chapter 8
CHAPTER NO.8 POLLUTANTS AND DISEASES
Pollutants are the substances or agents that cause
undesirable changes in the environment, e.g.smoke, carbon monoxide, plastics
and pesticides. A great variety of pollutabts is generated by varied
human activities. Pollutants are of two types,
biodegradable and non-biodegradable. Biodegradable
pollutants are those, which break into simpler
substances by activity of the natural decompsoers present in the environment
Le. wood, cloth, paper, faecal matter. On the contrary, non-biodegrad-able
pollutants do not break into simpler substances by the activity of
micro-organisms i.e. insecti-
cides, plastics, mercury, lead etc. These pollutants
persist in the environment for longer periods. After
entering the food-chains, these pollutants may
undergo biomagnification. On the basis of their re-lease in the atmosphere,
there are two types of pollutants viz., the primary pollutants and the
second-ary pollutants. The primary pollutants are harmful chemicals that enter
directly into the atmosphere,
e.g. carbon oxides, nitrogen oxides, sulphur dioxide
and hydrocarbons. Secondary pollutants are formed from chemical reactions
involving the primary pollutants, e.g. sulphuric acid, ozone and sul-phur
trioxide. On basis of physical nature, the pollutants can be divided into three
categories, solid
liquid and gaseous pollutants.
SOLID POLLUTANTS :
The major solid pollutants are as follows:
Industrial solid waste ; It includes solid
pollutants like construction material wastes, ash generated after burning of
coal and wood; wooden pieces of packing material; cotton, woollen
and nylon ropes and sheets; pesticides and other
toxic chemicals etc.
Domestic solid waste : It contains solid pollutants
such as plastuc pieces, polythene bags,broken crockery, leather
pieces, rubber pieces, waste paper, empty cans,
metal pieces, textiles, food waste etc. (Fig. 8.1)
Agricultural waste : Agri-cultural waste produced in
frams contains sclid pollutants like empty containers of pes-
ticides, belt pieces, rope pieces, plastics, crop
resi-dues, cow dung, fertilizers etc.
Hospital waste : It includes empty glass and plastic
bottles, discarded syringes, waste cot-ton, discarded instruments, bandages,
expired medicines etc.
Quarrying ; This operation also generates enormous
quantity of solid pollutants in the form of metallic ores, earthen material,
rock dust etc.
LIQUID POLLUTANTS :
The important liquid pollutants are as follow :
Industrial pollutants: The liquid waste released
from industrial plants contains chemical pollutants such as chlorides,
sulphides, zinc, lead, mercury, arsenic, boron, acids, alkalis,radioactive
wastes, pesticides and othe toxic chemicals.
Domestic pollutants : The waste water of the
domestic sewage contains liquid pollutants like human faecal matter, soaps,
detergents, disinfectants etc.
Agriculture pollutants : The surface run off from
agricultural fields carries away liquid pol-lutants such as fungicides,
weedicides, pesticides and fertilizers.
Oil spillage : The oil released from natural
seepage, tanker accidents, off shore drilling platforms, refineries and wastes
from industries, transportation and agriculture is another im-
portant liquid pollutant responsible for pollution
of water.
GASEOUS POLLUTANTS :
These pollutants may be released in the form of
primary pollutants that are directly released into the atmosphere from their
natural or man made sources or may be produced in the atmosphere by chemical
interaction of primary pollutant with other air pollutants or natural components
of the air. The major gaseous pollutants include oxides of carbon: carbon
monoxide (CO) and carbon dioxide (CO,); oxides of sulphur :
sulphur dioxide (SO,) and sulphur trioxide (SO,);
oxides of nitrogen: nitric oxide (NO), nitrogen dioxide
(NO,). The other gaseous pollutants are methane and
other hydrocarbons, suspended particulate matter (SPM), chloroflucrocarbons,
industrial and photochemical smog. A majority of these gaseous pollutants are
generated as a result of buming of fossil fuels in industries and automobiles
(Fig 8.2). Chlorofiurocarbons are released from air-conditioners and
refrigerators in which these are used as coolants.
