Asthma is a chronic and serious long-term disease of the lungs that causes wheezing, breathlessness, chest tightness, and coughing. It affects 1 in 11 children in the United States, with African American and Hispanic children disproportionately more likely to have it than non-Hispanic white children. In a new review, published in April 2018 in Current Allergies and Asthma Reports, researchers at the University of California, Berkeley, and University of California, San Francisco, shed light on a key reason for this disparity: the disproportionate exposure of children of color to ambient (outdoor) air pollution, often beginning in utero.
The role of pollution in asthma
Globally, between 11 and 17 percent of all asthma cases and asthma-related deaths are believed to be caused by environmental factors. One of the most important of these is air pollution, caused largely by the burning of fossil fuels. Researchers believe that exposure to such pollution triggers an immune response that can lead to both acute and chronic airway obstruction.
It’s well known that children of color (and adults of color) are more likely to live in poorerneighborhoods with greater air pollution levels, compared with whites. In one study, researchers found that in the year 2010, non-white people in the U.S. were exposed to 37 percent more nitrogen dioxide(a transportation-related air pollutant) on average than whites. That was only a tiny improvement over the year 2000, according to the study, in which non-whites’ exposure was 40 percent higher than white people’s.
In the new review, researchers looked at studies published between 2013 and 2017 on asthma in urban environments, asthma among children of color, and the pervasiveness of ambientair pollution exposure among children living in urban environments. They found that children living in inner-city urban areas in which more than half of the population identifies as a “person of color” are exposed to air pollution more or less everywhere: at home, outside at play, and at school.
For example, schools in which more than half of students are African American are 18 percent more likely to be located within two-tenths of a mile from a major roadway, compared to schools with a predominately white student body. Many children of color also experience prenatal exposure to ambientair pollution, which has also been linked with asthma development in childhood.
The role of stress and structural racism
The UC researchers also determined that psychosocial stress appears to play a role in the disproportionate burden of asthma on children of color. Even when compared with white children living in the same neighborhoods, children of color have higher rates of asthma. Low socioeconomic status, along with exposure to adverse childhood experiences, gun violence, perceived discrimination, and lack of high-quality health insurance, may help explain the difference, the researchers concluded. (Children of lower socioeconomic status are also exposed to more indoor air pollution and allergens, such as cockroach particles and unvented appliances.)
The study also points to structural factors that have put more children of color into the path of asthma-causing pollutants—particularly historical segregation and housing policies that have forced minorities into less desirable neighborhoods. Studies have shown that children of color are more likely to be in disadvantaged neighborhoods—ones with less green space, higher crime rates, greater racial segregation, and closer proximity to freeways or other major roads. Although the UC researchers looked mainly at traffic-related air pollution, people living in disadvantaged neighborhoods are also more likely to be exposed to pollution from industry, which carries its own risks.
Finally, although there is also some evidence that certain populations, including African Americans, may be genetically more prone to developing asthma—or that they may experience other environmental exposures that make asthma-related genes more likely to “turn on”—the authors cautioned against over-focusing on genetics as an explanation for the asthma gap between minority and white children.
“Research that focuses solely on ancestral genetic factors risk appearing myopic; the divide in asthma burden that currently exists between children of color and non-Hispanic white children likely exists due to disparities in access to resources, psychosocial stressors, and AAP [ambient air pollution] exposures,” they wrote.