Air pollution:
The introduction of a substance which has harmful or poisonous effects into the air”.
Air pollution is a mixture of solid particles and gases in the air.
Sources of air pollution
Air pollution is not a new for this planet even 65 million years ago during the cretaceous period
the earth had experienced huge air pollution due to the clouds and smoke formed after the crash
of meteorite, this caused mass extinction leads to the complete elimination of dinosaurs and
various other species. Currently pollution due to natural sources such as forest fires and volcano
eruption are creating several tones of greenhouse gases and other pollutants, which are unable to
find human solution as it is naturally occurred.
Sources of Air pollutants
Type and factors of air pollution vary country to country
Major sources of air pollution:
1) Anthropogenic or man made sources
2) Natural sources
Anthropogenic sources
I. Sources of Energy generation
This is where COx and SOx and water vapor are released in the atmosphere as large amount of
coal, oil, L.P/ Natural gas, gasoline and bio-fuels are used in combustion.
II. Transport
This is mobile and most leading source of CO. Combustion in engines is mainly fueled by Gas,
petrol, diesel, and kerosene. Jet engines of long range air crafts are major source of NOx
III. Industry
Most of the industries are directly or indirectly depend on fossil fuel, as they produce CO and
CO2, sulfur hexafluoride and particle matters. Mainly cement industry releases large amount of
particle matters in the environment. There is an array of hazardous volatile compounds that are
released from paints, electronics, dry cleansing, decreasing agents.
IV. Households
Indoor air pollutants are in a broad rage such as Products of Incomplete Combustion (PIC) from
stoves and hose hold burning of garbage, Tobacco and cigarette smoke, Plastic and metal fumes,
Toxic sprays, pesticide and insecticides, dust and particles, Volatile Organic Compounds,
Infectious agents.
Air pollutants and Major sources
Pollutant Major indoor sources
Fine particles Fuel/tobacco combustion, cleaning, cooking
Carbon monoxide Fuel/tobacco combustion
Polycyclic aromatic
hydrocarbons Fuel/tobacco combustion, cooking
Nitrogen oxides Fuel combustion
Sulphur oxides Coal combustion
Arsenic and fluorine Coal combustion
Volatile and semi-volatile Fuel/tobacco combustion, consumer products,
organic compounds furnishings, construction materials, cooking
Aldehydes Furnishing, construction materials, cooking
Pesticides Consumer products, dust from outside
Asbestos Remodelling/demolition of construction materials
V. Agricultural practices
Agriculture activities such as use of natural fertilizer release greenhouse gases. Pesticides release
persistent organic pollutants (POP). Toxic chemicals found in pesticide and weedicide also
reduces the quality of air inhaled.
VI. Land mining, earth moving activity and quarrying
Process of mining large mineral deposits in the earth accompanied with emission of dust and
other chemicals. Blasting, quarrying limestone in cement manufacturing produces dust particles.
VII. Construction and repair works
Drilling, blasting, transportation, loading and unloading activities often causes dust generation.
In addition, there are several anthropogenic sources related to dust generation such as welding,
painting, auto mobile repairing, etc.
VIII. Burning of wastes and incinerators
This is more severe threat to the environment as it contaminates the atmosphere with persistent
organic pollutants (POP) such as dioxins, furans probably major sources are plastics and
electronic wastes. Wastes are in a vast array such as plastic, electronic wastes, cement dust,
industrial chemicals, paper, glass, steel and various derivatives of soil minerals, biological and
medicinal wastes, drugs and other chemicals.
Natural sources
Compounds released from volcanic activities such as black smoke, ash, metals, SOx, COx and
release of methane . Forest fires and bush fires, dust storm, sea spray and conversion of land use
and release of isoprenes and terpenes by forest .
Air pollution from Natural Sources.
Sea spray
Salt mixing with air from sea spray increases the concentration of particulate matter in the air;
this contributes 80% of the particulate matter in coastal area. . This interferes the global
radiation pattern and subsequently the weather.
Volcanic ash
Pinatubo mount volcanic eruption of Philipines in 1991 caused large mass of 20- million ton
sulfur dioxide cloud to the stratosphere, altitude ranging up to 20 miles. Smoke also reflects the
sunlight back and causes temperature decline, reaction of chemical resulted in CFC which led to
the destruction of Ozone. Hydrogen sulfide, Sulphur dioxide, and Hydrogen chloride causes
health issues such as damaging mucus membrane, respiratory system and eye irritation.
