Spatio-temporal variation analysis of PM2.5 in Lahore using Beta Attenuation Monitor and Low-cost sensors

Spatio-temporal variation analysis of PM_2.5 in Lahore using Beta Attenuation Monitor and Low-cost sensors

Shahbaz A. ¹, Nizami A.S¹, Dillner A. M.², Anwar M. N.^1,2*

 

1Sustainable Development Study Center, Government College University, Lahore, Pakistan 

2Air Quality Research Center, University of California, Davis, Davis, CA 95618, USA  

 

*Corresponding author. Tel: 92-333-4881593;

E-mail address: naveedanwarenv@gcu.edu.pk

 

Air pollution (especially fine particulate matter PM_2.5) is a major global issue causing 7 million premature deaths each year. It also reduces the atmospheric visibility and interacts with overall ecosystem. The Low and Middle-Income Countries (LMICs), home to 6.62 billion people, are at forefront to air pollution exposure. Despite grave impact (89% of the premature deaths), LMICs lack sufficient air quality monitoring. Pakistan, like other LMICs, is faced with severe air pollution as well. Lahore, one if its metropolitans, was among top 10 most polluted cities globally in 2022. In this study temporal and spatial variability of PM_2.5 concentration in Lahore was investigated by using reference grade Beta Attenuation Monitor (BAM) and low-cost sensors based data from 2019 to 2025. Over the study period, daily PM_2.5 concentration was measured by BAM ranged from 0.1 µgm⁻³ to 910.1 µgm⁻³, with an overall mean concentration of 125.5 µg m⁻³. A strong seasonal trend was observed with winter frequently exceeding 300µgm⁻³ (far surpassing WHO and EPA guidelines of 15 µgm⁻³ and 35 µgm⁻³ respectively), even higher than 600µgm⁻³ occasionally. Data from a city-wide network of low-cost sensors was used to examine the spatial variation of the PM_2.5. Furthermore, this PM_2.5 mass concentration data was validated against the reference grade BAM data and tailored calibrations, catering the potential bias of different factors, were developed. These calibrations can be readily applied in the future on the low cost sensors data to reduce the need for the deployment of expensive reference grade monitors paving the way for routine and dispersed monitoring – much needed towards the prevention of recurrence of smog episodes in Lahore. In addition, the role of the transboundary agricultural residue burning towards the higher PM_2.5 mass concentrations was also investigated by using the satellite imageries and meteorological data. These findings underscore the urgent need to improve data integration approaches, strengthened air quality networks, and policy interventions that are evidence based to mitigate the increasing air pollution in urbanizing regions of LMICs.