Updated Exposure Estimate for Indonesian Peatland Fire Smoke using Network of Low-cost Purple Air PM2.5 sensors

Air pollutant emissions from wildfires on Indonesian peatlands lead to poor regional air quality across south-east Asia. Fine particulate matter (PM_2.5) emissions are particularly high for peat fires leading to substantial population exposure to PM_2.5. Despite this, air quality monitoring is limited in regions close to peat fires meaning the impacts of peatland fires on air quality is poorly understood and it is difficult to evaluate predictions from atmospheric chemistry models. To address this, we deployed a network of low-cost (Purple Air) PM_2.5 sensors at 8 locations across Central Kalimantan, where peat fires are frequent. The sensors measured indoor and outdoor PM_2.5 concentrations during August to December 2023. During the haze season (September 1^st to October 31^st), daily mean outdoor concentrations were 120 mg m^-3 but peaked at >400 mg m^-3. Indoor PM_2.5 concentrations were only ~10% lower (mean 110 mg m^-3), indicating that is difficult for the population to reduce their exposure to PM_2.5 from fires. The reduction in mean PM_2.5 concentrations between outdoor and indoor environments was larger in urban locations (-11%) compared with rural locations (-3%), suggesting urban housing may provide better protection from outdoor air pollution. To generate an updated assessment for the population’s exposure to peatland fire PM_2.5 we combine the information from monitoring both indoor and outdoor PM_2.5 concentrations with modelled ambient (outdoor) PM_2.5 concentrations from the WRF-Chem atmospheric chemistry transport model. Our updated exposure assessment accounts for the population’s personal exposure to peatland fire PM_2.5 for the first time.