Spectral ultraviolet albedo of roofing surfaces and human facial exposure.

Spectral field measurements were used to quantify the ultraviolet (UV) spectral albedos of four different metallic roofing surfaces. The effect of the albedos of two of these surfaces on erythemal exposure to human facial anatomical sites was quantified by UV dosimetry. The albedos of all roofing surfaces were greater than the albedo of grass. Little SZA dependence was observed for any of the surfaces. The albedos of the coloured metallic corrugated surfaces were strongly dependent on wavelength in the UVA, increasing from 3 to 12%. Facial erythemal measurements showed significant exposure enhancements over the galvanised corrugated surface compared to grass. The undersides of the chin and nose received exposure enhancements over the galvanised corrugated surface of about 1290 and 190%, respectively, of the exposure of these sites over grass. It is concluded that the albedo of the galvanised surfaces are higher than those of the coloured surfaces by at least 20%, and higher than grass by at least 27%. Consequently, normally shaded facial anatomical sites receive substantially higher UV exposures over these galvanised surfaces compared to grass.