Redefining Exposure: Using Mobile Technology and Geospatial Analysis to Explore When and Where Chicago Adolescents...

Differences in how individuals navigate and interact with physical space have clear implications for when and where they are exposed to environmental characteristics. To address this reality, we propose and test a novel method with a sample of Chicago adolescents that links individual GPS coordinates with locations of environmental characteristics as a strategy to increase precision in the measurement of environmental exposures. We use exposure to violent crime as an example and link the GPS coordinates of 51 youth collected over a one-week period during the summer of 2016 to locations and times of violent crime. We explore different spatial and temporal parameters to determine whether an exposure occurred. Using the 660-foot (201 m), 24-hour operationalization, we found that youth were exposed to a total of 126 violent crimes, with an average of 3.82 (SD = 3.24) per respondent. This was higher than the 12 that were identified when exposure was calculated as the number of violent crimes occurring within 660 feet (201 m) of youths' residential addresses during the week-long assessment period. Examining correlations between the different exposure variables and measures of youths' psychological functioning, we found the largest relationships when using the GPS-based indices. We present a strategy for measuring exposure to environmental characteristics using GPS data. Higher rates of crime exposure are found based on GPS coordinates than with residential address. GPS-based exposure measures are related to youths' psychological functioning.