Unequal exposure to urban air pollution in North American cities continues to challenge even leaders in sustainability like Seattle. In 1994, the city developed the first US comprehensive plan for sustainability but after two decades, progress on air quality remains uneven. Some neighborhood residents endure more than double the rates of childhood asthma hospitalizations in the city and disproportionate air pollution exposures. In the first part of our paper, we set the case of Seattle’s environmental justice politics within critical geography’s literature on scalar politics and the growing field of Community-Based Participatory Research. In the second part of our paper, we examine how these air pollution problems are obscured by the scalar constructions of Seattle’s riskscape through the institutionalized practices of regional air quality monitoring and reporting. Using data from the region’s 12 stationary monitors, data from mobile pollution sensors, and other air toxics studies, we document the substantial interurban variability in Particulate Matter (PM) pollution levels. In the paper’s third part, we consider the perils and opportunities provided by a community-based, and participatory monitoring response to the existing institutional arrangements regulating air quality in Seattle and beyond. We demonstrate how understanding air quality through the lens of scalar politics can complement conventional environmental justice analysis and contribute to the transformation of institutional practices from one way science communication to a more just, culturally sensitive and multilingual dialogue.