Air pollution in most Chinese cities is around five times higher than the World Health Organization's 'safe' levels—and this more than doubles the risk of hypertension (high blood pressure), coronary heart disease and stroke.
Deaths from chronic diseases such as heart and respiratory conditions have been steadily rising in China, which has severe air pollution problems from industrialisation and growing car ownership.
Cities that have the highest levels of fine particulate air pollution, known as PM2.5, also have higher mortality rates from heart and respiratory diseases, say researchers from Fudan University in Shanghai.
They looked at pollution levels and mortality rates in 272 Chinese cities, which have a combined population of 323 million people, so making it the largest ever epidemiological study in the developing world. Between 2013 and 2015, the average PM2.5 levels in the cities were five times higher than the WHO's safety levels. At the levels being recorded in China, heart disease is 1.35 times more likely, the risk for hypertension nearly doubles, while for coronary heart disease it increases 1.5 times.
The link is harder to see in Western countries, say the researchers, because air pollution has been improving over the past 40 years or more, and, as a result, heart disease has also been in decline.