Comparative analysis of major indoor air pollutants across residences, schools, and offices in Sri Lanka

Abstract

Indoor air pollution poses significant health risks, yet comprehensive data on exposure levels in Sri Lanka remains scarce. The study aimed to determine the predominant indoor air pollutant levels in 25 residences, 11 schools, and 23 offices across six districts in Sri Lanka, selected based on their geographical proximity and activities. The methodology involved monitoring a range of pollutants, including PM2.5, PM10, HCHO, Total Volatile Organic Compounds (TVOC), O3, CO, NO2, and SO2. Each monitoring session, conducted over a single day, involved eight hours of continuous sampling. Eight-hour mean values were PM2.5 (24 ± 1.53 μg/m3), PM10 (40 ± 1.63 μg/m3), HCHO (0.03 ± 0.03 mg/m3), TVOC (0.12 ± 0.10 mg/m3), O3 (0.021 ± 0.008 mg/m3), CO (1.11 ± 1.17 mg/m3), NO2 (13.30 ± 6.35 μg/m3), SO2 (33.39 ± 14.01 μg/m3). According to the “Guidelines for Indoor Air Quality in Sri Lanka 2022,” the results revealed that PM2.5 and PM10 levels in residences were below the reference values of 100 μg/m³ and 150 μg/m³, respectively. Schools and offices showed PM10 levels within the acceptable 200 μg/m³ limit. TVOC and CO levels across all locations were below 1 mg/m³ and 10 mg/m³, respectively, while SO2 and NO2 levels were below 200 μg/m³. The highest mean CO2 concentration of 692.47 ppm was observed in offices. Correlation analyses were conducted to identify potential relationships among pollutants, providing insights into their sources, pathways, and interactions within indoor environments. Statistical analyses using the Spearman rank correlation coefficient indicated strong positive correlations between PM2.5 and PM10 (R = 0.99) and between TVOC and HCHO (R = 0.73), while CO2 showed a moderate positive correlation with HCHO (0.496). Notably, there was a moderate negative correlation between RH and temperature (-0.528), and between CO2 and temperature (-0.484). This study highlights the need for targeted interventions to improve indoor air quality in various settings in Sri Lanka.