Spectral UV in public shade settings

The protective nature of specific shade environments was investigated by measuring the spectral UV in the shade for the three planes (horizontal, 45degrees and vertical) and comparing this to that on a horizontal plane in full sun. Spectral UV irradiance measurements were made under clear sky conditions at a sub-tropical southern hemisphere site. The solar UV in the shade of a shade umbrella, covered verandah, covered sand pit and covered walkway were measured for an increasing solar zenith angle, between March and August, for the times of 11:30 a.m.-12:30 p.m. and 2:30-3:30 p.m. The ultraviolet protection factors provided ranged from 1.4 to 10. This research shows that there is sufficient UV in the shade to cause erythema on the human body in a short period of time. For the shade umbrella placed on dry grass the time able to be spent in the shade in the middle of the day before experiencing mild erythema increased from 35 to 60 min as the solar zenith angle increased from 33 to 52degrees. Erythemal UV levels in the shade of a northern facing covered verandah, with trees in close proximity, were approximately up to five times less than the erythemal UV beneath the shade umbrella that had no surrounding trees. Shade structures must be given careful consideration when construction occurs. Even though the UV transmission through the materials may be very low, it is the construction of the entire shade setting that determines the exposure beneath the shade structure. (C) 2002 Elsevier Science B.V. All rights reserved.