title: Evaluating geostatistical modeling of exceedance probability as the first step in disease cluster investigations: very low birth weights near toxic Texas sites.
abstract: BACKGROUND
  The first step in evaluating potential geographic clusters of disease calls for an evaluation of the disease risk comparing the risk in a defined location to the risk in neighboring locations. Environmental exposures, however, represent continuous exposure levels across space not an exposure with a distinct boundary. The objectives of the current study were to adapt, apply and evaluate a geostatistical approach for identifying disease clusters.
  
  
  METHODS
  The exceedance probability for very low birth weight (VLBW; < 1.5 kg) infants was mapped using an Intrinsic Conditional Autoregressive model. The data were applied to a 20 by 20 grid of 1 km2 pixels centered on each of the 13 National Priority List Superfund Sites in Harris County, Texas.
  
  
  RESULTS
  Large clusters of VLBW were identified in close proximity to four of the 13 Superfund Sites. Three of the Superfund Sites, associated with disease clusters, were located close together in central Houston and these sites may have been surrounded by a single, confluent disease cluster.
  
  
  CONCLUSIONS
  Geostatistical modeling of the exceedance probability for very low birth weights identified disease clusters of varying size, shape and statistical certainty near Superfund Sites in Harris County, Texas. The approach offers considerable potential as the first step for investigating potential disease clusters.
authors.affiliation: Department of Large Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843-4475, USA. jthompson@cvm.tamu.edu.
authors.forename: James A
authors.initials: JA
authors.lastname: Thompson
authors.forename: Wesley T
authors.initials: WT
authors.lastname: Bissett
authors.forename: Anne M
authors.initials: AM
authors.lastname: Sweeney
mesh_terms: D016000:Cluster Analysis; D004781:Environmental Exposure / Q000009:adverse effects; D064371:Hazardous Waste Sites; D006801:Humans; D007231:Infant, Newborn; D019102:Infant, Very Low Birth Weight; D008962:Models, Theoretical; D011336:Probability; D013781:Texas / Q000453:epidemiology