More human research and animal experiments are needed to understand which components are the most harmful and why, said Marie Lynn Miranda, dean of University of Michigan’s School of Natural Resources and Environment and director of the Children’s Environmental Health Initiative.
"They live near highways, they live near where trucks spew diesel. That's the least desirable housing ... much different than a nice, leafy suburb." -Dr. Norman Edelman, American Lung Association, speaking of Hispanics and African Americans in the South Bronx“The notion of trying to figure out what are the different components and are there specific things in the PM2.5 that cause more of a problem… would have implications for how you regulate health effects,” Miranda said.
The EPA earlier this year proposed a more stringent health standard for fine particulate exposures that will force new regulations in some cities. Its final decision is expected in December. But the agency says too little is known about the specific ingredients of the particles to set individual limits for them.
“While different chemical components of PM may have different effects on health, the available scientific evidence to date supports setting standards that provide protection against exposures to PM from all sources,” the EPA said in a statement to EHN.
More racial disparities
The Yale study is part of a growing body of research on racial and social disparities in air quality.
African Americans are considerably more likely to live in areas with the worst levels of particulates and ozone, the main ingredient of smog, according to a nationwide study by Miranda and colleagues. Hispanics and low-income residents also are overrepresented in counties with high fine particle pollution.
Also, cancer risks from air toxics such as benzene and formaldehyde are greatest in the nation’s highly segregated metropolitan areas, according to research by UC Berkeley’s Morello-Frosch and Bill Jesdale. The risks increase with degree of segregation in all racial and ethnic groups, but are strongest for Hispanics, they found.
“Our question was: Are places that are more unequal disproportionately exposing communities of color more than other groups?” Morello-Frosch said. “The answer to that is ‘yes.’ Cities that are more segregated, you see higher pollution burdens for residents of color.”
As for why Hispanics seem to be facing some of the greatest air quality disparities, Morello-Frosch speculated that it may partly reflect the “L.A. Effect.”
“Because you have a lot of Latinos living in one of the largest and most polluted cities in the United States,” she said, “you might expect that contributing to the high population burdens of pollution.”
"Are places that are more unequal disproportionately exposing communities of color more than other groups? The answer to that is 'yes'."-Rachel Morello-Frosch, University of California, BerkeleyMany questions about the effects of unequal exposures remain. Stress from social and economic conditions seems to exacerbate the effects of pollution, according to some recent research. In other words, the same amount of pollution may harm poor people more than affluent people, or segregated minorities more than whites.
“So if I’m exposed to air pollution but I otherwise live in a pretty nice neighborhood, I don’t have a very stressful life… how does that differ from, I’m exposed to air pollution and I live in a cruddy house in a cruddy neighborhood and I have a very stressful life?” Miranda asked. “How do the social factors in my life affect my resiliency to environmental exposure?”