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.

It’s a common scenario in cities nationwide: Due to high housing costs and historical discrimination, low-income and minority neighborhoods are clustered around industrial sites, truck routes, ports and other air pollution hotspots.

In the South Bronx, a largely Hispanic and African-American district of New York City, nearly four in 10 live in poverty. Heavy traffic and a jumble of small industries taint the air with a load of fine particles that frequently exceeds the federal health limit.

Asthma rates are as much as four times higher in the Bronx than the national rates, said Dr. Norman Edelman, chief medical officer for the American Lung Association. “They live near highways, they live near where trucks spew diesel,” Edelman said. “That’s the least desirable housing… much different than a nice, leafy suburb.”

And just south of Pittsburgh, a slice of the Monongahela River Valley known as Liberty-Clairton tops the EPA charts with the nation’s worst fine particle pollution outside of California.

Clairton, a mill town, is “home to the [U.S. Steel] Clairton Coke Works, which is the largest coke-making facility in the nation,” said Rachel Filippini, executive director of the environmental organization Group Against Smog and Pollution. “The process of making coke is a pretty dirty one with lots of particulates and air toxics.”

Tom Hoffman, Western Pennsylvania director of the environmental group Clean Water Action, said childhood asthma is rampant in Clairton, but a lot of families in the hardscrabble town don’t have medical coverage. In some homes, the whole family shares a single inhaler, he said.

Particulates are complicated

The health effects of fine particle pollution are well-documented: Studies worldwide have shown that on days when fine particle concentrations increase in a community, more people die from heart attacks and respiratory problems.

But far less is known about whether specific types of particles translate to greater rates of illness or death.

“Some of these particles are not only composed of different things, but there are different gases and other things that adhere to them on the outside. So they’re complicated in a whole range of ways,” said Janice Nolen, author of the American Lung Association’s annual State of the Air Report.

Studies on the components are limited and have given varying results. But some associations are clear.

Sulfate, for instance, can trigger asthma attacks, while vanadium irritates lungs, and nitrate causes inflammation that may lead to heart attacks or strokes. Within cities, some studies have found cardiovascular deaths rise with certain particles, including nitrate, zinc, nickel, carbon, selenium and silicon.

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?”

This article originally ran at Environmental Health News, a news source published by Environmental Health Sciences, a nonprofit media company.