Smog is related to nearly one-third of deaths in China, putting it on a par with smoking as a threat to health, according to an academic paper based on the study of air pollution and mortality data in 74 cities and published in an international journal. The findings by Nanjing University’s School of the Environment, which were published in the November edition of the journal the Science of the Total Environment , provides the latest scientific estimates of the health cost of China’s notorious smog. Watch: Beijing smog halts children's playground The latest bout of smog began last Friday, affecting about half a billion people on the mainland, with the severest impact in the last three days. ‘Airpocalypse’ dirties credibility of Chinese government Previous research work have found equally alarming results about the country’s toxic air. The International Energy Agency published its first study on air pollution in June and estimated that severe air pollution has shortened life expectancy in China by an average 25 months. An academic paper co-authored by researchers from the Massachusetts Institute of Technology in the US, Tsinghua University and Peking University in China, plus the Hebrew University of Jerusalem in 2013 concluded that bad air has cut life expectancy by an average of 5.5 years in the north of the country. China’s smog knocks 2 years off life expectancy: International Energy Agency There are so far no concrete or widely agreed estimates on the impact of air pollution on health in China partly because it is scientifically complicated to measure and also because there is little historical precedent for prolonged exposure to such high levels of air pollution. The six researchers from Nanjing University said they conducted the study because air pollution was the “most severe and worrisome environmental problem in China”, but knowledge of its health effects was insufficient. When they looked into 3.03 million deaths in 2013 in 74 cities in the Beijing-Tianjin-Hebei region and the Yangtze River Delta and Pearl River Delta, they found 31.8 per cent could be linked to PM 2.5 pollution – the tiny smog particles most hazardous to health. Baoding, Shijiazhuang and Handan in Hebei province, the cities with the worst air pollution, each reported more than 30,000 deaths in 2013 related to smog. How scientists cracked the puzzle of Beijing’s wintertime smog By comparison, smoking-related illnesses cause about one million deaths in the country each year. An improvement in air quality would have an “outstanding” impact on the reduction of mortalities linked to smog, the report said. If Beijing can deliver its promise of reducing PM2.5 concentrations in the air by 25 per cent in 2017 compared with 2012 levels in areas around Hebei, mortality related to smog would be reduced significantly, it said. Over the past week, hundreds of flights were grounded, schools suspended classes, private cars were banned in northern China from city roads, highways were closed and hospitals were jammed with patients suffering from a level of air pollution that, in many places, exceeded the limit of air quality monitoring devices. The National Energy Administration said on Thursday that they will strictly limit the construction of petroleum coke-fired power plants to help preventing air pollution, and limit emissions of high-pollution fuels. The nation also launched a satellite to monitor carbon dioxide levels on Thursday. Analysts have warned that the air pollution problem would become a public policy outcry if Beijing fails to clean up the air. Leaders have vowed to make tackling air pollution a war. Even though the government pledged to scale down production, factories are still stepping up their operation and local authorities are worried that production suspension may lead to economic downturn. Some lawyers have filed suits against the governments of Beijing, Hebei and Tianjin.