Air Pollution

(Types, Sources, Causes, and Effects)

“Clean air is a basic right. The responsibility to ensure this lies with
every individual and nation.” — Dr. Maria Neira, WHO

Introduction
Air pollution occurs when the air contains gases, dust, fumes or odour
in harmful amounts which leads to adverse effects on health,
ecosystems, and the climate. The atmosphere has always been a sink-a
place of deposition and storage-for gaseous and particulate wastes.
When the amount of waste entering an area of the atmosphere
exceeds the atmosphere's ability to disperse or break down the
pollutants, problems result.

The major air pollutants include carbon oxides (COx), particulate

matter (PM), nitrogen oxides (NOx), sulfur oxides (SOx), tropospheric
ozone (O3), volatile organic compounds (VOCs), and dioxins.

The substances that cause air pollution are called pollutants. Pollutants
that are pumped into our atmosphere and directly pollute the air are
called primary pollutants.

Primary pollutant examples include carbon monoxide from car exhausts

and sulfur dioxide from the combustion of coal. Further pollution can
arise if primary pollutants in the atmosphere undergo chemical
reactions. The resulting compounds are called secondary pollutants.
Photochemical smog is an example of secondary pollutants.

Types and Sources of Major Air Pollutants

The two major categories of air pollution sources are stationery sources
and mobile sources.

Stationery sources have relatively fixed location.

Mobile sources of air pollution include automobiles, trucks, buses,

aircraft, ships, trains and anything else that pollutes as it moves from
place to place.

1. Carbon Oxides (COx)

 Types: Carbon monoxide (CO) and carbon dioxide (CO2).

 Sources:
 o CO: Incomplete combustion of fossil fuels in vehicles,
industrial processes, and biomass burning.
o CO2: Fossil fuel combustion, deforestation, and volcanic
eruptions.
 Effects:
o CO: Impairs oxygen delivery in blood, causing health issues.
o CO2: A greenhouse gas contributing to global warming.

2. Particulate Matter (PM)

 Types: PM2.5 (fine particles) and PM10 (coarse particles).

 Sources:
o Natural: Dust storms, wildfires, volcanic activity.
o Anthropogenic: Industrial emissions, vehicle exhaust,
construction activities.
 Effects:
o Respiratory and cardiovascular diseases.
o Reduces visibility, causing accidents.

3. Nitrogen Oxides (NOx)

 Types: Nitric oxide (NO) and nitrogen dioxide (NO2).

 Sources:
o High-temperature combustion in vehicles and power plants.
o Agricultural practices using nitrogen-based fertilizers.
 Effects:
o Acid rain formation.
o Ground-level ozone creation.
o Respiratory issues and reduced lung function.
4. Sulfur Oxides (SOx)

 Types: Sulfur dioxide (SO2) and sulfur trioxide (SO3).

 Sources:
o Burning of sulfur-rich fossil fuels.
o Industrial processes like smelting and refining.
 Effects:
o Acid rain, damaging buildings, soil, and water bodies.
o Respiratory diseases and lung damage.

5. Tropospheric Ozone (O3)

 Formation: A secondary pollutant formed by the reaction of NOx

and VOCs in the presence of sunlight.
 Sources:
o Vehicle emissions.
o Industrial discharges.
 Effects:
o Irritates respiratory pathways and exacerbates asthma.
o Damages crops and reduces agricultural yields.

6. Volatile Organic Compounds (VOCs)

Definition: Organic chemicals that vaporize easily at room temperature.

 Sources:
o Natural: Plants and wetlands (e.g., isoprene).
o Anthropogenic: Solvent use, vehicle emissions, and
industrial processes.
 Effects:
 o Ground-level ozone formation.
o Carcinogenic effects (e.g., benzene exposure).

7. Dioxins

 Definition: Persistent organic pollutants produced unintentionally

during combustion and industrial processes.
 Sources:
o Waste incineration, chemical manufacturing, and natural
forest fires.
 Effects:
o Highly toxic, causing cancer, reproductive and
developmental issues.
o Accumulate in the food chain, affecting humans and
animals.

Causes of Air Pollution

1. Emission from factories and industries:

Industries release unregulated emissions, including sulfur dioxide (SO₂),

nitrogen oxides (NOₓ), and particulate matter (PM), into the
atmosphere. Power plants burning coal or oil are major contributors.
This large-scale pollution stems from outdated technology, lack of
pollution control measures, and excessive reliance on fossil fuels.

2. Exhaust from transport vehicles:

The growth of cities increases vehicle emissions due to traffic
congestion and inefficient public transport systems. Construction
activities contribute dust and fine particles, while urban heat islands
amplify pollution effects.

