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Chengam, nestled in the Vellore district of Tamil Nadu, India, occupies a strategically important position within the Kaveri Delta region. Located at approximately 12.3112° N latitude and 78.7925° E longitude, the town sits at an elevation of roughly 170 meters (557 feet) above sea level, contributing to a relatively mild climate. The surrounding landscape is a blend of agricultural plains and gently undulating hills, characteristic of the Eastern Ghats foothills. Chengam’s proximity to the Palar River, though not directly on its banks, influences local humidity and microclimates. The town’s urban character is that of a developing market town, serving as a hub for the surrounding agricultural communities. The dominant land use is a mix of residential areas, small-scale commercial establishments, and agricultural fields, primarily cultivating rice, pulses, and vegetables. A gradual urban–rural gradient extends outwards, transitioning from built-up areas to intensive farming and then to more scattered rural settlements. Significant industrial activity is limited within Chengam itself; however, its location places it within reach of industrial belts concentrated around Sriperumbudur and Ambattur, approximately 80-100 kilometers away. This distance means that industrial emissions, while not a direct local source, can occasionally be transported via prevailing winds, impacting air quality. The topography, with its gentle slopes, can sometimes trap pollutants, particularly during periods of low wind speed, exacerbating local air quality challenges. The region's overall climate, a tropical savanna, plays a crucial role in shaping the atmospheric conditions and influencing pollution dispersal.

Chengam’s air quality experiences a distinct seasonal cycle dictated by the region’s tropical climate. The monsoon season, typically spanning June to September, brings relief from accumulated pollutants due to increased rainfall and robust winds that effectively disperse airborne particles. However, the pre-monsoon period (March-May) often witnesses a concerning rise in air quality degradation. High temperatures and decreasing humidity create stable atmospheric conditions, frequently leading to temperature inversions where cooler air is trapped beneath a layer of warmer air, preventing vertical mixing and concentrating pollutants near the ground. Agricultural burning, a common practice to clear fields for the Kharif season, significantly contributes to particulate matter pollution during this period. The post-monsoon season (October-November) sees a gradual improvement as winds pick up, but lingering agricultural activities and cooler temperatures can still lead to localized pollution episodes, especially during foggy mornings. Winter months (December-February) are generally characterized by calmer winds and cooler temperatures, which, combined with occasional fog, can trap pollutants and reduce visibility. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the pre-monsoon and winter months, limiting outdoor exertion and monitoring for any respiratory discomfort. Maintaining indoor air quality through ventilation and air purifiers is also advisable. The intensity of the monsoon dictates the overall annual air quality, with a stronger monsoon generally leading to better air quality throughout the year.