Levels of harmful air pollution over China have been falling steadily since 2015, due to stricter controls on emissions. Chinaās air is still terribly polluted, but the reduction has probably prevented 150,000 premature deaths per year.
āItās probably the fastest any country has improved their air quality ever,ā says Ben Silver at the University of Leeds in the UK. āBut itās still really bad.ā
Silver and his colleagues tracked levels of tiny particles, called PM2.5, using data from over 1600 monitoring stations dotted around China. In line with previous studies, they found that levels of PM2.5 declined from 2015 to 2017.
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Other researchers had expressed concern that the apparent decline in pollution might be nothing to do with falling emissions, but due to changes in weather patterns, which can affect where pollutants build up. So the team used a model of the air over China, which simulated wind patterns and the chemistry of the pollution.
They ran the model twice, once with a decline in emissions after 2015 and another with no decline. The latter model saw little change in pollution levels, suggesting weather changes alone couldnāt be responsible for the decline. āWe showed the weather was a relatively small effect, compared to emissions reductions,ā says Silver.
The most important source of Chinaās air pollution is industry, followed by people burning fuel for cooking and heating in their homes, power generation, transport and agriculture. āThe major decline has been in industry and power generation,ā says Silver. āThatās usually the easiest thing to target, because you have big point sources like factories.ā
It is difficult to determine how many people are killed by air pollution, and how many would be saved by cutting it. āYou canāt ever isolate a single death and say āPM2.5 killed this personā,ā says Silver. Instead, epidemiologists treat it as a risk factor for early death.
The team estimates that Chinaās PM2.5 reductions have cut annual premature deaths by 150,000. But this is far from a complete victory. āEven though itās declined a lot, thereās still a huge health impact,ā says Silver. The team estimates there were still 2.65 million deaths linked to PM2.5 in 2017.
Atmospheric Chemistry and Physics
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