Air pollution in China might be under-reported, study suggests

Air pollution data in China is statistically different depending on the type of air quality monitoring station, according to a new study published in the journal Plos One. 

Researchers at Harvard and Boston University analysed and compared measurements reported by local and U.S embassy-controlled monitoring stations in five large Chinese cities. 

The data covered a period from January 2015 – June 2018 and consisted of hourly measurements of particulate matter (PM2.5) pollution. 

The researchers identified that there was a statistical difference in the data from the different monitoring stations. 

They found that these differences occurred more often and were greater than one would expect by random chance. They also found that the hourly differences were also more likely when the air quality was particularly poor. 

Together, the results suggest that, when air pollution is high, local stations systematically report lower PM2.5 levels than reported by U.S. stations.

The authors note that these findings add to existing concerns about underreporting of air pollution by some local officials in China. In fact, they say, the general public and other observers are often sceptical of local data because some officials might have an incentive to underreport in order to avoid professional repercussions.

Still, the researchers emphasise the usefulness of local air pollution data in China and note that their study does not invalidate other findings that the country’s air quality has improved in recent years.

The authors state: ‘Our work finds evidence of systemic local government underreporting of air pollution levels in four out of five tested Chinese cities.

‘This suggests that, between 2015 and 2017, some local governments in China misreported air quality data disclosed to the country’s central environmental ministry, particularly on high-pollution days.’

In related news, successful clean air action has led to a dramatic reduction in air pollution in Beijing over the last few years, according to a new report published by a team of over 150 scientists. 

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