HSBTE. Environmental Science (EVS). Air Pollution: Source of air pollution, effects of Air Pollution on human health, Economy, air pollution control method. Unit-II

AIR POLLUTION

The presence of particles, gases, and chemicals in the air harmful to humans, animals, and vegetation is called air pollution. Substances that cause air pollution are called air pollutants.

Sources of air pollution: Sources of air pollution are fossil fuels and industries. Burning of fossil fuels releases several harmful gases. Industries also release several harmful gases and particulate matter into the air. There are three types of air pollution sources. These are stationary sources, mobile sources, and area sources.

• 1. Stationary sources (point sources): They add air pollutants into the air from a particular point. Most of the time their effects remain in limited areas. Ex. Chimney of industries.

• 2. Mobile sources (Line sources): They add air pollutants into the air over a long distance in a continuous line. For example, automobiles, smoking during walking, etc.

• 3. Area sources: A particular area generates air pollutants. Such as cities, towns, etc.

Air pollutants can also be divided into the following two groups

• 1. Primary air pollutants: Air pollutants directly from pollution sources are called primary pollutants.

• 2. Secondary air pollutants: Air pollutants develop by reaction between two or more primary pollutants are called secondary pollutants.

Source of individual air pollutants

1. Gasses: There are five primary air pollutants in gaseous form. These are

• a. Oxides of carbon: Such as carbon dioxide and carbon monoxide. Sources are Fuel burning in houses, industries, automobiles, and thermal power plants. Cigarette Smoking.

• b. Oxides of nitrogen: Such as Nitrogen monoxide and nitrogen dioxide. Sources are automobiles, chemical industries, and electric thundering.

• c. Oxides of sulfur: Such as sulphur dioxide and Sulphur trioxide. Sources are the burning of coal and oil in industries, thermal power plants, houses to cook food,

• d. Volatile organic compounds: Such as petroleum gases (hydrocarbons). Methane (marsh gas) and ethylene are the main air pollutants. Sources are automobiles and crop decomposition.

• e. Photochemical oxidants: Such as ozone, smog, aldehydes, and peroxyacetyl nitrate. Oxidation of nitrogen oxides and hydrocarbons in the air in the presence of sunlight form photochemical oxidants.

Ozone is formed by photochemical reactions in the atmosphere.

Smog is a condensation product of dust, vapor, and smoke particles in the air.

1. Particulate matters: It includes dust, mists, aerosols, pollen grains, and microbes. Sources are stone crushing, grinding, mixing, drilling, blasting, automobiles, industries, etc.

• a. Dust consists of asbestos fibers, stone fines, crop fibers, etc.

• b. Aerosols include chlorofluorocarbon (CFC), nitrogen, tobacco smoke, etc.

• c. Pollen grains from plants.

• d. Microbes spores, cysts, and active microbes in the air.

2. Radioactive elements: Sources are nuclear explosions and war explosions.

EFFECTS OF AIR POLLUTION ON HUMAN HEALTH

There are three types of air pollutants: Gases, Particulate materials, and Radioactive elements.

1. Gases: There are five primary air pollutants in gaseous form. These are

a. Oxides of carbon: Such as carbon dioxide and carbon monooxide:

• Carbon dioxide causes a greenhouse effect that causes a rise in atmospheric temperature. It also causes nausea and headache.

• Carbon monoxide is a poisonous gas. It combines with hemoglobin which decreases the oxygen-carrying capacity of haemoglobin. That will lead to laziness, reduced vision, nervous disorder, cardiovascular disorder, and death.

b. Oxides of nitrogen: Such as Nitrogen monoxide and nitrogen dioxide.

• Nitrogen monoxide (effects are similar to CO) combines with hemoglobin which decreases the oxygen-carrying capacity of hemoglobin. That will lead to laziness, reduced vision, nervous disorder, cardiovascular disorder, and death.

• Nitrogen dioxide with water vapor form nitric acid. It irritates the eyes, nose, respiratory tract, and lungs. It is toxic to the lungs, kidneys, and liver. It can cause death.

c. Oxides of sulfur: Such as sulphur dioxide and Sulphur trioxide.

• Sulfur oxides irritate the respiratory tract and may cause bronchitis and asthma. Sulfur dioxide with water vapor forms sulfurous acid. Sulfur trioxide with water vapor forms sulphuric acid. Both acids irritate the eyes, nose, and throat.

d. Volatile organic compounds: Such as petroleum gases (hydrocarbons). Methane (marsh gas) and ethylene are the main air pollutants.

• Hydrocarbons irritate the eyes, nose, and respiratory tract. They increase aging and also develop secondary pollutants.

e. Photochemical oxidants: Such as ozone, smog, aldehydes, and peroxyacyl nitrate.

• Ozone in low concentration causes chest pain, coughing, and eye irritation. In high concentrations it causes death.

• Smog decreases visibility which causes accidents on the road. It produces toxic effects on the respiratory system.

• Aldehydes cause gastric irritation and respiratory irritation.

2. Particulate matter: It includes dust, mists, aerosols, pollen grains, and microbes.

• a. Dust consists of asbestos fibers, stone fines, crop fibers, etc. These all create respiratory problems. Automobile exhausts also emit particulate matter such as lead, carbon, etc that cause dizziness, insomnia, anemia, weakness, headache, loss of appetite, etc.

• b. Aerosols include chlorofluorocarbon (CFC), nitrogen, tobacco smoke, etc. These aerosols decrease ozone layer thickness which increases UV radiation in air. UV radiation causes sunburn, and the inactivation of RNA, and DNA proteins.

• c. Pollen grains cause allergies and respiratory problems

• d. Microbes spores, cysts, and active microbes in the air cause several systemic infections.

