An estimated 8,572 premature deaths occurred in four major Chinese cities this year due to high levels of PM2.5, a study has found.

The report also said severe air pollution in Shanghai, Guangzhou, Xi'an and Beijing has led to a total economic loss of 6.8 billion yuan ($1.09 billion).

The study released on Tuesday by Peking University's School of Public Health and Greenpeace looked at the health and economic impact of PM2.5, particulate matter smaller than 2.5 micrometers in diameter.

Modern toxicology research has shown that exposure to PM2.5 can lead to significantly increased death rates due to cardiovascular, cerebrovascular and respiratory diseases, as well as increased cancer risk.

The study, the first of its kind, was based on available data and took into account varying conditions in the four cities, such as temperature and humidity.

In its conclusion, the report states that if the cities can effectively lower PM2.5 levels to meet the World Health Organization's Air Quality Guidelines — 10 micrograms per cubic meter — such deaths would be reduced by more than 80 percent.

Of the four cities, Shanghai had the highest amount of deaths, although its PM2.5 concentration is not the highest, the study found.

"The reason can be very complicated, but this phenomenon corresponds with research in other countries," said Pan Xiaochuan, a professor at the School of Public Health and lead author of the report.

"There are three main factors. First, Shanghai is the most populous city. Second, people from the south and the north have different sensitivities to pollution. Third, PM2.5 in different places has different components whose effects vary."

The methodology adopted by the study is a widely applied standardized method in epidemiological studies of air pollution, authors said.

"A mathematical model was developed based on PM2.5 laboratory monitoring values over the past three to four years in the four cities, as well as statistics from centers for disease control and prevention of deaths and their causes over the same period," said Li Guoxing, a lecturer at the School of Public Health and a co-author.

"From this, a PM2.5 exposure relative risk coefficient was calculated. The total of deaths related to PM2.5 pollution in 2010 was also estimated based on population sizes and PM10 concentration statistics published in the National Statistical Yearbook 2010."

He said the study also calculates mortalities caused by PM2.5 this year, together with figures based on potential improvement scenarios.

However, researchers conceded that the study has many limitations.

"The data we used, though they're the best we can get, are still limited," Pan said. He said the data mainly came from independent research institutions in the four cities, not official sources, which may affect the results.

The central government recently started to ask major cities to start releasing readings of PM2.5 levels to the public.

"The result is an estimation, based on a probabilistic method in statistics, with a possibility of uncertainty," Pan said.

Li said that the study only takes into consideration a relatively short-term effect of PM2.5 pollution, without measuring the possible health effects of other major pollutants in the air, such as black carbon and ozone, which may result in an underestimation of the health risks.

On Dec 12, a policy study executive report was released to the China Council for International Cooperation on Environment and Development, an organization chaired by Vice-Premier Li Keqiang. The report also mentioned the relationship between premature deaths and PM2.5.

It cited an estimate by the WHO that 470,000 Chinese died prematurely in 2008 due to air pollution.

"A World Bank study showed China's deaths and diseases caused by air pollution in 2003 brought an economic loss of 160 billion yuan, equivalent to 1.16 percent of GDP that year," read the Regional Air Quality Integrated Control System Research report, written by a team led by Hao Jiming, an academic at the Chinese Academy of Engineering and a professor at Tsinghua University's School of Environment. (China Daily)