What is Atmospheric Pollution?

In the atmosphere, the existence of large quantities of undesirable substances that could cause several health issues to living organisms and humans is atmospheric pollution. Air pollution is otherwise known to be atmospheric pollution. The presence of undesirable materials would also destruct the natural environment such as a change in climate, degradation of habitat, or depletion of ozone. Air pollution is generated by the natural processes and activities of humans.

Kinds of air pollutants

A substance that is present in the air which could cause destructive effects on ecosystems and human beings is an air pollutant. Air pollutants include solid substances, gases, or droplets of liquid. Primary pollutants and secondary pollutants are the two categories of air pollutants.

Primary air pollutants

A pollutant that is formed from a natural process like ash from the outbreak of a volcano is a primary pollutant.  Ammonia, sulfur oxides, nitrogen oxides, organic compounds such as hydrocarbons, oxides formed from carbon, lead, etc are primary air pollutants. In the atmosphere, the emission of pollutants by human activities is:

Carbon dioxide

Carbon dioxide (CO2) is definite leading pollutants, which causes air pollution. It is one among the important greenhouse gases. It is a natural compound found in the atmosphere that is needed for plants to live. Large quantities of CO2 are liberated into the atmosphere when fossil fuels are burnt.

Sulfur oxides

Sulfur oxides, mainly sulfur dioxide (SO2) are given out by volcanoes and other industrial processes. Sulfur dioxide is generated by the combustion of petroleum as well as coal that contains compounds of sulfur. When sulfur dioxide is oxidized with nitrogen dioxide as a catalyst, sulfuric acid is formed, and so, the production of acid rain occurs.

Nitrogen oxides

Nitrogen oxides, mainly nitrogen dioxide (NO2) are given out by combustion at higher temperatures and are formed at the times of thunderstorms. NO2 is one of the many compounds of nitrogen oxides. One among the significant air pollutants is NO2, which is a toxic gas, reddish-brown in color, and exhibits a sharp and biting odor.

Carbon monoxide

The combustion of coal, natural gas, or wood would result in carbon monoxide (CO) as a combustion product. The emission of abundances of CO into the atmosphere is through exhaust from vehicles. A smog kind formation is seen in the air by the emission of CO. The emission of CO in the atmosphere would lead to several diseases in the lungs & disrupts the natural environment.


Chlorofluorocarbons (CFCs) are the gases emitted out from aerosol sprays, air conditioners, etc. When CFCs are liberated into the air, they move to the stratosphere. In the layer of the stratosphere, the CFCs react with additional gases that are present and the layer of ozone. This permits the UV rays to come in contact with the surface of the earth and thereby, leading to diseases in plants and humans.

Secondary pollutants

A pollutant, which is produced from the reaction or interaction of primary air pollutants with extra gases is secondary pollutants. The emission of secondary pollutants is not direct. A predominant example of this kind of pollutant is ground-level ozone. Particulate matter and peroxyacetyl nitrate are secondary air pollutants.

Particulate matter (PM)

The other name of PM is particle pollution. Particle pollution is the combination of particles that are extremely small and droplets of liquids. The number of components that makes up particle pollution is:

  • Acids made from nitrates and sulfates.
  • Organic compounds.
  • Particles in the dust (or) soil.

As the particle size is very small (10 mm), it would lead to several health problems.


A kind of air pollution is smog. In photochemical smog, the compounds and primary air pollutants in the gaseous state form particulates. The emission of coal caused by the combination of smoke and SO2 leads to a classical smog. The emission from vehicles and emission from industries acts in the atmosphere by UV light forms secondary pollutants that result in modern smog. Photochemical smog is produced when secondary pollutants are combined with primary emissions.

Ground-level ozone

Volatile organic compounds (VOCs) and nitrogen oxides form ground-level ozone. Ground-level ozone is not directly liberated into the atmosphere. Ground-level ozone affects the ecosystems, cause lung diseases, and other health issues.

Sources of air pollution

Natural sources and man-made sources are the two kinds of sources of air pollution.

Natural source

The natural sources are:

  • Dust moved by the winds from regions with no vegetation or less vegetation.
  • Emission of gases by the body processes of living organisms.
  • The smoke formed through the ignition of several objects that are inflammable, eruptions of volcanoes.
  • Emission of smoke and CO from wildfires.

Man-made source

The man-made causes of air pollution are termed anthropogenic sources. The two divisions of man-made air pollution are,

  • Indoor air pollution.
  • Outdoor air pollution.

