ENVIRONMENTAL STUDIES-II

MODULE – I
ENVIRONMENTAL
POLLUTION
LECTURE – 2
AIR POLLUTION
 CONTENTS
• Introduction to Air Pollution
• Causes of Air Pollution
• Classification of Air Pollutants
• Effects of Air Pollution
• Air Pollution Laws
• Case Study on Air Pollution
 AIR POLLUTION
• Air pollution may be defined as any
atmospheric condition in which certain
substances are present in such
concentration that they can produce
undesirable effects on man and his
environment.
• Air pollution is the excessive concentration
of foreign matter in the air which adversely
affects the well being of individuals or cause
damage to property.

3
• Air pollution means the presence in the
outdoor atmosphere of one or more
contaminants such as dust, fumes, gas,
mist, odour, smoke or vapour in
quantities of characteristics and of
duration as to be injurious to human,
plant or animal life or to property or
which reasonably interferes with the
comfortable enjoyment of life and
property.
4
 CAUSES OF AIR POLLUTION

❑Natural:
➢ Pollen grains, fungal spores, cysts, bacteria,
methane, hydrocarbons.
➢ Carbon monoxide
➢ Volcanic eruption release many gases and
volcanic ash.
➢ Forest fires
➢ Electric storms, Solar flares
➢ Salt spray from Oceans
➢ Dust storms
5
❑Man made:
➢ Rapid industrialization
➢ Automobile revolution
➢ Deforestation
➢ Industries emits SO2, NH3, NO2, HF, HCL, H2S
fumes, tar.
➢ Advanced agricultural techniques like spraying
of crops for pest and weed control.
➢ Release of heavy metals.
➢6 Nuclear explosions etc.
 CLASSIFICATION OF
POLLUTION SOURCES
❑Point or stationary Sources:
➢The point or stationary sources of
air pollution are best shown by
industries as they add pollutants to
the air at particular points from
their tall chimneys.
➢Pollutants from such point sources
affects only restricted areas.
7
❑Line or mobile sources:
➢The line or mobile sources of air
pollution are the automobiles as these
add pollutants along narrow belts and
over long distances.
❑Area Sources:
➢Towns and cities add smoke and gases
over wide areas and so qualify as area
source of air pollution.
8
 CLASSIFICATION OF AIR
POLLUTANTS
❑According to origin:
➢ Primary Pollutants:
Pollutants that are emitted directly from the
source and are found in the atmosphere in the
form in which they were emitted e.g. Ash,
smoke, SO2, dust fumes etc.
➢ Secondary Pollutants:
The pollutants that are formed in the
atmosphere by chemical reaction between
primary pollutants and atmospheric
constituents e.g. O3, SO3, PAN, H2SO4 etc.
❑According to state of matter:
➢ Gaseous air pollutants:
Pollutants that are present in the gaseous
state in the atmosphere at normal temperature
and pressure. CO2, SOx, NOx, methane etc.
❑Particulate air pollutants:
➢ All atmospheric substances that are not gases
but may be suspended droplets, solid particles
or mixture of the two are generally referred as
particulate air pollutants.
10
 Gaseous Air Pollutants
Oxides of carbon:
▪ Carbon monoxide (CO):
▪ Nature - Colourless, odourless, tasteless gas,
which is chemically inert at normal conditions of
temperature and pressure. At low concentration it is not
harmful but at higher concentration it leads to serious
metabolic disorders and death.

▪ Effect – Effects Central Nervous System causing

laziness and exhaustion. Causes cardiovascular
disorders, reduces vision.
• Sources –
– Transportation
– Solid Waste disposal
– Forest Fires
– Charcoal stoves
– Coal mines
– Gas heaters

• Detection & Analysis

– Gravimetric, chemical, electrochemical and calorimetric process.
Through gas chromatography, catalytic conversion and flame
ionization detection.

• Control
– Adsorption, absorption, condensation, combustion.
Carbon dioxide (CO2):

CO2 is comparatively less dangerous than CO and

merely causes nausea and headache. Its major effect is
on the earth’s climate. CO2 absorbs infrared terrestrial
radiations. CO2 functions as one of the major green
house gases and increase temperature of the earth
ultimately causing global warming.

