Fioletov V E, McArthur L J B, Mathews T W, Marrett L
Environment Canada, 4905 Dufferin St., Toronto, Ontario, Canada M3H 5T4.
J Photochem Photobiol B. 2009 Apr 2;95(1):9-16. doi: 10.1016/j.jphotobiol.2008.11.014. Epub 2008 Dec 24.
Erythemally weighted solar ultraviolet (UV) radiation is often used to characterize the production of vitamin D in a human body. However, the vitamin D production action spectrum is different than that for erythemal UV. The vitamin D action spectrum weighted UV is more sensitive to UV-B, while the erythemal UV action spectrum has higher weighting coefficients than the vitamin D action spectrum in the UV-A part of the spectrum. Therefore, by using the erythemal UV as an estimate for the vitamin D action spectrum weighted UV can give results that differ by up to a factor of 5. This study examines the relationship between erythemal and vitamin D action spectrum weighted UV radiation using measurements of spectral UV at the surface by Brewer spectrophotometers that are part of the US and Canadian observational networks. It is shown that the ratio of vitamin D action spectrum weighted UV to erythemal UV is nearly constant for high levels of UV (UV Index greater than 5.5) and therefore vitamin D action spectrum weighted UV can be described in terms of erythemal UV. For lower levels of UV though this relationship should not be used. A simple formula that calculates vitamin D action spectrum weighted UV from UV Index is developed. An empirical formula that expresses the ratio of vitamin D action spectrum weighted UV to erythemal UV as a function of the solar zenith angle and column ozone is also suggested. The geographical distributions of vitamin D action spectrum weighted UV in the US and Canada are discussed.
红斑加权太阳紫外线（UV）辐射常被用于表征人体维生素D的生成情况。然而，维生素D生成作用光谱与红斑紫外线的作用光谱不同。维生素D作用光谱加权紫外线对UV - B更敏感，而红斑紫外线作用光谱在光谱的UV - A部分比维生素D作用光谱具有更高的加权系数。因此，用红斑紫外线来估计维生素D作用光谱加权紫外线，得到的结果可能相差高达5倍。本研究利用美国和加拿大观测网络中的布鲁尔分光光度计对地表光谱紫外线进行测量，研究了红斑和维生素D作用光谱加权紫外线之间的关系。结果表明，对于高水平紫外线（紫外线指数大于5.5），维生素D作用光谱加权紫外线与红斑紫外线的比值几乎恒定，因此维生素D作用光谱加权紫外线可以用红斑紫外线来描述。不过，对于较低水平的紫外线，不应使用这种关系。开发了一个根据紫外线指数计算维生素D作用光谱加权紫外线的简单公式。还提出了一个经验公式，将维生素D作用光谱加权紫外线与红斑紫外线的比值表示为太阳天顶角和大气柱臭氧的函数。讨论了美国和加拿大维生素D作用光谱加权紫外线的地理分布情况。
