Air and Noise Pollution

By BYJU'S Exam Prep

Updated on: September 25th, 2023

Air and noise pollution are the type of pollution that causes a harmful effect on human health. Combined, air and noise pollution topics are asked in the ESE exam and other state examinations, but in the GATE exam, questions about noise pollution are not asked. Air pollution is the pollution of the air due to the presence of harmful gases or ingredients in the air. And noise pollution is occurred due to high-intensity noise or unwanted noise in the surrounding environment.

Air and Noise Pollution PDF [GATE Notes]

Both air and noise pollution harm human beings and the environment. Here, we have discussed the causes, effects, and types of pollution. This article contains fundamental notes on the “Air and Noise Pollution” topic of Environmental Engineering subject.

What is Air and Noise Pollution?

Air and noise pollution is the type of pollution that may occur due to developmental activities such as construction, transportation, and manufacturing. These consume natural resources and produce a large amount of waste that leads to air, water, soil, and ocean pollution, global warming and acid rain.

Air and noise pollution in the environment occurs due to harmful ingredients and unwanted noise, respectively. Air pollution can be due to harmful gases, solid particles or colloidal particles present in the environment. But noise pollution is the occurred due to unwanted noise in the surrounding.

Meaning of Pollution and Pollutants

Any type of pollution, including air and noise pollution, can be caused due to the pollutants. Automobiles emit oxides of nitrogen, sulfur dioxide, carbon dioxide, carbon monoxide, and a complex mixture of unburnt hydrocarbons and black soot from their tailpipes, which pollute the atmosphere. Domestic sewage and run-off from agricultural fields, laden with pesticides and fertilizers, pollute water bodies. Effluents from tanneries contain many harmful chemicals and emit a foul smell.

  • Pollution may be defined as adding undesirable material into the environment due to human activities. The agents which cause environmental pollution are called pollutants.
  • Pollutants may be physical, chemical, or biological substances unintentionally released into the environment. These are directly or indirectly harmful to humans and other living organisms.

Types of Pollution

Air and noise pollution is also one type of pollution. Pollution can be classified into many types based on the polluting agent and pollutants. If the same pollutant is mixed with air, it will cause air pollution, and if it is added to the water, then the same pollutant will cause water pollution. Here a few types of pollution are listed below, including pollution due to pollutants.
• Air pollution
• Noise pollution
• Water pollution
• Soil pollution
• Thermal pollution
• Radiation pollution

Air Pollution: Sources and Effects

Air pollution may be defined as the presence of any solid, liquid, or gaseous substance, including noise and radioactive radiation, in the atmosphere in such concentration that may be directly and indirectly injurious to humans or other living organisms, plants, or property or interferes with the normal environmental processes. Air pollutants are of two types

  • suspended particulate matter, and
  • gaseous pollutants like carbon dioxide (CO2), NOx, etc.

Some of the major air pollutants, their sources and their effects are given in the table. 

Particulate air pollutants, their sources, and effects
Pollutant Sources Effects
Suspended particulate matter Smoke from domestic activities Depends on the specific composition
matter/dust industrial and vehicular soot Reduces sunlight and visibility,
increases corrosion, Pneumoconiosis,
asthma, cancer, and other lung diseases.
Fly ash

Part of the smoke released and Settles down on vegetation and houses. And chimneys of factories, the suspended participant matter (SPM),
power plants

Leachates contain harmful

Particulate pollutants

Particulate matter suspended in the air is dust and soot released from the industrial chimneys. Their size ranges from 0.001 to 500 µm in diameter. Particles less than 10µm float and move freely with the air current. Particles that are more than 10µm in diameter settle down. Particles less than 0.02 µm form persistent aerosols. The major source of SPM (suspended particulate matter) are vehicles, power plants, construction activities, oil refineries, railway yards, market place, industries, etc.

Fly ash

Fly ash is ejected mostly by thermal power plants as by-products of coal-burning operations. Fly ash pollutes air and water and may cause heavy metal pollution in water bodies. Fly ash affects vegetation due to its direct deposition on leaf surfaces or indirectly through its deposition on the soil. Fly ash is now being used for making bricks and as landfill material.

Lead and other metals particles

  • Tetraethyl lead (TEL) is used as an anti-knock agent in petrol for vehicle smooth and easy running. The lead particles from vehicles’ exhaust pipes are mixed with air.
  • Lead mixed with water and food can create cumulative poisoning. It has long-term effects on children as it lowers intelligence.
  • Oxides of iron, aluminum, manganese, magnesium, zinc, and other metals have adverse effects due to the deposition of dust on plants during mining operations and metallurgical processes.