Sources –
– Fossil fuel combustion
– Release by Jet planes
– Agricultural practices
– Forestry

13
❑Oxides of nitrogen:
• This includes NO and NO2, NO3, N2O2 etc.
• NO is a colourless, odourless gas which is
oxidized to NO2 through secondary
photochemical reactions. Being heavier than air,
NO2 is soluble in water and forms nitric acid
and fall on earth during rain. It is moderately
toxic.
• NO2 is relatively more toxic as it irritates the
alveoli of the lungs and high concentration may
even cause acute bronchitis.
14
• Sources:
– Fuel combustion in automobiles and industries
– Lightening
– Forest fires
– Bacterial decomposition of organic matter
– Natural ionising radiations
• Detection and Analysis
– Chemiluminescence, Ultraviolet Spectrophotometry, Electrical
Transducers, Dispersive Infrared Spectrometry.
• Control
– Modification of combustion condition to decrease NOX
production at utilization of various devices to remove NOX from
exhaust gas streams.
❖Oxides of sulphur:
These includes Sulphur dioxide (SO2) and
Sulphur trioxide (SO3).

Nature - SO2 is a colourless gas having a

characteristic sharp, pungent and
suffocating odour. It is photochemically
oxidised to SO3. It is highly soluble in water
and along with SO3 it forms sulphuric or
sulphurous acid is washed out of the
16
atmosphere by rain.
❑Effects:
✓ They are power pollutants and tend to irritate
the mucous membranes of the respiratory
tracts.
✓ Higher concentrations cause bronchitis.
✓ Attack building materials especially marble,
lime-stone and mortar.
✓ Affect clothes, leather and paper.
✓ Plants are highly sensitive to high
concentration of SO2 and suffer from chlorosis,
metabolic inhibition, plasmolysis and even
death.
17
• Detection & Analysis: Continuous and
intermittent sampling. Chlorimetric,
conductometric and coulometric methods.
Spectroscopic analysis and flame photometry.
• Sources: Burning of solid and fossil fuels and
transportation.
• Control: Burning fuel with less sulphur,
removing sulphur from fuel, converting coal by
liquification or gasification, substituting other
energy source, cleaning up combustion
products.
18
❖Hydrocarbons: The gaseous and volatile
hydrocarbons are the ones responsible for causing air
pollution. Methane, acetylene, ethylene are the
examples of pollutants belonging to this category.
▪ Sources:
▪ Coal fields
▪ Natural fires
▪ Incomplete combustion from car engines,
▪ industrial sources (Refineries)
▪ Forest fires
▪ Agricultural burning
▪ Coal waste fires
• Detection & Analysis
– Gas chromatography in combination with flame
ionization.
• Control
– Incineration
– Adsorption
– Absorption
– Condensation
– Substitution of other materials
❖Photochemical Oxidants:

❖In the presence of sunlight, the oxides

of nitrogen react with the unburned
hydrocarbons released by the exhausts
of automobiles by the process of fuel
combustion and following a series of
complex reactions produce secondary
pollutants namely Peroxyacylnitrate
(PAN), O3, aldehydes and ketones.
Effect
• Irritation of eye, nose and throat, headache, pharyngitis,
laryngitis in human. PAN cause lot of damages to
plants. O3 damage chromosomes. Both PAN & O3
damages plant cell metabolism.
Detection & Analysis
• Neutral phosphate buffered potassium iodide
solution. Calibration is done by Ultraviolet
Photometry.
Control
• Limiting hydrocarbon and nitrogen oxides
22emissions.
❑ Particulate air pollutants:
➢ All atmospheric substances that are not gases but may
be suspended droplets, solid particles or mixture of the
two are generally referred as particulate air pollutants.

➢ They differ widely in terms of particle density and

particle size varying from 0.1 µm to 200 µm. Particles
larger than 50 µm can be seen only through an electron
microscope. Larger particles like sand and water
droplets quickly settle down in still air and smaller
particles like dust remain in air for a long time whereas
very fine particles like tobacco smoke do not settle
down at all.
Particulate pollutants are classified
according to their size, mode of formation
or physical state into following groups -

Aerosols: All air borne suspension of solid or

liquid particles smaller than 1 µm e.g. Dust
smoke, mist and fumes.
✓ Dust: Small solid particles (1-200 µm). They remain
suspended in the air and ultimately settle down
under the influence of gravity.
✓ Smoke: It consist of fine solid particles (0.1-1 µm)
resulting from the incomplete combustion of organic
particles like coal , wood , tobacco or other chemical
material.

