Air Pollution

Causes, effects and control measures

Dr. Rahul Kumar Khadwalia

M.Sc., B.Ed., Ph.D.

Amity School of Applied Sciences (ASAS)

Amity University, Mumbai, Maharashtra
 Pure and impure air
The composition (%) of fresh (pure) air
Component
by volume: Percent
Nitrogen 78.084
Oxygen 20.846
• Argon 0.934
Total 99.964
Neon 0.0018
Helium 0.0005
Krypton and methane 0.0001
Hydrogen and Nitrous oxide 0.00005

Xenon 0.000008
Variable components:
Vapour 0-5
Carbon dioxide 0.01-0.1 (average 0.042)
Ozone 0-0.01
Sulphur dioxide 0-0.0001
 Zones of atmosphere
• Zones:
– Homosphere: chemically uniform
up to above 100-120 km the earth
– Heterosphere: above homosphere,
structurally uneven

• Altitude increases: change in

temperature pattern of atmosphere
On the basis of this change atmosphere
has been divided into 4 distinct
strata/zones:
1. Troposphere
2. Stratosphere
3. Mesosphere
4. Thermosphere
5. Ionosphere
 Zones of atmosphere
1. Troposphere: 2. Stratosphere:
 Immediately above surface of earth,
 Height from the earth: 40-50 km
 A gradual decline in temperature
 Thickness: 10-20 km  Thin layer above troposphere
 At 20 km the temperature falls to -56O C  Uniform temperature
(from 150 C)  The zone comprises of ozone layer
 The rate of temperature drop: 6.40 C/100 m
 Protects the earth against the ill-
 The zone contains: 99% mass of gases
found in the atmosphere (nitrogen, oxygen effects of UV irradiation
and carbon dioxide)  Ozone shield increases the
temperature from -560 C to -20 C
at 50 km height
3. Mesophere: 4. Thermosphere:
 Height from the earth: 70-80 km  Height from the earth: above 80 km
 Marked reduction in the temperature  Temperature: very high (upto 12000
C)
 At an altitude of 70 km,
 Thickness of the zone is 500 km
 the temperature falls to -92oC (from -
20C)  It contains O2, nascent oxygen &
nitrogen oxide.
Air pollution may be defined as,

It is the introduction of particulates, biological

molecules, or other harmful materials into the Earth's
atmosphere, causing disease, death to humans, damage
to other living organisms such as food crops, or the
natural or built environment.
 Air Pollution
• The Clean Air Act requires EPA to set National
Ambient Air Quality Standards (NAAQS) for
six common air pollutants (also known
as “criteria air pollutants").
• These pollutants are found all over the
country, some from natural sources and some
from man-made sources.
• They can harm your health and the
environment, and cause property damage.
 SOURCES OF AIR POLLUTION
• Emissions from Power stations

• Emissions from Industrial Processes

• Vehicular Emissions

• Emissions from Burning of Solid Waste

• Emissions from Natural Sources such as Volcanic

Eruptions & Forest Fires
AIR POLLUTION
• Air Pollution can impact your
– Health
– Environment
– Nation’s Economy
 Criteria Air Pollutants
• Ground level Ozone
• Particulate matter
• Carbon Monoxide
• Lead
• Sulfur Dioxide
• Nitrogen Dioxide
 Carbon Monoxide
• Incomplete oxidation of carbon results in the production of
carbon monoxide.
– Natural CO formation occurs from photochemical reactions
in the troposphere, volcanoes, forest fires, etc.
• Breathing air with a high concentration of CO
reduces the amount of oxygen that can be
transported in the blood stream to critical organs like
the heart and brain.
• At very high levels, which are possible indoors or in other
enclosed environments, CO can cause dizziness, confusion,
unconsciousness and death.
 Lead
• Sources of lead emissions vary from one area to another.
– At the national level, major sources of lead in the air are ore and
metals processing and piston-engine aircraft operating on leaded
aviation fuel.
– Other sources are waste incinerators, utilities, and lead-acid battery
manufacturers. The highest air concentrations of lead are usually
found near lead smelters.
– Volcanic activity and airborne soil are the primary natural sources of
atmospheric lead.
 Lead
• As a result of EPA's regulatory efforts including
the removal of lead from motor vehicle
gasoline, levels of lead in the air decreased
by 98 percent between 1980 and 2014.
 Lead
• Once taken into the body, lead distributes
throughout the body in the blood and is
accumulated in the bones.
• Depending on the level of exposure, lead
can adversely affect the nervous system,
kidney function, immune system,
reproductive and developmental systems
and the cardiovascular system.
• Lead exposure also affects the oxygen
carrying capacity of the blood.
 Ground Level Ozone
• Ozone is formed in the atmosphere when
energetic ultraviolet (UV) radiation dissociates
molecules of oxygen, O2, into separate oxygen
atoms.
• Free oxygen atoms can recombine to form
oxygen molecules but if a free oxygen atom
(O-2) collides with an oxygen molecule(O2), it
joins up, forming ozone (O3).
 Ozone
• Breathing ozone can trigger a variety of health
problems, particularly for children, the elderly,
and people of all ages who have lung diseases
such as asthma.
• Ground level ozone can also have harmful
effects on sensitive vegetation and
ecosystems.
Ozone
 Particulate Matter
• Sea salt, soil dust, volcanic particles, smoke from forest fires
account for particulate emissions each year.
• Small particles are removed from the atmosphere by
accretion to water droplets, which grow in size until they are
large enough to precipitate.
• Larger particles are removed by direct washout by falling
raindrops.
 Particular Matter
EPA groups particle pollution into two categories:

