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 percent 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 percent 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.