World Health Organisation has revealed that New Delhi is the most polluted city in the world.

The international organization, which measured pollution in cities around the world, found that Beijing's pollution measurements is far more less than that of New Delhi, the Sydney Morning Herald reported.

Thirteen of the dirtiest 20 cities were Indian, which included New Delhi, Patna, Gwalior and Raipur in the top four spots, while the Indian capital had an annual average of 153 micrograms of small particulates, known as PM2.5, per cubic metre.

The study of 1600 cities has revealed that air pollution has worsened since a smaller survey in 2011, especially in poorer countries, which increases the risk of cancer, stroke and heart disease in the city dwellers.

Beijing was in 77th place with a PM2.5 reading of 56, little over one-third of Delhi's pollution level, while at the cleaner end of the table, 32 cities reported a PM2.5 reading of less than 5 and three-quarters of those included Vancouver, Hafnarfjordur in Iceland and the other seven were American.

Maria Neira, WHO Director for Public Health, Environmental and Social Determinants of Health, said that the aim was to "challenge" cities and believed that the survey would help them to become more open about their dirty air.