24
✓ Fumes: These are fine solid particles (0.1-1 µm)
formed by the condensation of the vapours of
solid materials. They are released fromgr the
chemical or metallurgical processes.
✓ Mist: It consists of liquid droplets (<10 µm)
formed by the condensation of the vapour in the
atmosphere or are released from the industrial
operations such as sulphuric acid mist.
✓ Fog: If the mist is made up of water droplets
whose concentration is high or dense enough to
obscure the vision, then the mist is called fog.
25
✓ Fly ash: Consists of finely divided non
combustible particles present in the gases
arising from the fuel combustion. It contains
inorganic metallic or mineral substances
released when the organic content is burned.
✓ Soot: Incomplete combustion of carbon
containing materials release carbon particles
impregnated with tar.
✓ Natural particulates: Pollen grains, spores of
fungi and bacteria, viruses, protozoans, algal
filaments and volcanic dust.
❖Effects of particulates:
➢ Lead effects haemoglobin formation.
➢ Fly ash causes respiratory problems.
➢ Metal dust effects respiratory system.
➢ Aerosols deplete ozone layer in the atmosphere
and enhances entry of harmful UV ray of Sun to
reach the earth.
➢ Smog has toxic effect on man, animals, plants
and materials.
➢ Dust coating on leaves reduces photosynthesis
and plant growth.
➢27Particulates damage materials by corrosion.
• Detection and Analysis
• Settleable particulates are usually measured by
means of dust fall bucket, while suspended
particulate matter is sampled by means of a high
volume sampler or a paper tape sampler.
Centrifugal devices, impringers and impactors,
scrubbers, ESP and thermal precipitators are
used for analysis.

• Control: At the point of source and some time by

centrifugation, sedimentation, impaction,
filtration and electrical charge.
 EFFECT OF AIR POLLUTION
❑Effects of air pollution on human health:
➢ Irritation of the eye, nose and throat.
➢ Lead particulates causes lead poisoning resulting
in convulsions, delirium, coma and even death.
➢ Cadmium particulates cause cardiovascular
diseases, kidney and liver damage and even death.
➢ Nickel particulates result in respiratory damage.
➢ Mercury causes nerve, brain and kidney damage.
➢ Radioactive fallout has somatic and genetic effects.

29
❑Effects of pollutants on animals:
➢ When animals feeds on particulate coated plants,
they get affected with Arsenic poisoning. Lead
poisoning results in bronchitis and lack of appetite
in pet animals.
❑ Effect of pollutants on plants:
➢ SO2 bleaches the leaf surface and cause chlorosis.
➢ NO2 cause premature leaf fall and suppressed
growth of the plants.
➢ Ozone causes necrosis and damages leaves.
➢ PAN damage leafy vegetable causing premature fall,
discolouration and curling of sepals.
30
❑ Effect of Air pollution on materials:
➢ Corrosion
➢ Abrasion
➢ Deposition and removal of the materials
➢ Chemical attack.
❑ The damages caused to various materials by air
pollutants are:
➢ SO2, aerosols and acid rains damage the building materials.
➢ Paints are discoloured by SO2, H2S, particulates.
➢ Metals undergo corrosions and tarnishing by SO2 and acid
gases.
➢ Paper becomes brittle and leather undergoes disintegration
by SO2 and acid gases.
➢ Ozone, SO2, NO and acid gases discolour, deteriorate and
reduce the tensile strength of textiles.
31
❑Effect on climate:
➢Global warming.
➢Green house effects.
➢Melting of glaciers and polar ice.
➢Increase in the extinction rate of plants and
animals.
➢Poor growth of vegetation.
➢Change in rainfall pattern.
➢Ozone layer depletion.
32
❑Effect on Aesthetic beauty:

The aesthetic beauty of nature is

not visible in the haze formed by
dust and smoke in the air.
Industries, automobiles, sewage
and garbage heaps emit foul
odours causing further loss of
aesthetic beauty.
33
 Air Pollution Laws
• The need for strict monitoring and control of
air pollutants is very essential to reduce
pollutant concentrations to levels considered
safe for life and property. As a result pollution
laws are enacted and detailed regulations are
laid with the main objective of controlling
pollution.