Gaseous pollutants

Power plants, industries, and different types of vehicles – both private and commercial use petrol and diesel as fuel and release gaseous pollutants such as carbon dioxide, oxides of nitrogen and sulfur dioxide, along with particulate matter in the form of smoke. All of these have harmful effects on plants and humans.

Gaseous air pollutants: Sources and effects


Air Pollution Control and Principles

Air pollution affects human health and other living beings in the environment. So it is important to understand its control parameters and their principles.

1. Source Control Technology

  • Air quality management sets the tools to control air pollutant emissions.
  • Control measurements describe the equipment, processes, or actions used to reduce air pollution.
  • The extent of pollution reduction varies among technologies and measures.
  • The selection of control technologies depends on environmental, engineering, economic factors, and pollutant type.

2. Settling Chambers

  • Settling chambers use the force of gravity to remove solid particles.
  • The gas stream enters a chamber where the gas velocity is reduced. Large particles drop out of the gas and are recollected in hoppers. Because settling chambers are effective in removing only larger particles, they are used in conjunction with a more efficient control device.

3. Cyclones

  • The general principle of inertia separation is that the particulate-laden gas is forced to change direction. As gas changes direction, the particles’ inertia causes them to continue in the original direction and be separated from the gas stream.
  • The walls of the cyclone narrow toward the bottom of the unit, allowing the particles to be collected in a hopper.
  • The cleaner air leaves the cyclone through the top of the chamber, flowing upward in a spiral vortex, formed within a downward moving spiral. Cyclones are efficient in removing large particles but are not as efficient with smaller particles. For this reason, they are used with other particulate control devices.

4. Venturi Scrubbers

  • Venturi scrubbers use a liquid stream to remove solid particles. 
  • In the venturi scrubber, gas laden with particulate matter passes through a short tube with flared ends and a constricted middle.
  • This constriction causes the gas stream to speed up when the pressure is increased.
  • The difference in velocity and pressure resulting from the constriction causes the particles and water to mix and combine.
  • The reduced velocity at the expanded section of the throat allows the droplets of water containing the particles to drop out of the gas stream.
  • Venturi scrubbers effectively remove small particles, with removal efficiencies of up to 99 percent.
  • One drawback of this device, however, is the production of wastewater.

5. Electrostatic Precipitators (ESPs)

  • An ESP is a particle control device that uses electrical forces to move the particles out of the flowing gas stream and onto collector plates.
  • The ESP places electrical charges on the particles, causing them to be attracted to oppositely charged metal plates in the precipitator.
  • The particles are removed from the plates by
    apping and collected in a hopper below the unit.
  • The removal efficiencies for ESPs are highly variable; however, the removal efficiency is about 99 percent for very small particles alone.
  • Electrostatic precipitators are not only used in utility applications but also in other industries (for other exhaust gas particles) such as cement (dust), pulp & paper (salt cake & lime dust), petrochemicals (sulfuric acid mist), and steel (dust & fumes).

6. Absorption

  • Removing one or more selected components from a gas mixture by absorption is probably the most important operation in controlling gaseous pollutant emissions.
  • Absorption is when a gaseous pollutant is dissolved in a liquid.
  • As the gas stream passes through the liquid, the liquid absorbs the gas in much the same way sugar is absorbed in a glass of water when stirred.
  • Absorbers are often referred to as scrubbers, and there are various types of absorption equipment.
  • The principal types of gas absorption equipment include spray towers, packed columns, spray chambers, and venturi scrubbers.

In general, absorbers can achieve removal efficiencies greater than 95 percent. One potential problem with absorption is the generation of wastewater, which converts an air pollution problem into a water pollution problem.

7. Adsorption

  • When a gas or vapor is brought into contact with a solid, the solid takes part of it. The molecules that disappear from the gas either enter the inside of the solid or remain on the outside attached to the surface. The former phenomenon is absorption (or dissolution), and the latter is adsorption.
  • The most common industrial adsorbents are activated carbon, silica gel, and alumina because they have enormous surface areas per unit of weight.
  • Activated carbon is the universal standard for purifying and removing trace organic contaminants from liquid and vapor streams.
    Carbon adsorption systems are either regenerative or non-regenerative.
    – Regenerative system usually contains more than one carbon bed. As one bed actively removes pollutants, another bed is regenerated for future use.
    – Non-regenerative systems have thinner beds of activated carbon. In a non-regenerative adsorber, the spent carbon is disposed of when it becomes saturated with the pollutant.

