Why These Ten Dangerously Polluted Cities All Smell Different.

Leo Tolstoy once wrote “All happy families are alike; each unhappy family is unhappy in its own way”. The Earth today has hundreds of dangerously polluted cities but the sources of pollution vary widely from city to city, such that badly polluted cities indeed smell different. Here is a selection of some cities with some of the worst air and what’s in it.


1. Ahvaz, Iran 

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The World Health Organization says Ahvaz is the one of world’s most polluted cities.  Ahvaz is a city known for oil fields, heavy industry with a sugar processing plant and a coal-burning power plant. 

Air pollutants such as nitrogen oxides increase the susceptibility of respiratory infections.

Finally chronic exposure to ozone and certain heavy metals reduce lung function, while the later responsible for asthma, emphysema, and even lung cancer.


2. Beijing, China


Air pollution in Beijing is mainly caused by burning coal in factories, power plants and oil combustion by vehicles. Coal provides not only 80% of China’s electricity, but also generates air pollution, from soot to sulphur dioxide.

Chinese industrial cities, such as Shenyang and Lanzhou, are also known for theirhigh levels of smoke pollution. China, which now has over 120 cities with more than 1 million people, currently burns in excess of 2 billion tonnes tonesof coal per annum (and it is likely to remain its dominant fuel for decades to come).

In 2008, of the twenty most polluted cities in the world, nine were to be found in China. Population of Lanzhou inhales air with average levels of pollution that are more than 100 times the World Health Organisation’s (WHO) guidelines. Located at the bottom of a narrow river valley, Chinese city planners unsuccessfully attempted to solve Lanzhou’s pollution problem by blasting the tops off the surrounding hills to allow the smoke to escape.

As far as the impact on people’s health, the analysis revealed other repercussions from the emissions of its coal-fired plants in 2013, including: approx. 320,000 children and 61,000 adults suffering from asthma, 36,000 babies born with low weight, 340,000 hospital admissions and 2 million doctor visits, and approx. 141 million days of sick leave.

Map of the 257,000 premature deaths annually due to the air pollution from the coal-fired power plants in China

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The WHO’s Global Burden of Disease report estimated that 1.2 million people died prematurely in China in 2010 due to air pollution as a whole which includes emissions from industry and transport as well as the coal power sector. 

In 2012, the WHO estimated that over 1.5 million people of total work population annually were killed by respiratory and other diseases associated with air pollution (the great majority in developing countries).

3. Ulan Bator, Mongolia


Mongolia’s capital city, Ulan Bator, is a dangerously polluted city but the main cause is not industry but coal ovens in the Mongolian tents that house the majority of the population.

In recent years, Ulan Bator doubled its population of 1.2 million although Mongolia is still world’s least-densely populated country with only three million inhabitants with the territory size three times that of France.

Tens of thousands of nomads who came from the steppes seeking work set up their traditional houses called yurts in the suburbs.

Pollution in Ulan Bator is seasonal. In winter, the temperature drops to minus 30 and pollution in some parts of the city goes up to 2,000 micrograms.

In Mongolia the pollution problem is escalated through poverty. Lower-class residents often use old tires and various waste instead of coal boxes which produces toxic smoke.

Traditional Mongolian Drummer Stove

Both Mongolian government and American donors have incentivised residents to replace the traditional drummers with modern stoves that are more economical, use less coal and emit fewer pollutants into the air in an attempt to reduce pollution.

In addition to the “clean” stoves, the Mongolian government offered assistance with improving yurt isolation as well as through mass planting of trees in neighbourhoods with high yurt density that are built on higher elevations around the city.

One of the worst sources of the pollution is dust. The dust originates from the district of Ger’s heating activity, the desert, the dry ground condition and the ash ponds emanating from the power plants. Strong winds, particularly in spring, also allow dust from the Gobi desert and other arid regions of Mongolia to reach to city.

When breathing, the lungs of Ulan Bator citizens, especially those living in Ger districts act like air filters, catching and storing the harmful dust which scientists call “particulate matter” (PM). PM smaller than 2.5 microns or “PM2.5” can cause severe respiratory illnesses. Air pollution is responsible for one in every ten deaths in Ulan Bator. It is the number one cause of deaths in town and it is free to roam the city looking for new victims. It kills slowly and painfully, and there’s little one can do to protect against it.

