TEMPORAL AND SEASONAL TRENDS OF AMBIENT PM2.5 AND PM10 CONCENTRATIONS IN PUDUCHERRY, INDIA, 2021-2025: A CROSS-SECTIONAL TIME-SERIES ANALYSIS

Abstract

Background: Particulate matter is a major ambient air pollutant with important implications for respiratory, cardiovascular and population health. Local evidence on long-term PM2.5 and PM10 trends is needed for air quality surveillance and public health planning in smaller coastal urban settings such as Puducherry. Objectives: To assess annual, monthly and seasonal trends of 24-hour average PM2.5 and PM10 concentrations in Puducherry from 2021 to 2025, and to quantify exceedance of World Health Organization (WHO) guideline values and Indian National Ambient Air Quality Standards (NAAQS). Methods: A cross-sectional time-series analysis was conducted using daily 24-hour average PM2.5 and PM10 observations from the Jawahar Nagar, Puducherry monitoring dataset for 1 January 2021 to 31 December 2025. Seasons were classified as winter (January-February), summer (March-May), monsoon (June-September) and post-monsoon (October-December). Descriptive statistics, annual and seasonal comparisons, exceedance analysis, Spearman correlation and Kruskal-Wallis tests were used. Missing observations were excluded by available-case analysis. Results: Of 1,826 calendar days, valid observations were available for 1,762 PM2.5 days and 1,753 PM10 days. Annual mean PM2.5 ranged from 20.20 ± 13.89 µg/m³ in 2021 to 26.60 ± 19.09 µg/m³ in 2025. Annual mean PM10 ranged from 41.88 ± 19.17 µg/m³ in 2024 to 51.97 ± 21.64 µg/m³ in 2023. All annual means were below Indian annual NAAQS values for PM2.5 and PM10, but daily WHO 2021 guideline exceedance was frequent. PM2.5 exceeded the WHO 24-hour guideline on 52.9% to 68.2% of valid days across years, whereas PM10 exceeded it on 36.1% to 59.2% of valid days. Seasonal variation was significant for both PM2.5 and PM10 (both p<0.001), with winter and post-monsoon generally showing higher concentrations and monsoon showing lower concentrations. PM2.5 and PM10 were strongly correlated overall (Spearman ρ=0.870, p<0.001). Conclusion: Puducherry showed moderate annual particulate concentrations by Indian annual standards, but substantial daily exceedance of WHO guideline values and clear seasonal peaks. Continuous monitoring, season-specific mitigation and source-oriented control strategies are warranted.