8. Condensation

  • Condensation is the process of converting gas or vapor to liquid. Any gas can be reduced to a liquid by lowering its temperature and increasing its pressure.
  • Condensers are typically used as pretreatment devices. They can be used ahead of absorbers and incinerators to reduce the total gas volume to be treated by more expensive control equipment. Condensers used for pollution control are contact condensers and surface condensers.
  • The gas comes into contact with a cold liquid in a contact condenser.
  • In a surface condenser, the gas contacts a cooled surface in which cooled liquid or gas is circulated, such as the outside of the tube.
  • Depending on design and applications, the removal efficiencies of condensers typically range from 50 percent to more than 95 percent.

9. Incineration

  • Incineration, also known as combustion, is mostly used to control the emissions of organic compounds from process industries.
  • This control technique refers to the rapid oxidation of a substance by combining oxygen with combustible material in the presence of heat.
    The gaseous stream is converted to carbon dioxide and water vapor when combustion is complete.
  • Equipment used to control waste gases by combustion can be divided into three categories:
    – Direct combustion or flaring,
    – Thermal incineration and
    – Catalytic incineration.

Noise Pollution: Sources and Controls

  • A musical clock may be nice to listen to during the day but irritates during sleep at night. Noise, by definition, is “sound without value” or “any noise unwanted by the recipient”.
  • Noise level is measured in terms of decibels (dB). W.H.O. (World Health Organization) has prescribed an optimum noise level of 45 dB by day and 35 dB by night. Anything above 80 dB is hazardous.
  • Noise in industries such as stone cutting and crushing, steel forgings, loudspeakers, shouting by hawkers selling their wares, and movement of heavy transport vehicles, railways, and airports leads to irritation and increased blood pressure, loss of temper, decrease in work efficiency, loss of hearing which may be first temporary but can become permanent in the noise stress continues.

Sources of some noises and their intensity


Sources of noise pollution

  • Noise pollution is a growing problem. All human activities contribute to noise pollution to a varying extent. Sources of noise pollution are many and may be located indoors or outdoors.
  • Indoor sources include noise produced by radio, television, generators, electric fans, air coolers, air conditioners, different home appliances, and family conflict.
  • Outdoor sources of noise pollution include indiscriminate use of loudspeakers, industrial activities, automobiles, rail traffic, airplanes, and activities such as those at market place, religious, social, and cultural functions, sports, and political rallies.

Prevention and control of noise pollution

The following steps can be taken to control or minimize noise pollution-

  • Road traffic noise can be reduced by better design and proper maintenance of vehicles.
  • Noise abatement measures include creating noise mounds, noise attenuation walls, well-maintained roads and smooth surfacing of roads.
  • Retrofitting of locomotives continuously welded rail track, use of electric locomotives or deployment of quieter rolling stock will reduce noises emanating from trains.
  • Air traffic noise can be reduced by appropriate insulation and introducing noise regulations for the take-off and landing of aircraft at the airport.
  • Industrial noises can be reduced by soundproofing equipment like generators and areas producing a lot of noise.
  • Power tools, loud music, land movers, public functions using loudspeakers, etc., should not be permitted at night. The use of horns, alarms, refrigeration units, etc., is to be restricted. The use of noisy firecrackers that cause air pollution should be restricted.
  • A green belt of trees is an efficient noise absorber.

Adverse Effects of Air and Noise Pollution

Air and noise pollution impacts the environment in various aspects. Due to air pollution in the environment, the quality of air decreases and many people affects by a health issue. Poor air quality may cause respiratory problems, neuropsychiatric problems, cardiovascular problems and other complications in the body.

Noise pollution causes due to unwanted noise in the surrounding environment. Unwanted noise can be classified as not bearable for a specific person. The high sound intensity in the surrounding environment can cause heart attack problems and other human diseases.

How to Reduce Air and Noise Pollution

To reduce air and noise pollution, it is required to reduce the air and noise pollution causing pollutants in the surrounding environment. To reduce air pollution, we need to control the waste gases produced by the various industries in the environment, or we can also refine the waste gases produced.
To reduce noise pollution, we can control the different activities that cause much sound in the environment. For example, a person can use earphones while listening to songs. Sound intensity is measured in terms of the decibel unit. The government has regulated the limit of sound intensity for different public places.

Causes of Air and Noise Pollution

Air and noise pollution can be caused by various reasons. Pollutants can cause air pollution in the surrounding environment. These can be suspended in solid forms or in gaseous forms. And it is broadly classified into primary air pollutants and secondary air pollutants. Some common air pollutants are CO2, CO, NO2, NO, NO3, SO2, etc.

The high-intensity sound in the surrounding environment can cause noise pollution. It can be generated by various sources like road traffic, instrument sound, industrial noise, etc. Prevention of noise pollution can be done by controlling these sources of sound.

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