• "Inhalable coarse particles," such as those found near

roadways and dusty industries, are larger than 2.5
micrometers and smaller than 10 micrometers in diameter.
• "Fine particles," such as those found in smoke and haze, are
2.5 micrometers in diameter and smaller. These particles can
be directly emitted from sources such as forest fires, or they
can form when gases emitted from power plants, industries
and automobiles react in the air.
Particulate Matter
 Particulate Matter
Particulate matter contains microscopic solids or
liquid droplets that are so small that they can be
inhaled and cause serious health problems.
 Nitrous Oxides
• Nitrogen Dioxide (NO2) is one of a group of highly
reactive gases known as oxides of nitrogen or
nitrogen oxides (NOx).
• Although some is naturally occurring,
NO2 primarily gets in the air from the burning of
fuel.
• NO2 forms from emissions from cars, trucks and
buses, power plants, and off-road equipment.
 Nitrous Oxides
• Breathing air with a high concentration of NO2 can irritate
airways in the human respiratory system.
– Such exposures over short periods can aggravate respiratory diseases,
particularly asthma, leading to respiratory symptoms (such as
coughing, wheezing or difficulty breathing), hospital admissions and
visits to emergency rooms.
– Longer exposures to elevated concentrations of NO2 may contribute to
the development of asthma and potentially increase susceptibility to
respiratory infections. People with asthma, as well as children and the
elderly are generally at greater risk for the health effects of NO2.
– NO2 along with other NOx reacts with other chemicals in the air to
form both particulate matter and ozone. Both of these are also
harmful when inhaled due to effects on the respiratory system.
 Sulfur Oxides
• The largest source of SO2 in the atmosphere is
the burning of fossil fuels by power plants and
other industrial facilities.
Smaller sources of SO2 emissions include:
– industrial processes such as extracting metal from
ore
– natural sources such as volcanoes
– and locomotives, ships and other vehicles and
heavy equipment that burn fuel with a high sulfur
content.
 Sulfur Oxides
• At high concentrations, gaseous SO2 can harm trees and
plants by damaging foliage and decreasing growth and can
contribute to acid rain which can harm sensitive ecosystems.
• Short-term exposures to SO2 can harm the human respiratory
system and make breathing difficult. Children, the elderly, and
those who suffer from asthma are particularly sensitive to
effects of SO2.
 Classification of air pollutants
A wide variety of pollutants are present in the atmosphere
In order to understand their impact on health & ecology, & to
evolve appropriate strategies for their control, the
pollutants are classified in a number of ways:

(1) Source of emission,

(2) Physico-chemical characteristics &
(3) Effects on life processes
Depending upon the form (origin) of pollutants present in the
environment, they are classified as
PRIMARY AIR POLLUTANTS
 Primary air pollutants are those emitted directly in the atmosphere in harmful
form. Example  CO, NO, SO2, etc.

 Indoor air pollutants are primary air pollutants.

 The most important indoor air pollutant is radon gas.

 Radon gas is emitted from the building materials like bricks, concrete, tiles,
etc., which are derived from soil containing radium.

 It is also present in natural gas and ground water and is emitted indoors while
using them.

