Chapter 16: Pollution — A Rising Environmental Problem
In the first days of December 1952, a mass of cold, still air settled over London and refused to move. Below it, the city carried on as usual. Coal fires burned in hundreds of thousands of homes, power stations along the Thames burned more coal, and buses and lorries ran through the streets. Everything they sent upwards now had nowhere to go.
The smoke mixed with the fog already lying over the river. By 5 December the mixture had thickened into a yellow-brown blanket that Londoners came to call the Great Smog.
For four days you could not see across a street. Buses were led along their routes by men walking ahead with lamps. Soot settled on a coat collar within minutes of stepping outdoors.
At first nobody treated it as dangerous, because the city had lived with dirty winter fogs for a hundred years. Then the hospitals filled with people who could not breathe easily. About four thousand deaths were recorded in the weeks that followed, and later studies placed the figure higher. The wind changed on 9 December and the air cleared.
What did not clear was the argument that came after it. In 1956 Britain passed the Clean Air Act, which restricted the burning of coal in city chimneys and moved the dirtiest industry away from homes. For the first time, a government treated the air itself as something that could be spoiled — and something that could be repaired.
Diagram
Fig. 16.0-1 — A City Under Smog Line drawing of a city street on a still winter day; tall factory chimneys and house chimneys releasing smoke on the left, vehicles releasing exhaust in the foreground, and a low grey layer hanging over the rooftops through which the buildings behind are only faintly visible; label factory chimney smoke, household chimney smoke, vehicle exhaust, fog layer near the ground, reduced visibility.
16.1 What Is Waste?
Everything you use in a day leaves something behind. A meal leaves peels and scraps, a notebook leaves torn pages, a new pair of shoes leaves a box and a plastic wrapper. None of it disappears; it simply moves out of the house and becomes somebody else’s problem.
Material of this kind is called waste — anything unwanted that is left over once a process or an activity is finished. Homes produce it, but so do factories, shops, mines and farms, and in far larger quantities than any household does.
Why The Heap Keeps Growing
The amount of waste a place produces depends on how many people live there and how much each of them uses. As the population rises, both figures rise together, and the waste generated becomes difficult to manage. Open dumps and heaps of garbage are now a common sight on the edge of most towns.
An untreated heap is not simply ugly. It is a breeding ground for flies, rats and other pests, and these carry disease organisms from the rotting material to human food and water. The harm reaches people who never went near the dump.
Rain adds a second route. Water falling on the heap soaks through it, picks up dissolved and suspended material, and runs off into the surrounding soil and into nearby ponds and streams. In this way one heap of waste in one place can spoil land and water some distance away, as Fig. 16.1-1 shows.
Diagram
Fig. 16.1-1 — An Open Dump And The Harm It Causes Line drawing of an open garbage dump on the edge of a settlement; show flies and rats on the heap, arrows for rain falling on it, and an arrow of run-off water leading from the base of the heap downhill into a pond with fish; label garbage heap, flies and rats, rain water, run-off carrying dissolved waste, pond receiving the run-off, houses nearby.
Waste is not all of one kind, and the difference decides what happens to it after it is thrown away. On this basis, all the waste generated from various sources is placed in two categories: biodegradable waste and non-biodegradable waste.
16.1.1 Biodegradable Waste
Leave a pile of fallen leaves in a corner of a garden and come back after a few months. The pile is smaller, darker and crumbly, and the shapes of the individual leaves have gone. Nothing was removed; the leaves were taken apart.
The work is done by microorganisms living in the soil, chiefly bacteria and fungi. They feed on such material and break its complex substances down into simple, harmless and non-toxic ones. Waste that can be broken down in this way is called biodegradable waste.
Animal and agricultural wastes are the common examples — dung, fallen leaves and kitchen leftovers. All of them were once part of a living body, which is exactly why living organisms are able to take them apart again.
The breakdown does not end with the waste vanishing. The simple substances released enter the soil, and plant roots absorb them, so the material that left one organism returns to another. FC 16.1 sets out that path.
Flowchart
FC 16.1 — The Fate Of Biodegradable Waste Biodegradable waste (dung, leaves, kitchen leftovers) → bacteria and fungi in the soil feed on it → complex substances broken down into simple, non-toxic substances → simple substances released into the soil → absorbed by plant roots → built into the plant body once more
16.1.2 Non-Biodegradable Waste
Now leave a plastic carry bag in the same garden corner. Come back after the same few months and it is still a plastic carry bag, perhaps torn and faded, but not taken apart.
Non-biodegradable waste is waste that microorganisms cannot break down. The substances in it are not ones that bacteria and fungi can feed on, so nothing in the soil is equipped to dismantle them. Plastics, styrofoam, metallic cans, glass and electronic waste, or e-waste, all belong here.
That is why accumulation is the whole difficulty with this second category. A single glass bottle harms nothing; a few decades of glass bottles that nothing can break down fill land, block drains and choke water bodies. Accumulation of large amounts of these wastes results in pollution.
The two categories are compared feature by feature in Table 16.1, and Fig. 16.1-2 shows what a single day’s household waste looks like once it is sorted.
Diagram
Fig. 16.1-2 — A Day’s Household Waste, Sorted Line drawing of two labelled containers side by side; the left holding vegetable peels, tea leaves, fallen leaves and food scraps, the right holding a plastic bag, a glass bottle, a metal can, a piece of styrofoam packing and a broken mobile phone; label biodegradable waste, non-biodegradable waste, and name each item shown.
16.2 Pollution And Pollutants
Waste that is properly collected and dealt with is a nuisance. Waste that is released into the air, the water or the soil is something more, because those three are not storage spaces — they are the surroundings that every living thing depends on.
Air, water and soil each have a natural quality. Air is a fairly fixed mixture of gases, river water carries a certain amount of dissolved material, soil holds a particular balance of minerals and organisms. Add something to any of them that does not belong there, and that quality drops.
That addition is what pollution means. Note the two halves of the idea: something is added, and because of the addition the natural quality of the surroundings gets worse. A change that improves nothing and worsens nothing is not pollution.
The substance that does the damage has its own name. Any constituent added to the environment that causes pollution is a pollutant. Sulphur dioxide from a chimney is a pollutant; the spoiled air that results is pollution.
Rapid advancement over the last two centuries is what turned a small problem into a large one. Industries, transport, agriculture, growing residential settlements, and thermal and nuclear power generation plants all release material continuously, and all of them have expanded together. The result is a deterioration, and in places a poisoning, of air, water and soil alike, which threatens human health and almost every other kind of life in our surroundings.
16.2.1 The Five Major Types Of Pollution
Pollutants are of many kinds, but each one has to be released somewhere and each one acts through some route. Sorting them by that route gives five major types of pollution.
- Air pollution — pollutants released into the atmosphere.
- Water pollution — pollutants released into rivers, lakes, ponds, groundwater or the sea.
- Soil pollution — pollutants left in or on the land.
- Radiation pollution — high-energy radiation escaping from the places where it is produced or used.
- Noise pollution — unwanted, disturbing sound.
The last two look different from the first three, and it is worth seeing why they still belong on the list. Radiation and noise are not substances at all; they are forms of energy. But the test for pollution is not whether something is a substance — it is whether an addition to the surroundings worsens their quality. Energy added in excess does exactly that, so both count.
Diagram
Fig. 16.2-1 — The Five Major Types Of Pollution Line drawing of a single landscape carrying all five; a factory chimney and vehicle exhaust rising into the sky (air), a pipe discharging effluent into a river (water), a rubbish dump and sprayed field beside the road (soil), a nuclear power plant with a radiation hazard symbol on its wall (radiation), and a truck with a loudspeaker and horn beside a person covering their ears (noise); label each of the five types against the source shown.
The five are separated for study, but they are not sealed off from one another in nature. Smoke sent into the air settles onto soil; a pesticide sprayed onto soil is washed into a river; hot water released from a factory changes the water and the life in it together. You will meet these crossings repeatedly in this chapter.
16.3 Air Pollution
Air is a mixture of gases in fairly steady proportions, and every land organism has evolved to breathe that particular mixture. Change what is in it, and the change reaches straight into the lungs of everything living there.
Air pollution is the spoiling of that mixture — a degradation of air quality that harms living organisms, and damages certain non-living objects as well. The second half of that statement matters. Stone, paint and metal have no lungs, yet polluted air eats into all three.
Air also refuses to stay where it is put. Nothing separates the air above a factory from the air above the fields a hundred kilometres away, so a pollutant released in one place is carried off and diluted into a much larger volume. This is why air pollution is rarely a local problem for long.
16.3.1 Gaseous And Particulate Pollution
Hold a clean white saucer over a burning candle for a few seconds and look at its underside. Two quite different things came out of that flame — gases you could not see, and a black solid you can now scrape off with a fingernail. Every burning source behaves the same way, and air pollution is divided on exactly this basis.
