Premature deaths from air pollution will continue to rise unless changes are made to the way the world uses and produces energy, the International Energy Agency (IEA) has said.
Around 6.5m deaths globally are attributed each year to poor air quality inside and outside, making it the world's fourth-largest threat to human health, behind high blood pressure, dietary risks and smoking.
Harmful pollutants such as particulate matter - which can contain acids, metals, soil and dust particles - are responsible for the most widespread effects of air pollution.
Tiny particulate matter can cause lung cancer, strokes and heart disease over the long term, as well as trigger symptoms such as heart attacks that kill more rapidly.
The release of these pollutants is mainly due to the unregulated or inefficient production and use of energy, the IEA said in a report on energy and air pollution.
Without action, premature deaths attributable to outdoor air pollution will increase to 4.5 million in 2040 from around three million currently. Premature deaths due to household air pollution, however, should fall to 2.9 million from 3.5 million. Asia in particular is forecast to account for almost 90 per cent of the rise in deaths.
Chinese cities typically fare particularly badly with regards to air pollution due to dense populations and high levels of industrial activity. Last December, the Chinese capital Beijing suffered two red alerts over its smog levels. Subsequent attempts to clean up the air quality by the Chinese government led to the closure of thousands of small industrial firms and resulting unemployment.
Even though global emissions are forecast to decline overall by 2040, existing and planned energy policies will not be enough to improve air quality, the report said.
"Without changes to the way that the world produces and uses energy, the ruinous toll from air pollution on human life is set to rise," the IEA said.
Harmful greenhouse gas emissions should continue to fall in industrialised countries and recent signs of decline in China should continue, but emissions are set to rise in India, Southeast Asia and Africa as energy demand growth dwarfs efforts to improve air quality.
However, new energy and air quality policies can deliver cleaner air, such as access to clean cook stoves and fuels to replace inefficient biomass stoves; strictly enforced emissions standards for road transport; controlling emissions and switching fuels in the power sector and more energy efficiency in industry.
These measures could ensure global emissions of particulate matter fall by seven per cent, sulfur dioxide by 20 per cent and nitrogen oxides by 10 per cent to 2040.
As a result, premature deaths from outdoor pollution would fall to 2.8 million in 2040 and from household air pollution to 1.3 million, the report said.