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Perez, Quezon, Philippines, nestled within the broader Southern Luzon region, presents a compelling case study in how geography shapes urban air quality. Located at approximately 14.18° N, 121.93° E, the city sits on a gently sloping terrain, part of the larger Sierra Madre mountain range foothills. This location significantly influences local weather patterns and, consequently, air circulation. The surrounding landscape is a mosaic of agricultural lands – primarily rice paddies and coconut plantations – interspersed with patches of secondary forest. To the west, the Pacific Ocean exerts a moderating influence on the climate, bringing moisture and occasional sea breezes. However, the proximity to the Sierra Madre, while providing scenic beauty, can also trap pollutants under certain meteorological conditions, particularly during periods of low wind speed. Perez’s urban character is primarily rural, with a small, concentrated population of 12,767. The urban–rural gradient is relatively sharp, with agricultural activities dominating the immediate periphery. There are no major industrial belts directly adjacent to Perez, though regional industrial zones are located further afield, potentially contributing to transboundary pollution events. The elevation, though modest, contributes to localized temperature variations and can influence the formation of fog, which exacerbates air stagnation. The city’s position within a humid tropical climate, combined with its topography, creates a complex interplay of factors affecting air quality.

Perez, Quezon experiences a distinct wet and dry season, dictating the annual air quality narrative. The dry season, typically spanning from November to May, often sees a gradual increase in particulate matter concentrations. This is partly due to reduced rainfall, which limits the natural cleansing effect of precipitation, and increased agricultural burning practices as farmers prepare fields for the next planting season. The lack of consistent wind during this period can lead to stagnant air conditions, particularly in the lower-lying areas, allowing pollutants to accumulate. Temperature inversions, where a layer of warm air sits above cooler air near the ground, are also more frequent during the dry season, further trapping pollutants. The wet season, from June to October, brings frequent rainfall and increased humidity, generally leading to improved air quality as pollutants are washed from the atmosphere. However, heavy rainfall events can also mobilize dust and soil particles, temporarily increasing particulate matter levels. Monsoon winds, while bringing relief from heat, can also carry pollutants from distant sources. Fog, common during the transition periods between seasons, significantly reduces visibility and concentrates pollutants near the ground. Sensitive groups, such as children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, particularly during periods of agricultural burning or stagnant air. Outdoor activities are generally more favorable during the wet season, although vigilance regarding potential dust events following heavy rainfall is advised.