2. Radioactive elements: They are very harmful and kill cells and cause the death of humans.

AIR POLLUTION CONTROL METHODS

Human being lifestyles generate air pollution through vehicles and industries. Nature also generates air pollution. But nature itself cleans air by dispersing these pollutants through high wind. Human-generated air pollutions are controlled by using the following methods.

1. Separation of Gaseous pollutants: Gaseous pollutants are removed from the air by using the following techniques:

• a. Plantation: Trees absorb carbon dioxide from the atmosphere to release oxygen. Some small plants are very useful to absorb gaseous pollutants from air. Such as fern, aloe vera, snake plants, lilies, palm trees, etc.

• b. Combustion: Oxidisable pollutants are burnt at high temperatures at their source. This technique is especially used in petrochemical industries, paint industries, fertilizer industries, etc.

• c. Absorption: Calcium hydroxide or bed of lime, is used to absorb gaseous pollutants at the source of pollution. They are used as filter bed that absorbs gaseous pollutants. A fine spray of water easily dissolves nitrogen oxide, ammonia, and sulfur dioxide. Water is also used to absorb gaseous pollutant source.

• d. Adsorption: Very fine solid particles of activated charcoal are used to adsorb gaseous pollutants at their source. They are especially useful to remove toxic gases, inflammable compounds, vapors, etc.

• e. Catalytic convertor: It is used to reduce gaseous pollutants from automobile exhaust. It converts unburnt fuel gas from carbon dioxide and water. It also converts carbon monoxide to carbon dioxide; and nitric acid to nitrogen.

• f. Chimney: Industries release gaseous pollutants into the air through tall chimneys. This reduces gaseous pollution on the ground level.

2. Pollution emission restriction: Pollution emissions from their sources can be reduced by using the following measures.

• a. To minimize the use of automobiles,

• b. To use pollution-free fuel in automobile

• c. To promote LPG as fuel in-house,

• d. To promote electrification of railways,

• e. To control population growth,

• f. To use incinerator as ritual,

• g. To avoid nuclear explosions and wars,

• h. To generate energy without combustion of fuel,

• i. To locate industries far away from human habitat,

NOISE POLLUTION

Loud or unwanted sound is called noise. Normally sound level above 80 dB (decibel) is called noise.

Noise with harmful effects on the environment is called noise pollution.

Source of noise pollution: The main sources of noise pollution are industries, automobiles, agriculture machines, entertainment equipment, household gadgets, music concerts, brass bands, demonstrations, public addressing systems (loudspeakers), and defense equipment.

Unit of Noise: The unit of sound is decibel. One decibel is equal to one-tenth of a bel.

Effect of noise pollution: It mainly affects the general health and hearing ability of human beings. It develops psychological and physiological problems in human beings.

1. Hearing ability: Noise affects the hearing ability of human beings in the following manners

• a. Sudden sound above 150 dB may damage the tympanic membrane (ear drum) or disturb the ossicle bone in the ear. There may be permanent loss of hearing ability. Sudden bomb explosion,

• b. Long exposure to noise from 80 dB to 100 dB may damage the sensory cells of hearing. This may cause permanent loss of hearing ability.

• c. Prolonged exposure to noise in city, industry, etc may cause loss of ability to hear a whisper or soft voice. This loss of hearing ability increases gradually. That may lead to deafness.

2. General health: Prolong noise pollution produces the following effects on the general health of human beings

• a. Stress and anxiety that may lead to fear and shock.

• b. Emotional disturbance, insomnia, and sleeplessness,

• c. Psychomotor performance impairment,

• d. Altered breathing and GIT spasm,

• e. Headache with brain blood vessel dilation

• f. Increase in heart rate, blood pressure, and blood cholesterol,

• g. Damage to heart, brain and liver, even heart failure,

• h. Eye strain with pupil dilation, defective sight vision, and color blindness,

• i. Retarded growth of nervous system of unborn baby,

• j. In some cases decrease in heart rate,

Acceptable noise level: Sound above 100 dB becomes uncomfortable for the human ear. In India, the National Pollution Control Board recommends maximum permissible sound level below

• 1. Industries: 70 decibels in day time and 60 decibels in night

• 2. Silence zones such as hospitals, educational institutions, and worship places: 40 decibels in the daytime and 30 decibels at night.

• 3. Commercial place: 60 decibels in day time and 50 decibels in night

• 4. Residential area: 50 decibels in day time and 40 decibels in night

Different methods of minimizing noise pollution: The following measures are adopted to minimize noise pollution.

• · Noise-producing area is divided into four zones. These are industrial zones, commercial zones, residential zones, and silence zones. All zones are collectively called acoustic zones. These zones should be strictly followed. It will minimize the harmful effects of noise pollution.

• · All the zones should be located away from each other.

• · Maintain a silence zone (horn-free zone) around educational institutions, hospitals, meditation centers,

• · Maintain loudspeaker or DJ volume, sound volume under a restricted level and for a limited period of time,

• · Restriction of crackers sound level

• · Plantation on roadside lanes and in residential areas helps to minimize noise pollution from motor vehicles,

• · Use of silencers in motor vehicles.

• · Use a sound-proof chamber for noisy machines,

• · Insulating covering over noisy machine or machine parts,

• · Use proper lubrication for machinery parts.

• · Installation of the silent machine to replace the noisy machine,

• · Use of earplugs by persons working near a noisy area

• · Use a sound absorber or sound deflector

• · Use of construction materials to control sound such as acoustic tiles on walls, rough cement coating over walls, rubber plastic foam on ceiling and floor, wooden work on wall, and floor, thick Teflon glass on doors, etc make a soundproof room or soundproof buildings.

• · Enforcement of environmental laws strictly.Such as the environment act, water (prevention and control) act, Air (prevention and control) act, insecticide act, etc.

Dr Pramila Singh