Integrated GPS/Pollution-Sensor Datalogger for Personal Exposure Measurements of Children

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SS7 Symposium Title: Human Tracking Technologies for Exposure Analysis. Symposium Organizers: Kai Elgethun,* and Steen Solvang Jensen† *Texas A&M University and the †National Environmental Research Institute, Denmark. SS7-01 Personalized exposure assessment methodology is evolving rapidly with the miniaturization of sensors and the widespread availability of location-based services such as global positioning systems (GPS). GPS receivers can be used as tracking devices to record people's time–location and linear velocity. Velocity (when not traveling in a vehicle) in turn can be used as a metric for exertion level and thus as a weighting factor for breathing rate. Velocity above 10 m/s can be attributed to vehicle travel and therefore excluded from exertion estimates. Using differentially corrected GPS (dGPS), high-resolution (±3 m RMS), near-continuous human time–location data can be collected to replace traditional self-report categorical data for characterization of exposures within and between microenvironments. It may be argued that dGPS data even permit time–location and exertion to be attributed to specific “nanoenvironments” in areas where GPS reception is consistent. The aim of this project is to generate personal inhalation time–location–dose profiles that capture dynamic air pollution exposure patterns of children living in urban areas. Toward the further refinement of exposure profiles, particularly for transient peak exposures, it is logical to synchronize dGPS time–location measurements with those from a real-time air-contaminant microsensor (using time steps as short as 10 seconds). The GPS Personal Acquisition Logger (GPS-PAL) dGPS instrument (Elgethun et al, 2003, 2006) is being modified to integrate interchangeable air pollution microsensors. The logger has preexisting input slots and available memory for this purpose. The modified device, dubbed the GPS Personal Exposure Tracker (GPS-PET), will simultaneously record time, location, and contaminant concentration in the breathing space of children with the sensor mounted to the lapel of a lightweight vest. The unit is lightweight (approximately 250 g) and tamper-resistant and was designed for children, although it has obvious use for adults as well. The advantage of an integrated GPS datalogger over multiple instruments is 2-fold: 1) it is less heavy and less cumbersome, thus reducing burden on subjects; and 2) it records a single time-stamp for both location and concentration, thus reducing effort and potential error introduced by post hoc synchronization.