Air pollution is caused by both natural sources like dust storms and volcanic emissions, as well as human activities such as burning fossil fuels. The main primary pollutants from human activity are nitrogen oxides, sulfur oxides, carbon monoxide, particulate matter, and volatile organic compounds emitted from vehicles, power plants, industry, and other sources. These primary pollutants can then form secondary pollutants in the atmosphere through complex chemical reactions. Air pollution poses risks to human health through respiratory and cardiovascular issues and can also damage ecosystems and contribute to global warming through increased greenhouse gases.

1. ANTROPOGENIC
AIR
POLLUTION

2. The immediate environment of man
comprises of air on which depends all
forms of life.
The atmosphere is a complex, dynamic
natural gaseous system, essential to
support life on planet Earth.

3. Air is a mechanical mixture of gases.
The normal composition is approximately as
follows:
- Nitrogen-78%,
- Oxygen-21%,
- Carbon dioxide-0.03%
and other gases – argon, neon, helium, as well
as water vapor and suspended matter such as
dust, bacteria, spores.

4. Apart from supplying the life-giving oxygen,
air and atmospheric conditions serve several
functions:
The human body is cooled by the air contact;
the senses of hearing and smell function
through air-transmitted stimuli;
disease agents may be conveyed by air.
Pollution of air by dust, smoke, toxic gases
and chemical vapors could result in sickness
and death.

5. The phenomenon called “pollution” is an inescapable
consequence of the presence of man and his
activities.
The term “air pollution” signifies the presence in the
surrounding atmosphere of chemicals, particulate
matter, or biological materials generated by the
activities of man in high enough concentrations that
cause harm or discomfort to humans or other living
organisms, or damages the natural environment,
resulting in chemical entering the food chain or
being present in drinking-water and constituting
additional source of human exposure.

6. Air pollution is one of the present-day health
problems throughout the world.
Abundant amounts of air pollution changes
natural atmospheric processes, causing acid rains,
ozone hole, and enhancing greenhouse effect.
Additionally, it causes economic losses.
The direct effect of air pollutants on plants,
animals and soil can influence the structure and function
of ecosystems, including self-regulation ability, thereby
affecting the quality of life.

7. An air pollutant is a substance in the air that can
cause harm to humans and the environment.
Pollutants can be in the form of:
- solid particles,
- liquid droplets,
- gases.
In addition, they may be natural or man-made.
Examples of natural sources of air pollution include
forest fires, pollen, volcanic emissions, and dust.
Human sources of air pollutants include emissions
from industry, agriculture, forestry, transportation,
power generation, and space heating.

8. Pollutants are classified either as
primary pollutants, or those that enter the
atmosphere directly from various sources,
or as
secondary pollutants, or those that are
formed when primary pollutants react with
each other or with other compounds present
in the atmosphere.

9. Usually, primary pollutants are substances directly
emitted from a process, such as ash from a volcanic
eruption, the carbon monoxide gas from a motor
vehicle exhaust or sulfur dioxide released from
factories.
Secondary pollutants are not emitted directly. Rather,
they form in the air when primary pollutants react or
interact. An important example of a secondary
pollutant is ground level ozone - one of the many
secondary pollutants that make up photochemical
smog.
Note that some pollutants may be both primary and
secondary: that is, they are both emitted directly and
formed from other primary pollutants.

10. Major primary pollutants produced by human
activity include:
 Nitrogen oxides (NOx) - especially nitrogen dioxide are
emitted from high temperature combustion. This reddish-
brown toxic gas has a characteristic sharp, biting odor.
NO2 is one of the most prominent air pollutants.
 Sulfur oxides (SOx) - especially sulfur dioxide. SO2 is
produced by volcanoes and in various industrial processes.
Since coal and petroleum often contain sulfur
compounds, their combustion generates sulfur dioxide.
Further oxidation of SO2 , usually forms H2SO4, and thus
acid rain. This is one of the causes for concern over the
environmental impact of the use of these fuels as power
sources.

11. Sulfur and nitrogen oxides from power
plants, industry, cars and other sources cause
rain, snow and fog to become acidic.
The most serious damage caused by acid
rain today is acidification of water lakes and
rivers. In some cases they become so acidic
that they can no longer support fish and their
food chains.
Forest health can also be affected from
this in areas where the soils are being acidified.

