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 degrees 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.cm-2 respectively. If a hat is worn throughout the year, the exposures are reduced to 6, 19 and 20 J.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.

No abstract

A numerical model was used to calculate the facial UV-B exposure received during summer (December-February) by typical outdoor farm workers in south-east Queensland (27.5 degrees S), a population among the groups at highest risk of skin cancer. The exposure was calculated using new, more detailed measurements of the probability of outdoor activity of farmers (FO-measured by the Fraction of time spent Outside), the distribution of incident solar radiation on the human face (ER-the Exposure Ratio, measured by the fraction of the ambient radiation which falls on each site) and the ambient UV-B levels (AE-the Ambient Exposure) for the region. Only the exposure of unprotected faces was considered. An analysis of the distribution of exposure over a typical working day and of the likely spread of exposures is also presented. The group average of exposures at three facial sites (the forehead, nose and cheek) were 8.7 J cm(-2), 14.0 J cm(-2), and 9.5 J cm(-2), respectively, which is substantially higher than estimates for summer made for populations in more temperate latitudes.

New data on the distribution of solar ultraviolet B (UVB) radiation on the face are presented. Measurements made on human subjects and on rotating headform models are compared, and the effect of altering the orientation of the headform is considered. For a range of postures (standing, sitting, bending, kneeling) a corresponding headform angle (20 degrees, 30 degrees, 40 degrees, 60 degrees respectively) is determined that gives improved agreement with human-based measurements. This suggests that a more realistic simulation of human exposure is achieved by appropriately tilting the model.