Developing a Granular Scale Environmental Burden Index (Ebi) for Diverse Land Cover Types Across the Contiguous United States

Abstract

Critical to identifying the risk of environmentally driven disease is an understanding of the cumulative impact of environmental conditions on human health.  Here  we describe the methodology used to develop an environmental burden index (EBI). Two key features of the EBI are that its geography is at U.S. census tract level, and that the tracts are stratified by land cover type as per the National Land Cover Database (NLCD). The first recognizes that environmental determinations at a coarser geographic scale are too variable to be of practical use. The second enables a control for urbanicity, as cities are often areas of concentrated contamination. The EBI enables the identification of environmentally burdened census tracts of rural areas that would not stand out as such otherwise. The EBI was developed over the course of four stages: 1) literature review to identify potential indicators, 2) data source acquisition and indicator variable construction, 3) index creation, and 4) stratification by land cover type. For each potential indicator, data sources were assessed for completeness, update frequency, and availability. Indicators were statistically normalized and checked for collinearity. For each indicator, we computed and summed percentile ranking scores to create an overall ranking for each tract. Tracts having the same plurality of land cover type form a ‘peer’ group. We re-ranked the tracts into percentiles within each peer group for each indicator. The percentile scores were combined for each tract to obtain a stratified EBI. A higher score reveals a tract with increased environmental burden relative to other tracts of the same peer group. We compared our results to those of related indices, finding good convergent validity between the overall EBI and CalEnviroScreen 4.0. The EBI has many potential applications for research and use as a tool to develop public health interventions at a granular scale.

Keywords: Environmental Burden, Environmental Burden Index, Environmental Health, Public health, geographic information systems (GIS)