Indoor air pollution is typical of countries that heavily use wood, coal and other solid fuels as primary energy use (cooking and heating stoves without chimneys and open campfires in homes as well as inadequate furnaces). A major factor on the health conditions of poor households is the use of fossil fuels and pollution.

4. Lahore, Pakistan


Lahore has topped the list of most polluted cities with highest air pollution level of PM 10 =198 and PM 2,5= 68 in 2010. 

It was also revealed that the high pollution levels were mainly caused by emissions from vehicles, industrial activities and fine natural dust and aerosols. Moreover, the movement of air pollution from neighbouring countries has also worsened the air quality of the city.

Combustion of fossil fuels in transport, power plants, power stations and households all caused health problems with the lungs such as asthma, chronic bronchitis and respiratory tract irritation. There were also an increased number of hospital admissions of patients with heart problems. The mortality rate increases in the days of higher content of CO2 in the air.

5. New Delhi, India

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Even though New Delhi has had a public transportation system for the past three decades, the number of cars has grown from 180,000 to 3.5 million.

New Delhi has other sources of air pollution apart of increasing numbers of vehicles on the road. More than one thousand brick kilns produce vast quantities of smoke while feeding the city’s construction industry. Construction industry also generates its own pollution which is further increased by farmers setting agricultural waste on fire to clear cropland. Road dust comprises 50% of total pollution with industry contributing 23% while vehicles accounted for only 7% of air pollution.

In summer, in addition to the road dust already present on the Delhi roads, dust storms from the desert to the south-west contribute to increased fugitive dust, worsened by the growing number of vehicles. This is exacerbated by the low moisture content in the air, leading to higher suspension of road dust (40% of particulate pollution in summer, compared to 4% in winter). In the winter months, the mix of pollution sources changes dramatically. The use of biomass, primarily for heating, contributes to as much as 30% of air pollution in winter. In summer, biomass accounts for only 9% of particulate pollution.

With one fifth of deaths worldwide, India experiences the worst of outdoor air pollution and on a massive scale. Globally, air pollution-related deaths has increased by 300% since 2000. About 65% of these deaths occur in Asia.

6. Riyadh, Saudi Arabia


Sandstorms contribute to Riyadh’s air pollution. These occur in dry and semi-arid areas and are formed when a strong wind carries sand and dust from a dry surface. Particles are moving,causing soil erosion in one placeand is moved elsewhere.

Wide range of pollutants like dust, soot, fly ash, diesel exhaust particles, wood smoke and sulfate aerosols can be found in the form of tiny particles in the air. Some of these fine particles can become lodged in the lungs and could trigger asthma attacks. Studies have shown that the number of hospitalizations for asthma increases when levels of particulate matter in the air rise.

Sandstorms contribute to Riyadh’s air pollution. These occur in dry and semi-arid areas and are formed when a strong wind carries sand and dust from a dry surface. Particles are moving, causing soil erosion in one place and land elsewhere.

Wide range of pollutants like dust, soot, fly ash, diesel exhaust particles, wood smoke and sulfate aerosols can be found in the form of tiny particles in the air. Some of these fine particles can become lodged in the lungs and could trigger asthma attacks. Studies have shown that the number of hospitalizations for asthma increases when levels of particulate matter in the air rise.

8. Moscow, Russia

Moscow is the capital and the most populated region of Russia. The city is a major political, economic, cultural and scientific region in Russia and in Eurasia.


There are also smaller regions. Moscow occupies the central area of ​​the European part of Russia. Rich deposits of iron ore and brown coal have been found around Tula, Voronezh and Kursk, and large Podmoskovske basin. In the middle region is Moscow, the capital and the largest city and industrial centre of Russia. Around Moscow, there is a series of satellite cities with heavy industry. Moscow has five airports, harbour canals and navigable rivers linked to the five seas. Major industrial centres in the region are also Jaroslav, Ivanovo, Tula, Vladimir, Smolensk, and many others.

According to data, the content of harmful substances (carbon dioxide, nitrogen dioxide, nitrogen oxides and particulate matter) in the air exceeded the standard five to eight times over in some regions of Moscow.

Sulfur dioxide is produced when coal and crude oil are burned. Coal-fired power plants, particularly older plants that burn coal without SO2 pollution controls are the worst SO2 polluters. Oil refineries and diesel engines that burn high-sulfur fuel also release large amounts of SO2 into the air.

9. Mexico City

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Mexico City is one of the largest cities in the with a population of 19 million. It is located in a basin and surrounded on three sides by inaccessible mountains. The city still has major problems with the devastating earthquakes and lack of drinking water.

