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Air pollution monitoring using mobile ground-based measurement platforms can provide high quality spatiotemporal air pollution information. As mobile air quality monitoring campaigns extend to entire fleets of vehicles and embrace lower cost air quality sensors, it is important to address the quality assurance needs for validating these measurements. We explore collocation-based evaluation of air quality instruments in a mobile platform against fixed regulatory sites, both when the mobile platform is parked at the fixed regulatory site and when moving at distances of meters to kilometers from the site. We demonstrate agreement within 4 ppbv (for NO2 and O3 + NO2) to 10 ppbv (for NO) when using a running median of 40 hourly differences between the moving mobile platform measurements and stationary site measurements. The comparability is strong when only measurements from residential roads are used but are only slightly diminished when all roads except highways are included in the analysis. We present a method for assessing mobile measurements of ozone (O3), nitrogen dioxide (NO2), and odd oxygen (OX = O3 + NO2) on an ongoing basis through comparisons with fixed regulatory sites.

Disparity in air pollution exposure arises from variation at multiple spatial scales: along urban-to-rural gradients, between individual cities within a metropolitan region, within individual neighborhoods, and between city blocks. Here, we improve on existing capabilities to systematically compare urban variation at several scales, from hyperlocal (10km), and to assess consequences for the outdoor air pollution experienced by residents of different races and ethnicities, by creating a set of uniquely extensive and high-resolution observations of spatially-variable pollutants: NO, NO2, black carbon (BC), and ultrafine particles (UFP). We conducted full coverage monitoring of a wide sample of urban and suburban neighborhoods (93 km2, 450,000 residents) in four counties of the San Francisco Bay Area using Google Street View cars. Comparing scales of variation across the sampled population, greater differences arise from localized pollution gradients for BC and NO (pollutants dominated by primary sources) and from regional gradients for UFP and NO2 (pollutants dominated by secondary contributions). Median concentrations of UFP, NO, and NO2 are, for Hispanic and Black populations, 8%-30% higher than the population average; for white populations, average exposures to the same pollutants are 9%-14% lower than the population average. Systematic racial/ethnic disparities are strongly affected by regional differences in background concentrations due to sharp contrasts in demographic composition among cities and urban districts, while within-group extremes arise from local peaks. Our results illustrate how detailed and extensive fine-scale pollution observations can add new insights about differences and disparities in air pollution exposures at the population scale.

Experiments to Evaluate and Implement Passive Tracer Gas Methods to Measure Ventilation Rates in Homes Melissa Lunden, David Faulkner, Elizabeth Heredia, Sebastian Cohn, Darryl Dickerhoff, Federico Noris, Jennifer Logue, Toshifumi Hotchi, Brett Singer and Max H. Sherman Environmental Energy Technologies Division October 2012