- Gaseous pollution is caused by harmful gases given out from a variety of sources. The gases mix with the air completely and cannot be seen or filtered out of it.
- Particulate pollution is caused by solid particles suspended in the air — dust, smoke, and the fine material thrown up by mining, stone drilling and the wearing of rubber tyres on motor vehicles.
The distinction is not merely tidy-mindedness. It decides what the pollutant does to you, because a gas dissolves into the moist lining of your air passages while a particle is a solid object that lodges there. It also decides what can be done about it: a particle can be trapped by a filter, and a gas cannot.
16.3.2 Natural And Man-Made Sources
Air was never perfectly clean. It picks up material from two kinds of source, and the difference between them is a difference in what can be done.
Natural sources include ash from erupting volcanoes, dust raised by storms, and the smoke of forest fires. These have been adding material to the atmosphere for as long as there has been an atmosphere. They lie beyond human control and will continue to occur.
Man-made sources are the ones this chapter is really about, because they are the ones that can be changed. Four of them dominate: vehicles, industries, burning garbage, and brick kilns. All four are to a great extent under human control, and methods of controlling them are being developed and applied. Each is taken up in turn below.
Keep in mind, as you read them, that the scale keeps shifting. A single chimney spoils the air of a street; all the chimneys of a district spoil the air of a city; and the same gases, taken together across the world, change the whole atmosphere, which is what section 16.8 deals with.
16.3.3 Vehicular Air Pollution
Motor cars, trucks, buses, scooters, tractors, motor cycles and railway engines mostly run on petrol and diesel. Both are fuels burnt inside the engine, and the burning is never complete, so what leaves the exhaust pipe is a mixture of finished and unfinished products.
Three gaseous pollutants dominate that exhaust: carbon dioxide (\(CO_2\)), sulphur dioxide (\(SO_2\)) and carbon monoxide (\(CO\)). Carbon monoxide is the sign of incomplete burning — it forms when there is too little oxygen inside the cylinder for the fuel to burn fully to carbon dioxide.
A vehicle pollutes in a second way that has nothing to do with its fuel. Its rubber tyres wear against the road surface every kilometre it travels, and the worn material leaves the tyre as rubber particles in the air. Speeding vehicles also raise road dust particles from the surface itself. You will have noticed the same dust rising in clouds when the roads are swept every morning.
Diagram
Fig. 16.3-1 — Gaseous And Particulate Emissions From A Vehicle Line drawing of a moving car on a road, cut away to show both emissions at once; a plume from the exhaust pipe labelled with the three gaseous pollutants, and a separate cloud rising from the rear tyre and the road surface; label exhaust pipe, gaseous pollutants (\(CO_2\), \(SO_2\), \(CO\)), rubber particles from tyre wear, road dust raised by the moving vehicle.
Controlling Vehicular Pollution
Four measures work directly on the sources named above. Efficient engines burn the fuel more completely, so less carbon monoxide leaves the exhaust. Good quality automobile fuels contain fewer of the impurities that become pollutants. Lead-free petrol removes lead from the exhaust altogether. And the greater use of compressed natural gas, or CNG, replaces petrol and diesel with a fuel that burns more cleanly and produces very little particulate matter.
16.3.4 Industrial Air Pollution
Industry now ranges from small pottery and carpet-weaving units to enormous sugar factories, cloth factories, metal factories, automobile manufacturing units, drug manufacturers and oil refineries. Between them they give out pollutants of every kind.
The chief industrial gaseous pollutants are the same three as before — \(CO_2\), \(SO_2\) and \(CO\) — together with oxides of nitrogen, which form when the air inside a furnace is heated strongly enough for its own nitrogen and oxygen to combine. The smoke released by factory chimneys carries, in addition, a great deal of particulate pollutant.
Diagram
Fig. 16.3-2 — Emissions From A Factory Chimney Line drawing of a factory with two tall chimneys releasing dense smoke that drifts sideways over surrounding fields and houses; show the plume spreading and thinning with distance; label chimney, smoke plume carrying particulate pollutants, invisible gaseous pollutants, direction of wind, settlement downwind.
Not all industrial particles come out of a chimney. Stone drilling and the mining of coal and metals produce fine particles at the working face itself, where the people doing the work are breathing them.
Smog
Factory smoke does not always drift away. On a cold, still day it stays low, and it meets the tiny water droplets that make up fog. The smoke particles mix with the dust already in the air and with those droplets, and the result is smog — a name built out of ‘smoke’ and ‘fog’.
Smog is worse than either of its parents because it combines their effects. The fog holds the smoke down near the ground instead of letting it rise away, so the pollutants stay in the layer of air people are breathing, at a concentration far higher than smoke alone would reach. It damages plants, and when inhaled it may cause asthma and allergies in humans.
16.3.5 Burning Garbage
Household garbage is mostly kitchen material — peelings of vegetables and fruits, the shells taken off dry fruits, the washings of pulses and rice, and leftovers from food dishes. All of it is biodegradable, and that gives it two possible fates.
The first is composting, in which the material is allowed to break down and becomes manure for agricultural use. The second is burning in special enclosures. Burning is quicker, but it converts a solid waste problem into an air pollution problem.
On burning, the garbage releases \(CO_2\) along with other harmful gases, and the smoke given out adds to the particulate air pollution of the area. Kitchen waste that could have returned its nutrients to the soil instead sends its carbon into the atmosphere.
16.3.6 Brick Kilns
A brick kiln is a fire-heated enclosure for making construction bricks, and the way it works explains why it pollutes so heavily.
Raw moist clay bricks are stacked in heaps with firewood placed in between them. The heaps are then covered with a layer of a special mud mixture, which keeps the burning flames inside so the heat is not lost. The set-up is left burning for several days, and the smoke collecting inside is released through a hole left for the purpose. When the kiln is opened, the original mud-coloured bricks have turned red, and a great quantity of ash is left behind. FC 16.2 follows the whole sequence.
Flowchart
FC 16.2 — Working Of A Brick Kiln Raw moist clay bricks stacked in heaps with firewood between them → heaps covered with a layer of mud mixture to hold the flames and heat inside → kiln fired and left burning for several days → smoke released through a hole in the covering → kiln opened; mud-coloured bricks now red → ash and broken brick bits removed → wastes either reused or dumped
The wastes are of two kinds. The solid wastes are large quantities of ash and broken brick bits, which are either reused somehow or simply dumped. The other wastes leave through the hole: a great deal of smoke, carrying both gases and particles, and a great deal of heat.
Diagram
Fig. 16.3-3 — A Brick Kiln And Its Wastes Line drawing of a working brick kiln; clay bricks stacked in heaps with firewood between them, the mud covering over the stack, and smoke escaping from an opening at the top, with heaps of ash and broken brick pieces on the ground beside it; label stacked clay bricks, firewood, mud covering, smoke outlet, ash heap, broken brick bits.
16.4 Water Pollution
Water is useful precisely because so much dissolves in it. That same property is what makes it so easy to spoil: whatever is poured into a river does not sit on top of it but spreads through the whole body of water and travels downstream with it.
Water pollution is any change in the quality of water that makes it unsuitable for use by humans and by other living organisms. Notice that the test is fitness for use, not appearance. Water that looks perfectly clear may be polluted, and water that is merely muddy may not be.
The Five Major Sources
Water is polluted by five principal sources, and the sections that follow take them in turn.
- Household detergents
- Sewage
- Industrial wastes
- Oil spills
- Thermal pollution
16.4.1 Household Detergents
Every home uses detergents — cleansing agents used to wash soiled or worn garments, crockery, utensils and floors. The cleaning happens in the house; the dirty water leaves it and flows down the drains, carrying the detergent with it.
From the drain it reaches a water body sooner or later. Detergents do not simply disappear there: the foam they produce forms a layer on the water surface, and many of them contain phosphates, which act as nutrients for the microscopic plant life growing in the water.
16.4.2 Sewage
Sewage is the liquid waste from domestic activities. It consists of kitchen wastes, toilet waste and other household waste water, all carried away together through the same drains.
Most cities have sewage treatment plants, where the dirty part is removed and only the cleaned fluid is released into nearby water bodies or rivers. Small towns and villages may still have no such plant, and their fluid wastes go directly into a nearby river or lake. FC 16.3 sets the two routes side by side.
Flowchart
FC 16.3 — Two Routes Taken By Sewage Kitchen, toilet and other household waste water → household drain → (route 1) sewage treatment plant → dirty matter removed → cleaned fluid released into river or lake; (route 2, where no plant exists) untreated sewage released directly into a nearby river or lake → water pollution
At some places in India, dead bodies are still placed in rivers, and the ashes remaining after cremation are very commonly immersed in rivers such as the Ganga. Both practices add organic material to the water, and both are therefore sources of water pollution.
