Wildfire smoke kills an estimated 3,560 in one month in Southeast Asia's largest economy

Indonesia’s estimated air-pollution deaths reached 5,310 in September. The figure included deaths linked to wildfire smoke and pollution from power generation, industry and transport. CREA called the monthly estimate a record, showing how severely the country’s dry-season pollution affected public health.

August’s total was about 3,740 deaths. September therefore brought roughly 1,570 additional estimated deaths, a 42% increase. The estimate focused on deaths occurring within days of exposure to PM2.5, rather than only long-term health effects.

Fires were responsible for about 3,560 of September’s deaths, while non-fire sources caused 1,750. The highest increases occurred in Kalimantan and Sumatra, where smoke dominated the toll. Java’s total slightly declined, but industry and vehicle emissions remained major causes there. Rain later brought some relief, though several provinces stayed at fire risk.

PM2.5 means fine particulate matter measuring 2.5 micrometers or less across. These particles are small enough to travel deep into the lungs instead of being stopped higher in the airways. The World Health Organization links exposure with greater risks of illness and premature death.

Once inhaled, PM2.5 can irritate and inflame lung tissue. Some particles can cross into the bloodstream, where they may trigger inflammation and stress throughout the body. Those effects can strain blood vessels and the heart, increasing risks such as heart attacks and strokes. The article specifically highlights penetration into the lungs and bloodstream.

Indonesia’s nationwide population-weighted exposure averaged 36 micrograms per cubic meter in September. That was more than seven times the WHO annual guideline of 5 micrograms. Exposure was about ten times the guideline in Sumatra and 24 times it in Kalimantan, showing why the pollution posed a serious health threat.

Kalimantan and Sumatra were especially affected because wildfire smoke drove most of their estimated pollution deaths. In four Kalimantan provinces, deaths more than doubled to 1,470 in September. In five Sumatran provinces, they rose to 1,420. These regions also recorded the country’s highest PM2.5 exposure levels.

The key mechanism was smoke from fires spreading across populated areas during exceptionally dry conditions. Fire smoke caused 94% to 99% of deaths in the four Kalimantan provinces. It caused more than 90% in Riau, Jambi and West Sumatra. Dry conditions, which the study associated with El Niño, allowed pollution to build up.

Java showed a different balance. Its death estimate edged down from 1,570 to 1,530. In West Java, Central Java, Jakarta and Banten, non-fire sources caused about 80% of deaths. Industry and vehicle emissions therefore mattered more there than wildfire smoke, despite Java’s large population.

September’s estimated pollution death toll was 5,310. Of that total, about 3,560 deaths were linked to fire smoke, calculated by subtracting the 1,750 deaths attributed to non-fire pollution. Fires therefore caused roughly two-thirds of the estimated deaths nationwide.

Non-fire pollution came from power generation, industry and transport. These sources accounted for 1,750 deaths, or about one-third of the total. Their impact was especially visible on Java, where industry and vehicle emissions caused about 80% of deaths across West Java, Central Java, Jakarta and Banten.

The figures challenge the idea that the fires were the only major danger. CREA analyst Katherine Hasan said other pollution sources were just as dangerous as the smoke. The pattern also means cleaner power, industry and transport could reduce harm even when fire conditions improve. Rain brought some relief, but risks remained in several provinces.

The smoke caused widespread illness beyond the estimated 5,310 pollution deaths. Indonesia’s Health Ministry recorded 333,470 cases of acute respiratory infection in seven fire-hit provinces by Oct. 22. These cases show the immediate burden on clinics and families during the fires.

Young children were particularly affected. Nearly one-quarter of the recorded infections occurred in children under five. Their cases were part of the broader respiratory illness total, rather than a separate death estimate. The article does not give a precise child case count, but the share indicates a substantial burden among very young patients.

The government communications agency said it deployed 2,106 health workers and distributed 5.3 million masks. More than 72,000 personnel were sent across six provinces to tackle the blazes. Rain in parts of Sumatra and Kalimantan later brought relief, but forecasters expected only patchy showers and five provinces remained at fire risk through Oct. 31.

Declaring a national emergency would signal that the fires exceeded ordinary regional response capacity. It could help justify a more centralized national operation and reflect the scale of the health crisis. However, officials argued that regional capacity had not collapsed and that task forces were still operating, so President Prabowo Subianto did not make the declaration.

CREA suggested the decision also involved international and economic risks. A national declaration might make Indonesia liable for haze crossing its borders. The smoke had already raised pollution levels in Malaysia, Singapore, the Philippines and Timor-Leste. The think tank also said officials may have worried about reduced confidence in palm oil, pulp and paper exports.

The government instead reported deploying more than 72,000 personnel across six provinces, plus 2,106 health workers. This response continued without a national-emergency label. Rain offered temporary relief, but five provinces remained at fire risk through Oct. 31, leaving cross-border and economic concerns unresolved.

El Niño is a recurring climate pattern involving unusually warm surface waters in the central and eastern tropical Pacific. It can shift atmospheric circulation and reduce rainfall in parts of Southeast Asia. The article identifies El Niño as a driver of the dry conditions that peaked in Indonesia during September.

Less rain dries vegetation, soil and land, making fires easier to start and harder to control. Dry air and limited rainfall can also allow smoke to linger rather than being washed away. As a result, PM2.5 concentrations rise and more people breathe unhealthy or hazardous air. The article links the resulting smoke to deaths and respiratory infections.

September’s national average PM2.5 exposure reached 36 micrograms per cubic meter. It was about ten times the WHO guideline in Sumatra and 24 times higher in Kalimantan. Late-October rain brought relief in parts of those islands, but forecasters expected patchy showers, and five provinces remained at fire risk through Oct. 31.