Air
• Air is the major constituent of the human
environment. It plays a vital role for supplying
the life giving oxygen. Human being needs
continuous supply of air.
• The requirement for air is relatively constant
(about 10-20 m3 per day)
Composition of air
Air is a mechanical mixture of gases. The normal
composition of external air by volume is
approximately as follow:
• Nitrogen : 78.1%
• Oxygen : 20.93%
• Carbon dioxide: 0.03%
In additional to these, argon, neon, krypton, xenon,
helium and other gases are also present in trace
amount.
AIR POLLUTION
Air pollution is the introduction of physical,
chemical or biological materials that cause
harm or discomfort to humans or other living
organism, or damage the natural environment
into the atmosphere.
WHO defines air pollution as “ Limited to
situation in which the outer ambient
atmosphere contains material in concentration
which are harmful to human beings and their
environment.
SOURCES OFAIR POLLUTION
1. Automobiles
Motor vehicles are a major source of air
pollution throughout the urban areas. They
emit hydrocarbon, carbon monoxide, lead,
nitrogen oxide and particulate matter.
In strong sunlight, certain of these
hydrocarbons and oxides of nitrogen may be
converted in the atmosphere into
“photochemical” pollutants.
In addition diesel engines, when misused or
badly adjusted are capable of emitting black
smoke and malodorous fumes.
2. Industries
Industries emit large amount of pollutant into the
atmosphere. Combustion of fuel to generate heat
and power produces smoke, sulphur dioxide,
nitrogen oxide and fly ash.
Petrochemical industries generate hydrogen
fluoride, hydrochloric acid and organic halides.
Many industries discharge carbon monoxide,
carbon dioxide, ozone, hydrogen sulphide and
sulphur dioxide.
Industries discharge their wastes from high
chimneys at high temperature and high speed.
3. Domestic sources
Domestic combustion of coal, wood or oil is a
major source of smoke, dust, sulphur dioxide
and nitrogen oxides.
4. Tobacco smoking
The most direct and important source of air
pollution affecting the health of many people
is tobacco smoke. Even those who do not
smoke may inhale the smoke produced by
others.
5. Burning of Tyres
Tyres burning practice in different political
movement like strike and while burning dead
bodies in big cities like Kathmandu, Pokhara,
Biratnagar, Birjung, Nepalgunj is also the
source of air pollution.
6. Other sources
These comprises burning refuse, incinerators,
pesticide spraying, natural sources e.g. wind
borne dust, fungi, bacteria, etc
Major primary pollutant, their sources and
adverse effects are:
Agent Sources Adverse effect
1. Oxides of automobile exhaust gas respiratory tract
nitrogen stoves and heaters, wood infection, bronchial
burning stove, kerosene hyperactivity ,impaired
space heater lung defense
2. Hydrocarbons automobile exhaust, lung cancer
cigarette smoke
Agent Sources Adverse effect
3. Sulphur power plant, oil increase asthma
dioxide refineries, kerosene and COPD,
space heater respiratory tract
irritation, death may
occur
4. Lead impaired
Automobile exhaust
using leaded gas line neuropsychological
development in
children
INDICATORS OFAIR POLLUTION
1. Sulphur dioxide
This gas is a major contaminant in many urban and
industrial areas. Its concentration is estimated in
monitoring air pollution surveys.
It can affect the respiratory system and the function of
lungs, and causes irritation of eyes.
2. Carbon monoxide
Carbon monoxide is one of the most common and
widely distributed air pollutants. It is a product of
incomplete combustion of carbon containing
materials, such as in automobiles, industrial process,
heating facilities and incinerators.
3. Suspended particles
More than 10 micron is considered for total suspended
particles. Suspended particles are harmful to health and it is
measured per unit area.
4. Carbon dioxide
Carbon dioxide is a natural constituent of the air. Normal
content of carbon dioxide in air is 0.03% and if it is beyond
this standard concentration, then it is hazardous. However,
its global concentration is rising above the natural level by
human activity by an amount that could increase global
temperature enough to affect climate noticeably .
5. Hydrocarbons :
Man-made sources of hydrocarbons include incineration,
combustion of coal, wood, processing and use of
petroleum. Hydrocarbons exert their pollutant action by
taking part in the chemical reactions that cause
photochemical smog.
6. Cadmium
The steel industry, waste incineration, volcanic
action and zinc production emit cadmium in
the environment.
Tobacco contains cadmium, and smoking may
contribute significantly to the uptake of
cadmium. Cigarettes may contain from 0.5 to 3
μg cadmium per gram of tobacco, depending
on the country of origin.
7. Ozone
Ozone at ground level is one of the major constituents
of photochemical smog. It is formed by the
photochemical reaction of sunlight with pollutants such
as nitrogen oxides from vehicle, industry emissions and
volatile organic compounds (VOCs) emitted by
vehicles, solvents and industry.
The highest levels of ozone pollution occurs during
periods of sunny weather.
Excessive ozone in the air can have a marked effect on
human health. It can cause breathing problems, trigger
asthma, reduce lung function and cause lung diseases.
EFFECTS OFAIR POLLUTION
a. Health aspects
The extent to which an individual is harmed by
air pollution usually depends in the duration of
exposure and the concentration of chemicals
must be taken into account. Health effects must
be categorized as immediate and delayed effect.
