Assessing the health risk of air pollution exposure in Sri Lanka

Air pollution is an increasing public health concern in Sri Lanka, driven by rapid urbanization, regional pollutant transport, and continued reliance on solid fuels in rural areas. Exposure to fine particulate matter (PM2.5) is associated with elevated risks of cardiovascular and respiratory diseases, stroke, and premature mortality, contributing to over 20% of total disability-adjusted life years (DALYs) and deaths nationally, according to the most recent iteration of the Global Burden of Diseases Study. However, high-resolution exposure data and short-term health impact assessments remain limited.

In this study, we develop the first high-resolution (1 × 1 km, daily) PM2.5 dataset for Sri Lanka by combining in-situ measurements, satellite retrievals, and reanalysis products using a hybrid modeling framework. We then quantify the acute effects of PM2.5 exposure on respiratory health using daily hospital admission data (eIMMR) for 2020–2023, focusing on acute respiratory infections (ICD-10 codes J00–J06, J09–J18, J20–J22). We apply a Distributed Lag Non-Linear Model (DLNM) to capture non-linear exposure–response relationships and delayed effects, considering lags up to 50 days. Models control relative humidity, temperature, precipitation, carbon monoxide, day of week, and month. Confounding was assessed using a leave-one-out approach, while effect modification was examined through tertile-based stratification and pairwise statistical tests.

Population-weighted PM2.5 concentrations show a rapidly increasing trend, particularly in and around the national capital. We find that PM2.5 effects are strongest on the day of exposure (lag 0) and decrease with increasing lag. A 10-µg m^-3 increase in PM2.5 is associated with a 16.6% (10–22%) increase in hospitalizations for acute respiratory diseases. Relative humidity emerges as a key confounder, while precipitation significantly modifies the PM2.5–hospital admission relationship, with substantially stronger effects on low-precipitation days (RR ≈ 1.40). Children under 15 years’ experience higher risks compared to adults and the elderly.

These findings highlight the growing respiratory health burden of air pollution in Sri Lanka and underscore the need for integrated air quality management and health-informed policy. Future work will incorporate additional pollutants (NO2, O3), socioeconomic factors, and extend analyses to cardiovascular outcomes and joint PM2.5–temperature effects.