Indian city most polluted in the world

While pollution is a major problem in almost all cities, some are more polluted than others. According to United States's Environmental Protection Agency's air-quality index, one Indian city tops when it comes to pollution.

Let's take a look at some of the most polluted cities in the world's biggest economies.

Source: The Economist

NOTE: Environmental Protection Agency's air-quality index measures PM 2.5 (particulate matter of 2.5 microns across or less per cubic metre). Such particles are small enough to be inhaled and can damage lungs. The AQI range ends at 500. A reading above 100 is deemed "unhealthy for sensitive groups" and anything above 400 is rated "hazardous" for all, according to The Economist.

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Ludhiana

Country: India

Particulate matter with diameter of 10 microns or less per cubic metre: 251

Global rank: 1

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Lanzhou

Country: China

Particulate matter with diameter of 10 microns or less per cubic metre: 150

Global rank: 2

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Mexicali

Country: Mexico

Particulate matter with diameter of 10 microns or less per cubic metre: 139

Global rank: 3

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Medan

Country: Indonesia

Particulate matter with diameter of 10 microns or less per cubic metre: 112

Global rank: 4

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Anyang

Country: South Korea

Particulate matter with diameter of 10 microns or less per cubic metre: 68

Global rank: 5

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Busan

Country: South Korea

Particulate matter with diameter of 10 microns or less per cubic metre: 68

Global rank: 6

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Johannesburg

Country: South Africa

Particulate matter with diameter of 10 microns or less per cubic metre: 64

Global rank: 7

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Rio de Janeiro

Country: Brazil

Particulate matter with diameter of 10 microns or less per cubic metre: 62

Global rank: 8

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Turin

Country: Italy

Particulate matter with diameter of 10 microns or less per cubic metre: 46

Global rank: 9

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Seville

Country: Spain

Particulate matter with diameter of 10 microns or less per cubic metre: 44

Global rank: 10

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Zaragoza

Country: Spain

Particulate matter with diameter of 10 microns or less per cubic metre: 44

Global rank: 11

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Paris

Country: France

Particulate matter with diameter of 10 microns or less per cubic metre: 38

Global rank: 12

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Bakersfield, California

Country: The United States

Particulate matter with diameter of 10 microns or less per cubic metre: 38

Global rank: 13

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Montreal

Country: Canada

Particulate matter with diameter of 10 microns or less per cubic metre: 36

Global rank: 14

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Moscow

Country: Russia

Particulate matter with diameter of 10 microns or less per cubic metre: 35

Global rank: 15

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Dresden

Country: Germany

Particulate matter with diameter of 10 microns or less per cubic metre: 34

Global rank: 16

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London

Country: The United Kingdom

Particulate matter with diameter of 10 microns or less per cubic metre: 33

Global rank: 17

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Osaka

Country: Japan

Particulate matter with diameter of 10 microns or less per cubic metre: 25

Global rank: 18

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Brisbane

Country: Australia

Particulate matter with diameter of 10 microns or less per cubic metre: 18

Global rank: 19