Research in Action
Air Pollution Exposure Model for Individuals (EMI)
Air pollution health studies are used to help understand potential health risks people face from air pollution exposure. Because of the cost and participant burden associated with indoor and personal air monitoring, health studies often estimate exposures using outdoor ambient measurements from central site air monitors. However, these ambient levels may not always reflect personal exposures since people spend considerable time indoors and indoor air pollutant levels can differ from outdoor levels.
EPA scientists have developed an exposure model for individuals (EMI), designed for use by air pollution health study participants. EMI uses information from outdoor air pollutant concentrations, meteorology, global positioning system (GPS) data on time-location patterns, and questionnaire data on housing characteristics.
Using EMI with outdoor air quality models or monitors, personal GPS, movement sensors (accelerometers), and health monitors can allow air pollution scientists to estimate air pollution concentrations, location, and physical activity of health study participants prior to adverse health effects. Using smart phones with these data collection capabilities will further expand the use of EMI in health studies.
EPA’s MicroTrac model is also able to interface with EMI. MicroTrac uses GPS data on location and speed to estimate the time people spend indoors and outdoors at home, school, work, and in vehicles.
Results and Impact
EMI has been evaluated in various contexts and is currently being applied in an asthma air pollution health study in Detroit. This research is expected to improve exposure assessments for health studies that provide the scientific basis for air pollution regulations, and support the development of community health strategies to reduce air pollution exposure.
EMI inputs include outdoor air pollutant concentrations, meteorology, and questionnaire information such as building characteristics and operation, indoor sources, and time-location activity patterns. EMI consists of three primary modules: (1) indoor air quality module, (2) time-location-activity module, and (3) respiratory tract dosimetry module. EMI predicted exposure-dose metrics are then used for epidemiological analysis in health studies with individual health outcomes.