Spatial Variation and Land Use Regression Modeling of the Oxidative Potential of Fine Particles

Abstract

BACKGROUND: Oxidative potential (OP) has been suggested to be a more health relevant metric than particulate matter (PM) mass. Land use regression (LUR) models can estimate long-term exposure to air pollution in epidemiological studies, but few have been developed for OP. OBJECTIVES: We aimed to characterize the spatial contrasts of two OP methods and to develop and evaluate LUR models to assess long-term exposure to OP of PM2.5. METHODS: Three two-week PM2.5 samples were collected at 10 regional background, 12 urban background and 18 street sites spread over the Netherlands/Belgium in one year and analyzed for OP using electron spin resonance (OP(ESR)) and dithiothreitol (OP(DTT)). LUR models were developed using temporally adjusted annual averages and a range of land-use and traffic-related GIS variables. RESULTS: Street/urban background site ratio was 1.2 for OP(DTT) and 1.4 for OP(ESR), while regional/urban background ratio was 0.8 for both. OP(ESR) correlated moderately with OP(DTT) (R(2) = 0.35). The LUR models included estimated regional background OP, local traffic and large-scale urbanity with explained variance (R(2)) of 0.60 for OP(DTT) and 0.67 for OP(ESR). OP(DTT) and OP(ESR) model predictions were moderately correlated (R(2) = 0.44). OP model predictions were moderately to highly correlated with predictions from a previously published PM2.5 model (R(2) = 0.37-0.52); and highly correlated with predictions from previously published models of traffic components (R(2) > 0.50). CONCLUSION: LUR models explained a large fraction of the spatial variation of the two OP metrics. The moderate correlations among the predictions of OP(DTT), OP(ESR), and PM2.5 models offer the potential to investigate which metric is the strongest predictor of health effects.