According to the report by World Health Organization (WHO), In 2010, some 223,000 people around the world died from lung cancer caused by exposure to air pollution. And more than half of those deaths are believed to have been in China and elsewhere in East Asia. WHO released a list of world’s 10 most polluted cities. The list includes four Iranian cities, three Pakistani, two Indian and one city of Mongolia and Botswana.

The pollution is measured as the microgramme (mcg) concentration per cubic metre of air of particulate matter smaller than 10 micrometres (PM10)—about a seventh of the width of a human hair.

The Middle East and North Africa is the world’s most polluted region with an annual mean level well over 130 mcg/m3, followed by Southeast Asia with a level near 100 mcg/m3. Here are the ten world’s worst cities for air pollution, according to the WHO.

10. Lahore, Pakistan

Lahore – The most beautiful, famous and historical city of Pakistan is also one of the most polluted cities in the world. With an annual mean figure of 200 mcg/m3 according to 2003 data, it has been rated to be the third most contaminated city in Pakistan and 10th in the world.

9. Kanpur, India

Kanpur, famous for its leather industry, is one of the most polluted cities in the world. With an annual mean figure of 209 mcg/m3 according to 2008 data, it has been rated to be the second most contaminated city of India and 9th of the world.

8. Yasuj, Iran

With an annual mean level of 215 mcg/m3 according to 2009 data, Yasuj has been rated to be the fourth most contaminated city in Iran and 8th in the world.

7. Gaborone, Botswana

With an annual mean figure of 216 mcg/m3 according to 2005 data, Gaborone has been rated to be the most polluted city in Botswana and 7th in the world.

6. Peshawar, Pakistan

With an annual mean figure of 219 mcg/m3 according to 2003 data, Peshawar has been rated to be the second most contaminated city of Pakistan and 6th of world.

5. Kermanshah, Iran

Five million people are poisoned by pollution everyday in the developing world. With an annual mean figure of 229 mcg/m3, Kermanshah has been rated to be 3rd the most polluted city in Iran and 5th in world.

4. Quetta, Pakistan

According to a report, 25 per cent of all deaths in developing country are related to environmental factors. Pakistan’s Quetta ranks among top ten polluted cities in the world. With an annual mean level of 251 mcg/m3, Quetta has been rated to be th most contaminated city in Pakistan.

4. Ludhiana, India

Ludhiana has been rated to be the most polluted city in India, and 4th in world with an annual mean level of 251 mcg/m3 according to 2008 data. The Union environment ministry imposed a ban on industrial pollution in January 2010. The ban was lifted in February 2011 but the ministry instructed the industry to prepare an action plan to keep a check on pollution.

3. Sanandaj, Iran

At No.3 in the list of most polluted cities is the capital of Kurdish Culture and Kurdistan Province, The Sanandaj with an annual mean level of 254 mcg/m3 according to 2009 data.

2. Ulan Bator, Mongolia

According to a report by the World Health Organisation, Ulan Bator city of Mongolia is at second spot among the world’s most polluted cities, with an annual mean figure of 279 mcg/m3 according to 2008 data. According to a study produced by the Public Health Institute of Ulan Bator, the number of people sickened by respiratory disease increased 45 per cent between 2004 and 2008.

1. Ahvaz, Iran

Ahwaz, in southwestern Iran, which produces the country’s most oil, is topped the most polluted cities in the world, with an annual mean level of 372 mcg/m3 according to 2009 data.

Five million people are poisoned by pollution everyday in the developing world. According to UN’s health body, more than 2 million people die every year from breathing indoor and outdoor particle pollution. Particles are released by burning petrol and diesel for car and motorcycle combustion, or coal, fuel wood, charcoal and animal waste for heating and cooking. Weather conditions can drastically affect pollution levels. Other pollution yardsticks are gases—ozone, sulphur dioxide and nitrogen oxide that are potential irritants of the airways or eyes.

Chinese city Shanghai, which is notorious for being one of the most polluted cities in the world. Indonesian capital, Jakarta, is also among the world’s most polluted places. Paris, whose levels hit a high of 180 mcg/m3 last week, has an annual mean level of 38 mcg/m3 according to 2008 data. Beijing, which has also been in the news over smothering smog, is listed with an annual mean figure of 121 mcg/m3. Among other most polluted cities Dehli with an annual mean figure of 198 mcg/m3, Lucknow 186 mcg/m3, Indore 174 mcg/m3, Mumbai 132 mcg/m3, Lanzhou 150 mcg/m3, Xining 141 mcg/m3, Urumqi 140 mcg/m3, Jinan 123 mcg/m3 are toped the chart.