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Batu Pahat, a significant urban centre in Johor, Malaysia, occupies a strategic location within the southwestern region of the state. Situated at approximately 1.85°N, 102.93°E, the city’s geography is characterized by a gently undulating terrain, transitioning from coastal plains to slightly elevated inland areas. The surrounding landscape is a mosaic of agricultural land – primarily oil palm plantations and rice paddies – interspersed with smaller settlements and pockets of secondary forest. This agricultural intensity contributes to localized air quality considerations, particularly concerning biomass burning during land clearing and harvesting periods. The city lies relatively close to the Straits of Johor, offering a degree of maritime influence, though the prevailing winds often originate from the west, carrying pollutants from industrial zones further inland. Batu Pahat’s urban fabric is a blend of older, traditional shop houses and more modern developments, reflecting its growth as a regional trading hub. The urban–rural gradient is relatively gradual, with agricultural activities continuing within the city limits and surrounding suburbs. Elevation plays a minor role, with most of the city situated below 50 meters above sea level, which can exacerbate the trapping of pollutants under certain meteorological conditions. The proximity to the Johor Bahru industrial belt, while providing economic opportunities, also introduces the potential for transboundary air pollution events, particularly during periods of stagnant air. The Muar River, though not directly flowing through the city centre, influences local humidity and temperature patterns, impacting atmospheric stability.

Batu Pahat’s tropical climate dictates a distinct wet and dry season pattern, significantly influencing its air quality profile. The dry season, typically spanning from March to September, often sees a gradual increase in particulate matter concentrations. This is partly attributable to increased agricultural activity, including controlled burns for land preparation, and the reduced rainfall which limits the natural cleansing effect of precipitation. During this period, temperature inversions, particularly in the early morning hours, can trap pollutants close to the ground, leading to localized episodes of poorer air quality. The monsoon season, from October to February, brings increased rainfall and higher humidity, generally leading to improved air quality as pollutants are washed out of the atmosphere. However, periods of prolonged fog, common during the northeast monsoon, can also reduce visibility and trap pollutants, albeit to a lesser extent than temperature inversions. The months of September and October often present a transitional period where agricultural burning peaks, coinciding with the onset of monsoon rains, creating a complex interplay of factors. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, particularly on days with stagnant air or visible haze. Outdoor activities are generally more favourable during the monsoon season, although periods of heavy rainfall and fog can still impact visibility and comfort. Monitoring local weather forecasts and being aware of regional haze advisories is crucial for informed decision-making regarding outdoor exposure.