POLLUTION RELATED DISEASE
The environmental pollution has numerous harmful
effects on human health. Different types of pollutants present in air, water
and soil pose serious threats to quality of environment and result in
critical disease and health disorders. According to
World Health Organization (WHO), as much as 23 percent of the global burden of
disease is associated with environmental pollution. Depending
upon the economic growth, social development,
climatic conditions and geographical location, the magnitude of these health
problems varies in different nations. People in the poor countries are more
susceptible to the ill effects of environmental pollution. Different pollution
related disease are briefly discussed below:
AIR POLLUTION RELATED DISEASE :
The air pollution canses death of about three
million people every year. Despite the fact that human respiratory system has
sufficient defence mechanisms, the prolonged exposure to air pollut-
ants may induce several disease and disorders. These
diseases and disorders include chronic bron-chitis, emphysema, hing cancer,
asbestosis, silicosis, dizziness, headache, eye irritation, sore
throat,shortening of breath etc. Chronic bron-chitis results from long term
exposure of respiratory tract to
the air pollutants such as ozone, sulphur dioxide,
nitrogen dioxide and particulate matter. The exces-sive secretion of mucus blocks
the air passage. The muscles associated with respiratory tract be-come weak due
to prolonged coughing. In patients suffering emphysema, the alveoli of lungs
lose their capacity to expand and contract. This reduces the respiratory
surface for gaseous exchange in
lungs and the patient may die of suffocation or
heart failure.Radioactive pollutants and particulate matter especially the
particles of asbestos, beryllium, chromium, arsenic and nickel stimulate
abnor-mal growth of the mucous membranes which may lead to severe lung cancer.
Asbestos fibres and quartz dust generated during mining operations causes
asbestosis and silicosis respectively. The victims of these disease suffer from
coughing and shortness of breath. The smog produced by com-bination of smoke,
gas and fog causes respiratory disorders like asthma and allergies.
WATER POLLUTION RELATED DISEASES :
The polluted water harbours a variety of disease
causing agents such as bacteria, viruses, pro-tozoa and parasitic worms.
Discharge of untreated sewage into water bodies in the major sources of
these pathogens. Such organisms are responsible for
spread of several water bome disease. These include typhoid, cholera, bacterial
dysentery, enteritis, hepatitis, jaundice, polio, amoeboic dysentery and schistosomiasis.
Consumption of contaminated water for drinking purpose results in spread of
these disease. The standing water provides
favourable breeding grounds for mosquitoes which act as vectors for
transmission of dangerous diseases like malaria, filaria and dengue. Different
heavy metals present in polluted water also cause serious health problems.
Consumption of water contaminated
with mercury compounds leads to numbness of limbs,
lips and tongue, deafness, mental retardation and blurring of vision. Similarly,
cadmium can cause itai-itai disease, a painful disease of bones and joints.
The excessive amount of fluorides present in
drinking water cause teeth deformities hardening of bones and painful joints,
Every year, more than five million people die from diarrhoeal disease caused by
consumption of polluted water. Pesticides such as
dichloro-diphyenyl-trichloroethane (DDT), di-eldrin, mirex and aldrin added to
the water sources can induce cancer tumourous growths, chromo-somal aberrations
and brain damage.
SOIL, RADIATION AND NOISE POLLUTION
RELATED DISEASE : The intestinal
parasites present in the polluted soil cause serious
infections to man and his domestic animals. The radiation pollution can induce
abrupt changes in the genetic material of different animals, including man.
Long term exposure to ionizing radiation triggers the development of cancer in
body tissues.Noise pollution may cause temporary or permanent deafness, peptic
ulcers and damage to brain.
HANDLING AND MANAGEMENT OR HAZARDOUS
WASTES
The hazardous materials are those substances or
preparations that can cause harm to human health or the environment, when
improperly treated, stored, transported or disposed off. Similarly,any
discarded material that threatens human health or environment is known as
hazardous waste.These wastes or substances may be in solid, liquid or gas form.
