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Modeling Acute
Exposure and Dose to Solar Radiation
Streicher, John1,
Fornaro, Robert2, Dulberg, Martin2,
Culverhouse, William2, McConnell, Andrew2,
Gross, Mitch 2 and Heil, Margaret2
National Exposure Research Laboratory / US Environmental Protection
Agency1
Dept. of Computer Science / North Carolina State University2
4
Abstract-
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. Utilizing advances in computer graphics,
including high-resolution 3-dimensional mathematical representations
of the human form, the calculation of incident flux has been attained
to sub-centimeter precision. Lighting detail included partitioning of
direct beam and diffuse skylight, shadowing effects, and gradations
of model surface illumination depending on model surface geometry and
incident light angle. With the incorporation of 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 provides 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 allowed specific sun exposure
scenarios to 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.
Keywords: modeling,
exposure, graphics, dose
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