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Scattered ultraviolet radiation underneath a shade-cloth
1Centre for medical and Health Physics, Queensland University of Technology, Australia.
Photodermatology, Photoimmunology & Photomedicine
|October 1, 1994
Summary
Shade cloths significantly reduce ultraviolet (UV) radiation, but the protective shade ratio varies with object height and orientation. This impacts UV exposure assessment under shaded conditions.
Area of Science:
- Environmental Science
- Photobiology
- Public Health
Background:
- Ultraviolet (UV) radiation poses health risks, necessitating protective measures like shade cloths.
- Understanding UV radiation transmission and its effective shielding is crucial for sun safety.
- Previous studies often simplify UV shielding effects, overlooking environmental variables.
Purpose of the Study:
- To quantify the transmittance of erythemal UV radiation through shade cloths.
- To determine the 'shade ratio' considering object height and orientation.
- To assess UV dose reduction on human-like manikins at various body sites.
Main Methods:
- Utilized UV radiometers and polysulphone film badges to measure UV radiation.
- Investigated UV transmittance through a shade cloth (70 x 100 cm²).
- Employed two manikins with film badges at 10 sites, exposed in shadow and open areas in Durham and Brisbane under different sky conditions.
Main Results:
- Shade cloth transmittance for erythemal UV was 0.14 ± 0.03.
- Shade ratio varied significantly with detector height and orientation, differing from transmittance.
- Facial UV dose ratios on manikins were 0.70 ± 0.1 (Durham, overcast) and 0.35 ± 0.10 (Brisbane, clear).
Conclusions:
- Shade ratio is a more accurate measure of UV protection than simple transmittance.
- UV protection effectiveness is highly dependent on geometry (height, orientation) and environmental factors (sky conditions).
- Variations in shade ratio across body sites highlight the need for detailed UV exposure assessments.