The Chinese government may be effectively cracking down on some forms of air pollution, but toxic ozone levels are rising rapidly, according to an Unearthed analysis of official data.

The country’s average ground-level ozone pollution hit a new high in June, up 11% from the same point last year and 21% from the year before.

This alarming trend – pollution records were consistently broken in 2017 as well – has seen ozone emerge as an emerging health threat in China, causing 70,000 premature deaths in 2016.

While ozone in the upper atmosphere protects life on earth from deadly UV radiation, ozone on ground level is a corrosive, dangerous pollutant that directly harms lung tissue, causing respiratory symptoms and contributing to premature deaths from respiratory diseases.

In most places suffering from severe ozone pollution, such as Mexico City, northern Italy or Los Angeles, transport is the dominant source. In China, due to the country’s vast manufacturing sector, both industry and transport are important sources.