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Limbang, a town situated in the northern reaches of Sarawak, Malaysia, occupies a unique geographical position. Located at 4.7500°N, 115.0000°E, the town straddles the Limbang River, a crucial waterway connecting it to the South China Sea via Brunei. The terrain is largely defined by a coastal plain, gradually rising towards the interior hills and the rugged, forested landscape of the Ulu Limbang region. This proximity to both the sea and dense vegetation significantly influences local air quality. Limbang isn’t a heavily industrialised centre; its economy is primarily driven by agriculture – particularly oil palm plantations – and small-scale commerce. However, the surrounding areas, including Brunei, do have industrial activity, and transboundary haze events are a recurring concern. The urban-rural gradient is relatively sharp, with dense settlement concentrated around the riverfront and quickly transitioning to rural landscapes dominated by plantations and rainforest. The flat coastal topography can exacerbate pollution build-up, particularly during periods of calm weather, while riverine transport contributes to localised emissions. The town’s location within a tropical climate means high humidity and consistent rainfall play a key role in atmospheric cleansing, but also in fostering conditions for mould and biological pollutants.

Limbang experiences a tropical rainforest climate, characterised by high temperatures and humidity year-round, with a distinct wet and dry season rather than traditional four seasons. Air quality is generally better during the wetter months (September to February) as rainfall effectively washes particulate matter from the atmosphere. However, increased humidity can also promote mould growth, impacting indoor air quality. The dry season (March to August) typically sees a decline in air quality, particularly during the southwest monsoon. This period is often associated with increased bushfires and land clearing activities, both locally and in neighbouring Kalimantan (Indonesia) and Brunei, leading to transboundary haze. Smoke from these sources can significantly elevate particulate matter levels. Temperature inversions, common during calm mornings, can trap pollutants near ground level. Months of June and July are often the most challenging for those with respiratory sensitivities. Sensitive groups – children, the elderly, and individuals with asthma – should limit strenuous outdoor activity during haze events and monitor their health closely. Fog can also occur, reducing visibility and potentially carrying pollutants. Avoiding outdoor exercise during peak haze periods and utilising air purifiers indoors are recommended preventative measures.