A study has revealed that air pollution kills more than 5.5 million people around the world, making it the fourth leading cause of death after high blood pressure, poor diet and smoking. The research was presented at the annual meeting of the American Association for the Advancement of Science (AAAS).

The study also found that the deaths linked to indoor and outdoor pollution will continue to rise in the coming decades. Most of the deaths occur in the fastest growing economies: China and India with 55 percent or 3 million deaths. In 2013, about 1.6 million people in China and about 1.4 million people died in India. In the recent decades, Brazil, Japan and Pakistan have also experienced a significant rise in pollution.

“Reducing air pollution is an incredibly efficient way to improve the health of a population,” said Michael Brauer, from the University of British Columbia in Canada.

Researchers added that more air-pollution related deaths are likely to occur in the next two decades if carbon emission targets are not. Outdoor pollution is caused by vehicles, power plants and industries, while indoor pollution is caused by charcoal, wood and coal, used to cook or heat homes. The study supports a 2015 study, which showed that outdoor pollution alone caused over three million deaths per year.

Though China is committed to reduce emissions by limiting coal usage, bringing new standards for vehicles, the pollution in the country is about 10 times higher than normal standards set by the World Health Organization (WHO). The mortality rate would continue to increase as the aging population could become more susceptible to air pollution. In India, millions of poor families, who burn wood, charcoal, dung or any other biomass, contribute to indoor air pollution.

Health Effects Institute President Dan Greenbaum said that the issue is an important issue in China, somewhat less, though in China, where they have started to move people on to propane and natural gas to get them away from using coal. Though there is a decline in premature deaths in the U.S and Europe, air pollution is still linked to more than 80,000 deaths in the US and over 200,000 deaths in Europe annually.