Objective To investigate the intensity and time distribution of ocular exposure to ultraviolet spectral irradiance in different geographic directions based on a manikin head model.
Methods An on-site monitoring program was conducted in Sanya, China using a spectrometer with high ultraviolet sensitivity in stalled to a manikin head model to simultaneously measure simulated ocular exposure to ambient ultraviolet spectral irradiance beginning due south and recording data per 6° rotation clockwise.
Results For east and west geographic directions, the maximum ocular exposure to ultraviolet A (UVA) irradiance occurred at 9:00 and 16:15 (up to 50° solar zenith angle), being 2 324.88 and 2 442.68 μW/cm2 respectively; the maximum ocular exposure to ultraviolet B (UVB) irradiance occurred at 9:45 and 15:50 (up to 40° solar zenith angle), being 93.83 and 92.54 μW/cm2, respectively. For south and north geographic directions, the maximum ocular exposure to UVA and UVB irradiance both occurred at 12:00 (up to 7° solar zenith angle), namely 1 056.09 and 61.45μW/cm2, respectively. The maximum ocular exposure to ultraviolet irra diance occurred at east to north 12° and west to north 12°. The maximum ratios of hourly exposure over daily cumulated exposure to ultraviolet occurred at 9:00-10:00, 19.67% for the east direction, and 15:00-16:00, 17.11% for the west; for the south and north, the maximum ratios both occurred at 12:00-13:00, which were 12.68% and 12.98%, respectively.
Conclusion Time-depended high-level exposure to ultraviolet spectral irradiance are identified for different geographic directions.
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