List of paragraphs on article pollution :- 1. Introduction to Air Pollution 2. Biological Indicators for Air Pollution 3. Composition of Atmospheric Air 4. Causes of Air Pollution 5. Sources of Air Pollution 6. Effects of Air Pollutants 7. Air Pollution Control Strategies and Devices 8. Biotechnology for Air Pollution Abatement and Odour Control 9. Methods of Controlling Air Pollution 10. General Impact of Air-Pollution.
- Introduction to Air Pollution
- Biological Indicators for Air Pollution
- Composition of Atmospheric Air
- Causes of Air Pollution
- Sources of Air Pollution
- Effects of Air Pollutants
- Air Pollution Control Strategies and Devices
- Biotechnology for Air Pollution Abatement and Odour Control
- Methods of Controlling Air Pollution
- General Impact of Air-Pollution
Paragraph # 1. Introduction to Air Pollution:
Air pollution is considered to be one of the most dangerous and common type of environmental pollution that has been reported in most industrial towns and metropolitans of abroad and India such as New York, London, Tokyo, Mumbai, Delhi, Kolkata, Chennai, Jaipur, Hyderabad, Nagpur, Ahmedabad, Kanpur etc.
One can live without clean air for only two minutes! A clean air is defined as the air occurring in areas sufficiently distant from places of human activities and other abnormal influences. Air Pollution has become one of the vital and serious environmental problems of the modern society.
Air pollution refers to the undesirable change occurring in air causing harmful effects on man, domestic species, flora etc.
WHO defines air pollution as “limited to situations in which the output ambient atmosphere contains material in concentration which are harmful to man and his environment”.
Air pollution is generally disequilibrium condition of air caused due to the introduction of foreign elements from natural and anthropogenic (man-made) sources to the air so that it becomes deleterious or injurious to biological communities.
Precisely, air pollution can be defined as “the imbalance in quality of air so as to cause adverse effects on the living beings existing on earth”.
Air pollution may broadly be defined as the presence of one or more contaminants like dust, smoke, mist, and odour in the atmosphere which are injurious to human beings, plants and animals.
Normally, we breathe 22,000 times a day inhaling approximately 16 kg of air. It is, therefore, essential that we must know enough about the air around us and the means to keep it clean.
Sinks of Atmospheric Gases:
Sink is a medium, which is capable of retaining and interacting with a long-lived pollutant, though not necessarily indefinitely. Oceans as well as vegetation are the most important sinks for most atmospheric gases. For example, SO2, CO2, O2 find oceans as the ready sink. Vegetations (plants) are important sinks of CO2, N2 and O2. Limestone acts as the sink for atmospheric acid, which fixes the sulphate as part of the wall composition-
Paragraph # 2. Biological Indicators for Air Pollution:
Indication means “pointing out”. Biological indication or bioindication is defined as the use of living matter as qualitative measures of the environmental status.
Bioindicators can be classified into two main categories:
(a) Indicators, and
Indicators are also called ‘ecological indicator species’ and accumulators ‘chemical monitoring species’ or collector organisms. At times, some organisms may act as both indicator and an accumulator for a specific pollutant. But the organisms may be different in their usefulness; a good indicator, sometimes, is not a good accumulator, and vice versa. Both animals and plants are sensitive to air pollutants.
Woodiwiss (1964) reported that the disappearance of following macro-invertebrates indicate the pollution level:
Some plants are especially sensitive to air pollutants and these develop toxic symptoms as a result of exposure to specific pollutant (Table 4.8). These might be used to identify in general terms the pollutants in prevalence. Because of their non- specificity in response, it is often preferred to have a specifically sensitive species, that might be able to perform the function of signalling whenever the atmosphere levels of the air pollutants in question exceeds the normal limits.
In Table 4.9 are identified some plant species that serve as indicators of exposure to some air pollutants.
Moreover, lichens and mosses serve as excellent accumulators of a wide range of pollutants in the environment.
