UV protection provided by public shade structures during winter

Abstract

Purpose of study: As people become more aware about the damaging effects of UV radiation, they will seek shaded environments to reduce their personal UV exposure. Although shade does decrease direct UV, it is the diffuse UV that can still have significant levels in the shade. At this point in time very little is known about how UV radiation interacts with shade structures during winter. Broadband UV irradiance measurements in the field were conducted beneath three different sized public shade structures, small, medium and large. This research compares the scattered UV levels beneath these specific shade structures, built by the local council, with that of the diffuse UV on an unshaded horizontal plane for clear skies at a sub tropical Southern Hemisphere site during winter. The data gathered is significant, because the relative proportion of scattered UV in shade is at its greatest for the higher solar zenith angles seen during winter. Conclusions: The public shade structures used in this research are built to be effective in the middle of the day in summer when the sun is at its highest point. In Australia, erythemal UV in full sun can reach levels of approximately 2.5 MED/h or more in the middle of the day during winter. Therefore, it is necessary for people that live in similar latitudes to minimise UV exposure in all climatic conditions throughout the year. These specific shade structures are inadequate for providing the public enough protection against damaging UV radiation.