SINGAPORE – Even in a world committed to tackling climate change, premature deaths associated with air pollution could still rise in South-east Asia, new research has found.

Premature deaths are considered as such when they happen before the average life expectancy, typically due to preventable causes like socio-economic and environmental factors.

The findings by researchers from the Nanyang Technological University (NTU) and Macao Polytechnic University in China show that taking steps to deal with climate change may not necessarily help to reduce air pollution. Targeted measures to reduce the release of toxic particles are also needed to keep people safe.

Human activity, such as the burning of fossil fuels and deforestation, are major drivers of climate change. These gases trap the sun’s heat, raising global temperatures.

Within the region, PM2.5 – fine particulate matter that is a key component of air pollution – come directly from sources like fossil fuel combustion and vehicle exhaust, or is formed from chemical reactions between gases in the air.

As at 2024, more than 90 per cent of people living in East and South-east Asia

breathe air considered unsafe by the World Health Organisation

, according to the UN Environment Programme website.

In 2019, 64 per cent of total PM2.5 pollution in the region originated from sources like burning of biomass like wood, residential activities and fossil fuel combustion, said Professor Steve Yim, who led the study.

These pollutants, measuring no more than 2.5 micrometers in diameter, can penetrate the lungs and bloodstream, causing respiratory and cardiovascular diseases.

They are affected by climatic and meteorological conditions, such as wind, temperature and humidity. Each parameter affects how the pollutant is formed, dispersed and removed, said Prof Yim, who also heads the NTU Centre for Climate Change and Environmental Health.

But climate-driven impacts on PM2.5, human health and the economy in South-east Asia have not been thoroughly evaluated, the study noted.

The team used regional climate and air quality models and future climate data to determine how climate change would affect PM2.5 concentration over South-east Asia by 2050. To isolate the effects of climate change, they assumed no changes to air pollution in the region, and kept emission rates constant.

Then, the researchers modelled how PM2.5 concentrations across the region will change across three climate scenarios.

These scenarios are known as

shared socio-economic pathways

– a framework commonly employed in climate studies to describe global action towards tackling climate change.

The most optimistic scenario assumes global progress on tackling climate change, with countries committed to sustainable practices and low greenhouse gas emissions.

The fossil fuel-driven scenario, on the other hand, refers to the opposite, where progress on climate action stalls and countries step up fossil fuel use for economic and technological development.

The middle-of-the-road scenario assumes that countries continue their historical patterns of development.

The data shows that overall PM2.5 concentration across the region is projected to fall by 2.2 per cent to 9.8 per cent across all three trajectories. This is because increased precipitation, caused by climate change, helps disperse and remove pollutants from the air.

Precipitation refers to any form of water, including rain, snow and hail, which falls to the earth’s surface from clouds. Rain droplets, for example, can collect pollutants as they fall, acting as a cleaning agent.

However, the number of premature deaths will still increase in two scenarios.

In the most optimistic scenario, the region will experience slightly warmer temperatures with a modest increase in rainfall and humidity.

Although these conditions support pollutant removal from the air, localised dry conditions along densely populated areas, concentrated in Indonesia and Thailand, will cause people there to be more exposed to PM2.5.

This could lead to a 7.2 per cent increase in premature deaths, and economic loss will increase from $560 billion to $580.5 billion, the study found.

This is also the case in the fossil fuel-driven scenario, where the number of premature deaths is projected to increase by 9.6 per cent, causing an economic loss of $767.5 billion.

Singapore is especially vulnerable to such conditions, where unfavourable conditions aggravate accumulation of local pollutants and cause regional haze transport, Prof Yim said. He added that temperatures in Indonesia, Thailand and Myanmar could rise by up to 2 deg C.

In the middle-of-the-road scenario, overall premature deaths will decrease by 1.8 per cent and economic loss will fall to $319.5 billion.

This is because South-east Asia is projected to be warmer and wetter, helping to disperse pollutants in the air.

The findings suggest that climate change and PM2.5 pollution, intertwined as they are, require co-benefit strategies to mitigate, Prof Yim said.

He noted that climate mitigation policies that fail to address air pollution may exacerbate health and economic burdens in vulnerable and under-represented tropical regions.

According to Adjunct Associate Professor Koh Tieh Yong, who was not part of the study, however, there are currently no such tangible co-management strategies available.

Though a scientifically welcomed approach, the findings should not be taken at face value given that, in reality, “pollutant emission rates are never going to be constant in an economically fast-developing region like South-east Asia”, said Prof Koh, who specialises in atmospheric physics at the National University of Singapore.

“A starting point is to time efforts and channel resources that mitigate pollution according to monsoon seasons and inter-annual climate variations to optimise impact on air quality improvement,” he said.

Prof Yim’s team is also studying how climate change will affect ground-level ozone pollution, and plans to eventually assess how air pollutant emission, land use and climate change intersect.