16.4.3 Industrial Waste
A great many industries, small scale as well as large scale, produce waste water containing various types of chemical pollutants. Liquid waste material produced by factories in this way is called effluent, and it is commonly discharged into rivers.
Coastal industries do the same to the sea. Fish processing industries set up near sea coasts release toxic wastes into the water beside them.
Sewage and effluent are both liquid wastes discharged into water bodies, and it is worth being clear about the difference between them, which Table 16.3 sets out.
16.4.4 Oil Spills
Oil spills are the accidental discharges of petroleum into oceans or estuaries. The sources are overturned oil tankers, offshore oil mining, and oil refineries on the coast.
Oil does not mix with water and is lighter than it, so a spill spreads out into a thin film over a very large area of the surface. That film is where the damage begins, because the surface is exactly where a water body exchanges gases with the air and where sunlight enters it.
Oil pollution kills a great deal of marine life, including fish and birds. A sea bird that lands on an oiled patch of water comes out coated, as Fig. 16.4-1 shows, and the coating is what harms it.
Diagram
Fig. 16.4-1 — A Sea Bird Coated With Spilt Oil Line drawing of a sea bird standing at the water’s edge, its plumage soaked flat and matted with oil, with an oil film visible spreading over the water behind it; label oil film on the water surface, matted plumage, oiled feet and beak.
16.4.5 Thermal Pollution
Many industries — thermal power plants, oil refineries and even nuclear power plants — use water to cool their machinery. The water is drawn from a river or the sea, passed through the plant, and released back.
It comes back changed in one respect only: it is hot. The waste water may be \(8-10\ ^\circ C\) warmer than the water taken in, and it is released into nearby streams, rivers or the sea, causing warming there. Pollution of this kind, in which the added constituent is heat rather than a substance, is called thermal pollution.
Warming harms aquatic animals and may kill fish outright, and it harms the plant life growing in the water. Two things are happening together. Warm water holds less dissolved oxygen than cold water does, so the supply falls. At the same time the higher temperature speeds up the body processes of the animals living there, so their demand rises. The gap between falling supply and rising demand is what kills.
Diagram
Fig. 16.4-2 — Hot Water Discharge Into A River Line drawing of a power plant beside a river; an intake pipe drawing cool water from upstream and an outfall pipe releasing hot water downstream, with the warmer region shown by shading spreading from the outfall and fish shown avoiding it; label intake of cool water, cooling of machinery, outfall of hot waste water, warmed region of the river.
16.5 Soil Pollution
Air moves and water flows, but soil stays where it is. That single difference shapes the whole of this section: soil pollution is largely localised, while air and water pollution can spread over long distances from the place where the pollutant was released.
Five major sources account for most of it.
- Industrial wastes
- Urban commercial and domestic waste
- Chemical fertilisers
- Biomedical waste
- Pesticides
16.5.1 Industrial Waste
Industries have already appeared twice in this chapter, sending gaseous pollutants into the air and chemical-laden effluent into rivers. They give out a great deal of solid waste as well, and it is the solid waste that reaches the soil.
These wastes take the form of chemical residues, flyash — the fine ash carried up with the flue gases of a furnace and collected from them — and metallic ash. All three are dumped on land, and their chemical content passes into the soil beneath.
16.5.2 Urban Commercial And Domestic Waste
Cities and towns have a variety of markets selling food grains, vegetables and fruits, along with tailors, restaurants and banquet halls, and all of them give out solid waste in different forms. At home, the waste takes the form of plastic bags, glass bottles, electric bulbs, kitchen waste and paper packaging. All of this together is solid waste.
Municipal workers collect it and take it away for proper disposal. Part of it — the biodegradable part — can be converted into manure. The rest is dumped in sanitary landfills, shown in Fig. 16.5-1.
The daily covering is the whole point of the arrangement. A layer of earth over each day’s waste keeps flies, rats and birds off it, holds down the smell, and stops the lighter material from blowing away.
Diagram
Fig. 16.5-1 — Section Through A Sanitary Landfill Cut-away side view of a ground depression being filled; show alternating layers of compacted waste and thinner layers of covering earth built up from the base, a lining sheet beneath the lowest layer, and a truck tipping fresh waste at one end with a machine spreading earth over it; label ground depression, layer of waste, daily covering of dirt, lining at the base, finished covered surface.
16.5.3 Chemical Fertilisers
Chemical fertilisers — nitrates, phosphates and ammonium salts — supply crops with the nutrients they need in a concentrated, readily absorbed form, and they give faster growth and increased crop yield. Their excessive use, however, is harmful, and the harm shows up in the water rather than on the field.
Rain washes the surplus fertiliser slowly off the soil, and it reaches nearby lakes and ponds. There the same nutrients that fed the crop now feed the microscopic life of the water, which multiplies rapidly. When that sudden growth dies, the bacteria that decompose it grow faster still.
Those bacteria consume a great deal of oxygen from the water as they work. The dissolved oxygen falls, and fish and other water animals die of the shortage. FC 16.4 follows the chain from the field to the dead fish.
Flowchart
FC 16.4 — From Excess Fertiliser To Dead Fish Excess chemical fertiliser on farmland → washed off slowly by rain water → nitrates and phosphates reach lakes and ponds → rapid growth of microscopic aquatic life → this growth dies and settles → faster growth of decomposing bacteria → bacteria consume a lot of the dissolved oxygen → oxygen shortage in the water → death of fish and other water animals
Note what has happened along that chain. Nothing poisonous was added at any point; a nutrient was added. The killing was done by the shortage of oxygen that the nutrient set in motion.
16.5.4 Biomedical Waste
Biomedical waste is the waste generated by hospitals, clinics, laboratories and the treatment of patients. It covers a number of items:
- used needles, syringes and dirty dressings;
- unused medicinal tablets and powders that have been discarded;
- discarded biological research materials, carelessly disposed of in the municipal garbage.
Waste of this kind often reaches the soil, where it may harm soil organisms, and it reaches humans indirectly through various agents. Sharp items such as used needles carry a second, direct risk to anyone who handles the garbage.
16.5.5 Pesticides
Pesticides are chemical substances used to kill pests. Several of them, such as DDT — Dichloro Diphenyl Trichloroethane — were once used heavily in agricultural farms, in godowns and even in homes.
The difficulty was that most of these persisted. They stayed in the environment undegraded, year after year, acting as pollutants and causing much harm to life indirectly. Presently, milder pesticides are used in their place, but even these are pollutants.
A pesticide in the soil does three things. It alters the basic structure of the soil. It kills microorganisms living in it. And it may reach the human body through food grown in such soil, as Fig. 16.5-2 shows.
The second of those is worse than it sounds. The microorganisms killed are mostly the very ones that recycle nutrients in the soil — the organisms that break dead material down and return its substances for the next crop to use. A pesticide meant to protect a crop can quietly remove the machinery the soil depends on.
Diagram
Fig. 16.5-2 — Route Of A Persistent Pesticide Simple line sequence with arrows across the page; a crop being sprayed, the pesticide shown entering the soil below the plants, the soil organisms shown dying, the pesticide taken up into the crop, the harvested grain, and a plate of food; label sprayed pesticide, pesticide persisting in soil, soil microorganisms killed, uptake by the crop, food grown in such soil, human body.
16.6 Radiation Pollution
Everything so far in this chapter has been a substance — a gas, a particle, a chemical, a load of hot water. Radiation is not. It is a form of energy, travelling either as high-energy waves or as fast-moving particles thrown out by certain unstable materials.
Because it carries so much energy, radiation is put to work in two fields in particular. It is used extensively in medicine, where X-rays let a doctor see inside the body without opening it, and it is used in nuclear power plants to generate electricity.
The same energy that makes it useful is what makes it dangerous. Radiation passing through living tissue disturbs the molecules in its path, and among those molecules is the DNA of the cell. Radiation released where it is not wanted, or in amounts that are not controlled, is therefore a pollutant.
16.6.1 X-Rays And Their Medical Use
X-rays carry a great deal of energy. That energy travels in separate packets called photons, and a single X-ray photon carries enough energy to damage the body cells it passes through.
This is why an X-ray photograph is taken quickly and only when it is needed. Too frequent and too many X-ray exposures may cause serious health hazards — damaged chromosomes, genetic variations, and a raised risk of cancers such as bone cancer.
The risk falls on two different people, and it falls very unevenly. A patient is exposed for a fraction of a second, a few times in a life. The operator of the machine stands beside it all day, every working day, and so must take very special care to avoid exposure as far as possible — standing behind a shielded screen while the exposure is made, and wearing a badge that records the dose received. Fig. 16.6-1 shows the arrangement.