Outdoor air pollution

Outdoor air pollution is because of outdoor pollution components such as incineration of waste/vehicles, industries, furnaces, power stations of fossil fuels. An important component of this pollution is the feature of smoke. The emission of smoke is by the combustion in vehicles, factories, biomass, etc.

Indoor air pollution

Indoor air pollution is because by inner pollution components such as burning fuels in open hearths or stoves. The pollutants are methane, polyaromatic hydrocarbons (PAHs), CO, and VOCs.

The figure shows the several sources of air pollution along with their percentages.
CC-BY-SA 4.0 | Image Credits: https://commons.wikimedia.org | Laira Aggarwal

What are the several reasons for air pollution or atmospheric pollution?

The several reasons for air pollution are listed as follows:

Fossil fuels burning

When fossil fuels like coal and petroleum are burnt from power plants to liberate energy, SO2 is given out. The burning of fossil fuels is the most important reason for air pollution. A high level of pollution happens when pollutants like nitrogen dioxide, particulate matter, organic compounds, CO are released.

Agricultural activities

A familiar byproduct that is produced from activities that are based on agriculture is ammonia and it is a harmful gas in the atmosphere. Ammonia is found in pesticides, insecticides, and fertilizers. The emission of many unsafe gases occurs into the air and thereby leads to a high level of pollution.

Exhaust from industries

High quantities of CO, organic compounds, and hydrocarbons are liberated into the atmosphere by manufacturing factories. The release of these harmful gases reduces the air quality.

The other reasons for air pollution are natural occurrences and mining operations.

What are the consequences of air pollution?

The aftereffects of air pollution are:

  • Issues in heart and respiratory system.
  • Health problems in children.
  • Global warming.
  • Acid rain.
  • Ozone layer depletion.
  • Eutrophication.
The figure represents the causes and effects of air pollution.
CC-BY 3.0 | Image Credits: https://commons.wikimedia.org | Chris

Indoor Air quality

The air quality inside and around structures and buildings is indoor air quality. The Health and comfort of occupants who live in buildings are affected by the indoor air quality. Gases such as VOCs, CO, radon affect indoor air quality. Particulates, contaminants such as bacteria, & mold are the additional parameters that affect indoor air quality. In several buildings, the indoor air quality can be increased by techniques such as,

  • Filtration.
  • Use of ventilation.
  • Source control.

The indoor air quality could be determined by collecting the samples of air, observing the exposure of humans to pollutants, collecting the samples on the surface of buildings, and computer modeling the flow of air in the building.

Ways to prevent Air pollution

Air pollution can be prohibited by using public transports, by devices that consume less energy, by conserving energy (decreasing the burning of fossil fuels), etc.

Context and Applications

This topic is important for,

  • Bachelors and masters in chemistry.
  • Bachelors and masters in environmental science.

Practice Problems

Question 1: Among the following, the major reason for global warming is ____.

  1. Increase in the concentration of oxygen in the air
  2. Decrease in  CO2 concentration in the atmosphere
  3. Increase in CO2 concentration in the atmosphere
  4. None of the above

Answer: Option 3 is correct.

Explanation: Global warming happens due to changes in climate due to human activities. The key reason for global warming is the increment in CO2 concentration in the air.

Question 2: Among the following, an example of a primary air pollutant is _____.

  1. Ground-level ozone
  2. Peroxides
  3. Radioactive pollutants
  4. None of the above

Answer: Option 3 is correct.

Explanation: Radioactive pollutants are an example of primary air pollutant as it is a result of nuclear explosions.

Question 3: The chemical formula for peroxyacetyl nitrate is ____.

  1. C2H3NO5
  2. CH4
  3. CH3NO
  4. None of the above

Answer: Option 1 is correct.

Explanation: Peroxyacetyl nitrate is produced from nitrogen oxides and VOCs. Its formula is C2H3NO5.

Question 4: Among the following, air pollution is not caused by ____.

  1. Hydroelectric power
  2. Automobiles
  3. Industries
  4. None of the above

Answer: Option 1 is correct.

Explanation: Automobiles and industries emit harmful gases and are the chief causes of air pollution. Air pollution is caused by hydroelectric power.

Question 5: IEQ stands for ____.

  1. Inside environmental quality
  2. Indoor environmental quality
  3. International environmental quality
  4. None of the above

Answer: Option 2 is correct.

Explanation: Indoor environmental quality (IEQ) was formed to give well-being, productivity, and comfort to building occupants.

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Air Pollution; Author: Bozeman Science;https://www.youtube.com/embed/_dTtvtlct9k;License: Standard YouTube License, CC-BY

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