Positioning through play clothes: wearable GPS devices track exposures. (Science Selections).

Capturing children's exposure to pesticides is a complex and difficult task. It's especially difficult in an area where crops are sprayed, because the spray causes a one-time spike in pesticide concentrations at discrete locations. Yet getting a good estimate of exposure requires a detailed knowledge of the time children spend in pesticide-affected areas. Given the inexact methods of monitoring both time and location together, this knowledge has been hard to obtain. Now, however, wearable Global Positioning System (GPS) sensors developed by University of Washington researchers may provide a practical research tool for time-location analysis [EHP 111:115-122].

In the past, attempts at linking exposure duration and pollutant concentrations in well-defined areas relied on interviews or diaries, which may be subject to memory bias or reporting errors. GPS technology, in which a receiver determines its own location by comparing different satellite signals, has been used in many military and civilian applications to locate position to an accuracy or a few meters. It has not, however, been used previously in a time-location study of children's exposure to pollutants, although earlier research has shown that data gathered by a GPS unit can be effectively mapped to help assess human exposure to chemicals.

As the first part of a project to look at the role of pesticide spray drift in rural exposures, the researchers developed and tested some novel children's clothing. The clothing incorporates a GPS tracking device, allowing the researchers to map the child's location data with a geographic information system. The researchers sewed several pieces of the clothing in a variety of sizes and two styles: bib overalls and vests. Each GPS device, designed specifically for this study, contains a battery pack, central electronics unit, and antenna, and can record its position as often as every 5 seconds. In both outfits the battery and electronics unit are concealed in closed pockets on the front, and the antenna is laid horizontally along the shoulder for maximum reception.

The 11 participants in the study, who wore the clothing for 7 to 11 hours, were children of faculty and staff at the university. Elgethun says the key to the success of this feasibility study was ensuring that the 2- to 8-year-old children were receptive to the project by meeting with them early on and enlisting their parents' help. Children over age 4 preferred the vest, while the younger ones preferred the overalls. None of the children complained about the weight or restrictiveness of the clothes (although two 2-year-olds didn't care for the color or style of the overalls).

In testing the capabilities of the wired outfits, the researchers learned that the GPS signals were clearly recordable with a few exceptions. There was no reception when the child went inside a concrete/steel-frame building or walked near power substation transformers. Reception was reduced when the child went inside a wood-frame building or stood in front of an operating microwave oven. Typically the location could be resolved and mapped at 2-3 meters outdoors and 4-5 meters indoors, allowing the child to be located in individual rooms, on specific parts of a playground, or on one side or the other of a fence.

Based on this test, the researchers have been studying the time-location activities of children in rural areas, where pesticides are used routinely in crop production and may be dispersed over wide areas (publication of those results is upcoming). By combining their novel clothing with data about the time and place of pesticide applications and concurrent environmental monitoring, the researchers hope to characterize the children's activities and thus better understand the multiple pathways by which they may be exposed to pesticides.