 Burning of fuels in the kitchen, cigarette, smoke liberates the pollutants like
CO, SO2, formaldehyde, BAP (benzo-(a) pyrene).
SHORT-TERM EFFECTS
Short-term effects can be caused by single exposures, often to a large amount of
solvent. These effects usually take place very quickly.

Short-term exposure can cause:

In cases of exposure to very high concentrations of solvent vapour, unconsciousness

and even death can occur.
SECONDARY AIR POLLUTANTS

Some of the primary air pollutants may react with one another
or with the basic components of air to form new pollutants.
They are called as secondary air pollutants.
 Sources of air pollutants
Sources

Natural sources Man induced activities

Incineration: wood, coal,

Geochemical contamination, petroleum products,
 Photochemical reactions, Automobile industry: oxides of
 Change in climatic conditions, sulphur & nitrogen, carbon
 Volcanic eruptions, monoxide, smoke & fly ash
 Gaseous discharge from marshes Oil refineries
& swamps, Iron/steel mills, fertilizer plants &
 Forest fires rendering units metal fumes &
 Dust, fog & radiation fall-outs fluorides into the atmosphere
 Microbial agents Agricultural, textile, paper &
pharmaceutical industries
Dust particles: milling, crushing
/grinding
pesticide & drug residues
Organic/inorganic vapours
Physico-chemical characteristics
Two major groups

Particulate Gaseous pollutants:

pollutants:  Oxides of Sulphur &
 Dust particles, Nitrogen,
 Mist,  Carbon monoxide
 Fly ash  Hydrogen sulphide
 Droplets,  Vapours of gasoline &
 Fog, trichlorethylene
 Smoke,
 Fumes & soot Toxic to animals & man
Organic decomposition of waste
Methanogenesis: methane
(gobar gas) & Carbon dioxide
Carbon dioxide: respiration
SOURCES OF AIR POLLUTANTS
According to the World Health Organization (WHO), more than 1.1 billion
people live in urban areas where outdoor air is unhealthy to breathe.

The sources of air pollutants are given below

GASES
The gases which cause air pollution are
CARBON MONOXIDE (CO)

 It is a colourless, odourless gas that is poisonous to air-breathing animals.

 It is formed during the incomplete combustion of carbon containing fuels.

 The causes are Cigarette smoking, incomplete burning of fossil fuels.

about 77% comes from motor vehicle exhaust.

 The health effects are when this gas reacts with haemoglobin in red blood
cells, it reduces the ability of blood to bring oxygen to body cells and
tissues, and hence causes headaches and anemia.

 At high levels it causes coma, irreversible brain cell damage and death.

 The environmental effects are it increases the global temperature.

NITROGEN DIOXIDE (NO2)

 It is reddish-brown irritating gas that gives photochemical smog.

 When this gas reacts with moisture in the atmosphere, it can be converted into
nitric acid (HNO3).

 The sources are fossil fuel burning in motor vehicles and power industrial plants.

 The health effects are that it causes lung irritation and damage.

 The environmental effects of HNO3 deposition, causes damage on trees, soils and
aquatic life in lakes.

 HNO3 can corrode metals, statues and monuments.

 NO2 can damage fabrics.

SULPHUR DIOXIDE (SO2)

 It is a colourless and irritating gas.

 It is formed from the combustion of sulphur containing fosssil fuels such as coal
and oil.

 In the atmosphere, it can be converted to sulphuric acid (H2SO4) which is a major

component of acid deposition.

 The sources are coal burning in power plants and industrial processes

 The health effects include breathing problems for healthy people.

 The environmental effects are that it reduces visibilty , acid deposition of H2SO4
can damage trees, soils and aquatic life in lakes.
OZONE (O3)

 Highly reactive gas with an unpleasant odour that forms in the troposphere.

 It is a major component of photochemical smog.

 The sources are that there is a chemical reaction with volatile organic compounds (emitted
mostly by cars and industries) and nitrogen oxides.

 The Environmental effects are that it moderates the climate.

CHLOROFLOROCARBONS (CFC)

o Chloroflorocarbons (CFC) are gases that are released mainly from air-
conditioning systems and refrigerators.

o When released into the air, CFCs rise to the stratosphere, where they come in
contact with few other gases, which leads to a reduction of the ozone layer that
protects the earth from the harmful ultraviolet rays of the sun.

