a comprehensive approach using hazard screening , demographic analysis , and a geographic information system ( gis ) for mapping is employed to address environmental equity issues in oregon . 
 a media - specific chronic toxicity index [ or chronic index ( ci ) ] was used to compare environmental chemical releases reported in the epa 's toxic chemical release inventory ( tri ) database . in 1992 
 , 254 facilities reportedly released more than 40 million pounds of toxic chemicals directly into the environment on - site or transferred them to sewage treatment plants or other off - site facilities for disposal and recycling . 
 for each reported on - site tri chemical release , a ci based on oral toxicity factors and total mass was calculated . 
 cis were aggregated on a media- , facility- , and chemical - specific basis . 
 glycol ethers , nickel , trichloroethylene , chloroform , and manganese were ranked as the top five chemicals released statewide based on total ci . 
 in contrast , based on total mass , methanol , nickel , ammonia , acetone , and toluene were identified as the top five tri chemicals released in oregon . 
 tri facility rankings were related to the demographics and household income of surrounding neighborhoods using bivariate gis mapping and statistical analysis . 
 tri facilities were disproportionately located in racial and ethnic minority neighborhoods . 
 they were also located in areas with lower incomes compared to those in the surrounding county . 
 no relationship was observed between the hazard ranking of the tri facilities overall and socioeconomic characteristics of the community in which they were located.imagesfigure 1figure 2