Diagram
Fig. 16.6-1 — Protection During An X-Ray Examination Line drawing of an X-ray room in section; the patient on the table under the X-ray tube with a lead apron over the parts not being examined, and the operator standing behind a shielded partition with a viewing window, pressing the exposure switch; label X-ray tube, patient, lead apron, shielded partition, viewing window, operator, dose-recording badge on the operator’s coat.
16.6.2 Radiation From Nuclear Power Plants
A nuclear power plant holds intensely radioactive material inside heavy shielding, and while that shielding holds, nothing escapes. Radiation becomes a pollutant when the containment fails, and there are two ways it fails: through negligent disposal of radioactive wastes, and through an accident at the plant itself.
Two serious nuclear plant accidents show what follows. One occurred at Chernobyl, in Ukraine, in 1986, when a reactor exploded during a test and burned for days. The other occurred at the Fukushima Daiichi nuclear plant in Japan on 11 March 2011, when a major earthquake and the tsunami that followed it knocked out the plant’s cooling systems.
In both, radioactive material escaped into the surrounding air, land and water. At Chernobyl a number of plant workers and firefighters received doses high enough to be fatal within weeks, and many more people were exposed to lower doses over a wide area.
The chief radiation pollutant released in such an accident is Iodine-131. Iodine is the one element the thyroid gland actively collects from the blood, so a radioactive form of it does not spread thinly through the body but concentrates in that single gland — which is why Iodine-131 raises the risk of thyroid cancer in particular.
Radiation from Fukushima also leaked into the sea, where it entered marine life and reached humans passively through sea food. FC 16.5 traces that route, and Fig. 16.6-2 shows the monitoring that follows an accident.
Flowchart
FC 16.5 — How Radiation From A Leak Reaches People Radioactive material escapes from the plant → carried away by air and by water → settles on land, or enters the sea → taken up by crops, and by fish and other marine life → these are eaten as food → radioactive material enters the human body
Diagram
Fig. 16.6-2 — Monitoring Radiation Levels After An Accident Line drawing of a worker in full protective clothing, gloves and mask, holding a hand-held radiation survey meter close to the ground at the edge of a village street some distance from a nuclear plant; label protective clothing, survey meter, reading displayed on the meter, village in the background.
16.6.3 Carelessly Discarded Radioactive Material
An accident at a power plant is rare and heavily reported. A far commoner danger is radioactive material that leaves the place it belonged to and enters ordinary life, because it looks like nothing in particular.
The lesson generalises. A radioactive source is safe only as long as somebody knows where it is, and it must be accounted for from the moment it is made until it is finally sealed away.
16.7 Noise Pollution
Sound is not a pollutant. A conversation, a song, a warning shout — all of these are sound, and none of them spoils anything. What turns sound into a pollutant is being unwanted.
Noise is any unpleasant or loud undesired sound that interferes with a person’s hearing and concentration, and the pollution caused by such sound is noise pollution. Like radiation, noise is a form of energy rather than a substance, and like radiation it counts as pollution because its excess makes the surroundings worse to live in.
16.7.1 Sources Of Noise
The major sources are industrial machines and workshops, trains, automobiles on the streets, jet aircraft landing and taking off, loud conversation, the radio or television inside houses, and the loudspeakers and musical bands used in public places.
That list mixes very loud sources with quite ordinary ones, and the mixture is deliberate, because loudness is not the whole of the definition. Consider two situations:
- If you are reading something seriously, or solving a mathematical problem, even a mild conversation in the room becomes noise.
- But if you are doing some light reading in a running train, the far louder sound of the train may not disturb you at all.
The same sound, then, is noise for one person and not for another, and noise at one moment and not at the next. Whether it interferes is what decides — which is why the word ‘undesired’ sits in the definition alongside the word ‘loud’.
Diagram
Fig. 16.7-1 — Sources Of Noise In A City Line drawing of a busy city crossing with a person in the foreground covering their ears; show traffic with horns sounding, a train on an overhead track, an aircraft passing low overhead, a loudspeaker mounted on a pole, a construction site with a machine, and a television visible through an open window; label each source shown.
16.7.2 Harmful Effects Of Noise Pollution
Noise damages in two quite different ways: it interferes with what a person is trying to do, and at higher levels it injures the ear itself.
- It interferes in communication, because speech has to compete with it to be heard.
- It interrupts concentration of thought and disturbs peace of mind.
- It lowers efficiency of work, since attention has to be spent on holding the noise out.
- It disturbs sleep, and broken sleep leads in turn to nervous irritability.
- A sudden loud sound can damage the ear drum, and prolonged noise can even lead to deafness.
- Bird life is disturbed by aircraft landing at and taking off from airports.
The fifth effect deserves a closer look, because it is the one that does not repair itself. Sound reaching the ear sets the ear drum vibrating; the vibration is passed inwards to the fluid of the inner ear, where extremely fine hair cells convert it into signals for the nerve to carry to the brain. A sudden violent pressure can tear the ear drum, and continuous loud sound wears down those hair cells. FC 16.6 follows both paths.
Flowchart
FC 16.6 — How Loud Sound Damages Hearing Sound waves enter the ear → ear drum vibrates → vibration passed to the fluid of the inner ear → hair cells convert it into nerve signals → nerve carries signals to the brain → hearing; branch 1: a sudden very loud sound → ear drum torn or damaged; branch 2: prolonged loud noise → hair cells worn down and lost → permanent partial deafness
Effect number six is a reminder that people are not the only listeners. Many birds depend on calls to hold a territory, attract a mate and keep a flock together, and constant aircraft noise drowns those calls out.
16.7.3 Measures To Minimise Noise Pollution
Noise has one convenient property: it stops the moment its source stops. Every measure below therefore works either on the source or on the path between the source and the ear.
- Prohibiting the blowing of horns, particularly near hospitals and schools.
- Restriction on loudspeakers, specially during the night, when noise disturbs sleep.
- Planting trees along the roadside, and keeping doors closed in houses, both of which reduce the noise reaching our ears.
- Not burning fire crackers.
Trees work on the path rather than the source. A belt of leaves and branches scatters and absorbs sound waves passing through it, so the same street noise arrives at the house weaker than it set out. Fig. 16.7-2 shows the effect.
Diagram
Fig. 16.7-2 — A Roadside Tree Belt As A Noise Barrier Line drawing in section; a road with vehicles on the left, a row of leafy trees in the middle, and houses on the right; sound shown as arrows leaving the vehicles, with many arrows scattered and absorbed within the tree belt and only a few, drawn smaller, reaching the houses; label source of noise, tree belt, sound scattered and absorbed, reduced noise reaching the houses.
16.8 Effects Of Pollution On Climate And Environment
Pollution affects the environment, humans and other life in a great many ways. The effects on climate and environment are taken up here; those on human health follow in section 16.9.
Three of these effects are far more significant than the rest, and all three are worldwide rather than local: acid rain, the greenhouse effect and global warming, and ozone layer depletion. Each begins with gases released at ground level and ends with a change in the atmosphere itself.
16.8.1 Acid Rain
Rain has never been perfectly neutral. Carbon dioxide is naturally present in the atmosphere, and some of it dissolves in falling raindrops, so clean rain is always slightly acidic, with a pH of about \(5.6\).
Industrialisation changed what the raindrop meets on its way down. Large amounts of carbon dioxide (\(CO_2\)), sulphur dioxide (\(SO_2\)) and oxides of nitrogen are now emitted from vehicles, factories and power stations. These gases dissolve in the raindrops falling towards the earth, and the rain that reaches the ground is far more acidic than it should be. This is acid rain.
The two important gases behave in the same way but produce different acids: sulphur dioxide gives sulphuric acid, and oxides of nitrogen give nitric acid. Both are strong acids, which is why so little of them changes the rain so much. FC 16.7 follows the whole path.
Flowchart
FC 16.7 — Formation Of Acid Rain Burning of coal, oil and fuels in vehicles, factories and power stations → \(SO_2\) and oxides of nitrogen released into the air → gases carried up and mixed through the atmosphere → dissolved in water droplets of clouds and in falling rain → sulphuric acid and nitric acid formed → acid rain falls on soil, water bodies, vegetation and buildings
Harmful Effects Of Acid Rain
- Damage to vegetation, through pollution of the soil the plants are rooted in.
- Decay of building materials and paints.
- Erosion of ancient monuments, statues and sculpture, the acid reacting with the calcium in the stone.
- Degraded visibility, and harm to human health, from the fine sulphate and nitrate particles that form alongside.
- Harm to fish and other aquatic animals, because of the increased acidity of the water in such lakes and rivers.
The effect on plants can be seen directly, and Fig. 16.8-1 shows the result of a simple experiment in which spinach leaves were exposed to rain of two different acidities. The leaf given mildly acidic rain, at a pH between 5 and 6, stays whole and green. The leaf given rain at pH 3 is patchily discoloured, its tissue killed in spots where the acid settled. Nothing was done to the two leaves except changing the acidity of the water falling on them.
