Effects of biological and physical factors on ultraviolet erythemal and pigmentary response

For the purpose of investigating the related factors to the practical use of the sunscreen products in Japan, we have investigated about ultraviolet amounts, wavelength and reflectance in some outdoor sports environments, especially in skiing resort and summer beach as a physical factor, and the relationship between the skin complexions and their susceptibility to sunburn and suntan as a biological factor, For measuring the range of 300-320nm (UV-B) and 300-390nm of ultraviolet radiation, each 2 of 2 types integrating actinometers were equipped with the phototubes consisting of the optical filters and diffusion filters. The reflected or scattered UV-radiation from downwards was measured by setting the detecting surface of the phototube to downward in vertical position.Sun exposure tests for investigating Japanese suceptibility to sunburn and suntan were done at Okinawa (26°N) and Shizuoka (34°N) in July. Prior to the tests, Japanese skin complexions were classified to 3 groups, the fair, the medium and the dark based on the results of a selfassesment of his own skin, the visual evaluation by 3 examiners and the colorimetric study.Average UV-B ratio to 300-390nm from January to March was 9.9% on fair days, 7.9% on cloudy and 5.6% on rainy in Yokohama city, while in skiing resort was 8.7% on fair days and 6.4% on snowstormy days.The reflectace of UV-radiation under some natural environments was measured. Dry sands on beach reflected by 7.5%, while the reflectance was only 3.7% on wet sands. The average value on snow surface reached 88.0%, this is unusually high. Outside snow and sands, lawn reflected by 1.2% and concrete surface by 5.5%.MED (×0.18mw.min/cm2) was 600 for the fair skin subjects, 800 for the medium skin and 1100 for the dark skin, respectively. However, no difference was observed among the MMD (Minimum Melanogenesis Dose) regardless if the skin complexion of Japanese subjects.3 patterns of sunburn and sutan were deduced for the people with various skin complexions: 1) Fair-skinned people will not have suntan if they do not suffer sunburn to some extent 2) In the case of dark-skinned people, they will readily be suntanned without sunburn 3) People with medium skin are between the two that is some of them may be suntanned after slight sunburn.Furtheremore, colorimetric study on sunburn and suntan was made with fair skins and dark skins after single sun exposure.