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Lom Sak, nestled in the Phetchabun province of Thailand at coordinates 16.7798, 101.2422, presents a unique geographic setting influencing its air quality. The town sits within a valley surrounded by the Phetchabun mountain range, a landscape dominated by rolling hills and forested areas. This topography, at an elevation of approximately 180 meters above sea level, creates a natural basin that can trap pollutants, particularly during periods of atmospheric stability. The Pasak River flows nearby, providing a vital water source but also potentially contributing to localised humidity and fog formation, which can exacerbate particulate matter concentrations. Lom Sak’s economy is largely agricultural, with significant cultivation of rice, maize, and fruit trees in the surrounding plains. While not a major industrial hub itself, its proximity to larger agricultural processing zones further afield means seasonal burning of agricultural waste can impact air quality. The urban-rural gradient is pronounced; the town centre is relatively compact, transitioning quickly to agricultural land and forested hills. This proximity to natural landscapes generally provides some dilution of pollutants, but the valley’s topography remains a key factor in air quality dynamics. The prevailing winds, influenced by the monsoon patterns and the surrounding mountains, play a crucial role in dispersing or concentrating airborne particles.

Lom Sak experiences a distinct wet and dry season, heavily influencing its air quality. The dry season, typically from November to April, sees the lowest rainfall and highest temperatures. This period is often associated with increased agricultural burning to prepare fields for the next planting cycle, leading to elevated levels of particulate matter, especially PM2.5. January and February are typically the months with the poorest air quality due to these practices and stable atmospheric conditions. The onset of the wet season in May brings relief, with rainfall effectively washing pollutants from the air. However, increased humidity can also contribute to the formation of secondary pollutants. June to October sees generally improved air quality, although localised flooding can sometimes disrupt transportation and potentially release mould spores. Temperature inversions, common during the cooler months of November to February, trap pollutants near the ground, worsening air quality. Sensitive groups – children, the elderly, and those with respiratory conditions – should limit strenuous outdoor activity during the dry season, particularly in January and February. Monitoring wind direction is also advisable, as pollutants can accumulate quickly in the valley depending on prevailing winds.