Diagram
Fig. 16.8-1 — Effect Of Acid Rain On Spinach Leaves Two spinach leaves drawn side by side for comparison; the left one whole and evenly shaded, the right one carrying numerous pale dead patches scattered across the blade with the edges beginning to curl; caption the left as subjected to rain of pH 5–6, mildly acidic, and the right as subjected to rain of pH 3, much more acidic; label leaf blade, midrib, dead patches on the acid-treated leaf.
16.8.2 Greenhouse Effect And Global Warming
A greenhouse is a small glass house built to grow plants through cold winters. The glass panels all around let sunlight enter, but they do not let the heat escape, so the air inside stays warm while the air outside is freezing. You experience the same thing inside a car parked in the sun for a few hours.
The atmosphere does something similar, and the resemblance gives the effect its name. Sunlight passes through the air and is absorbed by the earth’s surface, which warms up and radiates energy back outwards. Certain gases in the atmosphere — specially carbon dioxide (\(CO_2\)) and methane (\(CH_4\)) — absorb a proportion of that outgoing energy instead of letting it pass into space, and so prevent the escape of heat. This warming of the air is the greenhouse effect, shown in Fig. 16.8-2.
Diagram
Fig. 16.8-2 — The Greenhouse Effect Line drawing of the curved earth’s surface with the atmosphere shown as a band above it and the sun at the top left; wavy arrows of short-wavelength radiant energy from the sun passing down through the atmosphere to the surface; the surface shaded to show it absorbing energy and warming; longer wavy arrows radiating back upwards from the warm surface, with some passing out into space and others turned back downwards by the atmosphere; label radiant energy from the sun, short wavelengths penetrate the atmosphere, earth’s surface absorbs energy and warms up, warm surface radiates energy back, a proportion of the long waves absorbed by the atmosphere.
The greenhouse effect itself is natural and necessary; without it the earth would be far too cold for life. The problem is that human activity has been strengthening it from both ends at once.
On one side, more \(CO_2\) is being released, by increased industrialisation, the burning of fuels in homes, and a rising population. On the other side, decreasing vegetation and deforestation mean less \(CO_2\) is being taken out of the air and used in photosynthesis. Both the tap and the drain have been altered in the same direction.
The overall rise in \(CO_2\) leads to greater retention of solar radiation in the atmosphere, and the result is global warming — a rise in the average temperature of the earth. Taking the decade 2011–2020 as a whole, the global average surface temperature was about \(1.1\ ^\circ C\) higher than in the period 1850–1900, before large-scale industrialisation.
That figure sounds small, and its consequences are not. Warming is melting snow caps and glaciers, and the meltwater together with the expansion of warming seawater is causing a rise in sea level. It is causing a decline in food production in agricultural fields, and a decline in the fishery resources of the oceans.
16.8.3 Ozone Layer Depletion
Ozone (\(O_3\)) is an allotropic form of oxygen (\(O_2\)) — the same element, built into a molecule of three atoms instead of two. High up in the atmosphere it forms a sort of sunscreen over the whole earth, preventing the harmful UV-B type of ultraviolet rays from the sun coming down to the surface.
That screen is now being thinned. Certain gaseous compounds, chiefly CFCs (chlorofluorocarbons), are released from refrigerators, aerosol sprayers and the styrofoam used as packing material. They are stable enough to survive the journey and rise slowly into the upper atmosphere.
There they break down and release chlorine atoms, and it is the chlorine that does the damage: it breaks ozone (\(O_3\)) down into oxygen (\(O_2\)) and a single oxygen atom (O). FC 16.8 sets out the sequence.
Flowchart
FC 16.8 — Depletion Of The Ozone Layer CFCs released from refrigerators, aerosol sprayers and styrofoam packing → rise slowly into the upper atmosphere → broken down there, releasing chlorine atoms → chlorine breaks ozone (\(O_3\)) into oxygen (\(O_2\)) and O → ozone layer thinned → more UV-B reaches the earth’s surface
The reduced ozone cannot prevent the entry of harmful UV-B rays to the earth. The extra ultraviolet reaching the surface causes sunburn, genetic disorders and skin cancers in humans, and reduces the productivity of forests and of the sea, where it damages the microscopic plant life that everything else there feeds on.
Acid rain, global warming and ozone depletion are all worldwide effects of polluting gases, and they are constantly confused with one another. Table 16.4 keeps the three apart.
16.9 Effects Of Pollution On Human Health
Pollution reaches the human body by three routes, and only three: the air a person breathes, the water they drink, and the food they eat. Each of the three kinds of pollution studied earlier acts through one of these, and Fig. 16.9-1 sets them side by side.
Diagram
Fig. 16.9-1 — Three Routes By Which Pollutants Enter The Human Body Line drawing of a human figure in outline, with three labelled arrows entering it; one from a smoking chimney and vehicle exhaust leading to the lungs, one from a river and a drinking glass leading to the stomach, and one from a sprayed field through a crop and a plate of food, also leading to the stomach; label air route to the lungs, water route to the digestive system, food route from polluted soil, and mark the lungs and the digestive system on the figure.
Effects Of Air Pollution
Polluted air causes respiratory problems and lung disorders, and the reason lies in the design of the lung itself. Its exchange surface is enormous and only one cell thick, and it is held in direct contact with whatever air is drawn in, because that is the only way oxygen can cross into the blood fast enough. Any harmful gas or particle in that air is offered the same thin, wet, richly supplied surface.
Three particular effects are worth naming. Particulate lead, released in the exhaust of vehicles running on leaded petrol, may cause a shortage of blood cells in a person exposed to it over time. Smog leads to asthma, as well as to poor visibility. And the exhaust gas \(SO_2\) causes serious damage to the air passages of the lungs, producing the disease bronchitis, in which those passages become inflamed and a person coughs persistently and breathes with difficulty.
Effects Of Water Pollution
Polluted water may lead to several diseases, among them cholera, jaundice and typhoid.
These are worth distinguishing from the effects just described. They are not caused by a chemical harming the body directly. Sewage entering a water body carries with it disease-causing organisms from human waste, and when that water is drunk, the organisms are swallowed alive and multiply in the person who swallowed them. FC 16.9 follows the route.
Flowchart
FC 16.9 — How Sewage In Water Causes Disease Untreated sewage released into a river or pond → disease-causing organisms from human waste enter the water → the water is drawn for drinking or for washing food → organisms swallowed → they multiply inside the body → cholera, typhoid or jaundice
Effects Of Soil Pollution
Soil pollution affects human health indirectly, since nobody eats soil. The pollutants in it are taken up by the crop growing there, and reach people through the food on the plate. The pesticides used in agricultural farming may in this way cause health problems in people far from the field that was sprayed.
16.10 Control Of Pollution
Pollution cannot be totally controlled. Every activity that feeds, moves, houses and supplies a population produces something unwanted, and no amount of care reduces that to nothing. What can be done is to curtail it — to cut the amount released, to catch it before it leaves the source, and to make less of it in the first place.
The measures below run through the sources studied in this chapter, and each one attacks a source you have already met.
- Use of unleaded petrol and of CNG (Compressed Natural Gas) in automobiles.
- Switching off automobile engines at red lights and whenever the vehicle is not in use.
- Installation of tall chimneys in factories, fitted with filters and electrostatic precipitators.
- Treating industrial effluents before discharging them into water bodies.
- Not throwing food wastes into open ground or into the drains.
- Setting up of sewage treatment plants in larger habitations, and septic tanks in individual houses.
- Greater use of compost — organic matter — instead of chemical fertilisers, and judicious use of pesticides. Farming that works this way, returning organic matter to the soil rather than relying on chemicals, is called organic farming.
- Recycling of plastic, metal and glass material, and incineration — controlled burning — of waste that cannot be recycled.
- Planting of trees along roadsides, on waste land and on mountainous slopes. Tree planting organised in this way, on common and public land for the benefit of the community, is called social forestry.
Two of these repay a closer look, because they work in ways that are not obvious.
A tall chimney does not remove anything by itself; it releases the pollutants higher up, where the wind disperses them over a much wider area instead of leaving them in the street below. The removal is done by what is fitted inside it. An electrostatic precipitator gives the particles in the rising smoke an electric charge, and then attracts them onto oppositely charged plates, where they collect and can be scraped off. Fig. 16.10-1 shows the arrangement.
Diagram
Fig. 16.10-1 — A Chimney Fitted With An Electrostatic Precipitator Cut-away view of a tall factory chimney; dirty smoke entering at the base, passing between a set of charged wires and a set of collecting plates in the middle section, particles shown moving sideways onto the plates, and clean gas leaving the top; a hopper at the bottom collecting the dislodged particles; label smoke inlet, charging wires, collecting plates, particles attracted to the plates, collecting hopper, cleaned gas leaving the chimney.
