The report, released by the World Bank and the Institute for Health Metrics and Evaluation, shows that in 2013 more than five million deaths worldwide were attributed to health conditions caused by air pollution. About 60% of them were in the world's two most populous countries.

Exposure to air pollution increases a person's risk of contracting ailments such as lung cancer, stroke, heart disease and chronic bronchitis.

China and India aren't among the worst hit in absolute terms because of the sheer size of their respective populations. Even after adjusting for population, these two countries along with Bangladesh, Sri Lanka and Pakistan were among the 15 nations with the highest toll per million population. China and India ranked 4th and 6th worst in the world respectively. Bangladesh, Sri Lanka and Pakistan were ranked 11th, 12th and 15th on this count.

The bank estimates that in 2013 Georgia saw the highest rate of air pollution deaths per million of its population at 2,117. It was followed by Cambodia with a death rate of 1,300 per million. Among the 142 countries for which the bank complied this data, there were 10 where the rate was higher than 1,000 deaths per million. Australiafared best on this parameter with an estimated death rate of 34 per million.

The report also estimated that air pollution cost the world economy more than $5 trillion - purchasing power parities (PPP) at 2011 prices - in welfare losses and an additional $66 billion worth of manpower loss.

China's overall welfare and manpower loss was $1.6 trillion while India lost more than $560 billion, which was equivalent to over 10% of China's and 8.5% of India's GDP.

Air pollution is estimated to be the fourth leading fatal health risk worldwide after metabolic risks, dietary risks and tobacco smoke. The estimates are based on exposure to PM2.5 pollutants. It is noticeable in the report that the risks are much higher in the developing world.

By damaging people's health and causing fatal diseases, air pollution can have a lasting effect on a person's economic productivity.

Experts argue that typically the economically weakest section is the worst hit because of limited access to health care facilities. Thus, exposure to bad air quality and other risks will ultimately widen the existing economic inequalities, they say.