Air Pollution

Pollution

Pollution is the introduction of contaminants into an

environment that causes instability, disorder, harm or
discomfort to the ecosystem i.e. physical systems or
living organisms . Pollution can take the form of
chemical substances, or energy, such as noise, heat, or
light. Pollutants, the elements of pollution, can be
foreign substances or energies, or naturally occurring;
when naturally occurring, they are considered
contaminants when they exceed natural levels.
The major factors that determine the impact
of pollution are :
1. Nature of pollutant
2. Concentration of pollutant
3. Duration of exposure
4. Health of the receptor
5. Age of receptor
Air pollution
Air pollution is the
introduction of
chemicals, particulate
matter, or biological
materials that cause
harm or discomfort to
humans or other living • Air pollution from World War II production.
organisms, or damages
the natural environment,
into the atmosphere.

• Opaque air seen in Santiagos skyes is smog,

major pollution problem
 sources
• Natural pollens, spores, microbes, SPM and
gases from volcano, dust storms, forest fires
• Man-made
(a) vehicles CO, CO2, NOX, SPM, unburnt
hydrocarbons
(b) industries smoke, SPM, oxides of S, N, C.
( c) garbage(organic) combustion CO, CO2,
SO2, NOX, SPM
(d) brick kilns wood/coal burnt, CO, CO2,
SO2, NOX, dust, smoke
 Air and its major pollutants

• Carbon monoxide (CO)is a colourless, odourless gas that is

produced by the incomplete burning of carbon-based fuels
including petrol, diesel, and wood. It is also produced from the
combustion of natural and synthetic products such as cigarettes.
It lowers the amount of oxygen that enters our blood . It can slow
our reflexes and make us confused and sleepy.
• Carbon dioxide (CO2)is the principle greenhouse gas emitted as
a result of human activities such as the burning of coal, oil, and
natural gases.
• Chloroflorocarbons (CFC) are gases that are released mainly
from air-conditioning systems and refrigeration. 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.
• Leadis present in petrol, diesel, lead batteries, paints, hair dye
products, etc. Lead affects children in particular. It can cause
nervous system damage and digestive problems and, in some
cases, cause cancer.
•Ozone occur naturally in the upper layers of the atmosphere.
This important gas shields the earth from the harmful
ultraviolet rays of the sun. However, at the ground level, it is a
pollutant with highly toxic effects. Vehicles and industries are
the major source of ground-level ozone emissions. Ozone
makes our eyes itch, burn, and water. It lowers our resistance
to colds and pneumonia.
•Nitrogen oxide (Nox) causes smog and acid rain. It is
produced from burning fuels including petrol, diesel, and coal.
Nitrogen oxides can make children susceptible to respiratory
diseases in winters.
•Suspended particulate matter (SPM) consists of solids in
the air in the form of smoke, dust, and vapour that can remain
suspended for extended periods and is also the main source of
haze which reduces visibility. The finer of these particles,
when breathed in can lodge in our lungs and cause lung
damage and respiratory problems.
•Sulphur dioxide (SO2) is a gas produced from burning coal,
mainly in thermal power plants. Some industrial processes,
such as production of paper and smelting of metals, produce
sulphur dioxide. It is a major contributor to smog and acid
rain. Sulfur dioxide can lead to lung diseases.
 Indoor air pollution

• In the developing countries, it is

the rural areas that face the
greatest threat from indoor
pollution, where some 3.5
billion people continue to rely
on traditional fuels such as
firewood, charcoal, and
cowdung for cooking and
heating. Concentrations of
indoor pollutants in households
that burn traditional fuels are
alarming.
• In urban areas, exposure to
indoor air pollution has
increased due to a variety of
reasons, including the
construction of more tightly
sealed buildings, reduced
ventilation, the use of synthetic
materials for building and
furnishing and the use of
chemical products, pesticides,
and household care products.
 Natural sources

• Dust from natural sources, usually large areas of

land with little or no vegetation.
• Methane, emitted by the digestion of food by
animals, for example cattle.
• Radon gas from radioactive decay within the Earth's
crust. Radon is a colorless, odorless, naturally
occurring, radioactive noble gas that is formed from
the decay of radium. It is considered to be a health
hazard. Radon gas from natural sources can
accumulate in buildings, especially in confined
areas such as the basement and it is the second most Dust storm approaching Stratford,
Texas
frequent cause of lung cancer, after cigarette
smoking.
• Smoke and carbon monoxide from wildfires.
• Volcanic activity, which produce sulfur, chlorine,
and ash particulates.
 Smog
• Smog is a combination of various gases
with water vapour and dust. A large part
of the gases that form smog is produced
when fuels are burnt. Smog forms when
heat and sunlight react with these gases
and fine particles in the air. During the
winter, wind speeds are low and cause
the smoke and fog to stagnate; hence
pollution levels can increase near ground
level. This keeps the pollution close to Smog in Cairo
the ground, right where people are
breathing. It hampers visibility and harms
the environment. Heavy smog greatly
decreases ultraviolet radiation. In fact, in
the early part of the 20th century, heavy
smog in some parts of Europe resulted in
a decrease in the production of natural
vitamin D leading to a rise in the cases of
rickets. Smog causes a misty haze similar
to fog, but very different in composition.
Smog refers to hazy air that causes
difficult breathing conditions.
 Acid Rain

• Another effect of air pollution is acid rain.