Tree planting works on several problems at once. Roots hold the soil against being washed away, so erosion is reduced on roadsides and hill slopes. The canopy traps dust and cuts noise. And the leaves take carbon dioxide out of the air in photosynthesis, improving air quality by reducing the very gas that section 16.8 identified as the chief cause of global warming.
16.10.1 Euro Bharat Vehicular Standards
Advice to vehicle owners can only do so much. A vehicle pollutes according to how it was built, and that is settled in the factory, long before anyone drives it. India therefore sets legal limits on what a new vehicle is allowed to emit.
Certain norms have been laid down under the title Euro/Bharat norms, applicable to automobiles. They aim to cut down sulphur and nitrogen oxides from automobile exhausts in particular. BS (Bharat Stage) emission norms were first set up in the year 2000 and have been upgraded since, through BS II, BS III and BS IV to the norms in force today.
The norms mean that any motor vehicle running on the road has to adhere to a specific emission limit. The emission standards are set up by the Central Government to check the levels of pollutants emitted by vehicles using combustion engines, and in India the Central Pollution Control Board sets the standards and the dates by which they must be met.
The BS numbers are based on the European emission norms referred to as Euro 4, Euro 5 and Euro 6. These are followed largely by automobile makers across the world and act as a common reference point for how much a vehicle pollutes.
The tightening has been steady. BS IV norms were in place from April 2010 in selected cities and were enforced for the entire country from 1 April 2017. India then skipped a stage altogether, moving directly from BS IV to BS VI, which came into force nationwide on 1 April 2020. FC 16.10 sets out the sequence.
Flowchart
FC 16.10 — Tightening Of Bharat Stage Emission Norms BS I norms first set up in 2000 → BS II → BS III → BS IV, enforced across the whole country from 1 April 2017 → BS V stage skipped → BS VI in force nationwide from 1 April 2020
Controlling the vehicle is only half of it; the fuel matters as well. Oil refineries must step up production of cleaner fuels, and automobile makers must speed up the research and development needed to meet each new stage. Neither works without the other.
16.11 Swachh Bharat Abhiyan
Every control measure in the previous section needs someone to carry it out. Sewage treatment plants and emission norms are the work of governments and industry, but litter, garbage and sanitation depend on what ordinary people do every day.
The Swachh Bharat Abhiyan, or Clean India Movement, is a national cleanliness campaign started by the Government of India with exactly that in view. It was officially launched on 2 October 2014, with the aim of a clean and hygienic India, and it emphasised a simple rule of conduct: neither litter, nor let others litter. Millions of people from different sections of society came forward and joined the movement.
Its main objectives are these.
- To clean the streets, roads and infrastructure of the country’s cities and towns.
- To eliminate open defecation through the construction of individual, cluster and community toilets, the goal being an Open Defecation Free (ODF) India, achieved by building toilets in rural India.
- To establish an accountable mechanism for monitoring the use of latrines that have been built.
- To achieve efficient solid and liquid waste management systems.
The second and third objectives belong together, and the reason is biological. Human waste left in the open is carried by rain into ponds, streams and wells, and it brings with it the disease organisms described in section 16.9. Building a toilet interrupts that route; but a toilet that is built and not used interrupts nothing, which is why monitoring its use is a separate objective rather than an afterthought.
Diagram
Fig. 16.11-1 — Two Halves Of A Cleanliness Campaign Two panels side by side. Left panel: a group of volunteers of different ages sweeping and clearing a public street, with sacks of collected waste and covered bins along the roadside. Right panel: a newly built village toilet block in use, with a covered pit behind it and a hand-washing point beside the door; label volunteers clearing waste, covered bins, community toilet, covered pit, hand-washing point.
16.12 Plastic Pollution
Plastic has become the material of everyday life because it is cheap, light, waterproof and strong. Every one of those qualities is useful while the object is in use, and every one of them becomes a problem the moment it is thrown away.
The difficulty is the one set out in section 16.1.2. Plastic is non-biodegradable, and an item of it may take hundreds of years to break down completely. Because of this, people are increasingly aware of the detrimental effects that plastic has on our environment and on the oceans.
Single-Use Plastics
Single use or disposable plastics are items intended to be used only once before they are discarded — polythene bags, straws, disposable cutlery and plates, and packaging materials such as plastic bottles, food wrappers and take-away containers.
These are the worst combination available: a material that lasts for centuries, made into an object meant to last for minutes. A polythene bag carries vegetables home once, and then exists for longer than the person who used it.
Discarded plastic ends up choking landfills, drains and rivers, and from the rivers it flows into the oceans. There it is ingested by marine animals, which take a floating bag or fragment for food and swallow something they can neither digest nor pass out. Wherever it is dumped, poisonous substances from the plastic also enter the soil and the water, contaminating both of these natural resources. FC 16.11 follows the whole journey.
Flowchart
FC 16.11 — Journey Of A Discarded Plastic Bag Bag used once and thrown away → collects in a landfill, or blows into a street drain → carried by drain water into a river → river carries it to the sea → floats as whole bags and broken fragments → swallowed by marine animals that mistake it for food, or settles on the sea bed; alongside, at every stage → poisonous substances leach out into the soil and water
Diagram
Fig. 16.12-1 — Plastic In The Sea Line drawing of a stretch of sea in section; floating polythene bags and fragments near the surface, a sea turtle approaching a drifting bag with its mouth open, small fragments dispersed through the water, and more plastic settled on the sea bed among the rocks; label floating bags and fragments, marine animal about to ingest a bag, fragments suspended in the water, plastic on the sea bed.
Reducing The Plastic You Use
The following are ways in which you can help lessen the plastic menace.
- Observe the three Rs — Reduce, Reuse, Recycle.
- Carry your own refillable water bottle.
- Avoid using disposable cutlery and straws.
- Carry your own reusable fabric bag, and do not ask for carry bags made of plastic.
- Give plastic containers and similar items to your nearby scrap dealer for recycling.
The three Rs are listed in that order for a reason, and the order is the whole idea. Reducing means the item is never made, so no waste exists at all. Reusing means one item does the work of many. Recycling comes last because it still costs energy and still ends, after a few rounds, with plastic to dispose of. The best of the three is the one that comes first.
16.13 Summary
- Waste is any unwanted or undesired material resulting from industrial, commercial, mining and agricultural operations, and from community activities.
- Untreated waste heaps breed flies and rats that spread disease, and rain run-off from them carries pollutants into the surrounding soil and water.
- Biodegradable waste — dung, fallen leaves, kitchen leftovers — is broken down by bacteria and fungi into simple, non-toxic substances that return to the soil.
- Non-biodegradable waste — plastics, styrofoam, metallic cans, glass, e-waste — cannot be broken down by microorganisms, so it accumulates, and its accumulation results in pollution.
- Pollution is the addition of any constituent to air, water or land which deteriorates the natural quality of the environment; a pollutant is the constituent that causes it.
- There are five major types of pollution: air, water, soil, radiation and noise. Radiation and noise are forms of energy rather than substances.
- Air pollution is the degradation of air quality that harms living organisms as well as certain objects. It is of two types: gaseous pollution and particulate pollution.
- Natural sources of air pollution — volcanic ash, dust storms, forest fires — are beyond human control. The four major man-made sources are vehicles, industries, burning garbage and brick kilns.
- Vehicle exhaust contains three main gaseous pollutants, \(CO_2\), \(SO_2\) and \(CO\), while tyre wear and speeding vehicles add rubber particles and road dust. Control lies in efficient engines, good quality and lead-free fuels, and greater use of CNG.
- Industries give out \(CO_2\), \(SO_2\), \(CO\) and oxides of nitrogen, along with heavy particulate pollution from chimney smoke and from stone drilling and mining.
- Smog is smoke mixed with dust and fog droplets. Held low over an area, it damages plants and may cause asthma and allergies in humans.
- Burning garbage releases \(CO_2\) and other harmful gases and adds smoke to particulate pollution; composting the same waste returns its material to the soil instead.
- Brick kilns fire stacked clay bricks under a mud covering for several days, giving out smoke and heat and leaving large quantities of ash and broken brick bits.
- Water pollution is any change in water quality that makes it unsuitable for use by humans and other organisms. Its five major sources are household detergents, sewage, industrial wastes, oil spills and thermal pollution.
- Sewage is liquid waste from domestic activities; treatment plants remove the dirty part before release, but untreated sewage still enters rivers and lakes where no plant exists.
- Effluent is the liquid waste of factories, carrying chemical pollutants into rivers and, from coastal units, into the sea.
- Oil spills are accidental discharges of petroleum into oceans or estuaries from tankers, offshore mining and refineries; the surface film they form kills marine life, including fish and birds.
- Thermal pollution is the release of cooling water 8–10 °C warmer than the intake water. Warm water holds less dissolved oxygen while the animals in it need more, and fish and aquatic plant life suffer.
