Air pollution has routinely been linked to increased risk of cardiovascular disease, but some groups are more affected than others, according to research from the University of Washington School of Public Health.

Studies examining the association between air pollution and cardiovascular disease commonly include individual-level socioeconomic status measures, such as education or income, but few incorporate neighborhood-level socioeconomic status measures.

A new study published in Environmental Health Perspectives suggests that multiple risk exposures – both individual and contextual neighborhood measures – may interact to increase susceptibility to air pollution-related outcomes.

“Understanding the potential interaction between socioeconomic status and air pollution – and the level at which it operates, individual or neighborhood – has been something air pollution epidemiology studies have been trying to understand for some time,” says Anjum Hajat, co-author of the study and assistant professor in the School’s Department of Epidemiology.

To gain more insight on both individual- and neighborhood-level socioeconomic status, researchers used data from the Women’s Health Initiative Observational Study. In the study, 93,676 women were screened to obtain information on demographics, lifestyle, medical history, cardiovascular risk factors, and anthropometric and blood pressure measurements. Participants’ home addresses were geocoded and annual average fine particulate matter concentrations were predicted at the residences. Annual mailed questionnaires collected updates on health outcomes, including incidences of myocardial infarction, stroke and death from heart disease.

Significant associations between air pollution exposure and cardiovascular disease risk were observed among the most disadvantaged neighborhood groups. Participants who experienced cardiovascular disease events “tended to have less education and lower income, were less likely to work in managerial or professional positions, and more likely to live in lower neighborhood-level socioeconomic status neighborhoods,” the researchers wrote.

“Individuals with low socioeconomic status tend to live in more polluted areas, have poorer health and have fewer resources to cope with the effects of air pollution,” says Gloria Chi, lead author and Department of Epidemiology alumna.

Researchers also suggest that multiple risk exposures may contribute to a causal link between air pollution and cardiovascular disease. For instance, increasing traffic as a pollution source may change the attractiveness of a neighborhood, causing more affluent groups to leave and more disadvantaged individuals to move in. The results may cause “negative changes in the neighborhood’s social, physical and built environments that could result in adverse health effects for residents,” the researchers wrote.

Joel Kaufman, professor of environmental and occupational health sciences and epidemiology at the School, is also a co-author.