The phenomenon occurs when sulphur
dioxide and nitrogen oxides combine with
water vapour in the atmosphere and fall as
rain, snow or fog. Acid rain causes extensive
damage to water, forest, soil resources and
even human health. Many lakes and streams
have been contaminated and this has led to
the disappearance of some species of fish in
Europe, USA and Canada as also extensive
damage to forests and other forms of life. It
can corrode buildings and be hazardous to
human health. Because the contaminants are
carried long distances, the sources of acid
rain are difficult to pinpoint and hence
difficult to control. For example, the acid
rain that may have damaged some forest in
Canada could have originated in the
industrial areas of USA.. The international
scope of the problem has led to the signing
of international agreements on the limitation
of sulphur and nitrogen oxide emissions
 Flyash
• Thermal power generation through
coal combustion produces minute
particles of ash that causes serious
environmental problems.
• Commonly known as fly ash,
these ash particles consist of silica,
alumina, oxides of iron, calcium,
and magnesium and toxic heavy
metals like lead, arsenic, cobalt,
and copper.
• To prevent the fly ash from getting
airborne, the dumping sites have
to be constantly kept wet by
sprinkling water over the area. Thermal power station
 Effects on Environment
Pollution has been found to be present widely in the
environment. There are a number of effects of this:
• Sulphur dioxide and nitrogen oxides can cause acid
rain which lowers the pH value of soil.
• Nitrogen oxides are removed from the air by rain
and fertilise land which can change the species
composition of ecosystems.
• Soil can become infertile and unsuitable for plants. Looking down from the Hollywood Hills, with
This will affect other organisms in the food web. Griffith Observatory on the hill in the foreground,
air pollution is visible in downtown Los Angeles
• Smog and haze can reduce the amount of sunlight on a late afternoon.
received by plants to carry out photosynthesis and
leads to the production of tropospheric ozone
which damages plants.
• Invasive species can out compete native species
and reduce biodiversity. Invasive plants can
contribute debris and biomolecules (allelopathy)
that can alter soil and chemical compositions of an
environment, often reducing native species
competitiveness.
• Biomagnification describes situations where toxins
(such as heavy metals) may pass through trophic
levels, becoming exponentially more concentrated
in the process.
• Carbon dioxide emissions cause ocean
acidification, the ongoing decrease in the pH of the
Earth's oceans as CO2 becomes dissolved.
• The emission of greenhouse gases leads to global
warming which affects ecosystems in many ways.
 Abatement of air pollution
• Control of vehicular pollution – public transport, phasing out old
commercial vehicles, laws, CNG/LPG vehicles, public awareness
• Preventive measures
(i) Replace petrol, diesel by low S fuel, CNG, unleaded petrol
(ii) Vehicular emmissions checked
• Control measures
(i) Improve internal combustion engines and vehicle weight
(ii) Reduce pollutants generated by using filters, catalytic filters
• Control industrial pollution
(i) Suitable location to dispose pollutants effectively
(ii) Tall chimneys
(iii) Green belts
(iv) Environment Protection Laws to be strictly followed
 Control devices
The following items are commonly used as pollution
control devices by industry or transportation devices. They
can either destroy contaminants or remove them from an
exhaust stream before it is emitted into the atmosphere.
• Particulate control
– Electrostatic precipitators -An electrostatic precipitator
(ESP), or electrostatic air cleaner is a particulate collection
device that removes particles from a flowing gas.
– Baghouses- Designed to handle heavy dust loads, a dust
collector consists of a blower, dust filter, a filter-cleaning
system, and a dust receptacle or dust removal system.
– Particulate scrubbers- can remove particulates as well as
gaseous pollutants. The polluted air is passed either through
dry packing material like activated carbon, silica gel or
through a wet material like water , alkali solution or oil.
• Arresters works on the principle of dust separation by
centrifugal force.
• Filters used to separate very fine particulate matter.
• Gravity settling chambers suitable for coarse particles.
The polluted air enters a rectangular chamber in a very low Electrostatic Precipitator
velocity which permits dust to settle down.