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A Novel Method to Calculate Solar UV Exposure Relevant to Vitamin D Production in Humans
Author(s) -
Seckmeyer Gunther,
Schrempf Michael,
Wieczorek Anna,
Riechelmann Stefan,
Graw Kathrin,
Seckmeyer Stefan,
Zankl Maria
Publication year - 2013
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/php.12074
Subject(s) - noon , solstice , irradiance , sunlight , radiance , environmental science , vitamin , radiation , sky , atmospheric sciences , meteorology , optics , physics , biology , latitude , geodesy , geography , endocrinology
We present a novel method to calculate vitamin D 3 –weighted exposure by integrating the incident solar spectral radiance over all relevant parts of the human body. Earlier investigations are based on the irradiance on surfaces, whereas our calculated exposure of a voxel model of a human takes into account the complex geometry of the radiation field. Assuming that sufficient vitamin D 3 (1000 international units) can be produced within the human body in one minute for a completely uncovered body in vertical posture in summer at midlatitudes ( e.g . Rome, June 21, noon, UV index of 10), we calculate the exposure times needed in other situations or seasons to gain enough vitamin D 3 . Our calculations show that the UV index is not a good indicator for the exposure which depends on the orientation of the body ( e.g . vertical (standing) or horizontal (lying down) posture). Without clothing the exposure is dominated by diffuse sky radiation and it is nearly irrelevant how the body in vertical posture is oriented toward the sun. At the winter solstice (December 21, noon, cloudy) at least in central Europe sufficient vitamin D 3 cannot be obtained with realistic clothing, even if the exposure were extended to all daylight hours.