12. Major primary pollutants produced by human activity
 Carbon monoxide - is a colorless, odorless, non-irritating but
very poisonous gas. It is a product by incomplete combustion of
fuel such as natural gas, coal or wood. Vehicular exhaust is a
major source of carbon monoxide.
 Carbon dioxide (CO2) - a greenhouse gas emitted from
combustion but is also a gas vital to living organisms. It is a
natural gas in the atmosphere.
 Volatile organic compounds - VOCs are an important outdoor
air pollutant. In this field they are often divided into the separate
categories of methane (CH4) and non-methane (NMVOCs).
Methane is an extremely efficient greenhouse gas which
contributes to enhanced global warming. Within the NMVOCs,
the aromatic compounds benzene, toluene and xylene are
suspected carcinogens and may lead to leukemia through
prolonged exposure.

13. Major primary pollutants produced by human
activity
Particulate matter (PM) - particulates, or fine
particles, are tiny particles of solid or liquid
suspended in a gas. Sources of particulate matter
can be man made or natural.
•
Some particulates occur naturally, originating
from volcanoes, dust storms, forest and
grassland fires, living vegetation, and sea spray.
•
Human activities, such as the burning of fuels
in vehicles, power plants and various industrial
processes also generate significant amounts of
aerosols.

14. Averaged over the globe, anthropogenic
aerosols currently account for about 10 percent
of the total amount of aerosols in our
atmosphere.
Increased levels of fine particles in the air are
linked to health hazards such as heart disease,
altered lung function and lung cancer.

15. Major primary pollutants produced by
human activity
 Toxic metals, such as lead, cadmium and copper.
 Chlorofluorocarbons (CFCs) - harmful to the ozone
layer emitted from products currently banned from use.
 Ammonia (NH3) - emitted from agricultural
processes. Ammonia contributes significantly to the
nutritional needs of terrestrial organisms by serving as a
precursor to foodstuffs and fertilizers. Although in wide
use, ammonia is both caustic and hazardous.

16. Major primary pollutants
 Odors - such as from garbage, sewage, and
industrial processes
 Radioactive pollutants - produced by nuclear
explosions, war explosives, and natural
processes such as the radioactive decay of
radon.

17. Secondary pollutants include:
Particulate matter formed from
gaseous primary pollutants and
compounds in photochemical smog.
Smog is a kind of air pollution; the
word "smog" is a portmanteau of smoke
and fog.
Industrial or gray smog is considered
the most serious type of air pollution.

18. Classic smog results from smoke and
oxides of that are released by burning coal
and oil containing minor amounts of sulfur.
The smoke gives the air a gray color.
Industrial smog has been known to cause
air pollution disasters. One of the worst
occurred in London in December of
1952. Five days of stagnant air brought
about high-pressure systems caused
between 3,500 and 4,000 deaths.

19. Modern smog does not usually
come from coal but from vehicular
and industrial emissions that are acted
on in the atmosphere by sunlight to
form secondary pollutants that also
combine with the primary emissions
to form photochemical smog (also
know as brown smog).

21. Ozone in the in the upper level occurs
naturally and protects life on earth but
ozone at ground level is a noxious
pollutant.
Ozone (O3) is a key constituent of the
troposphere (it is also an important
constituent of certain regions of the
stratosphere commonly known as the
Ozone layer).

22. Secondary pollutants include:
 Ground level ozone (O3) is secondary pollutant
formed in the atmosphere through a complex set of
chemical reactions involving hydrocarbons, oxides of
nitrogen, and sunlight. It is the major component of
photochemical smog and presents the most
intractable urban air quality problem.
Photochemical and chemical reactions involving
it drive many of the chemical processes that occur in
the atmosphere by day and by night. The rate at
which the reactions proceed is related to both
temperature and intensity of the sunlight.
 Peroxyacetyl nitrate (PAN) - formed from NOx and
VOCs.

23. Sources of air pollution
Sources of air pollution refer to the various
locations, activities or factors which are
responsible for the releasing of pollutants in
the atmosphere.
These sources can be classified into
two major categories which are:

24. 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.
 Smoke and carbon monoxide from
wildfires.
 Volcanic activity, which produce sulfur,
chlorine, and ash particulates.

25. Natural sources
•
- 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 frequent
cause of lung cancer, after cigarette smoking.

26. Anthropogenic sources (human
activity) mostly related to burning
different kinds of fuel:
"Stationary Sources" include
smoke stacks of power plants,
factories and waste incinerators, as
well as furnaces and other types of
fuel-burning heating devices.

27. Combustion of fuel to generate heat and
power produces sulfur dioxide, nitrogen oxides,
hydrocarbons, polynuclear aromatic
hydrocarbons, dust, fly ash and smoke and the
carcinogenic 3,4-benzepyrenes.
Domestic combustion of coal, wood or oil
is also a major source of these pollutants.
Many industries discharge carbon
monoxide, carbon dioxide, hydrogen sulfide,
sulfur dioxide, hydrogen fluoride, hydrochloric
acid, dust, ozone.