The study of smell (odour) is termed ‘osmics’ and an odourous substance is called an ‘osmogen’. The odourous materials are usually volatile, losing molecules to the atmosphere continuously.
The production of odours by chemical substances seems to be mainly confined to thermo-volatile organics.
There are two main sources of odourous pollution:
(1) Natural sources
(2) Anthropogenic sources (Man-made sources)
The important natural sources and types of odour emitted are:
i. Bluegreen algae viz. Anabaena circinalis → Earthy odours
ii. Synura petersenii (algae) → Fishy and cucumber-like odours
iii. Trichoderma viridae (fungus) → Coconut-like odour
Several other microbial species also emit different odours.
Volatile organics and unsaturated molecules of various industrial chemicals escaping into the atmosphere are also responsible for malodorous air. Various industrial operations emit different kinds of odourous substances or liberate products that emit malodours.
Table 4.10 gives a list of such industries and their odourous by-product or wastes:
The odour concentration at a point is dependent on several factors such as its distance from the height of the emission source, odour emission rate, air velocity and directions. Some typical pollutants, their odours and the odour thresholds are given in Table 4.11. The threshold concentration of odourous pollutant is the concentration at which its presence in air is not perceived by the human nose.
In general, children are considered to be more tolerant to malodours than adults. The problem due to odorants is more aesthetic than economical. The health effects of odours are extremely hard to quantify as such but exposure to odorants, in general, causes nausea and appetite loss. Continued exposure may result in the loss of sense of smell.
Paragraph # 3. Composition of Atmospheric Air:
The atmospheric air mainly consists of oxygen and nitrogen with traces of carbon dioxide, helium, argon, neon, krypton, nitrous oxide, etc. The normal composition of the atmospheric air is as shown in Table 23.1.
The air in the purer regions like above the sea or mountains may contain 20.999 percent of oxygen, whereas in the overcrowded halls it may be as low as 20.65 percent.
The factors contributing carbon dioxide to the atmosphere are combustion, putrefaction, fermentation, and respiratory processes of animal life. The quantity of carbon dioxide is reduced by vegetation, rain and high winds.
The increase in the content of carbon dioxide in the atmosphere leads to various adverse effects. If the content of carbon dioxide increases to 1.5 percent it causes nausea, depression and headache, and if it increases to 2.5 percent the candle will be extinguished. Further the presence of carbon dioxide to the extent of 5 percent leads to fatal accidents.
Paragraph # 4. Causes of Air Pollution:
The main sources of air pollution are the industries, agriculture and traffic, as well as energy generation. During combustion processes and other production processes air pollutants are emitted. Some of these substances are not directly damaging to air quality, but will form harmful air pollutants by reactions with other substances that are present in air.
Examples of large-scale air pollutants are VOC (Volatile Organic Compounds) and small dust particles. When large concentrations of these substances are emitted this negatively affects ecosystems, materials and public health.
Emissions of nitrous oxide (N2O) mainly stem from agriculture, because nitrogen in soils can easily be denitrified by bacteria. Nitrous oxide is emitted during the denitrification process. Additionally, the application of (artificial) fertilizers causes emissions of ammonia (NHa), nitrogen oxides (NOx) and methane (CH4), a greenhouse gas. The agricultural sector is known for its extensive use of pesticides. This application causes emissions of many toxic chemicals.
Industrial processes vary greatly and as a result there are many different chemical wastes. The industries are responsible for emissions of carbon monoxide, carbon dioxide, sulphur dioxide, nitrogen oxides, small dust particles, VOC, methane, ammonia and radioactive radiation.
During energy generation chemicals such as methane are released into the air as a result of oil and natural gas extraction. The combustion of coal and natural gas for electricity production causes the release of sulphur dioxide, nitrogen oxides and carbon dioxide into the air.
Traffic is held responsible for one-third of the greenhouse gas emissions. Emissions caused by traffic are mainly those of carbon dioxide, carbon monoxide, nitrogen oxides, VOC and small dust particles.
