Health benefits of climate and air pollution policies in the ASEAN region

Economic and social development in the Association of Southeast Asian Nations (ASEAN) region has led to increased greenhouse gas (GHG) emissions and elevated levels of fine particulate matter (PM_2.5), contributing to global warming and severe health impacts. More than 75 percent of population (about 500 million) is exposed to PM_2.5 levels above WHO guidelines with over 17 percent of urban residents experiencing concentrations above 35 µg/m³. Despite national and regional commitments on emission reductions, their current and future impacts on air quality and health remain poorly understood.

Using the Greenhouse Gases - Air Pollution Interactions and Synergies (GAINS) modelling framework, we projected CO₂ and PM_2.5 precursor emissions (primary PM_2.5, SO₂, NO_X, NH₃ and VOC), PM_2.5 population exposure and associated premature mortality from 2020 to 2040 under different policy scenarios. We also identified the contributing sectors with the largest mitigation potential.

We estimate CO₂ emissions of around 1,685 Mt in 2020 in the ASEAN region, and ASEAN-wide mean PM_2.5 exposure levels around 15 µg/m³, leading to 210,000 premature deaths. In a counterfactual scenario without further mitigation measures beyond those implemented in 2015, CO₂ emissions are projected to double and PM_2.5 levels increase by 33 percent by 2040 and doubling the number of urban residents exposed to PM_2.5 levels above 35 µg/m³.

While committed climate policies in power and transportation sectors achieve substantial CO₂ emission reductions (25 percent by 2040), they lead only to marginal improvements on PM_2.5 exposure and health co-benefits. The effective implementation of current legislation on air pollution on top of the climate measures reduces 2040 PM_2.5 exposure to about 2020 levels, however, premature mortality still exceeds current levels due to a higher share of exposure to very high levels especially in cities and to population aging.

Ample potential exists to reduce PM_2.5 exposure with existing technologies. Our maximum emission control scenario suggests that tightening air pollution controls could reduce health impacts by over two-thirds across ASEAN region, with largest emission reduction potential identified in the transport, industry and agriculture sectors.

These findings show that significant co-benefits of climate policies for air pollution related health impacts are not achieved without stringent measures beyond existing policies in the ASEAN region. The assessment lays the basis for developing regional strategies integrating climate and air pollution policies.