Why China’s fight on air pollution has slowed

In the 1990s and 2000s, as China’s economy steamed ahead, concerns about pollution were ignored. Air quality was poor and smog blanketed cities. But in 2014, partly because of popular discontent, the leaders decided to act. The prime minister, Li Keqiang, declared a “war on pollution”. Since then China has made much progress. The sky over Beijing is often blue.

Recently, however, the improvement has slowed. To calculate current pollution levels across the country, The Economist used data from the “China High Air Pollutants” dataset, created by Jing Wei of Peking University and others. The researchers use satellite data to capture a map of pollutants 2.5 micrometres in size (pm2.5), which are the leading cause of disease from air pollution (see map). We overlaid this map with another of population density in China to calculate weighted pm2.5. This emphasises cities like Shanghai and ignores places like the Taklamakan Desert, which is swirling with dust plumes but unpopulated. Our results show that between 2013 and 2021, pm2.5 fell from 66 micrograms per cubic metre to 33, a rate of 4.2 a year (see chart). But between 2021 and 2024, that decline slowed to just 0.5 per year.

There is no consensus as to why this slowdown has occurred, says Eric Zou of the University of Michigan. One explanation is that all the easy gains have been made. Before 2014, emissions treatment was inefficient. Many initial moves tried to stop pollutants from entering the air after they had been formed (so-called “end-of-pipe” measures), for instance by putting scrubbers in chimneys of power plants. These have run their course. Now comes the harder part: getting polluters to change their behaviour so the pollutants are not formed at all. Electrifying transport systems falls into this category.

There are also factors outside China’s control. Meteorological conditions affect pm2.5 levels a lot. In 2020 strong winds helped ventilate the air and heavy rainfall mopped up particles as they fell, reducing average pm2.5 levels, according to a study in Nature, a British journal. But the weather can act the other way, too. Climate change is making wildfires and sandstorms more frequent and also increasing occurrences of “atmospheric inversions”, which trap pollution at the ground level. In 2023, when dust storms struck northern China, pm2.5 readings jumped by over 30% in Beijing.

The pressure to clean up has also eased. One survey of Beijingers in 2015 by researchers from Princeton University found that high pollution lowered local support for the government. But pm2.5 levels have now entered a “tolerable range” for many, says Yanzhong Huang of the Council on Foreign Relations, an American think-tank. Choking on smog is rare. For several years now China has met its national limit of 35 micrograms of pm2.5 per cubic metre, which it set in 2012. A decline in public clamour has led to local authorities softening their line, so progress has stagnated.

Now the standards are being tightened again. The limit for average pm2.5 will be lowered from 35 to 25 micrograms per cubic metre, said the Ministry of Ecology and Environment on February 24th. Initially, a “transitional” limit of 30 micrograms will apply, starting from March 1st. From 2031, the full limit will come into force.

That is still well above the guideline set by the World Health Organisation (who), which in 2021 said that the level of pm2.5 should be no higher than 5 micrograms. Pollution in big cities remains much higher than those in the West (though London and New York do not meet the who’s strict criteria either, see chart). Air pollution is still a big cause of death in China. In 2021, 2.3m people died because of pm2.5, making up 19% of all deaths in China, found a study in the Lancet, another British journal. As China’s population ages, it will become more vulnerable, so the harm from grimy air will only rise.

But cutting pollution too fast would require stringent regulation, which could cut into economic growth. At some point, “the damage on the economy becomes larger than the benefit of health improvement,” says Mr Zou. There is, therefore, a difficult balance to strike between the two. ■