• An integrated approach to get rid of pollution

problem is provided by The Air (Prevention &
Control of Pollution)Act, 1981
According to this act
• There is a central board for the prevention and
control of Air Pollution
• The State Government has the power to declare
air pollution areas and to prohibit the use of
fuels or burning of any material likely to cause
pollution in any pollution control area.
• Effective anti-pollution control measures are also
advocated by the environmental protection
advisory committees formed by State
Government.
❑Control of air pollution:
➢Source correction methods
➢Pollution control equipments
➢Diffusion of pollutants in air
➢Vegetation
➢Zoning
➢Source correction methods:
✓Substitution of raw material
✓Process modification
✓Modification of existing
equipments
✓Maintenance of equipments.
37
➢Pollution control equipments
❖Devices for particulate contaminants:
✓Gravitational settling chamber.
✓ Cyclone separators (Reverse flow Cyclone)
✓Fabric filters (Baghouse Filters)
✓Electrostatic Precipitators
✓Wet collectors (Scrubbers)
– Spray Tower
– Venturi Scrubber
– Cyclone Scrubber
 Fabric Filter
Cyclone Separator
➢ Diffusion of the pollutants in air:

✓ Dilution of the contaminants in the

atmosphere by using tall stacks which
penetrate the upper atmospheric layer and
disperse the contaminants so that the ground
level pollution is greatly reduced. The height
of the stacks is usually kept 2 to 2.5 times the
height of nearby structures.
✓ Dilution of pollutants in air depend on
atmospheric temperature, speed and direction
of the wind.
41
➢Vegetation cover:

✓ Plants contribute towards controlling air pollution

by utilizing CO2 and releasing O2 through
photosynthesis. This purifies the air for the
respiration of human and other animals. Baseous
pollutants like CO2 are fixed by plants like Coleus
blumeri, Ficus variegata, Phascolus vulgaris.
✓ Species of Pinus, Quercus, Pyrus, Juniperus and
Vitis depollute the air by metabolising NOx.
✓ Umpteen number of trees should be planted in
high-risk areas under pollution.
➢ Zoning:
• This method of controlling air pollution can
be adopted at the planning stages of the city.
• Zoning advocates setting aside of separate
areas for industries so that they are far away
from the residential areas.
• The heavy industries should not be located
near to each other.
• New industries should be established away
from larger cities and the location wise
decisions of large industries should be
guided by regional planning.
43
 Air Quality Index (AQI)
• An air quality index (AQI) is a number used by
government agencies to communicate to the
public how polluted the air currently is or how
polluted it might become.
• As the AQI increases, an increasingly large
percentage of the population is likely to
experience increasingly severe adverse health
effects.
National Air Quality Index
(How healthy is the air we breathe?)

AQI = 230; Poor

Responsible Pollutant: PM10
 Pollutants Considered for AQI and
Air Quality Standards

Pollutant SO2 NO2 PM2.5 PM10 O3 CO (mg/m3) Pb NH3

Averaging time (hr) 24 24 24 24 1 8 1 8 24 24

Indian Standard (µg/m3) 80 80 60 100 180 100 4 2 1 400

AQI Categories and Range

Good Satisfactory Moderate Poor Very poor Severe

(0-50) (51-100) (101-200) (201-300) (301-400) (> 401)

[Colour, Category, AQI Number]

 AQI: Health Impacts
AQI Possible Health Impacts
Good minimal impact

Satisfactory minor breathing discomfort to sensitive people

breathing discomfort to the people with lung disease such as asthma and
Moderate
discomfort to people with heart disease, children and older adults

breathing discomfort to people on prolonged exposure and discomfort to people with

Poor
heart disease with short exposure
respiratory illness to the people on prolonged exposure. Effect may be
Very Poor
more pronounced in people with lung and heart diseases

respiratory effects even on healthy people and serious health impacts on people with
Severe
lung/heart diseases