Sayre R M, Kollias N, Ley R D, Baqer A H
Rapid Precision Testing Laboratories, Cordova, Tennesse.
Photodermatol Photoimmunol Photomed. 1994 Aug;10(4):148-53.
Sunscreen products are tested normally against a defined solar simulator spectrum that, in ultraviolet (UVB), closely resembles the noontime spectral composition of summer sunlight. Although such a spectrum may define the product for use in the most adverse sunlight conditions, little attention has been given to how such products perform against other natural sunlight spectra. Outdoor clinical trials suggest that indoor testing of sunscreens may overestimate the performance of many products. In this study we compared the predicted efficacy of specific products to a variety of natural sunlight spectra taken at different solar angles and under different atmospheric conditions. We found that a standard product always provides less protection for a natural sunlight spectrum than its label value would suggest. The deviation from the labeled value is the greatest when the sun is low in the sky, i.e., close to the horizon. The deviation is due to the changing ratio of UVA to UVB radiation in natural sunlight. The deviation can be as large as a factor of 2.0.
防晒产品通常是针对特定的太阳模拟器光谱进行测试的，在紫外线（UVB）方面，该光谱与夏季阳光中午时分的光谱组成非常相似。尽管这样的光谱可以定义产品在最恶劣阳光条件下的使用情况，但对于此类产品在其他自然阳光光谱下的表现却很少有人关注。户外临床试验表明，防晒产品的室内测试可能会高估许多产品的性能。在本研究中，我们将特定产品的预测功效与在不同太阳角度和不同大气条件下获取的各种自然阳光光谱进行了比较。我们发现，对于自然阳光光谱，标准产品提供的防护总是比其标签值所显示的要少。当太阳在天空中较低时，即接近地平线时，与标签值的偏差最大。这种偏差是由于自然阳光中UVA与UVB辐射比例的变化所致。偏差可能高达2.0倍。