NITROGEN OXIDE (Nox)

• Nitrogen oxide (Nox) causes smog and acid rain. It is from burning fuels including
petrol, diesel, and coal.

• Nitrogen oxides can make children susceptible to respiratory diseases in winters.

SMOKE

 Photochemical smog is an air pollutant which is of a smoke type.

 It is a brownish smoke like appearance that frequently forms on clear, sunny

days over large cities with significant amounts of automobile traffic.

 The sources are that it is mainly due to chemical reactions among nitrogen
oxides and hydrocarbon by sunlight.
PARTICULATE MATTERS

◙ "Particulate matter," also known as particle pollution or PM, is a complex

mixture of extremely small particles and liquid droplets.

◙ Particle pollution is made up of a number of components, including acids (such

as nitrates and sulphates), organic chemicals, metals, and soil or dust particles.

◙ The particulate matters include

SOLVENTS AND VAPOURS
Solvent is a substance that can dissolve another substance, or in which another
substance is dissolved, forming a solution. Water is the most common solvent.

PROCESS BY WHICH SOLVENT ENTERS THE HUMAN BODY

There are three ways that solvents can enter the body:

Most solvents are "volatile", that is, they evaporate into the air very quickly. The
fumes, dusts, gases and vapours that result can be breathed in and easily
passed through the lungs into the blood stream.

Solvent droplets can form in the hairs inside the nose, be sniffed in or swallowed.
Mouth contact with contaminated hands, food and cigarettes can also result in the
ingestion of solvents.

Solvents can be absorbed through the skin by direct contact and enter the
bloodstream in this way.
 Effects of pollutants
• Nonirritant pollutants (carbon monoxide) may not always be
associated with overt clinical manifestations.
• Studies have shown that zinc & lead pollution of air: marked
fatalities in cattle & horses in Germany
• Arsenic: Bloody diarrhea, vomiting & excessive thirst in
animals
• Smog pollution: Variety of respiratory problems in animals
• Lead pollution: Teeth grinding & laryngeal paralysis (roaring
sound) in cattle
• Fluorosis: Cattle & sheep reared near brick kilns and
iron/steel aluminum plants & ceramic factories
 In soil (0.1-1.0 g/kg)
 Water (in some areas in India, 25 mg/litre)
 Air (Volcanic eruptions & in the dust particles originating from soil)
 Conditions: lameness, mottled teeth, fragile bones & loss of milk yield in dairy cattle

• Metallic pollutants: Induce anemia & emaciation in animals

 Effects of pollutants
• In humans (atmospheric pollution due to metallic & gaseous
substances is manifested by
 Bronchitis, pulmonary asthma & inflammation of upper respiratory tract

• Nitrogen oxide: Pulmonary edema & congestion

• Sulphur oxide: Injury to mucosa
• Ozone: Effects similar to ionizing radiation
• Carbon monoxide: Depreciation of blood oxygen level following
its combination with hemoglobin)
• Particulate matter have been described in detail by many
workers
HEALTH EFFECTS OF SOLVENTS

♦ Different solvents have different health effects, which will depend on how
exposure happens, how much and for how long.

♦ Some solvents, for example, benzene, can cause cancer.

♦ Some solvents will have synergistic effects with other hazards and drugs. This
means that the solvent will have greater health effects when it is in combination
with other hazards.

♦ The effects of solvents can be classified into two types.

SHORT-TERM EFFECTS
Short-term effects can be caused by single exposures, often to a large amount of
solvent. These effects usually take place very quickly.

Short-term exposure can cause:

In cases of exposure to very high concentrations of solvent vapour, unconsciousness

and even death can occur.
LONG TERM EFFECTS

Repeated (long term) exposure to solvents may effect:

EFFECTS OF SOLVENTS ON THE NERVOUS SYSTEM

۵ There has been increasing attention on the damage to the nervous system from
solvent exposures. This is called neurotoxicity.

۵ Short-term effects (usually with high exposure and rapidly reversible) causes
altertions in the nervous system.

۵ Chronic (or long-term) effects are caused by degeneration of parts of the nervous
system because of repeated low level exposures.
 EFFECTS OF OZONE

 Air pollutants called chlorofluorocarbons(or CFCs) have destroyed parts of the ozone layer.

 The ozone layer, located in the stratosphere layer of Earth's atmosphere, shields our planet
from the Sun's ultraviolet radiation. The areas of thin ozone are called ozone holes.

