Prediction accuracy of available early warning systems for air pollution across WHO South-East Asia region: a systematic review.

BACKGROUND

Ambient air pollution is a major environmental health risk across developing nations in the WHO South-East Asia Region (SEARO), contributing substantially to premature mortality and the global disease burden. While Air Quality Early Warning Systems (AQEWS) enable proactive public health interventions, their regional predictive accuracy remains uncharacterized. Despite their increasing importance, the predictive performance and methodological quality of AQEWS across SEARO have not been systematically evaluated. To address this gap, this study systematically evaluated the accuracy of available AQEWS across the region.

METHODS

This systematic review (PROSPERO: CRD420251275901) searched major databases from inception to February 10, 2026, for observational modeling studies reporting quantitative AQEWS performance in SEARO. Reviewers extracted data and assessed bias using PROBAST+AI. Primary outcomes were RMSE, R2, categorical accuracy, and forecast bias.

RESULTS

Fourteen studies (India, Bangladesh, Thailand) from 839 records were synthesized; heterogeneity disallowed meta-analysis. Hybrid deep learning architectures consistently yielded the lowest RMSE (0.84-4.61 μg/m3) and highest explained variance (R 2 up to 0.998) across the studies, particularly for PM2.5 forecasting; however, evidence was heterogeneous and did not establish consistent superiority across pollutants, forecast horizons, validation settings, or operational AQEWS. Machine learning achieved up to 98.34% categorical accuracy. Chemical transport models demonstrated significant bias reduction (~70%) exclusively when integrated with satellite data assimilation. Most studies showed a high risk of bias due to inadequate external validation and algorithmic overfitting.

CONCLUSION

While hybrid and deep learning models demonstrated superior forecasting accuracy over traditional methods, widespread policy implementation across SEARO was hindered by poor methodological validation. This review provides a regional synthesis of AQEWS forecasting performance and identifies key methodological limitations that currently constrain their reliability for public health decision-making. Standardized reporting and rigorous external validation are urgently required to ensure these systems reliably inform regional public health emergency responses.

SYSTEMATIC REVIEW REGISTRATION: identifier: CRD 420251275901.