study of time-location and pm2.5 exposure for residents of port-adjacent communities

UCLA collaborates in the  Harbor Community Monitoring Study (HCMS) in which a specially instrumented electric vehicle (RAV4  with a full range of real-time gaseous and particulate pollutant monitors) is used to create a “map” of particulate matter concentrations in impacted neighborhoods as a basis for estimating the effects on individual who live there.  The mobile platform has demonstrated the great versatility and power of using an instrumented electric vehicle to rapidly collect pollutant concentration data over a wide range of microenvironments and with excellent spatial and temporal resolution. Urban Sensing researchers at CENS have developed an innovative system for collecting time-activity data, using GPS-enabled cell phones, to estimate individualized PM2.5 exposure estimates based on the data collected by the mobile platform. Previous time-activity studies have largely relied on interviews and diaries.  Recent work suggests that Global Positioning Systems (GPS) technology offers a valuable new tool to (a) track subject locations throughout the day as they go about their everyday activities in various microenvironments and (b) validate conventional time-activity diaries (Phillips et. al., 2001).  GPS tools provide temporal and location data on time-location activity patterns which can be used to more accurately classify subjects into location categories (in-vehicle, indoor and outdoor microenvironments) in air pollution exposure assessment studies, especially given potential recall errors in traditional time-activity diaries (Elgethun et al. 2003).  Elgethun et al. (2007) suggest data derived from diaries underestimates time indoors at home, and overestimates time spent outdoors, in transit, and indoors at other locations.  Since GPS offers the potential of increasing data collection efficiency and reducing participant’s burden filling out a daily activity record, they can be used to track subjects for longer periods of time, providing valuable data on within-subject variation (Xue et al., 2003) which is necessary to refine exposure assessment methodologies. CENS has a partnership with NOKIA which has provided blue tooth-enabled cell phones and GPS devices in order to demonstrate the usefulness of this technology for research.