Solar UV geometric conversion factors: horizontal plane to cylinder model
Stanley J Pope1, Dianne E Godar
1Sun Systems & Svc, Inc., Oak Park, MI, USA.
Photochemistry and Photobiology
|January 12, 2010
Summary
Most solar UV measurements overestimate actual human exposure. New geometric conversion factors (GCF) provide realistic UV doses for risk and benefit assessments, showing people receive less than half the horizontal plane UV dose.
Area of Science:
- Environmental science
- Photobiology
- Human health
Background:
- Solar UV measurements are typically relative to the horizontal plane.
- Horizontal plane UV data do not accurately reflect actual doses received by people outdoors.
- Accurate UV dose assessment is crucial for health risk and benefit analyses.
Purpose of the Study:
- To develop a simple geometric method for calculating UV doses on the human body.
- To introduce geometric conversion factors (GCF) to adjust horizontal plane UV irradiances.
- To provide realistic UV dose estimations for various human activities and body parts.
Main Methods:
- Developed a geometric method to convert horizontal plane UV irradiances to cylinder irradiances.
- Calculated GCF for unweighted, erythemally weighted, and previtamin D(3)-weighted UV.
- Modeled UV doses for full cylinder (entire body) and semicylinder (face, shoulders, hands, feet) models.
- Presented GCF averages for latitudes 20-70 degrees N, considering daily, monthly, and seasonal variations.
Main Results:
- The GCF demonstrate that actual UV doses are significantly lower than those measured on the horizontal plane.
- People receive less than half of their annual erythemally weighted UV dose.
- Consequently, previtamin D(3)-weighted UV doses are also less than half of horizontal plane measurements.
- Calculated GCF enable realistic UV dose estimations for diverse outdoor activities and body orientations.
Conclusions:
- The developed geometric method and GCF provide a more accurate way to assess human UV exposure.
- Scientists can now perform realistic UV risk and benefit assessments using these new factors.
- This research highlights the importance of considering body geometry in UV dose calculations.
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