28. Anthropogenic sources
 "Mobile Sources" include motor vehicles,
marine vessels, aircraft etc.
Automobiles are the major source of air
pollution in urban areas. They emit hydro-
carbons, carbon monoxide, lead, nitrogen
oxides and particulate matter. In strong
sunlight and UV-radiation certain of these
hydrocarbons and oxides of nitrogen may be
converted in the atmosphere into
“photochemical” pollutants of oxidizing
nature.

29. -Chemicals, dust and controlled burn
practices in agriculture and forestry
management. Controlled or prescribed
burning is a technique sometimes used in
forest management, farming, prairie
restoration. Controlled burning stimulates the
germination of some desirable forest trees,
thus renewing the forest.
- Fumes from paint, hair spray, varnish,
aerosol sprays and other solvents
- Military - such as nuclear weapons, toxic
gases.

30. • Waste deposition in landfills, which
generate methane.
Methane is not toxic; however, it is
highly flammable and may form
explosive mixtures with air. Methane is
also an asphyxiant and may displace
oxygen in an enclosed space. Asphyxia or
suffocation may result if the oxygen
concentration is reduced to below 19.5%
by displacement.

31. Meteorological factors
The level of atmospheric pollution
at any time depends upon meteorological
factors, e.g. topography, air movement
and climate. Winds help in the dispersal
and dilution of pollutants.
If the topography is dominated by
mountains (or tall buildings) the winds
become weak and calm, and pollutants
tend to concentrate in the breathing zone.

32. The vertical diffusion of pollutants depends
upon the temperature gradient. When there is a
rapid cooling of lower layers of air (temperature
inversion) there is a little vertical motion and the
pollutants and water vapours remain trapped at
the lower levels and the result is “smog” – this
way the temperature inversion is a threat to
human health.
All the mentioned factors must be carefully
studied prior to location of industrial factories
near towns and villages and a certain distance
should be kept to avoid health problems of the
residents.

33. Effects of air pollutants
Many urban residents are exposed to air
pollution level above the recommended limits.
In many developing countries air quality has
deteriorated because of raising industrial
activity, increasing power generation and the
combustion of streets with poorly maintained
automobiles that use leaded fuel.
Air pollution can affect by two main ways:

34. 1. Health aspects. The health effects
are both immediate and delayed.
The immediate effects are borne by
the respiratory system, the resulting
state is acute bronchitis. If the air
pollution is intense, it may result even
immediate death by suffocation.
The delayed effects most commonly
are chronic bronchitis, lung cancer,
bronchial asthma and respiratory
allergies.

35. Precise estimates of the risk of air
pollution to health are difficult to
quantify because of problems in
estimating the degree of exposure of
individuals and the influence of possible
compounding variables such as nutrition,
smoking, occupation and climate.
The elderly, children, smokers and
those with chronic respiratory difficulties
are most vulnerable.

36. Major air pollutants, their sources and adverse
effects
Noxious agent Sources Adverse effects
Oxides of nitrogen Automobile exhaust, Respiratory tract irritation,
combustion of fuel to generate bronchial hyperactivity,
heat and power, gas and wood impaired lung defences,
stoves, many industries bronchialitis obliterans
Hydrocarbons Automobile exhaust, Lung cancer
combustion of fuel to generate
heat and power, cigarette
smoke
Ozone Automobile exhaust, high Cough, substernal discomfort,
attitude aircraft cabins bronchoconstriction, respiratory
tract irritation
Sulfur dioxide Combustion of fuel to generate Exacerbation of asthma,
heat and power, smelters, oil respiratory tract irritation
refineries
Lead Automobile exhaust using Impaired neuropsychological
leaded gasoline development in children

37. Effects of air pollutants
2. Social and economic aspects.
Air pollution generates various economic losses
but their detailed estimation is extremely difficult.
They may be divided into four groups:
 expenses for air quality protection;
 expenses generated by the worse health condition of
the society;
 losses of raw materials which become air pollution;
 losses caused by the increased corrosion of machines,
buildings, and damage of historical buildings and
monuments.

39. Effects of air pollutants
Anthropogenic global warming (AGW),
a recent warming of the Earth's lower
atmosphere as evidenced by the global mean
temperature anomaly trend, is believed to be the
result of an "enhanced greenhouse effect"
mainly due to human-produced increased
concentrations of greenhouse gases in the
atmosphere and changes in the use of land.

40. The greenhouse effect refers to
the change in the steady state
temperature of a planet or moon
by the presence of an atmosphere
containing gas that absorbs and
emits infrared radiation.

