Air pollution caused the deaths of 1.2 million people in India in 2017, a study conducted by the Boston-headquartered Health Effects Institute said. Its State of Global Air report 2019, released on Wednesday, said the same number of people died in China in 2017. The two topped the list of the 10 countries “with the highest mortality burden attributable to air pollution” in 2017.

The cause of deaths were attributed to illnesses including lung ailments caused by air pollution.

Both countries together accounted for half of the total deaths (nearly five million) around the world attributed to air pollution in 2017. The study said the deaths were caused by long-term exposure to outdoor and indoor air pollution.

The report said annual PM2.5 (particulate matter with a diameter of less than 2.5 micrometres, which can enter the lungs and the bloodstream) exposures were highest in South Asia in 2017. Air pollution reduced life expectancy by one year and eight months on average worldwide, the report said. “This means a child born today will die 20 months sooner, on average, than would be expected in the absence of air pollution,” the report said.

The report, however, acknowledged that China’s “major regulatory reforms appear to be driving substantial reductions in PM2.5 exposure”.

Pakistan, Indonesia, Bangladesh, Nigeria, the United States, Russia, Brazil and the Philippines were the others in the list of 10 countries with the highest mortality rates attributed to air pollution. “Each year, more people die from air pollution-related disease than from road traffic injuries or malaria,” the report said.

In March, a report by Swiss-based company IQAir AirVisual and non-profit organisation Greenpeace said Delhi was the most polluted capital in the world. The March report had said air pollution is likely to cause the death of around seven million lives globally in the next year, and will cost the world’s economy nearly $225 billion.

Burning the stubble of paddy crops and firecrackers around Diwali have been some of the primary causes of air pollution in North India. The pollution leads to hazardous air quality and a blanket of smog over the National Capital Region and parts of North India from late October to the end of November. However, smog usually persists through most of winter in these parts of India.