This shortcoming, they contend, stems from the failure of a widely used approach for assessing disparities in the distribution of environmental hazards to adequately account for the proximity between such sites and nearby residential populations.
In an article appearing in the May 2006 issue of Demography, Paul Mohai of the University of Michigan and Robin Saha of the University of Montana report that when they use alternative" distance-based" methods to analyze the racial and socioeconomic disparities around the nation's hazardous waste facilities, those disparities are far greater than when the traditional measuring method is applied.
"Our study shows that race matters a lot more than previous studies show," said Mohai, who specializes in environmental-justice research." Often decisions about locating polluting facilities in or near communities are made without input from the residents, but the consequences affect them very significantly."
The traditional method used for determining the demographics of those living near hazardous waste sites has been to examine the demographics of only those geographic units" zip code areas or census tracts" containing the sites.
Not taken into account was the exact location of the hazards within the zip code areas or census tracts hosting the hazardous sites or the proximity of the hazards to nearby units. For example, Mohai and Saha found that 49 percent of all toxic waste facilities are located within a quarter mile of their host census tract boundaries while 71 percent are within a half-mile.
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"Using the traditional method, if I lived right across the street from a hazardous site but fell into a different zip code or census tract area, the location of my home would be considered the same as the home of someone living 100 miles from the site," Mohai said.
With distance-based methods, the exact locations of hazardous sites are found and the demographics of all units within a certain distance of the sites are taken into account. If zip code or census tracts lie only partially within the prescribed distance, their populations can be weighted based on the proportion of their areas that lie within.
"Distance-based methods produce neighborhoods that are consistently smaller and closer to hazardous sites than when the traditional approach is used," Mohai said." When we get closer to the hazardous sites we find that the percentage of minorities and people living below poverty increases."
He says that the distance-based methods also produce more consistently sized neighborhoods than do raw units such as zip code areas and census tracts. With consistently sized neighborhoods, researchers also are better able to conduct longitudinal analyses of demographic changes around environmentally hazardous sites." With this methodology, we can address the question, 'Is there a pattern for situating facilities near minority communities or does the shift take place after the sites are built?'" said Mohai who, together with Saha, have already begun this research." This has important policy implications."
The field of environmental justice, which centers around the fair distribution of environmental benefits including clean, healthy living conditions, has gained increasing significance in the wake of the Hurricane Katrina disaster and the subsequent failure of clean-up efforts in predominantly minority neighborhoods." Katrina showed what can happen when there isn't an equitable distribution of environmental resources or fair measures for correcting the problems that already exist," Mohai said.
In their study, Mohai and Saha reassess national data on 608 hazardous waste treatment, storage and disposal facilities and examine how the demographic characteristics change around these sites when distance-based, rather than traditional, methods are applied. Using distance-based methodology, the researchers compare the demographics of the populations residing in neighborhoods surrounding the hazardous waste facilities, as defined by 1.0-mile and 3.0-mile radii, to the demographics of neighborhoods farther away.
Their results reveal substantially larger proportions of minorities and poor people living near these facilities than previous studies based on the traditional methodology indicate.
"When distance-based methods are applied using a 1.0-mile radius, the African American and Hispanic percentages of the tract become highly statistically significant predictors of where hazardous waste facilities are located," Mohai said." This suggests that racial disparities in the distribution of these facilities are not solely a function of the labor force or other socioeconomic characteristics of nearby neighborhoods. Other factors associated with race, such as racial targeting or housing discrimination, also may be linked to the location of these facilities." Furthermore, Mohai reports that socioeconomic variables, such as percent employed in blue collar jobs, mean household income, and percent with college degrees, remain or increase in significance.
When a 3.0-mile radius is applied, similar results are obtained, except that percent employed in blue collar jobs is no longer a statistically significant predictor of hazardous waste location.
In contrast to Mohai and Saha's findings, national studies using the traditional method report that mostly occupational variables" not racial variables" are significant predictors of the locations of these facilities." Such conclusions might suggest that the disproportionate presence of hazardous waste facilities near minority communities is due to the tendency of the facilities being concentrated near industrial labor pools," Mohai said." This is not consistent with our results, which indicate the traditional approach has largely camouflaged racial and economic disparities that are much larger than previously reported."
At the University of Michigan, Paul Mohai is professor of natural resources in the School of Natural Resources and Environment and a faculty associate in the Survey Research Center at the Institute for Social Research. Co-author Robin Saha is formerly a post-doctoral fellow at Michigan and is currently assistant professor of environmental studies at the University of Montana. Their research paper is titled" Reassessing Racial and Socioeconomic Disparities in Environmental Justice Research."