Why is Singapore's haze back and what do PM2.5 readings mean for health?

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1. 1

   Southeast Asian haze (Wikipedia)

   WikipediaPublished Oct 10, 2026Checked Oct 10, 2026

   “The Southeast Asian haze is a fire-related recurrent transboundary air pollution issue. Haze events, where air quality reaches hazardous levels due to high concentrations of airborne particulate matter from burning biomass, have caused adverse health, environmental and economic impacts in several countries in Southeast Asia. Caused primarily by slash-and-burn land clearing, the problem flares up every dry season to varying degrees and generally is worst between July and October and during El Niño events. Transboundary haze in Southeast Asia has been recorded since 1972 with the 1997 and 2015 events being particularly severe. Industrial-scale slash-and-burn practices to clear land for agricultural purposes are a major cause of the haze, particularly for palm oil and pulpwood production in the region. Burning land occurs as it is cheaper and faster compared to cutting and clearing using excavators or other machinery. Fires started for this purpose sometimes spread and create forest fires, worsening the problem. The high concentration of peat in soil contributes to the haze's density and high sulphur content.”

2. 2

   Association between weather, air quality and asthma-related emergency department visits: a retrospective time-series study in Singapore.

   BMJ open (Toh et al.)Published Dec 18, 2025Checked Oct 10, 2026

   “Associations between ED visits and monsoons, transboundary haze and cultural festivals were evaluated using one-way analysis of variance. Weekly seasonal ARIMA models with exogenous regressors were fitted, incorporating PSI as a covariate and adjusting for demographic, clinical and socioeconomic factors.ResultsAsthma ED visits were positively correlated with PSI (lag 0: r=0.142; 95% CI 0.107 to 0.178) and inversely correlated with rainfall (lag 3: r=-0.062; 95% CI -0.099 to -0.026) and WBT (lag 1: r=-0.067; 95% CI -0.104 to -0.031). Wind speed (lag 2: r=-0.049; 95% CI -0.086 to -0.013) and ambient temperature (lag 6: r=-0.045; 95% CI -0.081 to -0.008) showed weaker inverse associations. Mean PSI was higher during haze (82.67 vs 51.46, pConclusionsPSI-ED association peaked on the same day of exposure but was no longer significant after adjusting for demographic and clinical factors. Pollution-linked festivals, transboundary haze and the Northeast monsoon were associated with increased asthma ED visits.”

3. 3

   Short-term exposure to fine particulate matter and asthma exacerbation: a large population-based case-crossover study in Southern Thailand.

   Environmental health : a global access science source (Varopichetsan et al.)Published May 7, 2025Checked Oct 10, 2026

   “PM2.5 concentrations > 50 µg/m³ were significantly associated with asthma exacerbations at multiple time lags (lag0, lag2, and lag01 to lag03), with odds ratios ranging from 1.41 to 1.64, compared to the lowest concentration group (PM2.5 0-15 µg/m³). Temperature showed no significant effect, while relative humidity was positively associated with asthma exacerbations at lag3, lag06, and lag07. Subgroup analyses revealed associations between PM2.5 exposure and asthma exacerbations at early lags for both males and females. Additionally, children aged 6-11 years and 12-17 years exhibited greater susceptibility to asthma exacerbations, particularly at PM2.5 concentrations of 15-25 µg/m³.ConclusionThis study underscores the short-term effects of PM2.5 on asthma exacerbations, particularly during high-pollution episodes of transboundary haze in regions that generally experience low levels of air pollution. These findings emphasize the importance of achieving the WHO air quality targets to mitigate the health impacts from PM2.5.”

4. 4

   Climate Change Adaptation to Smoke Haze for Improved Child Health in Southeast Asia: Analysis Situation in Palembang, Indonesia.

   Annals of global health (Haryanto et al.)Published Jun 8, 2026Checked Oct 10, 2026

   “Particulate matter showed strong associations with increased childhood respiratory morbidity. Pneumonia demonstrated more consistent relationships with PM2.5, reflecting the deeper penetration of fine particles into the respiratory tract. Regression models indicated that rises in PM2.5 predicted higher pneumonia incidence, while PM10 was more consistently associated with ARI. Associations involving SO2 were less consistent, though it may act synergistically with particulate matter to worsen respiratory outcomes. Haze exposure significantly elevates the risk of respiratory illness in children. PM2.5 is strongly linked to pneumonia, whereas PM10 is more closely related to ARI. The persistent nature of haze and children's heightened vulnerability highlight the need to integrate child-centered risk mitigation into national air quality management and disaster preparedness strategies.”

5. 5

   A scoping review on the health effects of smoke haze from vegetation and peatland fires in Southeast Asia: Issues with study approaches and interpretation.

   PloS one (Phung et al.)Published Sep 15, 2022Checked Oct 10, 2026

   “mpared to non-smoke haze periods; HBE studies estimated approximately 100,000 deaths attributable to smoke haze in the entire Southeast Asia considering all-cause mortality and all age groups, which ranged from 1,064-260,000 for specified mortality cause, age group, study area, and study period; HRA studies quantified potential lifetime cancer and non-cancer risks due to exposure to smoke-related chemicals. Currently, there is a lack of interconnection between these three approaches. The EPI approach requires extensive effort to investigate lifetime health effects, whereas the HRA approach needs to clarify the assumptions in exposure assessments to estimate lifetime health risks. The HBE approach allows the presentation of health impact in different scenarios, however, the risk functions used are derived from EPI studies from other regions. Two recent studies applied a combination of the EPI and HBE approaches to address uncertainty issues due to the selection of risk functions. In conclusion, all approaches revealed potential health risks due to smoke haze. Nonetheless, future studies should consider comparable exposure assessments to allow the integration of the three approaches.”