ASSESSMENT OF PM2.5 AND PM10 OVER SRI LANKA: SPATIOTEMPORAL TRENDS, POTENTIAL SOURCE REGIONS AND ASSOCIATED HEALTH EFFECTS

Abstract

Air pollution, specifically the presence of particulate matter (PM2.5 and PM10) is a growing concern in many parts of the world, including Sri Lanka because of their ability to cause serious health issues, mortality among the community and negative effects on the nation’s economy. This study analyzed the PM2.5 and PM10 concentrations at 17 locations in Sri Lanka over a two year period (Jan 2021-Dec 2022); impact of meteorological parameters on the PM levels, potential source regions for high PM; and human health risks associated with PM2.5 exposure. Jaffna showed the highest annual mean PM2.5 (29.9±19.4 µgm-3 ) and PM10 (55.8±37.8 µgm-3 ) in 2022, while Kurunagala exhibited the highest annual mean PM2.5 (21.4±7.8 µgm-3 ) and PM10 (41.1±14.8 µgm⁻3 ) concentrations in 2021. The annual average PM2.5 and PM10 concentrations at all the stations throughout both years were always higher than WHO guidelines (PM2.5: 5µgm-3 , PM10: 15µgm-3 ). However, the Sri Lankan Air Quality Standards (SLAQS) (PM2.5 : 25 µgm -3 , PM10: 50 µgm-3 ) were exceeded only in 2022 for PM2.5 at Colombo, Jaffna, Kurunagala, Vavuniya; and Puttalam with annual average PM2.5 ~ 25±20 µgm-3 and for PM10 at Jaffna and Vavuniya with annual average PM10 ~ 55±37 µgm-3 . No exceedances above SLAQS in 2021 may be attributed to the restricted activity during the lockdown period. Seasonally, the Northeast monsoon season (Dec.-Feb.) experienced highest average PM2.5 (54.7 µgm-3 ) and PM10 (104.2 µgm-3 ) in 2022, which may be attributed to the low rainfall (~ 4.5 mm), moderate temperature (~26 °C), and low wind speed (~24 mph). CBPF was used to find out the potential source regions for high PM2.5 and PM10 levels. During northeast and southwest monsoon, Colombo, Jaffna and Galle experienced high PM concentrations at 30-50 mph from South and South-East, while Jaffna, Vavuniya, Galle, Kurunagala and Puttalam experienced high PM concentrations at high wind speed of 30-40 mph from East, South-East and South-West. Potential sources in these areas could be motor vehicles (in Colombo, Galle, Kurunagala), biomass burning (at all sites), textile units (in Colombo, Kurunagala,), cement manufacturing plants (in Galle, Puttalam), fuel-based power stations (in Colombo, Jaffna) and coal-fired power plant (in Puttalam). Finally, the health effects of PM2.5 exposure were estimated using the AirQ+ software, which evaluated the mortality attributable to acute lower respiratory disease (ALRI) (in children 0-5 years) and iv mortality in adults aged ≥ 25 years old attributable to lung cancer (LC) and chronic obstructive pulmonary disease (COPD). For 2022, maximum attributable cases were discovered in Jaffna which was 130 for ALRI in children; and 6,621 for LC and 7,945 for COPD in adults. The results of this study may be taken up by the local and national government for appropriate policy intervention and implementation to control air pollution in Sri Lanka.