hat is estimated to increase by up to 100 times for basal cell carcinomas and 13 times for squamous cell carcinomas for a whole year of exposure.