Hazardous substances and wastes include a variety of acids, dioxins, abandoned
chemical, infectious hospital wastes, heavy metals,
organic solvents, polychlorinated biphenyls (PCBs),
pesticides and radioactive substances. These
chemicals are dangerously reactive, explosive,
poisonous or corrosive in nature. There are numerous such substances from the
nuclear power plants, pesticides manufacturing plants, defene research
laboratories, university research laboratories, big hospitals and military
bases are the most important
sites where the hazardous substances, hazardous
wastes and associated processes are handled.
In the past, a number of tragedies had occured due
to improper handling and processing of these substances. The worst nuclear
accident occured at Chemoby! plant in the former Soviet Union on April 26,
1986. In this accident, the explosion destroyed the reactor and released large
quantities
of radioactive material into the atmosphere. in
1984, the world's worst industrial accident occured at
Union Carbide pesticide plant in Bhopal, India.
Methyl isocyanate, a hazardous substance used in preparation of pesticides
leaked from the stroage tank and killed more than 2300 people, About
1400 people suffered from blindness, sterility,
tuberculosis, liver infections, kidney infections and
These are three basic ways to manage the hazardous
waste:
Reduction in quantity : The most effective way to
manage the hazardous waste is to reduce the total amount of waste produced.
This can be done by adopting better industrial processes
that reduce the quantity of hazardous waste. The
reuse or recycling of the hazardous waste also reduces the total quantity of
the waste. The hazardous waste produced by one industrial firm can also be used
as raw material by other industrial unit.
Conversion to less hazardous materials : Conversion
of more hazardous waste to less hazardous waste is helpful in reducing its
toxicity. This can be done by physical, chemical or biological treatment of the
hazardous waste. The physical treatment of hazardous waste involves physical
processes like sedimentation, screening, Moatation, centrifugation, evaporation
etc. The
chemical treatment includes neutralization, precipitation, absorption
etc. The biclogical treatment of hazardous waste makes use of micro-organisms
for decomposition of more hazadous waste into less hazardous substances.
Another important method to detoxify hazardous waste is incineration.It
involves burning of hazardous waste at high temperature under controlled
conditions. The com-
bustion of high temperature in the incinerators
reduces the toxic wastes to less hazardous ash. The plasma torchs are capable
of producing temperature greater than 10000°C and convert the haz-ardous wastes
to hammless ases. Although incineration is an excellent method for treatement
of solid hazardous waste but it is quite expensive. In India, incinerators are
used for treatment of hazardous wastes from the hospitals.
Long-term storage: The third way for management of
hazardous waste is its long-term storage in specially designed pits known as
landfills. The site for construction of a landfill is very
carefully selected. It is geologically stable and
safe from earthquakes and floods. At the bottom of the landfill, compact layers
of clay and plastic are present. This prevents the percolation of hazardous
waste into groundwater. The hazardous waste is filled in sealed containers and
stored in the landfills.
Then these landfills are covered with soil. It is
being emphasized that the dangerous nuclear radioac-tive waste should be deposited
deep under ground in rocks.
EXERCISE
(A) Very short answer type questions (1
mark each) :
1. What are pollutants?
2. Name three different types of pollutants on the
basis of physical nature.
3. Make a list of solid pollutants present in the
hospital waste.
4. Give the sources of chlorofluorocarbons.
5. What is the cause of chronic bronchitis?
6. How is smog produced?
7. Name different disease causing agents.
8. How does noise pollution affect human health?
9. Name the chemical associated with Bhopal gas
tragedy?
(B) Short answer type questions (2
marks each) :
1. What are pollutants?
2. How are secondary pollutants formed?
3. Enlist different solid pollutants present in the
domestic solid waste.
4, Give different oxides of nitrogen and sulphur.
5. How does polluted standing water harm human life?
6. Name different physical processes used for
treatment of hazardous wastes.
(C) Short answer type questions (4
marks each):
1. Differentiate between biodegradable and
non-biodegradable pollutants.
2. Give a brief account of different liquid
pollutants.
3. Write a short note on hazardous substances.
4. How does incineration help in management of
hazardous wastes?
(D) Long answer type questions: (5
marks each):
1. Discuss different types of solid pollutants.
2. Describe briefly the disease and disorders caused
by air pollution.
3. Describe the adverse effects of polluted water on
human health.