- Soil pollution is largely localised, unlike air and water pollution which spread far. Its major sources are industrial wastes, urban commercial and domestic waste, chemical fertilisers, biomedical waste and pesticides.
- Sanitary landfills are places where wastes are dumped in a ground depression and covered with dirt every day.
- Excess chemical fertiliser washed into ponds and lakes causes rapid growth of aquatic life, whose decay lets bacteria multiply and consume the dissolved oxygen, killing fish and other water animals.
- Biomedical waste — used needles, syringes, soiled dressings, discarded medicines and research material — harms soil organisms and reaches humans indirectly.
- Persistent pesticides such as DDT alter the structure of the soil, kill the microorganisms that recycle its nutrients, and may reach the human body through food grown in such soil.
- Radiation is a form of energy used in medicine and in nuclear power generation. Excessive X-ray exposure may damage chromosomes and raise the risk of cancers.
- Radiation escapes from nuclear plants through negligent waste disposal or accidents, as at Chernobyl in 1986 and Fukushima Daiichi in 2011. Iodine-131 is the chief radiation pollutant, and it raises the risk of thyroid cancer.
- Noise is any unpleasant or loud undesired sound interfering with hearing and concentration. It hinders communication, concentration, efficiency and sleep, damages the ear drum, and prolonged exposure can lead to deafness.
- Acid rain forms when \(SO_2\) and oxides of nitrogen dissolve in rain to give sulphuric and nitric acids, taking rain below its natural pH of about 5.6. It damages vegetation, buildings, monuments and aquatic life.
- Greenhouse gases, chiefly \(CO_2\) and methane, prevent the escape of heat from the atmosphere. Rising emissions with falling vegetation have caused global warming, melting snow caps, rising sea level and falling food and fishery yields.
- CFCs released from refrigerators, aerosol sprayers and styrofoam rise and release chlorine atoms, which break ozone into oxygen. The thinned ozone layer lets more UV-B reach the earth, causing sunburn, genetic disorders and skin cancers.
- Air pollution harms the lungs and air passages because their thin moist surface is held directly against the air; water pollution spreads cholera, jaundice and typhoid; soil pollution reaches people indirectly through food.
- Pollution is curtailed by unleaded petrol and CNG, switching off idle engines, tall chimneys with filters and electrostatic precipitators, treatment of effluents, sewage treatment plants and septic tanks, compost in place of chemical fertilisers, recycling, and tree planting.
- Bharat Stage emission norms, first set in 2000 and based on the European norms, fix the limits a new vehicle must meet; BS IV applied nationwide from 1 April 2017 and BS VI from 1 April 2020.
- The Swachh Bharat Abhiyan, launched on 2 October 2014, works for clean streets, an Open Defecation Free India, monitored use of latrines, and efficient solid and liquid waste management.
- Single-use plastics last for centuries but are used for minutes. They choke landfills, drains and rivers, reach the oceans and are ingested by marine animals; the three Rs — Reduce, Reuse, Recycle — are listed in order of preference.
Flowchart
FC 16.12 — The Argument Of The Chapter In One Chain Human activity produces waste → waste that is not broken down or properly disposed of is released into air, water or land → these additions deteriorate natural quality, giving air, water, soil, radiation and noise pollution → effects on the environment (acid rain, global warming, ozone depletion) and on health (lung damage, waterborne disease, pollutants in food) → control at the source (cleaner fuels and legal emission norms, treatment of effluents and sewage, compost and judicious pesticide use, recycling, tree planting, reduced single-use plastic) → less released, and the chain weakened at its start
16.14 Key Terms
- Acid rain — rain made unusually acidic by sulphur dioxide and oxides of nitrogen dissolving in it to form sulphuric and nitric acids.
- Air pollution — degradation of air quality that harmfully affects living organisms as well as certain objects.
- Biodegradable waste — waste that microorganisms can break down into simple, harmless and non-toxic substances.
- Biomedical waste — waste from hospitals, clinics and laboratories, such as used needles, syringes, soiled dressings and discarded medicines.
- Bronchitis — inflammation of the air passages of the lungs, causing persistent coughing and difficulty in breathing.
- BS (Bharat Stage) emission norms — legal limits on the pollutants a motor vehicle may emit in India, set by the Central Government and tightened stage by stage since 2000.
- CFCs (chlorofluorocarbons) — stable gaseous compounds from refrigerators, aerosol sprayers and styrofoam that rise and release ozone-destroying chlorine atoms.
- Chemical fertilisers — nitrates, phosphates and ammonium salts added to soil to increase crop yield.
- CNG (Compressed Natural Gas) — a cleaner-burning automobile fuel used in place of petrol and diesel.
- Deafness — partial or complete loss of hearing, which prolonged loud noise can cause permanently.
- Detergents — cleansing agents used in homes, whose waste water carries foam and phosphates into water bodies.
- Ear drum — the membrane that vibrates when sound reaches the ear, and which a sudden loud sound can damage.
- Effluent — liquid waste containing chemical pollutants, produced by factories and discharged into rivers or the sea.
- Electrostatic precipitator — a device fitted in a chimney that charges the particles in rising smoke and collects them on oppositely charged plates.
- E-waste — discarded electronic goods, a non-biodegradable waste.
- Flyash — the fine ash carried up with the flue gases of a furnace and collected from them.
- Gaseous pollution — air pollution caused by harmful gases given out from a variety of sources.
- Global warming — the rise in the average surface temperature of the earth caused by greater retention of heat in the atmosphere.
- Greenhouse — a small glass house that lets sunlight in but does not let heat escape, used to grow plants in cold weather.
- Greenhouse effect — the warming of the air caused by gases such as carbon dioxide and methane preventing the escape of heat from the atmosphere.
- Iodine-131 — the chief radioactive pollutant released in nuclear accidents; it collects in the thyroid gland and raises the risk of thyroid cancer.
- Man-made sources — sources of pollution created by human activity, and therefore controllable, such as vehicles, industries, burning garbage and brick kilns.
- Natural sources — sources of air pollution beyond human control, such as volcanic ash, dust storms and forest fires.
- Noise — any unpleasant or loud undesired sound that interferes with a person’s hearing and concentration.
- Noise pollution — the pollution caused by noise.
- Non-biodegradable waste — waste that microorganisms cannot break down, so that it accumulates.
- Nuclear power plant — an installation that generates electricity using radioactive material, and a potential source of radiation pollution.
- ODF (Open Defecation Free) — the goal of eliminating open defecation through the construction and use of toilets.
- Oil spills — accidental discharges of petroleum into oceans or estuaries.
- Organic farming — farming that returns organic matter to the soil instead of relying on chemical fertilisers.
- Ozone — an allotropic form of oxygen, \(O_3\), which high in the atmosphere screens the earth from UV-B rays.
- Particulate lead — lead released as fine particles in vehicle exhaust, which may cause a shortage of blood cells.
- Particulate pollution — air pollution caused by fine solid particles suspended in the air.
- Pesticides — chemical substances used to kill pests, some of which persist undegraded in the environment.
- Photon — a separate packet in which the energy of radiation such as X-rays travels.
- Pollutant — any constituent added to the environment which causes pollution.
- Pollution — the addition of any constituent to air, water or land which deteriorates the natural quality of the environment.
- Radiation — a form of energy travelling as high-energy waves or fast-moving particles, used in medicine and in power generation.
- Radiation pollution — pollution caused by radiation escaping from where it is produced, used or stored.
- Road dust particles — dust raised into the air from the road surface by speeding vehicles.
- Rubber particles — particles released into the air by the wearing of vehicle tyres against the road.
- Sanitary landfill — a place where wastes are dumped in a ground depression and covered with dirt every day.
- Septic tank — a tank in a house in which sewage is held and partly broken down instead of being released directly.
- Sewage — the liquid waste from domestic activities, consisting of kitchen waste, toilet waste and other household waste water.
- Sewage treatment plant — an installation that removes the dirty part of sewage before the cleaned fluid is released into a water body.
- Single use plastics — plastic items intended to be used only once before being discarded, such as polythene bags, straws and disposable cutlery.
- Smog — smoke mixed with dust particles and the small water droplets of fog, held low over an area.
- Social forestry — the planting of trees on common and public land for the benefit of the community.
- Soil pollution — pollution of the land, which unlike air and water pollution remains largely localised.
- Solid waste — the solid material discarded by homes, markets and commercial establishments.
- Swachh Bharat Abhiyan — the national cleanliness campaign launched by the Government of India on 2 October 2014.
- Thermal pollution — pollution of water by heat, caused by the release of hot waste water used for cooling machinery.
- UV-B — the harmful type of ultraviolet radiation from the sun that the ozone layer screens out.
- Waste — any unwanted or undesired material resulting from industrial, commercial, mining and agricultural operations, and from community activities.
