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Last Edited: 10/13/2005

Exposure Insights Using GIS in a Case-Control Study
06/2002 - 05/2006


Little is known about the causes of childhood leukemia, but there is considerable public concern about the potential contribution of environmental toxicants.  One of the great challenges in environmental epidemiology is characterizing the spectrum of exposure opportunity to individuals, especially for chemical agents that may be commonly encountered in a variety of settings.  There are serious limitations with self-reported sources of information as well as with information from broader ecologic attributes of time and place.  This study is designed to address some of these shortcomings by building on an innovative childhood cancer research program undertaken jointly by the California Department of Health Services (CDHS) and the University of California at Berkeley (UCB); including one of the first large scale geographic information system (GIS) studies of patterns of childhood cancer, and one of the most extensive case-control studies of childhood leukemia undertaken to date.  The study is predicated on the hypothesis that perinatal or early life exposures to environmental chemicals are associated with increased risk of developing childhood leukemia.  Primary exposure sources of concern for this project include agricultural pesticides, motor vehicle emissions and other sources of air toxicants.   Using detailed residential and school history data collected in the first five years of the ongoing case-control study, metrics are being developed that account for personal and environmental exposures to these agents.  A particular innovation is the use of GIS tools in combination with household dust and air samples to validate generated metrics.  The full case-control data set will be available midway through the study, consisting of a projected 800 cases and 1200 controls, providing sufficient power to detect even modest estimates of risk associated with potential exposure to the chemical agents of concern.  The study presents an unusual opportunity to extend the capabilities of GIS tools to assist epidemiologists in attributing population exposures, to validate generated exposure attributes and to integrate these metrics with individual measures for a more comprehensive assessment of environmental risk factors.