The spatial analysis of covariates in a study of environmental epidemiology.
Kanawha County, West Virginia, includes a deep river valley with a large population living in close proximity to many chemical manufacturing centres. One study of this area combined an epidemiologic survey of children attending Kanawha County schools with the measurement of the concentrations of 15 volatile organic compounds at each of the 75 elementary schools. Results have been reported by Ware et al. This paper further examines the associations of the concentrations of the ten individual volatile organic compounds related to chemical manufacturing processes with observed lower respiratory symptoms, generalizing the model of spatial variability and measurement error proposed by Donnelly et al. and using semi-variograms to assess the validity of model assumptions.