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Human Exposure and Atmospheric Sciences

Research in Action

MicroTrac: Personal Time-Activity Modeling

In order to understand people’s contact with pollutants, and their potential for adverse effects, scientists must be able to accurately estimate how much time people spend in different locations and what they are doing in those locations. Using questionnaires to collect this information has limitations, including burden on participants and inaccuracies.

To address these data collection limitations, there is a growing commitment to utilize modern common personal electronic devices such as smart phones, global positioning systems (GPS), and movement sensors (accelerometers) to collect data on personal activities. This information can then be integrated with data from personal pollutant sensors (such as air quality sensors) and health monitoring devices.

EPA scientists have developed MicroTrac, a computer model that uses GPS data on location and speed to estimate the time people spend in various “microenvironments” such as inside and outside their home, school, workplace, and motor vehicle.

Using MicroTrac with personal GPS devices, accelerometers, and health monitors in exposure and health effects studies will allow scientists to link the location and activities of study participants with air pollution measurements and measures of health effects during a study. Using smart phones with these data collection capabilities will facilitate and expand the use of MicroTrac in these studies, and will support community applications of MicroTrac such as alerting susceptible populations (such as asthmatics) to behavior or activities that may compromise their health.

Results and Impact
MicroTrac has been evaluated in a pilot study in central North Carolina. The model is being applied to various health studies, including a childhood asthmatic health study in Detroit, Mich., and a cardiovascular health study in central North Carolina.

This research is expected to improve exposure assessments for health effects studies, which provide the scientific basis for air pollution regulations. It is also expected to assist in the development of public health strategies to reduce air pollution exposure among vulnerable populations.

Technical Contact
Michael Breen, Ph.D.

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