Consumers are also partly responsible for air pollution. Firstly because the products they use have caused air pollution during their production and distribution and secondly because heating of houses and offices causes chemicals release into the air.
When people use paints or cosmetics VOC is released and perspiration, pet fertilizer use and cleanser use cause ammonia emissions. Last but not least, many chemicals (carbon dioxide, carbon mono-oxide) are emitted during smoking.
Paragraph # 5. Sources of Air Pollution:
The various sources producing air pollutants and thus contributing to the pollution of the atmospheric air may be grouped in the following two categories:
(1) Natural sources of air pollution
(2) Man-made sources of air pollution
(1) Natural Sources of Air Pollution:
The natural sources of air pollution produce air pollutants of natural origin.
The following are the natural sources of air pollution and the resulting air pollutants:
(i) Products from Atmospheric Reactions:
In the lower atmosphere, the natural chemical reactions such as oxidation, combination, condensation or polymerization lead to the conversion of gases or vapours into solid and liquid products. In the upper atmosphere, the photo-chemical reactions may break down more complex molecules by absorption of high energy ultraviolet solar radiation. The products resulting from these atmospheric reactions may lead to the air pollution.
Aerosols are finely divided solid or liquid particles of microscopic size held suspended and dispersed in a gas or in atmosphere, such as water droplets in the case of mist, fog and haze, liquid and/or solid particles in smoke, dust, salt particles from sea water, dust of meteoric origin, etc. The liquid particles are spherical in shape but the solid particles exist in the forms of spheres, filaments and various irregular shapes.
In general particulates include all atmospheric substances that are not gases, and they can be suspended droplets or solid particles or a mixture of the two. The term aerosol is used to represent the particulate matter as long as it is held suspended in the atmospheric air.
Thus a particulate matter is an air pollutant only when it is an aerosol. However, a particulate matter is nuisance both as an aerosol causing visibility reduction and as settled or deposited matter resulting in soiling of surfaces, corrosion, etc.
The term aerosol is also applied to a colloidal system of dispersed phase and dispersing medium together (in which dispersed phase is solid or liquid particles and dispersing medium is a gas), while particles alone are called ‘aerosol particles’.
Aerosols differ widely in terms of particle size, particle density and their importance as pollutants. Their diameters generally range from 0.1 μ or less, up to about 100 μ.
The various types of aerosols are:
(e) Paze and
These consist of viable particles in the form of algae, fungi, bacteria, yeasts, rusts, moulds, spores, etc. All these micro-organisms except algae can be transported by wind to great distances and they can infect plants animals and human beings.
Pollens are the small grains from the anthers of flowers which may cause allergic reactions in sensitive human bodies and hence these are known as aero-allergens. They enter the atmosphere from trees, grasses and weeds and are transported from one place to the other by the wind currents. While most of the pollen grains range between 10 and 50 μ in size, some are found to be as small as 5 and as large as 100 μ in size.
The pollens may cause asthma and hay fever. While most victims have an uncomplicated type of hay fever in which the symptoms disappear at the end of the pollen season, some develop bronchitis, bronchial asthma and dermatitis. The asthma patients are quite allergic to some of the pollens such as pollens of parthenium plants, grass pollens, and pollens of cassia species.
(v) Radioactive Minerals:
The radioactivity of the atmosphere may be caused by the radioactive minerals in the crust of earth and the action of cosmic rays from outer space on the gaseous constituents of the atmosphere.
(vi) Volcanic Ash and Gases:
The ash and gases such as hydrogen sulphide and hydrogen fluoride emitted from volcanoes lead to air pollution.
(vii) Gases and Odour:
Gases and odour emitted from swamps and marshy lands lead to air pollution.
(2) Man-Made Sources of Air Pollution:
The man-made sources of air pollution produce air pollutants resulting from man’s activities.
The following are the man-made sources of air pollution and the resulting air pollutants:
(i) Combustion of Fuels:
The burning of fuels like oil, coal, etc., in industrial plants, locomotives, furnaces, hearths and domestic ovens leads to the formation of undesirable gases such as carbon dioxide (CO2), sulphur dioxide (SO2), nitrous oxide (NO2), etc., which accumulate in the atmosphere.
