Half of the air pollution-related deaths in the world in 2015 took place in India and China, according to a study conducted by the US-based Health Effects Institute. More than 4.2 million people died from conditions triggered by air pollution across the world, of which 2.2 million were from the two countries, the study revealed on Tuesday.

Air pollution was the fifth-highest cause of death in 2015, the researchers said. Moreover, the study added that 92% of the people in the world live in regions with unhealthy air.

Though China and India each reported 1.1 million air pollution-related deaths during the period, Beijing has been more proactive in taking steps to curb the pollution, the scientists claimed. “[India] has got a longer way to go, and they still appear to have some ministers who say there is not a strong connection between air pollution and mortality in spite of quite a lot of evidence,” HEI president Dan Greenbaum told Reuters.

The Chinese government, too, has said that it is too early to draw conclusions about the extent of the impact of smog on health, especially its long-term impact on the body, the news agency reported. Air pollution has been linked respiratory diseases, as well as higher rates of cancer, stroke and heart disease.

North India has been especially affected by air pollution in the past few years. The situation has been getting worse during Diwali every year because of the firecrackers burnt during the celebrations. Stubble burning in the region during winter season adds to the problem.

While the Supreme Court has imposed a ban on firecrackers in the region to control air pollution, the Delhi government has taken various steps to handle the situation such as temporarily introducing the odd-even rule, deploying vaccuum cleaners and sprinklers, and keeping schools shut. The central government has also put together a Graded Response Action Plan to fight air pollution in Delhi-National Capital Region area.