The Western Pacific Region, a grouping of 37 countries and areas that includes China, was hit hardest by air pollution in 2012, according to a report released on Tuesday by the World Health Organization.

An estimated 2.8 million deaths in the region were caused by air pollution in 2012, the United Nations agency said in its report. Worldwide, an estimated 7 million people died from illnesses linked to air pollution that year.

The agency said most of the deaths occurred in low- and middle-income countries.

The Western Pacific Region, one of six regional groupings by the WHO, is home to roughly 1.8 billion people, more than a fourth of the world’s population. The area stretches from China in the north and west, to New Zealand in the south, and to the French Polynesia in the east.

Data for individual countries will be completed and published in the months ahead, the agency said.

"Air pollution is one of the most significant global health risks today — comparable to the health risks from tobacco," said Bernhard Schwartlander, WHO representative in China.

"The new data released highlight the importance of strong action now to tackle the causes of air pollution in countries such as China and to protect the public from the range of serious health risks air pollution causes — both in the short- and long-term."

Coronary artery disease and strokes led to 69 percent of the deaths linked to air pollution around the world. Twenty-five percent were due to chronic obstructive pulmonary disease or acute lower respiratory infections and 6 percent were due to lung cancer.

Last year, the International Agency for Research on Cancer, which is affiliated with the WHO, concluded that outdoor air pollution is carcinogenic to humans, and particulate matter in air pollution is most closely associated with the increased likelihood of cancer, especially lung cancer.

The primary sources of ambient or outdoor air pollution include industrial and motor vehicle emissions and household heating.

The major sources indoor pollution fossil fuels — such as solid fuels in open fire cooking stoves — and secondhand smoke from tobacco products.

"Air pollution is now the world's single largest environmental health risk. The WHO is concerned about the situation in China, where cities such as Beijing regularly experience dangerously high levels of outdoor air pollution," Schwartlander said.

He added that the WHO is greatly encouraged by the strong commitment from the Chinese government to tackling this problem.

"Of course, the air pollution crisis did not occur overnight and the solutions will not occur overnight. But let this new data serve as a call to action for governments, the health sector, environmental sector and industry to work together to address this crisis. The imperative could not be clearer: Reducing air pollution could save millions of lives," he said.