 Ultraviolet radiation causes skin cancer and damages plants and wildlife.

 Affected Ozone molecules near the ground damages lung tissues of animals and prevent
plant respiration by blocking the openings in leaves where respiration occurs.
Continued….

 Depleted ozone can lead to more frequent asthma attacks in people who have
asthma and can cause sore throats, coughs, and breathing difficulty. It may
even lead to premature death.

 Depleted ozone also hurts plants and crops.

 If the ozone in the stratosphere is destroyed, people are exposed to more

radiation from the sun (ultraviolet radiation).

 This can lead to skin cancer and eye problems.

 Higher ultraviolet radiation can also harm plants and animals.

GLOBAL WARMING HARMS LIVING THINGS
 Our planet is currently warming much more rapidly than expected because additional
greenhouse gases are being released into the atmosphere from air pollution.

 When fuels are burned, some of the polluted gases are released as greenhouses gases.

 Global warming is causing changes to the places where plants and animals live around the
world.

 For example: Near the poles, ice and frozen ground are melting. This causes changes in the
habitat and resources for plants and animals living there.Ocean warming, rising sea levels,
runoff, and coral diseases are causing change in shallow marine environments such as coral
reefs (ridge of rocks).

 Global warming is causing less rain to fall in the middle of continents. This makes these areas
very dry and limits water resources for plants and animals.
EFFECTS OF GASES
CARBON MONOXIDE

 Carbon monoxide makes it hard for body parts to get the oxygen.

 Exposure to carbon monoxide makes people feel dizzy and tired and gives them
headache. In high concentrations it causes fatal.

 Elderly people with heart disease are hospitalized more often when they are exposed
to higher amount of carbon monoxide.

NITROGEN DIOXIDE

 High levels of nitrogen dioxide exposure can give people cough and can make them
feel short of breath.

 People who are exposed to nitrogen dioxide for a long time have a higher chance of
getting respiratory infections.

 Nitrogen dioxide reacts in the atmosphere to form acid rain, which can be harmful for
plants and animals.
SULPHUR DIOXIDE
Θ Sulphur dioxide exposure can affect people who have asthma or chronic lung disease by
making it more difficult for them to breathe.

Θ It can also irritate people's eyes, nose, and throat.

Θ Sulphur dioxide can harm trees and crops, damage buildings.

EFFECTS OF PARTICULATE MATTER

Particulate matter that is small enough can enter the lungs and cause health problems.

Some of these problems include more frequent asthma, respiratory problems, and
premature death.

EFFECTS OF LEAD
High amount of lead can be dangerous for small children and can lead to lower IQ and
kidney problems.

For adults, exposure to lead can increase the chance of having heart attacks or strokes.
 GREEN HOUSE EFFECT

 The greenhouse effect is a naturally occurring process that aids in heating the Earth's surface
and atmosphere.

 It results from the fact that certain atmospheric gases, such as carbon dioxide, water vapour,
and methane are able to change the energy balance of the planet by absorbing long wave
radiation emitted from the Earth's surface.

 Without the greenhouse effect life on this planet would probably not exist as the average
temperature of the Earth would be a chilly -18° Celsius, rather than the present 15° Celsius.

 The greenhouse effect can lead to changes in the climate of the planet. Some of these
changes might include more temperature extremes, higher sea levels, changes in forest
composition, and damage to land near the coast.

 Human health might be affected by diseases that are related to temperature or by damage to
land and water.
ACID RAIN
"Acid rain" is a broad term used to describe several ways that acids fall out of the atmosphere.
A more precise term is acid deposition, which has two parts: wet and dry.

Wet deposition refers to acidic rain, fog, and snow. As this acidic water flows over and through
the ground, it affects a variety of plants and animals.

The strength of the effects depend on many factors, including how acidic the water is, the
chemistry and buffering capacity of the soils involved, and the types of fish, trees, and other
living things that rely on the water.

Dry deposition refers to acidic gases and particles. About half of the acidity in the atmosphere
falls back to earth through dry deposition.

The wind blows these acidic particles and gases onto buildings, cars, homes, and trees. Dry
deposited gases and particles can also be washed from trees and other surfaces by rainstorms.

When that happens, the runoff water adds those acids to the acid rain, making the combination
more acidic than the falling rain alone.
Continued….

Prevailing winds blow the compounds that cause both wet and dry acid deposition across
state and national borders, and sometimes over hundreds of miles.

