Air Pollution

Nov 04, 2022, 16:45 IST

Air Pollution is the release of gases, particles, biological molecules, etc. into the air that are harmful to human health and the environment.

Air Pollution

Table of Content
What is Air Pollution? Types of Air Pollutants Causes of Air Pollution Effects of Air Pollution Air Pollution Control Frequently Asked Questions (FAQs)

What is Air Pollution?

Air Pollution refers to the undesirable change occurring in air, causing harmful effects on man and domesticated species. The common air pollutants are Dust, Smoke, Carbon monoxide (CO), Ammonia (NH₃), Sulphur dioxide (SO₂), Hydrogen sulphide (H₂S), Nitrogen dioxide (NO₂), Hydrogen cyanide, Hydrogen fluorides, Chlorines, Phosgenes, Arsines, Aldehydes, Ozone, Ionising, and radiations. CO₂ is not a normal air pollutant. There is 0.03% CO₂ in the air; its higher percentage is the cause of greenhouse effect.

Types of Air Pollutants

It is two types :

Primary Air Pollutants:

Air is polluted by poisonous gases and undesirable substances. They are released by burning fossil fuels. These substances are called primary air pollutants. The primary air pollutants are the following :

Sulphur dioxide (SO₂).
Benzopyrene (hydrocarbon) is released from cigarette smoke.
Ammonia (NH₃).
Oxides of nitrogen.
Carbon monoxide (CO).
Lead (Pb).

Secondary Air Pollutants

Secondary air pollutants are poisonous substances formed from primary air pollutants. In bright sunlight, nitrogen, nitrogen oxides, hydrocarbons, and O₂ interact to produce more powerful photochemical oxidants like ozone (O₃), peroxyacetyl nitrate (PAN), aldehydes, sulphuric acid, peroxides, etc. All these constitute photochemical smog, which retard photosynthesis in plants.

Causes of Air Pollution

Agriculture: Hydrocarbons released by plants, pollen grains, insecticides, etc., cause air pollution.
Dust: Dust in the air is increased by dust storms, wind, volcanoes, automobiles, etc.
Industries: Combustion of fossil fuels like coal, petroleum, etc. Industrial smoke is the main source of pollution.
Automobiles: The combustion of petrol and diesel in automobiles releases harmful gases into the air. They also produce dust.
Ionizing radiations: Ionizing radiations include alpha particles, beta particles and gamma rays. They are released into the air by testing atomic weapons.
Freons: The use of freons and other chloro-fluoro-carbon compounds in refrigerants, coolants, and as filling agents in aerosol also causes pollution.
Aerosols: Aerosols are small particles of all sorts of solid or liquid substances suspended in the air. They block the stomata of plants and prevent the gaseous exchanges between plants and the atmosphere. They may also change the climate of an area.

Effects of Air Pollution

Diseases

Air pollution results in several respiratory disorders and heart diseases in humans. In recent decades, the number of lung cancer cases has increased. Children living near polluted areas are more prone to pneumonia and asthma. Many people die each year due to air pollution's direct or indirect effects.

Global Warming

As a result of greenhouse gas emissions, there is an imbalance in the gaseous composition of the atmosphere. This led to an increase in the Earth's temperature. This increase in Earth's temperature is known as global warming. This resulted in melting glaciers and rising sea levels. Many areas are submerged under water.

Ozone Layer Depletion

In the atmosphere, about 30 km above the surface of the earth, the ozone molecules (O₃) form an umbrella. It prevents the penetration of harmful ultraviolet radiation from the sun and thus protects the life of the earth. It is now feared that there is a danger of depletion of the ozone umbrella, which may occur by the use of freons and other CFC-compounds in refrigerants, coolants in domestic refrigerators and cold storage facilities, and as filling agents in the form of plastics and in aerosol packages. On reaching the ozone umbrella, they destroy ozone molecules as a result of photochemical reactions. Over the past 16 years, the density of the ozone layer has been diminishing at an average rate of 3%. It is calculated that the depletion of the ozone layer by 1% results in an increase in the incidence of skin cancer by 5% to 7%. A hole in O₃ layer has been discovered in Antarctica.

Acid rain

One of the major environmental issues facing human society at the national and international level is the problem of rainwater having a low pH. The rainwater is always slightly acidic as CO₂ in the atmosphere gets dissolved in it. However, during recent years, it has been noted a further lowering of the pH of rainwater, often as low as 2.4. This lowering of pH is due to the dissolution of acids in the rainwater. Precipitation of oxides of sulphur and nitrogen with rain is termed acid rain. Acid rain is caused by air pollution. When atmospheric air contains sulphur dioxide (SO₂) and oxides of nitrogen such as nitrous oxide (N₂O) and nitric oxide (NO), they dissolve in rainwater, forming sulphuric acid and nitric acid. The rainwater falls as acid rain. The main source of releasing oxides of sulphur and nitrogen are the power plants based on coal and oil. They contribute more than 60% of all sulphur oxides and 25 to 30% of nitrogen oxides in the atmosphere. Automobiles make a substantial contribution to large cities. Ozone is now recognized as a major factor in the formation of acid rain.

Acid rain affects both materials and organisms. It attacks building materials, principally sandstone, limestone, marble, steel, and nickel. In plants, it leads to chlorosis (gradual yellowing in which the chlorophyll-making mechanism is impeded) or depigmentation of leaves. The concentration of SO₃ in the atmosphere is around 0.01 ppm.

Acid rain increases the acidity of lakes and rivers. Vast tracts of forests and lakes in Europe and North America have been destroyed by acid rain. Acidity kills fish, bacteria, and algae, and the aquatic ecosystem collapses into sterility, leaving a crystal clear but ultimately dead lake.

Air Pollution Control

The emission of exhaust from automobiles can be reduced by devices such as positive crankcase ventilation valves and catalytic converters.
Electrostatic precipitators can reduce smoke and dust from industries.
Gaseous pollutants arising from industries can be removed by the differential solubility of gases in water.
A fine pray of water in the device called a scrubber can separate many gases like NH₃, SO₂, etc. from the emitted exhaust.
Certain gases can be removed by filtration or absorption through activated charcoal.
Certain gases can be made chemically inert by chemical conversion.
At the Government level, pollution can be controlled by framing legislation.
Vehicles based on compressed natural gas (CNG) should be introduced.