We will determine how, when, and where children are exposed to particulate air pollution (PAP) in Kathmandu and Bandung in order to develop targeted exposure reduction practices. We will use real-time PurpleAir II sensors (Purple Air, USA) to monitor both PM2.5 personal exposures (mobile measurements with added power packs) and ambient PAP (static measurements), outside and inside the home and school environment. These sensors have been proven to have a high level of precision and accuracy in independent testing. Sensor calibration to local conditions will be conducted by co-location experiments at governmental ambient PM monitoring stations. Thirty children will be recruited in each city to participate in WP1.

1) Exposure measurements: Each child’s personal exposure will be monitored consecutively over 5 school and 2 non-school days to understand exposure during routine activities. Time-stamped PM2.5 concentrations will be matched with GPS data and time-activity questionnaires to apportion exposure to different places/activities (microenvironments). We will examine the contribution as a percentage of each microenvironment to total personal exposure.

2) Ambient PM2.5 measurements: Monitoring will be conducted outside the children’s school for one week, allowing us to determine indoor and outdoor PAP concentrations. Official air quality data will also be obtained to assess air quality variations across seasons and beyond the studied cities.

3) Questionnaires and field observations: Data will be gathered on contextual issues, such as proximity to pollutant sources, and behaviours which affect the measured exposures. Information about the home and school building construction/design will also be gathered, as will details of any PAP mitigation measures already being used.

Data from WP1 will inform the HIA (WP3) and uptake activities (WP7).