Reflection of ultraviolet radiation from different skin types.

In this study using 43 male subjects, the spectral reflectance of ultraviolet radiation (UVR) has been measured from the skin of each subject's forearm. The total diffuse reflectance and directional characteristics of reflection were determined for different wavelengths. Mean values were determined for four skin types in both the ultraviolet A (UVA) and ultraviolet B (UVB) range from 280 to 400 nm. Reflection occurs in all directions and with cylindrical symmetry that is normal to the skin surface. The ability of skin to reflect UVR decreases rapidly with decreasing wavelength. Reflection is as high as 20% for 400 nm and falls below 1% at 280 nm. Average UVA (315 to 400 nm) reflectance can reach 12%, but is only about 2.5% in the UVB (280 to 315 nm) spectral range. The significant differences in reflectance occur between different skin types and are determined primarily by complexion. Skin types with moderate sensitivity to solar radiation, neither too pale nor too tanned, reflect the greatest UVR. In this skin type the protective mechanism of reflection dominates over a mechanism based upon the absorption of UVR by melanin pigment.