Why is Singapore's haze back in 2026 and what do PM2.5 readings mean for health?

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1. 1

   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 12, 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.”

2. 2

   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 12, 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.”

3. 3

   The burden of acute conjunctivitis attributable to ambient particulate matter pollution in Singapore and its exacerbation during South-East Asian haze episodes

   The Science of The Total Environment (Aik et al.)Published Jun 11, 2020Checked Oct 12, 2026

   “Every 10 μg/m3 increase in PM2.5 was associated with a 3.8% (Incidence Rate Ratio (IRR): 1.038, 95% Confidence Interval (CI): 1.029–1.046, p < 0.001) cumulative increase in risk of conjunctivitis over the present and subsequent week. Every 10 μg/m3 increase in PM10 was associated with a 2.9% (Incidence Rate Ratio (IRR): 1.029, 95% Confidence Interval (CI): 1.022–1.036, p < 0.001) cumulative increase in risk of conjunctivitis over the present and subsequent week. Acute conjunctivitis reports exhibited an inverse dependence on ambient air temperature and relative humidity variability. Approximately 3% of all acute conjunctivitis reports were attributable to PM2.5. Particulate matter attributed acute conjunctivitis was disproportionately higher during transboundary haze episodes. Our study strengthens the evidence linking particulate matter exposure to an increased risk of conjunctival disease, with a disproportionately higher disease burden during South-East Asia transboundary haze episodes. Our findings underscore the importance of reducing the health impact of indigenous and transboundary sources of ambient particulate matter pollution.”

4. 4

   Attributing climate-related health burdens in Southeast Asia: a scoping review.

   The Lancet regional health. Western Pacific (Simion et al.)Published Aug 21, 2026Checked Oct 12, 2026

   “Although growing evidence demonstrates substantial health impacts from air pollution, heat, and extreme weather, the regional research landscape remains critically imbalanced, marked by neglect of other major hazards-including floods, droughts, extreme rainfall, storms and sea-level rise-and substantial methodological fragmentation. From 5294 records screened, 77 studies met our inclusion criteria. The evidence is dominated by air pollution research, the focus of 70% of studies and linked to up to 31% of all-cause mortality and an estimated 296,000 annual deaths from wildfire smoke during El Niño events. Heat, the second most studied exposure, was associated with up to 8.61% of mortality in Bangkok. In contrast, extreme events such as heatwaves, floods and storms were least frequently investigated. These findings reveal a critical misalignment between regional climate risks and current research focus. Standardized attribution frameworks are urgently needed to support integrated climate-health modeling and guide equitable, evidence-based adaptation across Southeast Asia.”

5. 5

   Acute Health Impacts of the Southeast Asian Transboundary Haze Problem—A Review

   International Journal of Environmental Research and Public Health (Cheong et al.)Published Sep 6, 2019Checked Oct 12, 2026

   “In light of growing public health concerns, recent studies have begun to examine the health effects of this seasonal haze problem in Southeast Asia. This review paper aims to synthesize current research efforts on the impact of the Southeast Asian transboundary haze on acute aspects of public health. Existing studies conducted in countries affected by transboundary haze indicate consistent links between haze exposure and acute psychological, respiratory, cardiovascular, and neurological morbidity and mortality. Future prospective and longitudinal studies are warranted to quantify the long-term health effects of recurrent, but intermittent, exposure to high levels of seasonal haze. The mechanism, toxicology and pathophysiology by which these toxic particles contribute to disease and mortality should be further investigated. Epidemiological studies on the disease burden and socioeconomic cost of haze exposure would also be useful to guide policy-making and international strategy in minimizing the impact of seasonal haze in Southeast Asia.”