Fast population increase is causing a rapid growth of Mexico City and the authorities are taking a number of measures in order to control the growth. Population growth brought a host of problems such as the lack of housing, increase the number of homeless people, air pollution, etc.

It has been all too common to make a direct association between population growth and factors like CO2 emissions, environmental degradation, global warming, and other manifestations of climate change. Indeed, human activities now contribute to a substantial percentage of the accumulation greenhouse gases. However, more people does not necessarily mean more emissions.

Although the air pollution in Mexico has vastly decreased in the last two decades, levels of harmful pollutants such as particulate matter and ozone are still above the World Health Organization’s recommended levels for Mexico City.

Acceptable levels of sulphur dioxide stated by the Norma Oficial Mexicana are 0.130 ppm as a maximum daily average and 0.030 ppm as a yearly average.

Current levels of sulphur dioxide are 0.076 ppm as a maximum daily average and 0.10 ppm as a yearly average. Both levels are acceptable according to the Norma Oficial Mexicana.

However, the standards set by the World Health Organization are 20 µg/m3 as a daily average and 500 µg/m3 as a peak 10 minute average. Against these standards, Mexico City fails with 156 µg/m3 of sulphur dioxide daily and 967 µg/m3 maximum average over 10 minutes.

According to the Norma Oficial Mexicana, Mexico City is above limits of ozone with 0.123 ppm every 8 hours. According to the World Health Organization, who creates guidelines on safe limits at 100 µg/m3, Mexico City pollution in 2011 is PM 10 = 93 and PM 2,5= 25.

One of the main culprits is the transportation sector: the country’s fleet of inefficient trucks and cars consume dirty diesel fuels and emit high levels of black carbon (the second most powerful contributor to climate change behind carbon dioxide) and particulate matter. These contaminants not only impact the environment and worsen climate change but they also have grave effects on people. The International Agency for Research on Cancer has classified black carbon, particulate matter and outdoor air pollution generally as carcinogens. In 2013, the World Health Organization said that 14,700 people in Mexico died from outdoor air pollution.

The city’s government plans to further reduce vehicle emissions which are the city’s greatest source of pollution. Pemex, the state oil monopoly, plans to build a $9.3 billion plant to produce low-sulfur fuel. Officials plan to add hybrid buses. A suburban train system is to replace hundreds of thousands of vehicles.

10. Dhaka, Bangladesh

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Dhaka is capital of Bangladesh and one of the world’s largest cities.

According to the WHO, old, poorly serviced vehicles, brick kilns (there are currently about 1,000 in and around Dhaka), dust from roads and construction sites, and toxic fumes from industrial sites are major sources of air pollution. 

Air pollution in Dhaka to the World Health Organization in 2013. is PM 10 = 180 and PM 2,5 = 86.

According to the Department of Environment, the density of airborne particulate matter (PM) reaches 463 micrograms per cubic metre (mcm) in the city during the dry season (December-March) which is the highest level in the world.

During the dry season (October to March), vehicular emission, particular motor cycles, diesel trucks and buses (most do of the sources), and open land wind erosion; biomass burning in the brickfields and city incinerators (to the fine mode); are the major sources of PM pollution. The source apportionment study conducted by the Bangladesh Atomic Energy Centre, Dhaka, Bangladesh for fine and coarse particulates at two stations: farm gate and Dhaka University premises.

A study, Environmental Performance Index 2012, conducted by the US universities Yale and Columbia, found Dhaka to be the 31st most polluted city out of 132 cities across the world. The study concluded that an estimated 15,000 premature deaths, as well as several million cases of pulmonary, respiratory neurological illness are attributed to poor air quality in Dhaka.

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  2. Seoul in South Korea is another one. 20 million people, it get the yellow winds in March April when Sand is blown over from the Mongolian Deserts and everyone has to wear masks. Also polluted and air quality is constantly scrutinised there.

  3. Being a person who is experiencing this almost everyday I am not surprised in seeing these in the form of some statistics. With that said, the growth of the city cannot be controlled, as it is important for job oppurtunities, fo r the economy etc., But one fair and good solution for this could be providing cheap and quality transport so that those cars we see with only one person in it can be avoided. This will considerably reduce RSPM as well as traffic to a great extent. Thanks The Hindu for this article. Let’s hope for a balanced tomorrow!

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