- Water pollution — any change in water quality that makes it unsuitable for use by humans and by other living organisms.
- X-rays — high-energy radiation used to see inside the body, which in excess can damage cells and chromosomes.
16.15 Points To Ponder
Volcanic ash, dust storms and forest fires have added material to the atmosphere for millions of years without the air ever being called polluted. What is it about the man-made sources that makes the same word apply to them and not to these?
Excess fertiliser kills fish without poisoning a single one of them, and warm water from a power station does the same. Two very different additions produce the same death. What does that tell you about how aquatic animals actually depend on their surroundings?
Biodegradable waste disappears because living organisms can take it apart. Suppose a bacterium appeared tomorrow that could digest polythene. Which of the problems described in section 16.12 would that solve, and which would remain untouched?
Noise stops the instant its source stops, while a persistent pesticide stays in the soil for years. Compare what this difference means for anyone trying to control the two — in the cost of acting, and in the cost of delay.
The chapter describes acid rain and ozone depletion as effects of gases released at ground level, sometimes thousands of kilometres from where the damage appears. What difficulties does this create for a single country deciding what its own industries may emit?
Almost every control measure in section 16.10 asks somebody to spend money or effort now so that somebody else — often elsewhere, often later — is spared harm. Which of the measures escapes that pattern by benefiting the person who acts, and does that make it easier to bring about?
16.16 Objective Questions
Multiple Choice
- A gas that dissolves in rain drops to form nitric acid is: (1 mark)
- methane
- an oxide of nitrogen
- carbon monoxide
- chlorofluorocarbon
- Rubber particles in city air come mainly from: (1 mark)
- burning of garbage
- brick kilns
- wearing of vehicle tyres against the road
- factory chimneys
- Which of the following is a form of energy acting as a pollutant? (1 mark)
- Effluent
- Flyash
- Thermal pollution
- Styrofoam
- Waste that microorganisms cannot break down is described as: (1 mark)
- particulate
- non-biodegradable
- gaseous
- radioactive
- The daily covering of earth is what distinguishes a sanitary landfill from: (1 mark)
- a compost pit
- an open dump
- a septic tank
- an incinerator
- Fish die in a pond receiving heavy fertiliser run-off chiefly because: (1 mark)
- the fertiliser is itself poisonous to fish
- the water becomes too acidic for them
- the dissolved oxygen in the water is used up
- the water temperature rises sharply
- The radioactive pollutant that collects in the thyroid gland is: (1 mark)
- Cobalt-60
- Iodine-131
- flyash
- particulate lead
- Ozone differs from ordinary oxygen in: (1 mark)
- the element it is made of
- the number of atoms in its molecule
- its ability to dissolve in water
- being a compound rather than an element
- Hot water released from a power plant harms aquatic animals because warm water: (1 mark)
- holds less dissolved oxygen while the animals need more
- holds more dissolved oxygen than the animals can use
- becomes acidic on warming
- prevents sunlight from entering the water
- Of the three Rs, the one that prevents the waste from ever existing is: (1 mark)
- Reduce
- Reuse
- Recycle
- all three equally
Assertion–Reason
For each of the following, choose the correct option: (a) Both A and R are true, and R is the correct explanation of A. (b) Both A and R are true, but R is not the correct explanation of A. (c) A is true but R is false. (d) A is false but R is true.
Assertion (A): Soil pollution is largely localised. Reason (R): Soil does not flow or move about as air and water do. (1 mark)
Assertion (A): An electrostatic precipitator fitted in a chimney reduces particulate pollution. Reason (R): It gives the particles in the rising smoke an electric charge and collects them on oppositely charged plates. (1 mark)
Assertion (A): Composting kitchen waste causes less air pollution than burning it. Reason (R): Kitchen waste is non-biodegradable and cannot be broken down by soil microorganisms. (1 mark)
Match The Following
- Match each item in Column I with the closely related item in Column II. (5 marks)
| Column I | Column II |
|---|---|
| a. Effluent | i. Thinning of the ozone layer |
| b. CFCs | ii. Damage to the hair cells of the inner ear |
| c. Prolonged loud noise | iii. Liquid waste discharged by factories |
| d. Smog | iv. Persistent pesticide |
| e. DDT | v. Smoke mixed with dust and fog droplets |
Clean rain is already slightly acidic, with a pH of about ____________. (1 mark)
Liquid waste produced by factories and discharged into rivers is called ____________. (1 mark)
The fine ash carried up with the flue gases of a furnace is known as ____________. (1 mark)
Energy carried by radiation such as X-rays travels in separate packets called ____________. (1 mark)
Planting of trees on common and public land for the benefit of the community is called ____________. (1 mark)
A pollutant and pollution are two names for the same thing. (1 mark)
Carbon monoxide is formed when fuel in an engine burns incompletely. (1 mark)
Every sound that is loud counts as noise, whatever the listener is doing. (1 mark)
The greenhouse effect is entirely man-made and would not exist otherwise. (1 mark)
Pesticides in the soil kill mainly those microorganisms that recycle nutrients. (1 mark)
Name The Following
Name the following: (5 marks)
- The type of ultraviolet radiation screened out by the ozone layer.
- The liquid waste that comes from kitchens, toilets and household washing.
- The disease of the air passages of the lungs caused by the exhaust gas \(SO_2\).
- The fuel used in place of petrol and diesel to cut particulate emission from vehicles.
- The category of plastic items intended to be used only once before being discarded.
Dung, fallen leaves, styrofoam, kitchen leftovers. Give a reason for your choice. (1 mark)
Volcanic ash, dust from storms, brick kiln smoke, forest fires. Give a reason for your choice. (1 mark)
Household detergents, sewage, oil spills, chemical fertilisers applied to a field. Give a reason for your choice. (1 mark)
16.17 Check Your Concepts
Define pollution, and state how a pollutant differs from it. (2 marks)
State the two types of air pollution, giving one example of each. (2 marks)
What is a sanitary landfill? (2 marks)
Name the five major sources of water pollution. (2 marks)
Give a reason why an operator of an X-ray machine must take greater precautions than the patient being examined. (2 marks)
State two harmful effects of acid rain on non-living objects. (2 marks)
Explain why waste from an untreated open dump can pollute a pond some distance away. (3 marks)
Differentiate between biodegradable and non-biodegradable waste, stating the basis of difference. (3 marks)
Why is smog more harmful than the smoke from which it forms? (3 marks)
Explain, with an example, why the same sound may be noise for one person and not for another. (3 marks)
Give a reason for each of the following: (3 marks)
- Rain is slightly acidic even where there is no industry.
- A tall chimney alone does not reduce the total pollutants released.
- Reuse is preferred to recycling.
Differentiate between sewage and effluent, stating the basis of difference. (4 marks)
What would happen to the soil of a field treated repeatedly with a persistent pesticide, and how would this affect the crops grown there later? (4 marks)
Explain how excess chemical fertiliser applied to a field ends up killing fish in a nearby pond. Set out the steps in order. (4 marks)
Describe how carelessly discarded radioactive material can harm people who had nothing to do with the place it came from. (4 marks)
Explain the greenhouse effect, and state why an increase in it is the cause of global warming. Mention two consequences of the warming. (5 marks)
Describe the sources of vehicular air pollution and the measures used to control it. (5 marks)
What is ozone layer depletion? Explain how CFCs bring it about, and state two effects on living organisms of the extra UV-B that reaches the earth. (5 marks)
16.18 Figure-Based Questions
- Fig. 16.3-1 shows the emissions from a moving vehicle. (3 marks)
- Name the three main gaseous pollutants marked at the exhaust.
- Name the two particulate pollutants shown, and state where each comes from.
- State one measure that would reduce the gaseous emissions shown.
- Fig. 16.5-1 shows a section through a sanitary landfill. (3 marks)
- Identify the layer that is added at the end of every working day.
- State two purposes served by that layer.
- Fig. 16.8-1 shows two spinach leaves from an experiment. (3 marks)
- State the single difference in the treatment given to the two leaves.
- Describe the difference in appearance between them.
- What conclusion does the experiment support?
- Fig. 16.8-2 represents an effect occurring in the atmosphere. (4 marks)
- Name the effect represented.
- Explain what happens to the radiation reaching the earth’s surface from the sun.
- Name two gases responsible for turning part of the outgoing energy back.
- Redraw the figure and label the earth’s surface absorbing energy and the long waves absorbed by the atmosphere.
- Fig. 16.9-1 shows three routes by which pollutants enter the human body. (3 marks)
- Name the three routes.
- State one function of the organ shown at the end of the first route, and explain why that organ is damaged by air pollution.
- Fig. 16.10-1 shows a device fitted inside a factory chimney. (3 marks)
- Name the device.
- Name the type of pollution it reduces.
- Redraw the figure and label the charging wires, the collecting plates and the cleaned gas leaving the chimney.