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Track: Health Care Services
Robert Chastain
North Carolina State Center for Health Studies
PO Box 29538
Raleigh, NC 27626-0538
Telephone: 919-715-4473
Fax: 919-733-8485
E-mail: rchastai@gis.sches.ehnr.state.nc.us
Examining Spatial Relationships Between Brain Cancer Incidence, High Voltage Power Lines, and Geomagnetic Fields Using a GIS
Defining Issue: Applying a complex physical model in the examination of the spatial relationship between residences, linear high voltage powerline features, and geomagnetic fields requires the capture and derivation of a varying array of data sources. The storage, conversion between formats, and identification and rectification of errors in these data are important challenges to meet when designing appropriate methodologies to perform research of this nature. GIS Solution: A GIS is used to (a) locate (geocode) an epidemiological sample of brain cancer cases and controls; and (b) capture, derive, and combine a number of data sources needed to apply a physical model that incorporates background geomagnetic field (GMF) intensity, dip angle, the angle of residences relative to nearby powerlines, and the orientation of powerlines relative to magnetic north into the calculation of a metric known as ion cyclotron resonance (ICR). The ICR values are then used to determine the potential level of risk linked to
powerlines at individual sites. Various techniques are employed to identify and control error introduction among the input digital map layers. Methodology: Whereas the primary component measured in powerline epidemiological studies has been AC magnetic intensity, this study involves the derivation and measurement of the ICR linked to the GMF surrounding powerlines so that its relevance to the spatial distribution of brain cancer distributions is the fact that residential access is not required to obtain the values needed to determine the GMF at that computational strength of a GIS to calculate the component variables. Software: ArcInfo NETWORK, ARC GRID, ARC COGO, and other modules; USGS 1995 EPOCH World Magnetic Mode; and Microsoft Excel were used for the numerous data format transformations and variable generation tasks associated with undertaking this research.
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