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MODELING ACUTE EXPOSURE TO SOLAR RADIATION
Streicher, J J., R. Fornaro, M. Dulberg, B. Culverhouse, A. McConnell, M. Groce, K. King, AND A. Price. MODELING ACUTE EXPOSURE TO SOLAR RADIATION. Presented at 13th International Congress on Photobiology, Proceeding, 28th Annual American Society of Photobiology Meeting, Augusta, GA, July 1-6, 2000.
To understand and characterize the factors, including optical transmission properties of aerosols, which affect the intensity of UV-B radiation measured at the earth's surface in order to improve our estimates of ecosystem and human exposures to UV-B radiation; to understand the relationship between UV radiation and total column ozone; to model UV-B exposures at different locations, conditions, and times in order to estimate UV-B exposures throughout the US. This objective is achieved by maintaining a strict quality assurance program for both the Brewer Spectrophotometers in the network and the UV data obtained from the Brewers.
One of the major technical challenges in calculating solar flux on the human form has been the complexity of the surface geometry (i.e., the surface normal vis a vis the incident radiation). The American Cancer Society reports that over 80% of skin cancers occur on the face, head, neck, and back of the hands. The quantification, as well as the mapping of the anatomical distribution of solar radiation on the human form is essential if we are to study the etiology of skin cancers or cataracts or immune system suppression. With advances in computer graphics, including high-resolution 3-dimensional mathematical representations of the human form, the calculation of incident flux is now attainable to sub-centimeter precision. Lighting detail includes partitioning of direct beam and diffuse skylight, shadowing effects, and gradations of model surface illumination depending on model surface geometry and incident light angel. Incorporation ray tracing and radiosity algorithms, the results are not only realistic renderings, but also an accurate representation of the distribution of light on the model. The calculation of light illumination for various receptor points across the anatomy will provide information about differential exposure [Watts per square meter] as a function of model posture, orientation relative to the sun, and sun elevation. Illustration of instantaneous exposure is achieved using a false color rendering - mapping light intensity to color - creating exposure isopleths. The integration of a geodesic sun-tracking model into the lighting module allows specific sun exposure scenarios may be simulated, with instantaneous exposure, as well as the cumulative dose [Joules per square meter] calculated for a given latitude, date, time of day, and duration. This approach may find application in the determination of the reduction in exposure that one achieves by wearing a hat, shirt or sun glasses. More fundamentally, such an analysis tool could estimate the "dose" factor needed to develop dose-response functions for sunlight-induced disease.