Incorporating Local Land Use Regression And Satellite Aerosol Optical Depth In A Hybrid Model Of Spatio-Temporal PM2.5 Exposures In The Mid-Atlantic States

Abstract

Aims: We aimed at extending our previous work by validating our model in another region with different geographical and metrological characteristics, and incorporating fine scale land use regression and nonrandom missingness to better predict PM2.5 concentrations for days with or without satellite AOD measures. Methods: We start by calibrating AOD data for 2000-2008 across the Mid-Atlantic. We used mixed models regressing PM2.5 measurements against day-specific random intercepts, and fixed and random AOD and temperature slopes. We used inverse probability weighting to account for nonrandom missingness of AOD, nested regions within days to capture spatial variation in the daily calibration, and introduced a penalization method that reduces the dimensionality of the large number of spatial and temporal predictors without selecting different predictors in different locations. We then take advantage of the association between grid-cell specific AOD values and PM2.5 monitoring data, together with associations between AOD values in neighboring grid cells to develop grid cell predictions when AOD is missing. Finally to get local predictions (at the resolution of 50m), we regressed the residuals from the predictions for each monitor from these previous steps against the local land use variables specific for each monitor. Results: For all days without AOD values, model performance was excellent (mean "out-of-sample" R2=0.81, year-to-year variation 0.79-0.84). Upon removal of outliers in the PM2.5 monitoring data, the results of the cross validation procedure was even better (overall mean "out of sample" R2 of 0.85). Further, cross validation results revealed no bias in the predicted concentrations (Slope of observed vs. predicted = 0.97-1.01). Conclusions: Our model allows one to reliably assess short-term and long-term human exposures in order to investigate both the acute and effects of ambient particles respectively).