41. Greenhouse gases include water vapor,
carbon dioxide and methane.
The greenhouse effect, is generally
believed to come from the build up of carbon
dioxide (CO2) gas in the atmosphere.
Plants convert carbon dioxide back to
oxygen, but the release of carbon dioxide
from human activities is higher than the
world's plants can process. The situation is
made worse since many of the earth's forests
are being removed, and plant life is being
damaged by acid rain.

42. Basic mechanism
The Earth receives energy from the Sun
mostly in the form of visible light. The bulk of
this energy is not absorbed by the atmosphere
since the atmosphere is transparent to visible
light.
50% of the sun's energy reaches the
Earth which is absorbed by the surface as
heat. Because of its temperature, the Earth's
surface radiates energy in infrared range.

43. Basic mechanism
The Greenhouse gases are not transparent
to infrared radiation so they absorb infrared
radiation.
They warm the atmosphere by efficiently
absorbing thermal infrared radiation emitted by
the Earth’s surface, by the atmosphere itself,
and by clouds.
As a result of its warmth, the atmosphere
also radiates thermal infrared in all directions,
including downward to the Earth’s surface.

45. Basic mechanism
Thus, greenhouse gases trap heat
within the surface-troposphere system.
Infrared radiation is absorbed from all
directions and is passed as heat to all gases
in the atmosphere. The atmosphere also
radiates in the infrared range (because of its
temperature, in the same way the Earth's
surface does) and does so in all directions.

46. The surface and lower atmosphere are
warmed because of the greenhouse gases and
makes our life on earth possible.
In the absence of the greenhouse effect
and an atmosphere, the Earth's average
surface temperature of 14 °C (57 °F) could be
as low as −18 °C (−0.4 °F). In our solar
system, Mars, Venus, and the moon Titan also
exhibit greenhouse effects according to their
respective environments. In addition, Titan
has an anti-greenhouse effect and Pluto
exhibits behavior similar to the anti-
greenhouse effect.

49. This mechanism is fundamentally
different from the mechanism of an
actual greenhouse, which instead isolates
air inside the structure so that the heat is
not lost by convection and conduction.

50. Effects of air pollutants
Stratospheric ozone depletion due to
air pollution has been recognized as a
threat to human health as well as to the
Earth's ecosystems.
The ozone layer in the stratosphere
protects the earth from harmful ultraviolet
radiation from the sun.

51. Ozone depletion describes two
distinct, but related observations:
- a slow, steady decline of about 4 percent
per decade in the total volume of ozone in
Earth's stratosphere (ozone layer) since the
late 1970s, and
- a much larger, but seasonal, decrease in
stratospheric ozone over Earth's polar
regions during the same period.

53. The latter phenomenon is commonly
referred to as the ozone hole. In addition to
this well-known stratospheric ozone
depletion, there are also tropospheric ozone
depletion events, which occur near the surface
in polar regions during spring.
The detailed mechanism by which the
polar ozone holes form is different from that
for the mid-latitude thinning, but the most
important process in both trends is catalytic
destruction of ozone by atomic chlorine and
bromine.

54. The main source of these halogen atoms in the
stratosphere is photodissociation of
chlorofluorocarbon (CFC) compounds,
commonly called freons, and of bromo-
fluorocarbon compounds known as halons.
These compounds are transported into
the stratosphere after being emitted at the
surface. They are released from aerosol
sprays, polystyrene containers, refrigerator
coolant and air conditioning units. Both ozone
depletion mechanisms strengthened as
emissions of CFCs and halons increased.

55. CFCs and other contributory substances
are commonly referred to as ozone-depleting
substances (ODS).
Since the ozone layer prevents most
harmful UVB wavelengths (270–315 nm) of
ultraviolet light from passing through the
Earth's atmosphere, observed and projected
decreases in ozone have generated worldwide
concern leading to adoption of the Montreal
Protocol banning the production of CFCs and
halons as well as related ozone depleting
chemicals such as carbon tetrachloride and
trichloroethane.

56. It is suspected that a variety of
biological consequences such as increases
in skin cancer, damage to plants, and
reduction of plankton populations in the
ocean's photic zone may result from the
increased UV exposure due to ozone
depletion.

57. Consequences of ozone layer
depletion
Increased UV
Although decreases in stratospheric ozone are
well-tied to CFCs and there are good theoretical
reasons to believe that decreases in ozone will lead
to increases in surface UVB, there is no direct
observational evidence linking ozone depletion to
higher incidence of skin cancer in human beings.
This is partly due to the fact that UVA, which
has also been implicated in some forms of skin
cancer, is not absorbed by ozone, and it is nearly
impossible to control statistics for lifestyle changes
in the populace.

