Vitamin D effective ultra violet wavelengths due to scattering in shade

Vitamin D effective ultra violet wavelengths due to scattering in shade

Solar UVB radiation (280-320nm) is an initiator of vitamin D3 production in the
human skin. While numerous studies have been conducted in relation to the biological
impact of UV exposure in full sun, less research has investigated the irradiances in
shade. The purpose of this study was to determine the levels of UV radiation in
relation to vitamin D3 induction with six commonly encountered shade environments
for the larger solar zenith angles observed during autumn and winter. Spectral UV
irradiance measurements were made under relatively clear sky conditions at a subtropical
Southern Hemisphere site for six specific shade environments and solar
zenith angle between 35 degrees to 60 degrees to investigate the biologically effective UV
irradiances for pre-vitamin D3 production. Data from this research indicates that previtamin
D3 effective UV wavelengths in the shade were most significant for tree
shade and a shade umbrella. Compared to that in full sun, pre-vitamin D3 effective
UV wavelengths were at levels of approximately 52 and 55 percent respectively, beneath
the shade umbrella and in tree shade. UVB irradiance levels in the shade of a northern
facing covered veranda and in a car with windows closed were significantly less than
those beneath the shade umbrella, with levels of approximately 11 and 0 percent
respectively of those in full sun. Shade is important as a UV minimisation strategy;
however, it may also play an important role in providing the human body with
adequate levels of UVB radiation for pre-vitamin D3 production without experiencing
the relatively higher levels of UVA irradiances present in full sun.

Copyright 2005 Elsevier : Reproduced in accordance with the copyright policy of the publisher. First published in Journal of Steroid Biochemistry & Molecular Biology. This journal is available online: use hypertext links above.