What's the Downside of China's War on Pollution?

With more than five years now having passed since China declared war on pollution in 2018, the country is reporting very encouraging progress on targeting pollution in certain parts of the country. Particular improvements have been seen regarding the harmful contaminant particulate matter 2.5 (PM2.5), so named for the 2.5micrometre (microscopic) diameter of its particles.

However, the reduction of PM2.5 isn’t the only change that has been observed in the Chinese atmosphere - and other developments have been less positive. A new collaborative study suggests that another deadly pollutant, ozone, has been on the increase in the same time period. What’s more, it’s thought that ozone’s rise may be directly linked to the reduction of PM2.5, causing a headache for Chinese policymakers going forwards.

Impressive progress

As recently as 2011, the air quality situation in China was dire; in that year, it was found that Chinese power plants emitted as much nitrogen oxides (NOx) as all of the passenger cars in the world. Meanwhile, PM2.5 levels across eastern parts of the country were particularly rampant, prompting the government to announce an ambitious plan to reduce the number of cars on their roads, shut down tens of factories all over the country and pour money into more environmentally-friendly methods of industry and energy production.

Those efforts have paid dividends. A recent study conducted by Harvard University in conjunction with the Nanjing University of Information, Science and Technology (NUIST) in China found that in affected areas, PM2.5 levels had fallen by as much as 40% since 2013. Such rapid progress shows that in the last five years, China has achieved similar progress to the US over the last 30 years. Unfortunately, that wasn’t the only thing the study uncovered.

Unwanted side effects

The network of more than a thousand air quality monitoring stations all over China indicated that the drop-off in PM2.5 corresponded with a concurrent hike in levels of ozone, especially in dense urban metropoles like Beijing and Shanghai. While ozone is instrumental in protecting the Earth from the most serious effects of ultra-violet radiation in our atmosphere, at ground level it can be deadly. The scientists behind the study suspect the two phenomena may be linked.

“There was so much particulate matter in Chinese cities that it stunted the ozone production,” explained Daniel Jacob, an atmospheric chemist from Harvard who worked on the study. “We haven't observed this happening anywhere else because no other country has moved this quickly to reduce particulate matter emissions.” The results of the study demonstrate that while China may be winning its war on pollution on one front, it will require further action to combat ozone proliferation. Specifically, this must take the form of implementing better controls on the emission of non-methane hydrocarbons (NMHCs), also known as volatile organic compounds (VOCs), to prevent further ozone generation.