Tiny particles of air pollution contain more hazardous ingredients in non-white and low-income communities than in affluent white ones, a new study shows.
The greater the concentration of Hispanics, Asians, African Americans or poor residents in an area, the more likely that potentially dangerous compounds such as vanadium, nitrates and zinc are in the mix of fine particles they breathe.
Latinos had the highest exposures to the largest number of these ingredients, while whites generally had the lowest.
The findings of the Yale University research add to evidence of a widening racial and economic gap when it comes to air pollution. Communities of color and those with low education and high poverty and unemployment face greater health risks even if their air quality meets federal health standards, according to the article published online in the scientific journal Environmental Health Perspectives.
Los Angeles, Pittsburgh, Cincinnati, St. Louis and Fresno are among the metropolitan areas with unhealthful levels of fine particles and large concentrations of poor minorities. More than 50 counties could exceed a new tighter health standard for particulates proposed by the Environmental Protection Agency.
Communities of color and those with low education and high poverty and unemployment may face greater health risks even if their air quality meets federal health standards. A pervasive air pollutant, the fine particulate matter known as PM2.5 is a mixture of emissions from diesel engines, power plants, refineries and other sources of combustion. Often called soot, the microscopic particles penetrate deep into the lungs.
The new study is the first to reveal major racial and economic differences in exposures to specific particle ingredients, some of which are linked to asthma, cardiovascular problems and cancer.
"Numerous studies indicate that some particles are more harmful than others," said lead author Michelle Bell, a professor of environmental health at Yale's School of Forestry and Environmental Studies.
The particles people breathe include a variety of metals and chemicals, depending on their source. For instance, people living near refineries are exposed to more nickel and vanadium, while those near coal-fired power plants breathe particles with higher sulfate content. Neighborhoods along busy roads have more nitrates from vehicle exhaust.
One such community is Boyle Heights, in East Los Angeles. It is more than 90 percent Hispanic and one of the poorest parts of the city.
Boyle Heights is "surrounded by freeways," said Susan Nakamura, planning manager for the region's South Coast Air Quality Management District, "and a lot of those freeways are used for shipping commercial goods." Four major rail yards emit diesel exhaust nearby, and the area is home to "multiple auto body shops and chrome-platers in close proximity to neighborhoods," she said. She is especially concerned about the particulate sources near schools.
A Nationwide Look
Bell and colleague Keita Ebisu examined exposures to 14 components of particulates in 215 Census tracts from 2000-2006. The components, including sulfate, a powerful respiratory irritant, and nickel, a possible carcinogen, were chosen because they had been associated with health impacts or accounted for a substantial amount of particulates overall.
Census tracts with a greater proportion of Hispanics had significantly higher levels of 11 substances. Included is more than 1.5 times the whites' exposure to nickel, nitrate, silicon, vanadium – all linked in some studies to hospitalizations or deaths from cardiovascular and lung disease – and aluminum, which is associated with low birth weights.
Communities with larger Asian populations had higher levels of seven components. Asians registered far greater exposures than whites to nickel, nitrate and vanadium.
And areas where more African Americans lived showed significant elevations in four compounds, including sulfate and zinc.
People with less than a high-school education, unemployed or living in poverty had more exposure to several components, including silicon and zinc. Also, children and teenagers were more likely than adults to breathe most of the substances.
The demographic differences raise important policy questions, said Rachel Morello-Frosch, an associate professor at the University of California, Berkeley, who studies the health risks of air pollution but was not involved in the Yale study.
Census tracts with a larger proportion of Hispanics had significantly higher levels of 11 substances, including more than 1.5 times the whites' exposures to nickel, nitrate, silicon, vanadium and aluminum. She said targeted monitoring may be needed in problem areas. "Then regulatory agencies may want to assess how they can encourage emissions reductions from sources that are having localized impacts," Morello-Frosch said.
"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."
"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?"