A Comparative analysis of inter-regional air pollution trends in Sri Lanka

Abstract

Air pollution is a major environmental and public health concern in Sri Lanka, yet island-wide comparative evidence covering both fine and coarse particulate matter remains limited. This study evaluated spatial and temporal patterns of PM2.5 and PM10 using daily observations from twenty National Building Research Organisation monitoring stations from March 2020 to December 2024. Daily rainfall records were available for nine stations and were used to examine the relationship between precipitation and particulate concentrations. Descriptive statistics, annual and seasonal comparisons, Pearson correlation and compliance assessment against World Health Organization guidelines and Sri Lankan national standards were applied. Mean PM2.5 concentrations ranged from 15.10 μg/m³ at Nuwara Eliya to 28.28 μg/m³ at Badulla, while mean PM10 concentrations ranged from 21.86 μg/m³ at Nuwara Eliya to 40.11 μg/m³ at Jaffna. All twenty stations exceeded the World Health Organization annual guidelines for both pollutants, although period-average concentrations remained within the Sri Lankan national annual standards. The lowest annual concentrations occurred in 2021, followed by substantial increases from 2022 onwards. Both pollutants were consistently higher during the northeast monsoon period. Rainfall showed only weak negative-to-negligible relationships with particulate concentrations. The results demonstrate substantial spatial and temporal variability and indicate that regional transport and seasonal atmospheric processes are important considerations for particulate pollution management in Sri Lanka.