Air Pollution

As the population of the world increases, air pollution is becoming an increasingly critical issue that needs to be addressed on many levels. Our reliance on fossil fuels and the increasing consumption of petroleum for our motor cars is starting to send some highly populated cities beyond the tipping point for air quality, or lack thereof. Air pollution started to become a problem with the commencement of the industrial revolution in the nineteenth century, where coal was first utilised on a large scale basis. This article will look at the different types of air pollution that the globe is currently dealing with, what the effects have been and possible mitigation and adaptation strategies.

Types Of Pollution

There are many different types of pollution can affect areas in which humans live. These types of pollutions can be isolated or each city can suffer from a combination of different types. The severity of the pollution can be dependent of several different factors, including geographical location, city layout, prevailing wind speeds and directions or high concentrations of heavy industry. These are some of the different types of pollution:

__Industrial Smog__

Industrial smog can be a combination of particulate matter, sulphur dioxide and mist or fog. This also sometimes called the 'London Smog' and typically occurs when the weather is cloudy, damp and there is a lack of wind. This type of smog is often the result of the burning of fossil fuels such as coal and often causes the build up of soot on building surfaces, damages plants and trees by causing deposits of acids and heavy metals on their leaves and also cause severe health problems for humans in the form of cancer and lung disease.


Industrial smog, North Birmingham, United States 1)

__Photochemical Smog__

Photochemical smog is the type of smog that is often seen in large cities such as Los Angeles. This occurs when the weather is sunny, as the sun's rays activate the nitrogen oxides in the air which produces ozone, nitrogen dioxide and other oxidised hydrocarbons which occurs after the reaction between oxygen and hydrocarbons. This often gives the air a hazy look, and is mainly attributable to motor vehicle emissions, and can also damage human, animal and plant tissue. Many cities which are prone to photochemical smog need to plant resistant trees on the roadside as normal trees cannot survive in such an environment. Despite the improvements in motor vehicle engines and the advent of catalytic converters, the problem has not improved notably.

__Acid Precipitation__

Acid precipitation, or acid rain, occurs when the levels of industrial smog or photochemical smog gets high, and the smog itself raises high into the atmosphere. This then causes the acids to combine with water vapour and produces corrosive rain droplets. Europe was a major problem area for this, with countries that did not have emission controls producing pollutants which then caused acid rain in neighbouring countries. The advent of high smoke chimneys or smoke stacks combined with precipitators that help to remove particulate matter from furnaces and chimneys. Acid rain can have serious impacts on plants and trees, both by physical damage by direct contact with leaves or roots, but also by lowering the ph levels of soil thus destroying the ability of anything to grow in that soil.


Acid Rain Forest in the Czech Republic 2)

__Heavy Metals__

Heavy metals are a common name for metals which are harmful, even though they may not always be 'heavy'. These can include metals such as arsenic, mercury, lead, cadmium and beryllium. The most prevalent and concerning of these heavy metals is lead. Lead can cause severe health implications and was once commonly found in petroleum. The lead particles are absorbed by the lungs and can cause a build up in lead levels in the blood stream. Lead is a nerve poison and can cause several illnesses such as paralysis, palsy, dementia and intellectual impairment in younger humans. People who live in modern westernised communities have lead concentrations in their blood that is between 500 and 1000 times greater than people during the pre industrial revolution 3). The abolition of lead fuel has helped decrease the levels of lead in the local atmosphere, however the amounts of lead that are present in the bloodstream cannot be so easily reduced.


Asbestos is a naturally occurring mineral which contains small fibres which can be interwoven. This mineral was used in a number of building materials, fire blankets, fireproof suits, gloves and was also once used to make napkins which were cleaned by throwing into the fire. Asbestos fibres are minuscule in size and can be extremely brittle, which causes the tiny fibres to be inhaled and lodged in human lungs, and are even small enough to be absorbed via the skin. These fibres then penetrate human cells and cause cancerous cells to emerge. The fibres that are lodged in the lungs can trigger an autoimmune response which tries to expel the fibres, causing scar tissue on the lung. As these fibres are pushed up through the lungs, the lung capacity decrease and levels of scar tissue increase, eventually consuming it, and this is called Asbestosis or Mesothelioma. Asbestos was banned by many countries in the late 70's and early 80's, however there are still many buildings that contain asbestos walls, roofing, insulation, paint, tiles or cement and there has been a concerted effort to remove it or make it safe. There are an increasing number of people affected by asbestos, and health professionals expect this number to increase significantly in the next three decades 4).

