Hurricane Katrina and the subsequent flooding of New Orleans in late August of 2005 highlighted the geographic disparities among racial groups in the United States, as the predominantly African American neighborhoods were subsumed following the collapse of a sea levee.

Americans watching the disaster on television immediately noticed one thing: most of the victims waving to helicopter-mounted cameras were black.

Now, a new study from researchers at the University of California, Berkeley says racial minority groups in the United States face a greater risk than whites of health dangers from extreme heat, based on where they live. Publishing their findings in the journal Environmental Health Perspectives on Tuesday, the investigators used satellite imagery to identify areas with no tree canopy to provide shade from the sun, and where half or more of the land is covered by pavement, concrete, or roofing materials, which absorb heat. These more urbanized settings put people at greater risk during high heat, the study's authors noted.

"This study highlights a mechanism by which racial and ethnic minorities will likely suffer more from the effects of climate change," researcher Bill Jesdale, from UC Berkeley's Department of Environmental Science, Policy and Management, told media. "It may not be surprising that minorities live in inner cities, but this is the first paper to assess what that means in terms of heat vulnerability at a national level."

The researchers compared the satellite imagery data with information from the U.S. Census Bureau, finding that areas prone to high heat and with heat-absorbing qualities were disproportionately populated by blacks, Asians, and Hispanics. Compared to whites, African Americans were 50 percent more likely to live in such areas, while Hispanics were 37 percent more likely and Asians about a third more likely.

Rachel Morello-Frosch, a professor with joint appointments at the College of Natural Resources and the School of Public Health at UC Berkeley, said their study codified previous observations conducted on the regional level. "Segregation tends to concentrate racial and ethnic minorities into more densely populated urban areas," she said. "While some of this residential choice is based upon preference, a lot is based upon where people can afford to live."

The researchers recommended mitigating the impact of global climate change by planting more trees and lightening the coloring of roofs and pavements. When possible, city planners should replace harder surfaces such as pavement and concrete with more permeable materials.

"Planting trees and changing the heat-absorbing characteristics of our built environment may be crucial to protecting our public's health by mitigating heat risks, particularly in densely populated central areas of cities," Jesdale added.

The study also received funding from the Hewlett Foundation and the California Environmental Protection Agency.