Scientists discovered, and have confirmed, that sulphur dioxide (SO2) and nitrogen oxides
(Nox) are the primary causes of acid rain.

In the US, About 2/3 of all SO2 and 1/4 of all Nox comes from electric power generation.

Acid rain occurs when these gases react in the atmosphere with water, oxygen, and other
chemicals to form various acidic compounds. Sunlight increases the rate of these reactions.
EFFECTS OF ACID RAIN
When acidic air pollutants combine with water droplets in clouds, the water becomes acidic.
When those droplets fall to the ground, the acid rain can damage the environment.

Damage due to acid rain kills trees and harms animals, fish, and other wildlife.

Acid rain can destroy the leaves of plants.

When acid rain soaks into the ground, it can make the soil an unfit habitat for many living
things.

Acid rain also changes the chemistry of the water in lakes and streams, harming fish and other
aquatic life.

Acid rain causes acidification of lakes and streams and contributes to damage of trees at high
elevations and many sensitive forest soils.

In addition, acid rain accelerates the decay of building materials and paints, including
irreplaceable buildings, statues, and sculptures that are part of our nation's cultural heritage.

Prior to falling to the earth, SO2 and Nox gases and their particulate matter derivatives,
sulphates and nitrates, contribute to visibility degradation and harm public health.
 Microbial pollution of air
• A variety of microbes are carried by air
• Meteorological conditions (temperature, humidity, solar radiation)
• Amount of particulate & gaseous pollutants contribute immensely to
the variation in the load and type of microbes
• Most of the atmospheric microflora emanates from the soil or due to
stirring action induced by animal/human activity within the animal
houses
• The microbes are adsorbed on the dust particles
• Carried over long distances under favorable weather conditions
(high wind velocity) especially during outbreaks of diseases
• A large numbers of organisms (many of them pathogens) can be
transmitted through air in an area
• Animals suffering from respiratory diseases discharge the
microorganisms during sneezing & coughing
• In man:
 Sneeze can release upto 10,000-10,00,000 droplets
 Microbes released by animal & human sources survive in the
environment for varying lengths of time
 Some organisms may not survive for more than few minutes
(Leptospira in dry atmosphere),
 Can resist the adverse environmental conditions for as long
as 28 years (spores of Bacillus anthracis in soil)
 Brucellae can survive in soil for about one month
 Exposure to sunlight causes destruction of many
environmental microorganisms (Mycobacterium spp)
 In soil: mycobacteria can survive for up to 6 months
 How You Can Help Reduce Air
Pollution?
• Conserve Energy
• Drive Wisely / Ride Wisely
 Thermal Inversions
Thermal inversion occurs when a layer of warm air
settles over a layer of cooler air that lies near the
ground. The warm air holds down the cool air and
prevents pollutants from rising and scattering.
 Influence of metrological conditions
 The atmospheric pollution is influenced:
meteorological conditions present in an area
 Meteorological factors influences: magnitude of
vertical & horizontal transfer of air pollution

Major parameters are:

Temperature:
 Direct bearing on the movement of air pollutants
 Influences the diffusion of pollutants
Wind:
 The direction & speed of wind is an important determinant in the movement of air pollutants
Humidity
 Influences the precipitation of pollutants on earth
 Many toxic pollutants combine with water vapor precipitate to the surface of earth
Atmospheric pressure
 Influenced the movement of pollutants in an area
 Important consideration for many pollution parameter
 Air pollution: a historical perspective
1. Meuse Valley (Belgium), December, 1930
• The area was covered by a blanket of thick fog
for about 5 days
• More than 60 persons died as a result of
toxicity due to oxides of sulphur (and
metals) & soot
• A large section of the population became ill

2. Donora (Pennsylvania), October, 1948

◦ Intense foggy condition that lasted few days.
◦ A large proportion of the population (more than 40%)
became ill due to exposure to
◦ Manifested ocular & throat irritation, cough & other
respiratory symptoms &vomiting
◦ Caused due to excessive sulphur compounds
including sulphuric acid from industries
 Air pollution: a historical perspective
3. London, December, 1952, 1962
 Famous smog disaster (1952) for 5 days
 Death of thousands people, children & the old
 Caused acute respiratory disease in cattle
 Another episode of smog (Dec., 1962) that also caused substantial
morbidity& mortality
 Sulphur compounds: probable causes of the illness

