According to the reports, the research, conducted as part of the Global Burden of Disease Project (GBDP), indicated that the key factor for the massive toll is the emission of small particles from power plants, factories, vehicle exhausts as well as the burning of coal and wood.
According to the study, air pollution causes more casualties than other global risk factors such as malnutrition, alcohol and drug abuse and obesity.
The GBDP sets air toxins as the fourth highest health risk behind high blood pressure, dietary risks and smoking.
Scientists from the US, Canada, China and India said illnesses caused by air pollution killed 1.6 million people in China and 1.4 million in India during 2013.
They presented their findings at the annual meeting of the American Association for the Advancement of Science (AAAS) in Washington DC.
They further said the figures indicate how far and how rapidly some countries must proceed in efforts to improve the air quality for their citizens.
“In Beijing or Delhi on a bad air pollution day, the number of fine particles (known as PM2.5) can be higher than 300 micrograms per cubic meter,” said Dan Greenbaum of the US-based Health Effects Institute.
“The number should be about 25 or 35 micrograms.”