Jan. 27 (UPI) -- The discriminatory practice of "redlining" neighborhoods may be history, but its legacy includes health effects that linger today, a new study suggests.
In an analysis published Monday in the The Lancet Planetary Health, researchers report that current rates of asthma-related emergency room visits are more than twice as high in areas that were once redlined -- or categorized as high risk for investment as part of government-sponsored programs.
The analysis was based on findings in eight California cities.
"Redlining may have shaped neighborhood development in ways that compound risk factors for asthma," study co-author Neeta Thakur, assistant professor of medicine at the University of California San Francisco, said in a press release.
Overall, approximately 8 percent of all Americans have asthma, a disease of airway inflammation often linked with pollution or poor air quality that causes difficulty breathing.
However, past research has suggested that the disease disproportionately affects communities of color. According to the Centers for Disease Control and Prevention, more than 10 percent of black Americans and nearly 13 percent of Puerto Ricans have asthma.
Thakur and her colleagues sought to determine whether this discrepancy might be traced to where these people live. The researchers specifically considered if study participants lived in areas that had been redlined by the Home Owners' Loan Corporation, or HOLC, a New Deal-era federal government-sponsored corporation created to provide mortgages to homebuyers and spur real estate sales during the Great Depression.
In evaluating loan applicants, the HOLC essentially graded their neighborhoods based on investment risk, with "A" areas -- typically affluent ones -- considered lowest risk and "D" areas -- those marked in red on maps -- considered highest risk.
The redlined areas were typically low-income neighborhoods with high minority and immigrant populations. Many were located in industrial areas and subsequently earmarked for development projects not wanted in more affluent neighborhoods, like highways and railroad lines, further worsening the air quality.
"Redlined neighborhoods had high rates of low socioeconomic status, which are associated with decreased access in health service and increased psychosocial stress, both contributors to asthma incidence, prevalence and severity," Thakur said.
The researchers reviewed HOLC maps for Fresno, Los Angeles, Oakland, Sacramento, San Diego, San Jose, San Francisco and Stockton against rates of ER visits due to asthma between 2011 and 2013. They also looked at levels of diesel exhaust particle emissions, or PM2.5 levels, in these areas, and the proportion of the current residents living with incomes below twice the federal poverty level.
In all, they found the risk for ER visits due to asthma was 2.4 times higher in neighborhoods that were redlined than those in A-graded neighborhoods -- 63.5 versus 26.5 visits annually per 10,000 residents. In "D" neighborhoods, they authors also noted that there were more people who were non-Hispanic black and Hispanic, more people living in poverty and higher amounts of diesel exhaust particle emissions.
"Eighty years or more after the development of the security maps, we observed persistently higher asthma-related emergency department visits in redlined neighborhoods compared with higher-graded neighborhoods," said co-author John Balmes, a professor of pulmonary and critical care medicine at UCSF.
"These areas also see higher diesel particle emission levels and rates of poverty. Together these might partly reflect a discriminatory legacy of redlining," Balmes added. "Similar research is needed to assess whether our findings apply beyond the eight Californian cities we studied."