Using Personal Air Sensor and GPS to Determine Microenvironment-specific Exposures to Volatile Organic Compounds
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Human exposure to volatile organic compounds (VOCs) from indoor sources including consumer products is a public health concern that is understudied. In the context of a 10-day nine-person pilot study designed to test and demonstrate methods for monitoring personal VOC exposures, we examined time-resolved sensor-based measurements of geocoded total VOC (TVOC) exposures across individuals and microenvironments (ME). We integrated continuous (1-min) data from a personal TVOC sensor and a global positioning system (GPS) logger, with a GPS-based ME classification model to determine TVOC exposures in four ME, including indoors at home (Home-In), indoors at other buildings (Other-In), inside vehicles (In-Vehicle), and outdoors (Out) across 45 participant-days for a subset of five participants. To examine potential exposure factors when Home-In, we applied a residential air exchange rate (AER) model based on building characteristics and weather conditions. To help identify large emission sources, we identified high exposure events (HEE; TVOC > 500 ppb) and used geocoded TVOC time-course data overlaid on Google Earth maps to determine the type of place visited (e.g. store, restaurant). For HEE when Home-In, we estimated TVOC emission rates and removal rates with a dynamic mass-balance model. The ME ranked from highest to lowest median TVOC were: Home-In (165 ppb), Other-In (86 ppb), In-Vehicle (52 ppb), and Out (46 ppb). For the two participants living in single-family houses with attached garages, the median exposures when Home-In were substantially higher (209, 416 ppb) than the three participant homes without attached garages: one living in a single-family house (129 ppb), and two living in apartments (38, 60 ppb). The daily average Home-In exposures exceeded the LEED building guideline of 108 ppb for 60% of the participant-days. For the daily residential AER, the medians were lower for the homes with attached garages (0.04, 0.07 h-1) than the homes without attached garages (0.19, 0.23, 0.29 h-1), which corresponded to days with smaller and larger indoor-outdoor temperature differences, respectively. We identified 94 HEE across all participant-days, and 67% of the corresponding peak levels exceeded 1000 ppb. The ME ranked from highest to lowest number of HEE were: Home-In (60), Other-In (13), In-Vehicle (12), and Out (9). For Other-In and Out, most HEE occurred indoors at fast food restaurants and retail stores, and outdoors in parking lots, respectively. For Home-In HEE, the median TVOC emission and removal rates were 5.8 g h-1 and 1.1 h-1, respectively. Our study demonstrates the ability to determine individual sensor-based time-resolved TVOC exposures in different ME, in support of identifying potential sources and exposure factors that can inform exposure mitigation strategies.