3. Deforestation:

Clearing forests reduces the Earth's ability to absorb CO₂, a major

greenhouse gas. Slash-and-burn practices not only release stored
carbon but also produce black carbon and other pollutants,
exacerbating global warming.

4. Agricultural Practices:

Synthetic fertilizers and pesticides release ammonia (NH₃), a key

contributor to PM formation. Livestock farming produces methane
(CH₄), a potent greenhouse gas. Agricultural burning adds to PM and
NOₓ emissions.

5. Waste Management:

Improper disposal and open burning of municipal waste emit dioxins,

furans, and other toxic substances. Landfills release methane and
contribute to smog and greenhouse gas emissions.

6. Energy Production:

Burning fossil fuels for electricity and heating emits large quantities of
CO₂, NOₓ, SOₓ, and PM. Power generation facilities without emission
controls worsen the air quality significantly.
7. Power Stations (Thermal Energy)

Thermal power stations burn fossil fuels like coal, oil, or natural gas to
generate electricity. This process releases pollutants such as carbon
dioxide (CO₂), sulfur dioxide (SO₂), nitrogen oxides (NOₓ), and
particulate matter (PM) into the atmosphere, contributing to air
pollution and global warming. Inefficient combustion and outdated
technology exacerbate these emissions.

8. Chemical Industry, Aerosols, and CFCs

The chemical industry emits hazardous gases like ammonia (NH₃),

volatile organic compounds (VOCs), and other pollutants during
manufacturing processes. Aerosols, which are tiny particles or droplets
in the air, include industrial emissions and secondary particles formed
by chemical reactions. Chlorofluorocarbons (CFCs), previously used in
refrigeration and aerosols, not only pollute the air but also deplete the
ozone layer.

9. Wildfires and Volcanic Activity

Wildfires release large quantities of smoke, carbon monoxide (CO), and

fine particulate matter, which degrade air quality and contribute to
greenhouse gases. Volcanic eruptions emit sulfur dioxide, ash, and
other gases that can spread over large areas, affecting both local and
global air quality. These natural events can have short-term and long-
term environmental impacts.

Effects of Major Air Pollutants

1. Health Impacts:

 Respiratory Diseases: Pollutants like PM₂.₅ penetrate deep into

the lungs, causing asthma, chronic bronchitis, and lung cancer.
Long-term exposure aggravates pre-existing conditions.
 Cardiovascular Problems: Fine particulates and CO can lead to
arterial inflammation, increasing the risk of heart attacks,
arrhythmias, and strokes.
 Developmental Issues: Pollutants such as lead and dioxins impair
cognitive development and cause physical growth delays in
children. Prenatal exposure may result in low birth weight or
congenital disabilities.

2. Environmental Impacts:

 Acid Rain: SO₂ and NOₓ react with water vapor to form sulfuric
and nitric acids, which fall as acid rain. This damages aquatic
ecosystems, leaches nutrients from soils, and corrodes historical
monuments.
 Smog Formation: High levels of ground-level ozone, formed by
NOₓ and VOCs in sunlight, cause photochemical smog. This
reduces visibility, disrupts photosynthesis in plants, and irritates
respiratory systems.
 Ozone Layer Depletion: Though not directly linked to air
pollutants discussed here, VOCs and NOₓ contribute indirectly to
ozone depletion by altering atmospheric chemistry. This increases
UV radiation exposure, leading to skin cancers and cataracts.
3. Economic Impacts:

 Healthcare Costs: The surge in pollution-related illnesses places a

significant financial burden on public health systems, reducing
overall productivity.
 Crop Loss: Ground-level ozone damages plant cells, reducing crop
yields for staples like wheat, rice, and soybeans. Acid rain alters
soil chemistry, further lowering agricultural productivity.
 Damage to Infrastructure: SO₂ and acid rain corrode metal
structures, bridges, and buildings, increasing maintenance costs
and reducing lifespan.

Recent Developments and Applications

1. Emission Reduction Technologies:
a. Catalytic converters in vehicles.
b. Flue-gas desulfurization in power plants.
2. Alternative Energy Sources:
a. Solar, wind, and nuclear energy to reduce fossil fuel
dependence.
3. Air Quality Monitoring:
a. Use of satellite-based and ground-based systems for real-
time data.
4. Policy Interventions:
a. Implementation of the Paris Agreement to reduce
greenhouse gases.
b. Stricter emission standards for industries and vehicles.
5. Innovations:
a. Development of air-purifying paints and materials.
b. Biofilters to absorb VOCs and COx emissions.