LAUSR

In the US, concentrations of criteria air pollutants have declined in recent decades. Questions remain regarding whether improvements in air quality are equitably distributed across subpopulations. We assess spatial variability and temporal trends in concentrations of particulate matter <2.5μm (PM2.5) and ozone (O3) across North Carolina (NC) from 2002-2016, and associations with community characteristics. Estimated daily PM2.5 and O3 concentrations at 2010 Census tracts were obtained from the Fused Air Quality Surface using Downscaling archive and averaged to create tract-level annual PM2.5 and O3 estimates. We calculated tract-level racial isolation (RI) of non-Hispanic Blacks; educational isolation (EI) of non-college educated individuals; the neighborhood deprivation index (NDI); and percentage of the population in urban areas. We fit hierarchical Bayesian space-time models to estimate baseline concentrations of and time trends in PM2.5 and O3 for each tract, accounting for spatial between-tract correlation. Concentrations of PM2.5 and O3 declined by 6.4μg/m3 and 13.5ppb, respectively. Tracts with lower EI and higher urbanicity had higher PM2.5, and more pronounced declines in PM2.5. RI was associated with higher PM2.5, but not with the rate of decline in PM2.5. Despite declines in pollutant concentrations, over time, disparities in exposure increased for racially and educationally isolated communities.