Ludhiana and Kanpur are among the 10 most polluted cities in the world, according to the World Health Organization.
According to a 2011 World Health Organisation (WHO) report, Ludhiana made it to the fourth position along with Quetta in Pakistan.
Kanpur made it to the ninth position. The most polluted city in the world was Ahvaz in Iran.
The pollution is measured as the microgramme (mcg) concentration per cubic metre of air of particulate matter smaller than 10 micrometres (PM10), the Express Tribune reports.
Below is the list of the top 10 most polluted cities in the world:
1) Ahvaz, Iran 372 mcg/m3 (2009 data)
2) Ulan Bator, Mongolia 279 mcg/m3 (2008 data)
3) Sanandaj, Iran 254 mcg/m3 (2009 data)
4) Ludhiana, India (2008 data) and Quetta, Pakistan (2003/4 data) tied at 251 mcg/m3
5) Kermanshah, Iran 229 mcg/m3 (2009 data)
6) Peshawar, Pakistan 219 mcg/m3 (2003/4 data)
7) Gaborone, Botswana 216 mcg/m3 (2005 data)
8) Yasuj, Iran 215 mcg/m3 (2009 data)
9) Kanpur, India 209 mcg/m3 (2008 data)
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