Why We Should Care

Ecosystems and humans rely on air and oxygen in order to survive. The increasing levels of pollution in the air can cause serious implications both for the present and more importantly the future. There can also be serious consequences for agriculture and farming, so it must be noted that air quality is one of the parts of the ecological puzzle. High levels of air pollution can cause health problems including cancer and lung diseases, cause water pollution, increase levels of mortality and cause the extinction of many species 5). China is the nation that is currently considered to have the greatest amounts of air pollution. In 2005 the World Health Organisation (WHO) put into place guidelines for what it considered to be 'safe' levels of air quality. These guidelines take into consideration different types of pollution and pollutants in the air and created a matrix which calculates the mixture of pollutants and generates a 'score', called the Air Pollution Index (API) or also called the Air Quality Index (AQI) in some countries. Different nations have their own matrix and what they consider to be safe API indicators. The amount of particulate matter that is in the air is calculated both on a 24 hour basis and on a yearly mean basis. Most cities use the PM10 indicator, which measures the coarseness of the matter, so PM10 refers to particles that 10 micrometers in size or smaller per cubic metre6).

The API index measures different concentrations of carbon dioxide, sulphur dioxide, ozone, nitrogen dioxide and the PM10 level and then calculates the score in the matrix. Scores of 0-50 and 51-100 are considered to be good to moderate, with no discernible health implications at this level, although higher than the recommended safe levels by the WHO, which is predictably as low as possible. Levels of 101-150 and 151-200 are considered to be slightly to moderately polluted, with possible health implications for people with respiratory or heart conditions advised to reduce the amount of time spent outside. When the scores start to reach 201-250 and 251-300 it is considered as heavily polluted, with healthy people at risk of suffering health problems. If the matrix score goes beyond 300, it is considered to be extremely polluted and all outdoor activities should be avoided. The interpretation and warnings can vary from country to country, but regardless the health impacts remain very dangerous. These impacts can of course vary by the amount of time exposed to the air and the activity which is performed during this time 7).

Most Polluted Cities

According to average yearly data collected between 2003 and 2010 by the World Health Organisation, the ten most air polluted cities in the world are as follows:

__City, Country: PM10 Per Cubic Metre__

Ahwaz, Iran: 372

Ulanbator, Mongolia: 279

Sanandjaz, Iran: 254

Ludhiana, India: 251

Quetta, Pakistan: 251

Kermanshah, Iran: 239

Peshawar, Pakistan:219

Gaberone, Botswana: 216

Yasouz, Iran: 215

Kanpur, India: 209

Delhi,India: 198


Delhi, India 8)

Here is the data for some of the bigger cities worldwide:

__City, Country: PM10 Per Cubic Metre__

Sydney, Australia: 12

Vienna, Austria: 25

Brussels, Belgium:28

Ottawa, Canada: 16

Beijing, China: 121

Copenhagen, Denmark: 26

Paris, France: 38

Berlin, Germany: 26

Athens, Greece: 41

Mumbai, India: 132

Rome, Italy: 35

Kuala Lumpur, Malaysia: 49

Amsterdam, Netherlands: 24

Seoul, Republic of Korea: 64

Madrid, Spain: 26

Stockholm, Sweden: 28

Bangkok, Thailand: 54

Istanbul, Turkey: 59

London, United Kingdom: 29

Los Angeles, United States: 25

New York, United States: 21

Possible Solutions

Whilst we are on the right track for reducing air pollution, as we can see on the list above there is still a lot of work to do. Countries and governments need to find a balance between economic growth and the cost of this growth, one of which is air pollution. However the best solutions still start at home, on a person by person, suburb by suburb basis and so on. We as individuals can help the cause by choosing greener options, buying local produce, driving low emission vehicles, recycling and just generally looking to reduce our carbon footprint. The planting of trees and other plants can help absorb carbon dioxide and produce cleaner air and buy products from companies committed to environmental improvement solutions. On a larger scale governments are starting to commit to tackling the problem by doing things such as carbon taxes and emissions trading schemes, subsidies for cleaner energy solutions and discouraging the use of high energy using vehicles and helping industry reduce emissions.


Acid Rain in Czech Republic by Nipik, Available:
World Health Organisation, 2014, 'Lead', Available:
4), 2014, 'Asbestosis', Available:
Brunekreef, B., & Holgate, S. T, 2002, 'Air Pollution and Health', The Lancet, vol.360, pp.1233-1242
World Health Organisation, 2005, 'WHO Air Quality Guidelines for Particulate Matter', Available:
European Centre for Environment and Health, 2000, ' Quantification of the Health Effects of Exposure to Air Pollution', Available:
Delhi, India by wili hybrid licence CC 2.0, Available:,_India.jpg

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