As low-cost air sensors become readily available, communities have opportunities to collect air quality and exposure data to improve their knowledge and contribute to environmental health research and policy decisions. Citizen scientists in Globeville, Elyria Swansea (GES), an environmental justice community in Denver, with help of researchers, conducted air quality and exposure measurements for PM2.5 in the Summer and Fall of 2018. RTI MicroPEM sensors were placed at 12 sites within the community as a neighborhood-scale sensor network, including near-road sites (NRS) collocated with reference monitors. Nineteen citizens measured their exposures wearing MicroPEM and completed time-activity diaries for two 72-hour monitoring periods. MicroPEMs data were highly accurate (>90%) after adjustment using filter-based gravimetric data and correcting temperature-associated bias. Ambient PM2.5 data showed variability with up to 3 times difference between site pairs. We observed up to 2.5 times higher PM2.5 levels in Summer. The temporal measurements among the most sites were highly correlated with NRS data (r > 0.7), suggesting a large influence of traffic on the community air quality. However, few sites such as parks showed a significant difference from NRS during weekends. Individual's personal exposure levels varied by day, influenced by activity types. Real-time peak concentrations matched with participant-reported exposure events such as proximity to combustion sources and cleaning. On average, personal PM2.5 exposures were higher than the nearby ambient sensor measurement and lower than the NRS. However, for the individuals with high exposure events, the personal levels were 6-24 times higher than nearby ambient sensor levels. This study shows the value of low-cost sensors in assessing the spatial and temporal variabilities of air quality and the degrees of exposure measurement error, which is critical for accurate epidemiologic models. Additionally, the sensors are useful tools for behavioral intervention to reduce air pollution exposure. EPA Grant Number: RD83618701
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