The incomplete combustion of coal, fire wood etc., leads to the production of smoke which consists of a mixture of finely divided carbon particles, carbon monoxide (CO), carbon dioxide (CO2), etc. Smoke is produced from steam locomotives, coke oven plant, brick kilns, fire wood and other domestic fuel and from various industrial units.
The various industrial activities like non-ferrous metal smelting and refining, iron and steel manufacturing, oil refining, chemical producing factories, pulp and paper industries, cement plants, fertilizer plants, etc., develop serious air pollution problems in the areas where they are located. The undesirable gases such as carbon dioxide (CO2), sulphur dioxide (SO2), nitrous oxide (NO2), ammonia (NH3), carbon monoxide (CO), acid vapours, frames, etc., are produced which accumulate in the atmosphere.
A considerable amount of dust is also generated by handling, crushing, grinding and decrepitation of organic and inorganic materials such a rock, ore, metal, coal, wood, etc. The dust finds its way into the atmosphere in floating condition.
(iii) Thermal Power Plants:
The thermal power plants are the main contributors of sulphur dioxide (SO2) to the atmosphere.
The exhaust from the automobiles contains carbon monoxide (CO), methane, hydrogen, unburnt carbon and products of incomplete combustion. Due to increased use of automobiles in the urban areas it has become a great source of air pollution in the congested cities and towns of our country.
(v) Agricultural Activities:
The agricultural activities such as crop spraying and field burning may result in various substances such as organic phosphates, chlorinated hydrocarbons, arsenic, lead, etc., as well as dust and smoke entering the atmosphere.
(vi) Nuclear Power Plants:
These may emit various radioactive substances which may enter the atmosphere.
Table 23.2 indicates the various man-made source of air pollution and the air pollutants produced by each of these sources.
Classification of Man-Made Sources of Air Pollution:
The man-made sources of air pollution may be classified as:
(i) Stationary sources and
(ii) Mobile sources.
The stationary sources of air pollution may be further classified as:
(a) Large stationary sources and
(b) Small stationary sources.
The large stationary sources of air pollution include industrial processing units, power plants, combustion of fuels such as coal oil and gas for industrial purposes, solid waste disposal through municipal incinerators or open burning, etc.
The small stationary sources of air pollution include residential heating using coal, gas and oil, institutional and commercial heating using coal, oil and gas, on site incineration, open burning, evaporative losses, etc.
The mobile sources of air pollution may be further classified as:
(a) Mobile sources with definite routes, and
(b) Mobile sources with indefinite routes.
The mobile sources of air pollution with definite routes include highway vehicles, railroad locomotives, and channel vessels.
The mobile sources of air pollution with indefinite routes include light, medium and heavy duty motor vehicles, railyard locomotives, port vessels, air crafts at airports, etc.
The man-made sources of air pollution may also be classified as:
(i) Point sources,
(ii) Area sources and
(iii) Line sources.
Area sources of air pollution include the various small stationary sources of air pollution and the mobile sources of air pollution with indefinite routes.
Line sources of air pollution includes the various mobile sources of air pollution with definite routes.
An inventory of the various man-made sources of air pollution mentioned above is given below for reference.
Paragraph # 6. Effects of Air Pollutants:
a. Carbon Monoxide:
CO has got 200 times more affinity for haemoglobin than CO2 Due to this property it combines with haemoglobin giving rise to carboxyhaemoglobin which is an irreversible change. The symptoms of this are headache, nausea, exhaustion, muscular weakness and psychomotor disturbance etc. Excessive formation of carboxyhaemoglobin can lead to death due to CO poisoning.
Suspended particulate matter when enters the respiratory system causes bronchitis, asthma and also cardiovascular problem. SPM is the most dangerous pollutant as every year it causes maximum deaths which are due to pollution.
c. Nitrous Oxide:
It causes lung oedema, blood congestion, eye irritation etc. It also acts as mutagens.
d. Sulphur Dioxide:
It causes emphysema, bronchitis and asthma.