4. New York (United States)

 Air pollution disasters were reported during 1953, 1962 & 1966
 The smog caused substantial morbidity and mortality in 1962

5. Bhopal (India),1984
 Leakage of a toxic gas (methyl isocynate) from a pesticide plant.
 More than 5000 people died
 Many more thousands were affected by a variety of illnesses including
respiratory dysfunction, blindness & deformities in the infants
 Air pollution: a historical perspective
• Chernobyl (erstwhile USSR), 1986
 Most famous radiation disasters that occurred in as a result of
massive leakage of radioactivity from a nuclear reactor
 The melting of & explosion in the reactor led to death of about
2000 persons & contamination of the environment in the
neighboring areas

o Los Angeles (California)

 The smog pollution in the city has more to do with petrol than
coal
 The area is highly industrialized and densely populated
 The problem that was associated with various respiratory
symptoms was recognized as early as 1940(s)
 Caused ocular & respiratory irritation& damage to vegetation
 Air pollution: a historical perspective
– Coal dust explosion (China, 1942 and Chasnala, India, 1957)
– Forest fires (South East Asia, 1997-98): impact on health &
productivity

• Nitrogen oxide & hydrocarbons present in the atmosphere

(following use of petrol by the automobiles) reacted with
sunlight
• Toxic compounds were produced through a photochemical
reaction between sunlight & the two pollutants
• The photochemical smog pollution of 1969 has been reported
in detail as a part of episode 104 (associated with hurricane
Camille emanating from Gulf of Mexico)
 Measurement of air contamination
• The microbial load of moving air is determined
 To assess the level of contamination within a building or given area

• Several techniques are used

 To collect the samples & conduct qualitative & quantitative
analysis of air
1. Sedimentation
2. Impaction
3. Impingement
4. Precipitation
5. Filtration
6. Sieve cascade sampler
 Methods of air sampling
1. Sedimentation (settling plate method)
– Permits settlement of atmospheric air on the
surface of an agar plate for 10 min or more
– It does not allow the settlement of suspended
particles the air

2. Impaction
 Collecting the atmospheric particles on the surface
of a solid/semi-solid agar medium
 Air centrifuge is used
 The air flow on the sides of a rotating cylinder lined
with a culture medium
 Suitable for large sized particles
 A better known device called slit sampler is
preferred by many to test air quality
 The air is sucked through a slit onto a rotating
culture plate kept underneath the device
 The flow rate one cu ft .( 28.3 cu cm)/min
 Rotation rate is kept at 0.5, 2 or 6 min/revolution
 Methods of air sampling

3. Impingement
 To collect atmospheric particles in a liquid medium
 The air is sucked through a glass instrument at a
defined rate into the fluid
 The microbial load: determined by examining the fluid

4. Precipitation
 The precipitation of atmospheric particles in two ways:
1. Thermal precipitation
 A slowly moving air current (3 lit/min) is directed
between heated & cooled surfaces (distance 0.038 cm)
 The heated wire/surface repulses the particles towards
cold surface
 They get collected in cold surface
 The organisms are then transferred on to the agar
medium
2. Electrostatic precipitation
 Collects the organisms on the basis of their electric
charge
 It is a highly efficient instrument for collecting the
airborne particles
 Methods of air sampling
5. Filtration
 The microorganisms are trapped on a filter (cotton, glass
wool or paper) or membrane filter
 Membrane filter technique is considered to be better for
the purpose
 Air is filtered through the membrane
 The particles (with microbes) are impunged on this
membrane
 The membrane is then placed on a paper saturated with an
appropriate medium & incubated

6. Sieve (cascade) samplers

 It is desired to collect samples of air on the basis of
the particle size of the pollutant
 Sieves of varying sizes are arranged in a cascading
manner (one upon the other)
 Larger particles are collected on top
 Smaller ones towards the bottom sieves
 Cascade impactor is a highly efficient trap
 Control of air pollution
• Minimize the production & release of pollutants near the animal or
human dwellings
• Control of dust particles: by improving sanitary conditions within the
houses
• Frequent washings of floor & equipment: controlling the dust within
the buildings
• Vacuum cleaners: used effectively
• Proper ventilation: a prompt clearance of foul gases & particulate
pollutants
Filters can be installed to check the entry of external contaminants
o Use of laminar air flow systems for closed compartments/ cabins
Allows unidirectional passage of air through cellulose acetate filters