Characterizing Indoor-Outdoor PM2.5 Concentrations Using Low-Cost Sensor Measurements in Residential Homes in Dhaka, Bangladesh
| Published | 19 August 2024 |
|---|---|
| Publisher | American Chemical Society (ACS) |
| DOI | 10.26434/chemrxiv-2024-7wrlw |
Open access (green)
Low-cost sensor networks, data science and forecasting Urban and indoor air quality in Dhaka
Abstract
We collected paired measurements of indoor and outdoor PM2.5 concentrations at 17 homes in Dhaka, Bangladesh, to quantify indoor-outdoor levels, their spatio-temporal variations, and influencing factors. A pair of PurpleAir PM2.5 sensors were deployed at each home, one indoors and the other outdoors, during the wet (June to August 2021) and dry (December 2021 to February 2022) seasons, and the locally calibrated (against a beta attenuation monitor) and quality-assured data were used for analysis. Indoor and outdoor PM2.5 levels were three times higher during the dry season (indoor 146 ± 22 µg/m³, outdoor 153 ± 23 µg/m³) than during the wet season (indoor 52 ± 12 µg/m³, outdoor 50 ± 11 µg/m³). Indoor to outdoor (I/O) ratios were close to 1 in both seasons (dry: 0.97 ± 0.14, wet: 1.05 ± 0.19). This suggests that regional background pollution levels significantly influence indoor levels observed in different households. Higher infiltration factors (dry: 0.83 ± 0.12; wet: 0.87 ± 0.14), determined through mixed effect regression of parallel indoor and outdoor timeseries data, further highlight the substantial impact of outdoor pollution on indoor levels. Data from individual households exhibited strong temporal correlation between indoor and outdoor levels in both seasons (Pearson R: 0.82 ± 0.12 during the dry season and 0.83 ± 0.14 during the wet season), whereas indoor-outdoor spatial correlations across measured households were moderate (R: 0.49 and 0.62 during dry and wet seasons, respectively). These spatial correlations and empirical regression modeling suggest that while the spatial variation of outdoor PM2.5 levels significantly influences indoor levels’ spatial variation, other factors such as indoor source activities and ventilation-related features play crucial roles in explaining variabilities in indoor PM2.5 across homes. Overall, our study suggests that indoor environments in Dhaka city are nearly as polluted as outdoor settings, and this locally derived scientific evidence can be valuable for enhancing public awareness and developing mitigation measures to reduce PM2.5 exposures in Bangladesh.
Abstract © the authors, published under a CC BY NC ND licence.
Cite this
Provat Saha, Ahsan Habib, Dipika Prapti, Talha Jubair, Abu Zarrah, Chowdhury Hossain, Sheikh Rahman, Abdus Salam, Aynul Bari, Julian Marshall (2024). Characterizing Indoor-Outdoor PM2.5 Concentrations Using Low-Cost Sensor Measurements in Residential Homes in Dhaka, Bangladesh. American Chemical Society (ACS). https://doi.org/10.26434/chemrxiv-2024-7wrlw
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