Coal is responsible for about 40 per cent of the deadly fine particulate matter known as PM 2.5 in China's atmosphere, according to a study the researchers released in Beijing.

Those figures are consistent with what Chinese scientists have been saying in recent years about industrial coal burning and its relation to air pollution.

The study, which was peer-reviewed, grew out of a collaboration between Tsinghua University in Beijing, one of China's top research universities, and the Health Effects Institute, based in Boston, a research center that receives funding from the U.S. Environmental Protection Agency and the worldwide motor vehicle industry. The researchers' primary aim was to identify the main sources of air pollution leading to premature deaths in China.

The study attributed 155,000 deaths in 2013 related to ambient PM 2.5 to industrial coal burning, and 86,500 deaths to coal burning at power plants. Fuel combustion of both coal and biomass in households was another major cause of disease that year, resulting in 177,000 deaths, the study concluded.

The researchers also found that transportation was a major cause of mortality related to PM 2.5, with 137,000 deaths attributed to it in 2013. In recent years, Chinese scientists have said that motor vehicle emissions are a leading source of air pollution in cities, although not as great as coal burning. Vehicle ownership is rising fast in China, and officials, carmakers, and oil and gas companies have quarreled over setting emissions standards.

China consumes almost as much coal annually as all other countries combined, and coal burning in the country is the biggest source of both air pollution and greenhouse gas emissions, the leading cause of climate change. Chinese cities are among the most polluted in the world. Provinces in northern China, where steel, cement and power plants are common, have the highest concentrations of PM 2.5 in the country.

But the growth in China's coal consumption has begun to slow. Last year, there was a slight decline in coal use compared with 2014, largely because of an economic slowdown that has been faster and deeper than many experts had expected.

In addition, the Chinese government announced plans in 2013, when popular anxiety over air pollution reached new heights, to curb coal use in three major population centers in the east. Placing limits on coal use is also consistent with pledges made by President Xi Jinping to try to reduce the effects of climate change.

The new study projected four scenarios based on different possible government policies, and each projection showed a decline in the average levels of PM 2.5 in coming years.

But in the study's executive summary, the researchers said that "despite these air pollution reductions, the overall health burden is expected to increase by 2030 as the population ages and becomes more susceptible to diseases most closely linked to air pollution."

Even under the most stringent policies on coal use and energy efficiency, coal is expected to remain the single biggest contributor to PM 2.5 and China's health burden in 2030, the study said.

The study was a follow-up to a Global Burden of Disease study examining deaths in 2013, which estimated that PM 2.5 contributed to 2.9 million premature deaths worldwide, with 64 per cent of those in China, India and other developing countries in Asia. Premature deaths due to PM 2.5 exposure were also high in Eastern Europe. A larger study on 2013 deaths was published last year by The Lancet, a British medical journal.

That study estimated the number of premature deaths in China in 2013 related to PM 2.5 exposure at 916,000, out of a population of 1.4 billion. Researchers found that outdoor air pollution was the fifth leading cause of premature deaths in China, behind high blood pressure, smoking, high consumption of sodium and low consumption of fruit. Household air pollution was the sixth leading cause.

An earlier Global Burden of Disease study that examined health figures for 2010 found that outdoor air pollution contributed to 1.2 million premature deaths, nearly 40 per cent of the global total. Exposure to ambient particulate matter that year was the fourth leading cause of premature deaths in China.

In 2013, the Organization for Economic Cooperation and Development, based in Paris, warned that "urban air pollution is set to become the top environmental cause of mortality worldwide by 2050, ahead of dirty water and lack of sanitation." It said that as many as 3.6 million people could end up dying prematurely from air pollution each year, mostly in China and India.