Aug 22, 2019 07:31 PM

Ozone Pollution Is Becoming a Bigger Threat to China’s Air

A view of downtown Beijing's Sanlitun commercial district. Photo: VCG
A view of downtown Beijing's Sanlitun commercial district. Photo: VCG

Ozone will be the main pollutant in many parts of China in the latter half of August, according to forecasts from China’s meteorology and environment monitoring centers.

While China has made progress in reducing fine particulate matter pollution, or PM2.5, ozone pollution has increased over the last few years, creating a new front in the war on pollution that has been underway since 2015. In a study published in July in Environmental Research Letters, Chinese and American researchers estimated that ozone pollution caused 67,000 premature deaths in China in 2015.

While the average level of ozone pollution in the first half of 2019 was unchanged at 143 micrograms per cubic meter compared with the same period in 2018, the annual average in 2018 was 151 micrograms per cubic meter, up 1.3% from 2017. This average remains below China’s standard of 160 micrograms per cubic meter, but is well above the World Health Organization’s standard of 100 micrograms per cubic meter. The 1.3% increase was lower than the rise in previous years.

The China National Environmental Monitoring Centre, the Beijing Municipal Environmental Protection Monitoring Center and environmental monitoring stations in six major regions in China have predicted that many areas in China will see a rise in ozone pollution this month. The Beijing-Tianjin-Hebei province region is expected to experience some light ozone pollution, while the southwestern Chengdu-Chongqing region may see moderate ozone pollution due to high temperatures and strong sunlight. “Moderate” ozone pollution may occur in the far western region of Xinjiang.

Ozone is an atmospheric gas. When in the stratosphere, it protects the lower levels of the atmosphere from the sun’s ultraviolet rays. However, when it is at ground-level — formed by a reaction of nitrogen oxides and volatile organic compounds (VOCs) in sunlight — it can cause health problems such as chest pain and coughing when it reaches high concentrations. At lower concentrations, it can also damage materials such as rubber and plastics.

Burning fossil fuels in cars, factories or power plants creates the nitrogen oxides and VOCs needed for the reaction that produces ground-level ozone. China’s latest air pollution action plans aim to cut emissions of nitrogen oxides and VOCS by 2020.

However, researchers found that the prevalence of PM2.5 can prevent ozone from being formed, so the drop in PM2.5 in China may actually be contributing to the ozone pollution, according to a study published in the Proceedings of the National Academy of Sciences of the United States in January.

Scientists believe that climate change could be increasing ground-level ozone pollution due to changing jet streams and mixing patterns in the atmosphere, increasing the flow of ozone from the stratosphere down to ground level.

The July study in Environmental Research Letters found that an 11% increase in ground-level ozone due to climate change could cause an additional 62,000 premature deaths by 2050. However, a 60% decrease in ozone-forming emissions could prevent 330,000 premature deaths.

Contact reporter Ren Qiuyu (

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