Temporal and spatial variation of the metal-related oxidative potential of PM2.5 and its relation to PM2.5 mass and elemental composition

Oxidative potential (OP) of particulate matter (PM) has been proposed as a more health relevant metric than PM mass. However, little is known about the temporal and spatial variation of OP, which is crucial if OP were to be used as an exposure metric in epidemiological studies. We studied OP on routinely collected PM2.5 samples (every 6th day) from three regional, five urban background, and three street sites over a one-year period across the Netherlands. OP was measured as the ability to generate hydroxyl radicals in the presence of hydrogen peroxide using the electron spin resonance (OPESR). correlated poorly with PM2.5 mass both spatially (Spearmanʹs rs = 0.29) and temporally (median rs = 0.34). The temporal correlations across sites for OPESR were moderate (median rs = 0.50) compared to PM2.5 (median rs = 0.87), suggesting that exposure misclassification is higher when using OPESR as an exposure metric in time series studies. Street/urban background and street/regional background ratios for OPESR were 1.4 and 2.4 respectively; higher than for PM2.5 (ratio of 1.1 for both street/urban background and street/regional background). arge scale, nationwide study found that PM2.5 correlated poorly with OPESR in space and time. Spatial contrasts were much larger for OPESR than for PM2.5, which offers the possibility to use OPESR to assess long-term exposure health effects.