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Ghorāhī, nestled in the Lumbini province of Nepal, occupies a strategically important position within the Terai plains, a vast lowland region bordering India. Located at approximately 28.0408° N, 82.4861° E and an elevation of roughly 275 meters (902 feet) above sea level, the city’s geography is characterized by a gently undulating terrain, typical of the Terai. The surrounding landscape is predominantly agricultural, a patchwork of rice paddies, maize fields, and sugarcane plantations, contributing to both the local economy and, occasionally, to air quality challenges. The city sits near the Rapti River, providing a vital water source and influencing local microclimates. While not directly adjacent, the Chure Hills rise to the north, acting as a partial barrier to prevailing winds and potentially trapping pollutants under certain meteorological conditions. Ghorāhī’s urban form is expanding outwards, exhibiting a gradual urban–rural gradient as it encroaches upon agricultural land. The proximity to the East-West Highway (National Highway 18) introduces vehicular emissions as a significant factor. While large-scale industrial zones are not immediately present within Ghorāhī itself, the broader Lumbini region experiences some industrial activity, and the city’s location within a densely populated area means it is susceptible to transboundary pollution. The flat topography and relatively low elevation contribute to temperature inversions, particularly during the cooler months, which can exacerbate air quality issues by trapping pollutants close to the ground. The surrounding agricultural practices, including burning of crop residue, can also significantly impact local air quality.

Ghorāhī’s air quality experiences a distinct seasonal cycle heavily influenced by Nepal’s monsoon climate. The pre-monsoon season (March-May) often sees a noticeable increase in particulate matter. This is driven by a combination of factors: increased agricultural activity, including the burning of crop residue to clear fields, and the build-up of dust due to drier conditions and windblown soil. Temperature inversions are more frequent during this period, trapping pollutants. The monsoon season (June-September) brings relief, with heavy rainfall effectively scrubbing the atmosphere and significantly reducing pollution levels. However, intense rainfall can also lead to flooding and associated issues. The post-monsoon season (October-November) presents a complex picture. While rainfall decreases, the lingering effects of agricultural burning continue, and the cooler temperatures can again promote temperature inversions, leading to periods of poorer air quality. Winter months (December-February) are generally the most challenging, with colder temperatures, reduced wind speeds, and frequent fog, all contributing to pollutant accumulation. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the pre-monsoon and post-monsoon seasons, limiting outdoor exertion during peak pollution periods. During the winter months, indoor air quality also becomes a concern due to the use of solid fuels for heating. Public health advisories regarding agricultural burning practices and promoting cleaner heating alternatives are crucial for mitigating air quality risks throughout the year.