Air Pollution

We explain what air pollution is and what its causes and consequences are. Also, its characteristics, possible solutions and more.

What air pollution?

Air pollution occurs when substances or forms of energy are present in the air that damage or affect in a reversible or irreversible way the human being, the rest of the living beings and the environment that surrounds them.

Air pollutants can be solid, liquid or gaseous substances, and can be chemical, physical or biological pollutants. Most air pollutants They are produced in various industries and in the use of fossil fuelsmainly in its use in vehicles that use internal combustion engines and in electricity generating plants.

The main air pollutants are carbon monoxide (CO), sulfur dioxide (SO₂), chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), nitrogen oxides, sulfur hexafluoride (HF₆), methane (CH₄), particulate matter and smog (mixture of air and pollutants at high pressures that causes stagnation of the air and also of the pollutants).

Besides, air pollutants can be deposited on peopleanimals, crops, rivers, lakes, seas and various structures built by humans. For example, when it rains in areas where polluting gases are present in the air, the rainwater drags these pollutants down, which in turn contaminate the water of rivers, lakes, seas, soils and the living organisms that live in these zones.

Sources of air pollution

The sources that cause air pollution are the activities, operations or natural or artificial processes that produce pollutants that are released into the air. Sources of air pollution can be:

• Natural sources. They are the result of a natural phenomenon. Many times they are not considered properly as emitters of pollutants, unless they affect living organisms and the environment with which they interact. For example: eruption of volcanoes and excess population of animals that generate a lot of feces.
• artificial sources. They are the result of different industrial, domestic or recreational activities of human beings. For example: oil refineries and vehicles with internal combustion engines.
• Local sources. They are those that contaminate a small area. For example: a small factory or a carpentry shop.
• Global sources. They are those that contaminate a very large area or directly influence the balance of the entire planet. For example: industries that produce gases that enhance the greenhouse effect and influence global warming.
• Mobile sources. They are those that do not remain in the same place. For example: transport vehicles that use combustion engines, such as cars, trains and airplanes.

Effects of air pollution on the environment

Air pollution is generating changes in the climate that over the years have affected the different ecosystems of the planet. These changes have been produced mainly by the greenhouse effect and damage to the ozone layer.

What is the greenhouse effect? It is the process by which thermal radiation produced by the Earth's surface is absorbed by greenhouse gases and then returned to the Earth's surface. This process naturally heats the Earth's surface.

There are gases that are produced as a result of the burning of fossil fuels and that have an important contribution to the increase in the greenhouse effect, which causes the thermal radiation returned to the Earth's surface to be much greater and, therefore, there is an increase in the global warming. Some of these gases are nitrous oxides, chlorofluorocarbons, tropospheric ozone and methane.

The ozone layer is a layer made up of ozone (O₃). This layer absorbs part of the ultraviolet rays, and prevents them from reaching the Earth's surface and causing damage to living beings and their environment. The main compounds that damage the ozone layer are chlorofluorocarbons.

Effects of air pollution on humans

The World Health Organization (WHO) estimates that approximately 7 million people may die each year from causes associated with air pollution.

The people most vulnerable to air pollutants are the elderly, people with underlying illnesses and children. Breathing contaminated air can cause severe damage to the lungs, cardiovascular accidents and death. It can also cause bronchitis, pneumonia and asthma.

Air pollutants can also be incorporated into living organisms through the ingestion of contaminated foods.

Types of air pollutants

Primary pollutants

They are those that are released directly from the emission source. These pollutants directly affect living organisms and the environment that surrounds them. For example: sulfur dioxide (SO₂), which affects the vegetation and the lungs.

Secondary pollutants

They are those that are formed as a result of chemical reactions between primary pollutants or non-polluting species, and atmospheric chemical phenomena. For example: sulfuric acid (H₂SW₄), which is formed due to the oxidation of sulfur dioxide (SO₂).

Most air pollutants are gaseous or exist in the form of aerosols:

• Gaseous pollutants. They are pollutants in a gaseous state that come mainly from the burning of fossil fuels. For example: carbon dioxide, carbon monoxide, nitrogen dioxide, ozone and smog.
• Aerosols. They are heterogeneous mixtures of solid or liquid particles in a gas, which, if polluting and mixed with air, cause severe damage to living organisms and the environment. For example: paint aerosols, insecticides and CFC aerosols.

Main air polluting gases

• Chlorofluorocarbons (CFCs). They are a set of gases that are mainly used in the refrigeration industry and in thermal insulators. They have a very long duration in the atmosphere (50 – 200 years). They are mainly responsible for the destruction of the ozone layer.
• Carbon Monoxide (CO). It is a very toxic gas that can cause death if breathed in high doses. It is produced in the combustion of gasoline, kerosene, coal, petroleum, tobacco and wood.
• Carbon dioxide (CO₂). It is a colorless gas that exists naturally in the Earth's atmosphere. It is the gas that is generated during the respiration of aerobic organisms. It is obtained artificially by burning fossil fuels, which increases its levels in the atmosphere, causing an increase in the greenhouse effect.
• Sulfur dioxide (SO₂). It is a very irritating gas. It is one of the main causes of acid rain because it is transformed into sulfuric acid (H₂SW₄) in the atmosphere.
• Methane (CH₄). It is a colorless gas that does not dissolve in water. It is produced naturally as a result of the anaerobic decomposition of plants. In addition, it is part of natural gas, and its concentration varies depending on the field from which it is extracted. Methane is a greenhouse gas.
• Ozone (O₃) tropospheric. It is a colorless gas that is produced by a chemical reaction between nitrogen oxides and volatile organic compounds obtained from the burning of fossil fuels. It is part of smog and can cause damage to living beings.
• Nitrogen oxides (NxOy). They are a set of chemical compounds that usually form as a result of combustion at high temperatures. They are produced by the combustion of vehicle engines that use diesel, and are also generated by the combustion of coal, oil or natural gas. These gases have harmful effects on the health of living beings.

How to avoid air pollution?

There are actions that each citizen can take on an individual level to reduce air pollution:

• Choose public transport or bicycle.
• When possible, install non-polluting home energy sources (solar or wind energy).
• Avoid excessive use of gas and other fossil fuels in heating and cooking.

Additionally, governments and various organizations can:

• Establish a network of clean energy sources, such as water, wind or solar energy, based on state investments or encouraging private investments.
• Increase green areas, since plants consume carbon dioxide and convert it into oxygen.
• Promote scientific research and technological development of alternative fuels to fossil fuels.

References

• “Fixed sources” At: https://ambientebogota.gov.co Available at: https://ambientebogota.gov.co. Accessed: March 29, 2023.
• “Sources of Atmospheric Pollution” At: www.gob.mx Available at: https://www.gob.mx/semarnat/articulos/fuentes-de-contaminacion-atmosferica. Accessed: March 29, 2023.
• “Causes of air pollution” In: www.ecologistsenaccion.org Available at: https://www.ecologistsenaccion.org/. Accessed: March 29, 2023.
• “Smog” In: es.wikipedia.org Available at: https://es.wikipedia.org/ Accessed: March 29, 2023.