Cement and brick factories contribute elevated levels of NO2 pollution in Nepal: Evidence of high-resolution view from space

Gyawali, M., Lamsal, L. N., Neupane, S., Gyawali, B., Bhattarai, K., Fisher, B, Krotkov, N., van Geffen, J., Eskes, H., Sharma, S., Brunt, C. and Aryal, R.: 2025,
Atmospheric Environment X 26, 100324, 11 pp.
doi: 10.1016/j.aeaoa.2025.100324

Abstract

An upsurge in the pollution level in areas with a high concentration of brick and cement factories in Nepal is concerning. Nitrogen dioxide (NO2), a key air quality indicator, can be effectively monitored from space. This study utilizes high-resolution satellite observations of NO2 from the TROPOspheric Monitoring Instrument (TROPOMI). It examines the NO2 distribution over areas with emerging sources of nitrogen oxides from brick and cement factories from 2018 to 2021. Rapid growth of brick and cement factories has turned the Lumbini-Butwal-Palpa corridor, in Midwest Nepal, more polluted than the capital city Kathmandu. Between 2019 and 2021, NO2 levels in this corridor rose considerably, while it remained steady in the Kathmandu Valley. TROPOMI-derived NO2 levels and inferred NOx emissions over the corridor nearly doubled in the span of three years. Conversely, Kathmandu Valley exhibited no significant changes except in 2020 when NO2 and NOx levels declined. This drop coincided with COVID-19-related travel restrictions and other reduced activities. NO2 pollution recorded by the Ozone Monitoring Instrument (OMI) from 2005 to 2019 shows an annual NO2 increase of ~3.5 % over both regions. A comparison between NOx emissions from the 2018 EDGAR inventory and TROPOMI-derived estimates for 2019 reveal comparable values over the Lumbini-Butwal-Palpa corridor but around 35 % higher estimates over Kathmandu. This discrepancy over the capital city, as well as the rapid rise in emissions over the Lumbini-Butwal-Palpa corridor due to a large-scale development of cement and brick industries, highlights the need for timely updates in bottom-up emission inventory.

 
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