Swiss monitor IQAir recorded an Air Quality Index of 166 for Kuala Lumpur, making it the world’s most polluted major city, while Singapore’s AQI stood at 155, ranking it third globally.

The AQI translates pollutant measurements into a single number; readings above 150 are classified as unhealthy, and levels above 300 are considered hazardous.

Hot, dry conditions associated with the El Niño weather phenomenon have fuelled the fires in Indonesia, and many of the blazes are linked to land‑clearing activities, making them harder to contain.

Residents report reduced visibility of landmarks, such as Kuala Lumpur’s Merdeka 118, and have stayed indoors, worn masks, and cut back on outdoor activities. Izzah Irdina, a recent graduate from Kuala Lumpur, said she cannot see the building and prefers to stay inside.

The transboundary haze shows how weather patterns and human land‑use practices can combine to create severe air‑quality crises that affect multiple countries at once.