It causes respiratory disorders.
It damage the spleen, liver, lungs and kidney.
g. Acid Rain:
It causes damage to heritage monuments. The best known example of this is Taj Mahal of Agra. It also reduces the pH of water bodies which damages the aquatic life.
Paragraph # 7. Air Pollution Control Strategies and Devices:
Pollution control is a term used in environmental science and engineering. It means the control effluents into air, water or soil. Without pollution controls the undesirable waste products from human consumption, industrial and agricultural activities, mining, transportation and other sources will accumulate or disperse and degrade the natural environment. In this regard, pollution prevention and waste minimization are more desirable than pollution control.
(A) Dust collection systems:
These are designed to handle dust loads. A dust collector consists of a blower, dust filter, a filter-cleaning system, and a dust removal system.
Cyclonic separation is a method of removing particulates from air without the use of filters through vortese separation. Rotational effects and gravity are used to complete the method.
In this method, a high speed rotating air-flow is required within a cylindrical container called a cyclone. Air flows in a spiral pattern, beginning at the top (wide end) of the cyclone and ending at the bottom (narrow end) and exit from the top. Larger particles or group of smaller particles in the, rotating air stream have too much inertia to follow the light curve of the air stream and strike the outside wall, falling then to the bottom of the cyclone where they can be collected and removed.
Cyclones are used in saw mills to remove sawdust from extracted air. Cyclones are also used in refineries to separate oils and gases and in the cement industry as components of kiln preheaters.
Analogous devices for separating particles (or solids) from liquids are called hydrocyclones.
2. Electrostatic precipitators:
An electrostatic precipitator (ESP), or electrostatic air cleaner is a particulate collection device that removes particles form a flowing gas (such as air) using the force of an induced electrostatic charge. Electrostatic precipitators are highly efficient filtration devices that minimally impede the flow of gases through the device, and can easily remove fine particulate matter such as dust and smoke from the air stream.
3. Baghouses (Fabric Collectors):
Fabric collectors are used to separate dust particulates from dusty gases. They are one of the most efficient and cost effective types of dust collectors available and can achieve a collection efficiently of more than 90% very fine particulates.
Dust-laden gases enter the baghouse and pass through fabric bags that act as filters. The bags can be of woven cotton, synthetic, or glass-material in a bag shape. The dust cake formed on the surfaces of the bags. Because the fabric provides a surface on which dust particulates collected.
Sulphur oxides, nitrogen oxides, carbon monoxides, hydrogen sulphides, hydrocarbons and particulate matter are the major components of air pollution and are responsible for health and environmental hazards. Equally important are the substances that cause unpleasant/offensive odour.
A range of malodorous substances, including phenol, styrene, trichloroethane (TCE), volatile organic compounds (VOCs), amines, hydrogen sulphide, mercaptans and ammonia, are present in gaseous effluents of various industries, treatment plants, animal rendering activities, etc. Deodourisation technology makes use of physical, chemical and biological means for odour removal. Biodeodourisation, though applied since 1923, is relatively less studied and less applied. Its importance and application is, however, increasing.
Increase in environmental awareness has resulted in an increasing attention of the people to pollution problems. Offensive odour from pollution is easily sensed and regulations obviously target this aspect, leading to the development of deodourisation technology. A number of industries produce offensive waste gases. These include pesticide, petrochemical, explosive, mining, meat processing, paints and varnishes, textile, chemical, pharmaceutical, animal rendering, and fermentation industries.
The sources of malodorous substances are many and they may originate:
1. During the production process.
2. From storage areas.
3. From pumps and compressors which leak.
4. During transfer of material.
5. From open waste-water treatment plants and garbage composting plants.
Abatement of these odours is difficult because:
1. A number of different compounds are often involved.
2. Odour producing compounds may be present in very low concentrations—some mercaptans, for example, have an odour threshold of below 1 ppb.
