An inequality study of ambient nitrogen dioxide and traffic levels near elementary schools in the Tampa area

Environmental equity has been identified as a challenge and goal of national to global air quality management. Here, relationships between traffic-related air pollution measures and the social demographics of elementary schools are investigated. Ogawa passive samplers were used to measure ambient nitrogen dioxide (NO2) levels near 75 randomly selected elementary schools in the county containing Tampa, FL over one week in March 2008. Concentrations were determined using colorimetric reaction using Hach nitrite reagent and photometric detection at 545 nm. NO2 levels, two metrics of traffic (highest annual average daily traffic count within 500 m and 1000 m), and school enrollment data by demographic subgroup (racial/ethnic and socioeconomic) were then compared. Data were analyzed for distribution statistics, linear correlations, and differences in subgroup category means. Weighted average values of NO2 and traffic count were also calculated for each subgroup. All measured NO2 levels were low, with a mean of 2.7 ppbv and range from 0.8 to 4.7 ppbv. Values were largest at sites near downtown. Results from all analyses show comparatively higher potential exposures to measured NO2 and traffic count for black school children, and lower values for white and Asian or Pacific Islander school children. The economically disadvantaged and Hispanic subgroups were also associated with higher levels of NO2 and traffic counts, but the relationship was not as strong or robust. Although measured NO2 levels were low and the differences between groups are small, results suggest disparities by racial/ethnic and economic status in children's exposures to air pollution for the Tampa area. (C) 2011 Elsevier Ltd. All rights reserved.