Volcanic emissions also elevate the level of greenhouse gases(CO2 and H2O) in the atmosphere .
Forest fires
Forest fires are more frequent in Australia, Indonesia, Brazil, Russia, and Southern United States
. In 2007 forest fires in Southern California caused the release of 7.9 million metric tons of CO2
just in a period of one week, it is also estimated that annual release of CO2 by forest fire events
alone is 290 million metric tons. This shows there is no doubt that though we go for solutions to
anthropogenic CO2 emission such human induced changes are comparatively far smaller than
natural CO2 emission process. .
Sandstorms (sand paper) and Desert dust
Turbulences of Sahara during extremes of hot weather condition (as high as about 50 oC & lack
of rain fall), It could effects Asthmatic patients or causes respiratory problems
Major air pollutants and their effects
Primary pollutants
These are gases and particles released to the atmosphere and remain in the same form as it is
from the source.
Sulphur compound
SO2, H2S, CS2, COS, Dimethyl sulphur, and Dimethyl disulphide. Health effects are generally
wheezing, bronchoconstriction, chronic bronchitis, Chronic obstructive and lung disease.
Nitrogen compounds
Major source is combustion such as get engines, NH3 come from fertilizers, livestock & poultry
wastes, and vegetation, burning of biomass and ocean spray, energy production, petroleum
refinery, forest fire, volcanic activity, bacterial breakdown of organic nitrates. It promotes
acidification. NO2 favours photochemical smoke and reduce visibility. 77% of combustion gas of
coal consist oxides of Nitrogen. In high concentration causes pulmonary edema, airway injury,
impaired lung defenses, dissolved atmospheric NOx as in acid rain destroys fish and plant life
and N2O is a greenhouse gas causes global warming.
Carbon monoxide
Mainly from automobiles and during the combustion of fossil fuel, gas, charcoal and wood,
naturally from forest fires and volcanoes causes difficulty in breathing as it damage to heart and
nervous system.
Carbon dioxide
CO2 is considered as an air pollutant . And it is a greenhouse gas increasing levels of CO 2
causing global warming. CO2 emission is available from all kind of combustion both natural and
manmade.
Polycyclic aromatic hydrocarbon
Which are released from cigarette smoke and stove smoke, can cause lung cancer.
Radon
Released naturally from volcanic eruption, it is a radioactive material ionizes biological
molecules, causes cell disruption and causing lung cancer
Arsenic
Found cigarette smoke causing in lung cancer.
Allergens
House dust, Pollen, causes Asthama,.
HCl
Released naturally from volcanic activities, causes eye irritation and damages mucus membrane
and affects respiratory system.
Dioxin
Dioxin is a toxic gas produced from burning of electronic wastes and plastic materials; it could
cause cancer and affect the immune system and leads to developmental reproductive disorders.
Furans
Furans are released during the burning of plastic products such as nylon, containing various
harmful compounds.
Mercury
Gold refinery is the major source of Mercury and it is a known carcinogen
Lead
Lead particle found in petrol smoke and cause health issues such as affects respiratory system,
blood and kidneys . Burning of lead containing electronic wastes causes the adverse effect to the
atmosphere.
Compounds of Cadmium, Antimony, Arsenic, Zinc and Copper.
These metallic elements often toxic and irritating smoke causes adverse health effects, generally
found in pesticides and fumes and gas emission during the burning of plastic and electronic
wastes.
Secondary pollutants
These compounds are generated by the chemical reaction of primary pollutants in the
atmosphere.
Ground level Ozone
It is the major component of Fog and it is produced by the photochemical reaction between NO x
and Volatile Organic Compounds. Causes breathing difficulty and causes the lung diseases such
as Emphysema and chronic bronchitis.
peroxyacetylnitrate (PAN)
PAN is formed due to photochemical reaction of NOx with hydrocarbons in the sunlight, it is a
component of photochemical smog, smog is a mixture of air pollutants such as gases and
particles react with sun light. PAN often causes irritation to eye and together with Ozone it
lowers the lung capacity and increases breathing rate.
CFC
CFC formed by chemical reaction of fog in the atmosphere during volcanic activity, causes
depletion of Ozone layer.
Halons
Brominated organic compounds used as fire retardant which is also an Ozone depleting
compound.
H2SO4
Sulpuric acid formed due to the reaction of oxides of Sulphur with atmospheric water vapour,
causes acid rain and respiratory problems.