3. Sources are often complex, multi-point and difficult to accurately trace.
4. Odours that escape from transfer, filtration and drying operations are more difficult to contain.
Preventive as well as corrective methods are useful for control of odour. In the first category, process modification and equipment modification can be included, while processes of corrective nature are roughly classified into physical, chemical and biological methods. Dispersion, water washing, adsorption, thermal incineration and catalytic incineration are amongst the dominant physical methods, while chemical methods include catalytic oxidation. Physical and chemical methods, in general, are not flexible for volume, concentrations, or composition of gas changes that may occur.
This can be overcome by biological methods. Biological processes earlier required skilled control and large space, but recent developments have overcome some of these restrictions. These processes are now characterised by low running costs (one-third of other processes), easy operation/maintenance and control, and low energy intensity. There are five types of biological waste gas purification systems in operation—bioscrubbers, biofilters biobeds, trickling filters, biotrickling filters.
Applications of biological processes depend on physical and microbiological phenomena. While the former include: mass transfer between gas and liquid phase; mass transfer to micro-organisms; and average residence time of mobile phase; microbiological phenomena are dependent on rate of degradation; substrate/product inhibition; diauxy, etc. There is a lot in literature on laboratory experiments and successful field applications. Although biological deodourisation is considered to be an effective tool, applications are relatively limited.
Biologically active materials, like peat, compost, humus, woody heather, bushwood carrying micro-organisms, activated sludge of effluent treatment units or mixture of organisms, or a single organism immobilised as a biofilm on an inert material or in suspended form, are used in biological oxidation of gases. In the biological deodourisation process, target molecules are decomposed by micro-organisms, but the deodourisation mechanism is not clear in many cases.
Paragraph # 9. Methods of Controlling Air Pollution:
There are following four methods of controlling air pollution:
(1) Control of air pollution by zoning
(2) Dilution of source discharge by use of tall stacks
(3) Control by using source correction methods
(4) Reduction of pollutant discharge at source by use of controlling equipment
(1) Control of Air Pollution by Zoning:
Air pollution can be effectively controlled by adopting the zoning system at the planning stage itself. If zoning is properly done, it results in considerable improvement of health of the community as a whole. It prevents the invasion of undesirable industries on the residential areas. Thus the harmful gases and odours are prevented from entering or attacking the residential area.
One of the best systems of zoning is exclusive zoning system which provides for compatible uses for each zone, excluding other uses. In this system a separate zone or area is set aside for industries known as industrial zone or industrial area, thereby reducing the ill effect of air pollution on urban dwellers.
By proper zoning, the city should be planned in such a way that residential areas and heavy industries are not located too close to each other. This is achieved by providing a green belt between the industries and the township.
Zoning for industrial areas is based on two considerations:
(i) Functional requirements, and
(ii) Performance characteristics.
The Functional requirements of industries include inter-industries linkage, railway sidings, land traffic generation utilities, groupings, etc. The performance characteristics of industries include obnoxious and hazardous character of the industry, industrial nuisances such as dust, smoke odour, heat, fire, hazardous gases, noise, etc. Separate areas must be earmarked according to their performances so that neat industries are placed away from obnoxious industries.
In India zoning system varies from city to city. For example, in the industrial estate of Bangalore, only three zones are provided for light, medium and large industries.
On the other hand Bombay plan has listed four zones:
(i) Small repairing and light manufacturing units, permissible in residential areas,
(ii) Service industrial zone,
(iii) Special industrial zone, and
(iv) General industrial zone.
(2) Dilution of Source Discharge by Use of Tall Stacks:
The atmosphere, like natural streams or rivers, possesses self-cleansing properties, which continuously clean and remove the pollutants from the atmosphere under natural conditions, provided the pollutants are discharged in the atmosphere judiciously so that effective dispersion takes place.
If the pollutants are carried away to some distance or taken to high attitudes, they are reduced in concentration by diffusion and dilution. The pollutants are taken to high altitudes through tall stacks or chimneys. The height of the stack or chimney should be such that the maximum ground level concentration is within the permissible limits.