58. Because it is this same UV radiation that
creates ozone in the ozone layer from O2
(regular oxygen) in the first place, a reduction
in stratospheric ozone would actually tend to
increase photochemical production of ozone at
lower levels (in the troposphere), although the
overall observed trends in total column ozone
still show a decrease, largely because ozone
produced lower down has a naturally shorter
photochemical lifetime, so it is destroyed before
the concentrations could reach a level which
would compensate for the ozone reduction
higher up.

59. Effects of ozone layer depletion on
humansradiation absorbed by
UVB (the higher energy UV
ozone) is generally accepted to be a contributory factor to
skin cancer. In addition, increased surface UV leads to
increased tropospheric ozone, which is a health risk to
humans. The increased surface UV also represents an
increase in the vitamin D synthetic capacity of the
sunlight.
The cancer preventive effects of vitamin D represent
a possible beneficial effect of ozone depletion. In terms of
health costs, the possible benefits of increased UV
irradiance may outweigh the burden.

60. Effects of ozone layer depletion on
humans
1. Basal and Squamous Cell Carcinomas
The most common forms of skin cancer in humans,
have been strongly linked to UVB exposure. The
mechanism by which UVB induces these cancers is
well understood — absorption of UVB radiation
causes the pyrimidine bases in the DNA molecule
to form dimers, resulting in transcription errors
when the DNA replicates. By combining
epidemiological data with results of animal studies,
scientists have estimated that a one percent
decrease in stratospheric ozone would increase the
incidence of these cancers by 2%.

61. 2. Malignant Melanoma - Another form of
skin cancer, is much less common but far
more dangerous, being lethal in about 15% -
20% of the cases diagnosed. The relationship
between malignant melanoma and ultraviolet
exposure is not yet well understood, but it
appears that both UVB and UVA are
involved. Experiments on fish suggest that 90
to 95% of malignant melanomas may be due
to UVA and visible radiation whereas
experiments on opossums suggest a larger
role for UVB.

62. Because of this uncertainty, it is difficult
to estimate the impact of ozone depletion on
melanoma incidence. One study showed that a
10% increase in UVB radiation was
associated with a 19% increase in melanomas
for men and 16% for women. A study of
people in Punta Arenas, at the southern tip of
Chile, showed a 56% increase in melanoma
and a 46% increase in nonmelanoma skin
cancer over a period of seven years, along
with decreased ozone and increased UVB
levels.

63. 3. Cortical Cataracts - Studies are
suggestive of an association between ocular
cortical cataracts and UV-B exposure.
4. Increased Tropospheric Ozone -
Increased surface UV leads to increased
tropospheric ozone. Ground-level ozone is
generally recognized to be a health risk, due
to its strong oxidant properties. At this time,
ozone at ground level is produced mainly by the
action of UV radiation on combustion gases
from vehicle exhausts.

64. Prevention activities
The problem of air pollution is
worldwide and transcends national
boundaries.
Though air pollution is still a serious
problem, in many countries in the world,
steps are being taken to stop the
damage to our environment from air
pollution.

65. Many electric power plants, factories,
and facilities that burn wastes are
equipped with devices called scrubbers.
Scrubbers remove sulfur dioxide and other
pollutants before the wastes are released
into the air.
Also, today's cars are designed to
create less pollution. Many are equipped
with anti-pollution devices called catalytic
converters, which reduce the amount of
pollution from automobile engines.

66. Most polluted cities
Air pollution is usually concentrated
in densely populated metropolitan areas,
especially in developing countries where
environmental regulations are relatively lax
or nonexistent.
However, even populated areas in
developed countries attain unhealthy levels
of pollution.

67. Most Polluted World Cities by PM
Particulate matter,
City
μg/m³ (2004)
169 Cairo, Egypt
150 Delhi, India
128 Kolkata, India (Calcutta)
125 Tianjin, China
123 Chongqing, China
109 Kanpur, India
109 Lucknow, India
104 Jakarta, Indonesia
101 Shenyang, China

68. Carbon dioxide emissions
Total CO2 emissions
106 Tons of CO2 per year:
• United States: 2, 795
• China: 2,680
• Russia: 661
• India: 583
• Japan: 415
• Germany: 356
• Australia: 300
• South Africa: 232
• United Kingdom: 212
• South Korea: 185

69. Per capita CO2 emissions
Tons of CO2 per year per capita:
• Australia: 10
• United States: 8.2
• United Kingdom: 3.2
• China: 1.8
• India: 0.5