Air Pollution, Social Disadvantage, and Walking in Six United States Cities: the Multi-Ethnic Study of Atherosclerosis

Physical activity may be influenced by walking opportunities, which can differ substantially across neighborhoods. Air pollution similarly varies by location. It remains unclear whether more walking occurs in highly polluted neighborhoods and whether socially disadvantaged populations are less likely to experience walkable neighborhoods with clean air. We studied the spatial distributions and associations of neighborhood level air pollution, walkability, and social factors with self-reported walking. Overall walking was reported between 2010-2012 by 3,661 Multi-Ethnic Study of Atherosclerosis participants from Baltimore, MD, Chicago, IL, Los Angeles, CA, New York, NY, Minneapolis, MN, and Forsyth County, NC. Fine particulate matter and oxides of nitrogen concentrations and walkability were estimated for all participant homes and Census block groups (“neighborhoods”). Neighborhoods having low air pollution/high walkability and high air pollution/low walkability were classified as sweet and sour spots, respectively. We described the spatial distribution of sweet and sour spots within the cities. We then estimated associations of air pollution with walking activity, and investigated whether sweet and sour spots differed in neighborhood race, education level, and poverty using multinomial and binary logistic regression. Geographical distributions of sweet- and sour-spots differed across cities with the most neighborhoods classified as sweet and sour spots in Chicago and the fewest in New York City. More walking for transport and less walking for leisure occurred in neighborhoods with higher levels of air pollution. Lower education neighborhoods were consistently more likely to be sour spots across all cities, and less likely to be sweet spots except in NY and MN. Walkability, air pollution, and walking behavior vary by place and may contribute to health disparities in US communities.