(3) Control by Using Source Correction Methods:
This method is known as ‘air pollution prevention at source’, and just as prevention is better than cure, this method is quite effective in the control of air pollution.
By this method air pollution can be achieved through:
(a) Change in raw materials,
(b) Process modification, and
(c) Equipment modification or replacement.
(a) Change in Raw Materials:
If one type of raw material, currently in use, results in air pollution problem, while a substitute material, which may be of purer grade, does not, the substitution would be more desirable. A typical example in this context is the use of low-sulphur fuel in place of high-sulphur fuel.
In some cases the raw material may contain certain ingredient which is not essential for the process but which contributes to pollution – the non-essential ingredient should be removed through prior processing so that pollution is minimized.
(b) Process Modification:
The emission of air pollutants can sometimes be reduced by adopting modified or new processes. A typical example is the use of exhaust hoods and ducts over several types of industrial ovens, which have not only reduced pollutants but have also resulted in the recovery of valuable solvents that otherwise would have become air pollutants. Similarly volatile substances can be recovered by condensation and the non-condensable gases can be recycled for additional reactions.
Another example of process modification is in petroleum refinery where hydrogen sulphide gas produced was earlier passed to the flare system and burnt which resulted in SO2 emission to the atmosphere, but now a process is used in the refinery that yields elemental sulphur as a refinery by-product besides preventing the problem of air pollution.
(c) Equipment Modification or Replacement:
Old equipment which contribute to greater degree of air pollution may be modified or completely replaced. For example in steel industry replacing the open-hearth furnaces with basic oxygen furnaces results in lesser pollution problems. In many cases new types of equipment are less prone to pollution problems.
For example new types of equipment in paper and pulp industry cut down the quantity of pollutants emitted considerably. Similarly development of a suitable replacement for the internal combustion engine for automobiles is another example of equipment alteration. Moreover, air pollution emissions from industrial operations can be reduced by proper equipment maintenance, housekeeping and cleanliness in the facilities and premises.
(4) Reduction of Pollutant Discharge at Source by Use of Controlling Equipment:
This is a method of reducing the pollutants at source by use of air pollution control equipment. The various pollutant control methods commonly adopted both for aerosols (particulates) as well as for gaseous pollutants.
Paragraph # 10. General Impact of Air-Pollution:
Air pollution has unhealthy effects on environment, people, animal and plant-life across the globe.
i. Environmental Conditions (Global Warming):
Some pollutants cause environmental conditions such as acid rain and climate change. Increase in the average temperature of the earth’s atmosphere and oceans over a period of time predominantly due to greenhouse gases, burning of fossil fuels, deforestation, solar variation etc. Greenhouse gases contain water vapour (60%), carbon dioxide (26%), methane, nitrous oxide, ozone (8%), PFC, CFC, etc. According to climate scientists, carbon dioxide is a primary contributor to climate change.
If carbon dioxide levels continue to increase, the planet will become warmer, in the next century, affecting human health and environment. Increase in temperature will most likely result in a variety of impacts including more health-related illness, more severe weather events such as floods and droughts, and resulting damage, an increase in cases of vector-borne and water-borne diseases and sea-level rise. As pollution gathers in the earth’s atmosphere, it traps heat and causes average temperature to rise.
ii. Acid Rains:
A significant air pollution problem, affects areas that are down-wind of major industrial areas. Acid rain is caused when oxides of sulphur and nitrogen pollution from industrial smoke-stacks is combined with moisture of atmosphere. The resulting rain is acidic which destroys lakes, rivers, diminishes crop yields and deteriorates buildings.
iii. Toxic Effects:
Some air pollutants are toxic and hazardous. These pollutants are known or suspected to cause series of health disorders such as reproductive disorders, birth defects and cancer beside environmental hazards. Examples of these toxic pollutants include benzene (in gasoline), organic compounds such as dioxin and metals like lead and mercury.