Leiktho, nestled within Kayin State, Myanmar (coordinates 19.2222° N, 96.5811° E), occupies a geographically significant position at the edge of the Sittaung River basin. The city’s terrain is characterized by gently rolling hills and alluvial plains, a consequence of the river’s sediment deposition over millennia. Elevation varies subtly within the urban area, generally ranging from 60 to 120 meters above sea level. This relatively low elevation, combined with the surrounding landscape of dense tropical forest and agricultural lands, influences local air circulation patterns. Leiktho’s proximity to the Sittaung River provides a degree of humidity, which can trap pollutants under certain meteorological conditions. The surrounding region is a mosaic of small-scale agriculture – primarily rice cultivation and fruit orchards – interspersed with pockets of teak forests. This agricultural activity, while vital to the local economy, contributes to seasonal particulate matter, particularly during burning seasons. The urban–rural gradient is gradual; the city blends seamlessly into the agricultural landscape, with rural communities and farms existing within the city limits and surrounding areas. There are no major industrial belts immediately adjacent to Leiktho, however, transportation routes connecting it to larger regional hubs do funnel vehicle emissions into the area. The prevailing winds, generally easterly, carry pollutants from upstream agricultural areas and potentially from distant industrial zones, impacting air quality. The topography, therefore, creates a complex interplay of factors affecting the dispersion and accumulation of airborne pollutants.

Leiktho’s tropical climate dictates a distinct wet and dry season, profoundly impacting its air quality. The dry season, typically spanning November to April, presents the greatest air quality challenges. Reduced rainfall and lower humidity allow particulate matter to persist longer, and agricultural burning practices, common during land preparation for the monsoon planting season, significantly elevate PM2.5 and PM10 levels. Temperature inversions, frequently occurring during the cooler months (December-February), trap pollutants near the ground, exacerbating the problem. Fog, common in the mornings during this period, further restricts dispersion. The monsoon season (May to October) brings relief through frequent rainfall, which naturally cleanses the atmosphere. However, heavy rainfall can also lead to increased levels of ozone due to increased sunlight and humidity. Wind patterns shift during the monsoon, often bringing cleaner air from the west, but localized flooding can temporarily release pollutants from inundated areas. The transitional months of April and October experience variable conditions, with air quality fluctuating as the climate shifts. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, particularly during periods of agricultural burning. Limiting outdoor exertion and wearing masks can mitigate exposure. During the monsoon, while generally cleaner, vigilance is still advised due to potential flooding-related pollutants and ozone spikes. Maintaining awareness of local weather patterns and agricultural practices is crucial for informed decision-making regarding outdoor activities.