1. Immediate/ short term effects
Irritation to the eye, nose and throat
Chest pain, burning eyes and cough
Acute bronchitis
Other symptoms can include headache,
nausea, allergic reaction
Suffocation, it may lead to death
2. Delayed/ long term effects
Chronic bronchitis
Bronchial asthma
Emphysema
Lung cancer
Respiratory allergies
Lead poison may lead to impaired
neuropsychological development in children
b. Social and economic aspects
These comprises destruction of plant and
animal life, corrosion of metals, damage to
building, cost of cleaning and maintenance and
repairs.
Air pollution reduces visibility in town.
It can damage soil and clothing.
AIR POLLUTANT
An air pollutant is known as substance in the air that
can cause harm to humans and the environment.
Pollutants can be in the form of solid particles,
liquid droplets or gases. In addition, they may be
natural or man made.
Pollutants can be classified as Primary & secondary
A. Primary pollutant
Primary pollutant are the substance directly emitted
from a process such as ash from a volcanic
eruption, carbon monoxide gas from motor vehicle
exhaust.
B. Photochemical smog
Particulate matter formed from gaseous primary
pollutant and compound is photochemical smog. It is of
2 types:
1. Classic smog
Classic smog results from large amount of coal burning
in an area caused by a mixture of smoke and sulfur
dioxide.
2. Modern smog
Modern smog doesn’t usually come from coal but from
vehicular and industrial emission that are acted upon in
the atmosphere by sunlight to from secondary pollutant
that also combine with primary emission to form
photochemical smog.
Ground level ozone formed from nitrogen oxide and
volatile organic compounds.
CONTROLOFAIR POLLUTION (WHO)
Prevention and control of air pollution
The control of air pollution is ultimately an engineering
problem. The WHO recommended the following
procedures for the prevention and control of air pollution.
1. Containment
It is the prevention of escape of toxic substance into the
ambient air. Containment can be achieved by a variety of
engineering methods such as enclosure, ventilation and
air cleaning.
2. Replacement
It is replacing a technological process causing air
pollution by a new process that does not. Increased use
of electricity and natural gas in place of coal has greatly
helped in smoke reduction.
3. Dilution
Dilution is valid so long as it is within the self
cleaning capacity of the environment. The
establishment of “GREEN BELT” between
industrials and residential areas is an attempt at
dilution
4. Legislation
Air pollution is controlled in many countries by
suitable legislation.
5. International action
To deal with air pollution on worldwide scale, the
WHO has established as international network of
laboratories for the monitoring and study of air
pollution.
Following measures can be adopted for the prevention and control of
air pollution
1. Carpool
Carpool is the shared use of car by the driver and one or more
passengers, usually for commuting. ( commuting is regular
travel between one’s place of residence and place of work or
full time study)
2. Vehicle care
Timely servicing of the car helps to keep it in good condition
and also minimize fuel exhaust.
Driving the car at an average speed and turning off in traffic is
a key to save fuel.
3. Public transport
Whenever possible try to travel by public transport. This helps
in 2 ways:
a. Prevent air pollution
b. Increase public income
If you are going to a nearby place, go by walking and
use bicycle, instead of using your vehicle.
4. Alternative energy source
Another effective way to prevent air pollution is to use
alternative energy source such as solar energy,
hydroelectric energy and wind energy. Nowadays,
sophisticated technology such as wind turbine, solar
water heater are introduced to generate electricity and
other energy forms for the household use.
5. Saving energy
Saving energy will, of course help to prevent air
pollution. Switch off the lights, fans, air conditioner,
TV, etc when not in use. You can also share a room with
others when the air conditioner or fan is in on, instead
of switching them on in every room.
6. Minimize air pollutants
Always try to minimize smoke emission, as it
can contribute to air pollution. One way is to
compost dried leaves and kitchen waste, instead
of burning them. Composting will also give you
organic fertilizer for your garden.
7. Social awareness
Awareness program and or advertisement should
be encouraged, so that people understand the
potential health hazards of air pollution.
DISINFECTION OFAIR
In recent years, disinfection of air has received
much attention. The methods employed are:
1. Mechanical ventilation
This reduces vitiated air and bacterial density.
2. Ultraviolet radiation
This has been found to be effective in special
situation such as operation theatres and
infectious disease wards. Since direct exposure
to ultraviolet radiation is a danger to the eyes
and skin, the ultraviolet lamps are shaded and
located in the upper portion of the rooms near
the inlet of air.
3. Chemical mists
Triethylene glucol vapours have been found to
be effective air bactericides, particularly
against droplet nuclei and dust.
4. Dust control
Application of oil floors of hospital wards
reduces the bacterial content of the air.
Air Pollution in Nepal
Air pollution has been a major problem of 21st
century for both developed and developing world. It
has a negative impact on various environmental
aspects which directly or indirectly affect the quality
of human health. Nepal, especially Kathmandu, in the
current situation, is observing rapid urbanization and
various infrastructure development projects. As a
result, these sorts of human activities have been
responsible for increasing air pollution in an
enormous rate inside Kathmandu Valley. Chronic
exposure of deteriorated air increases the chance of
Non-communicable Disease (NCD) like lung disease,
heart disease, and cancers. Short term exposures also
invite respiratory diseases and allergy
In 2018, Environmental Performance Index (EPI) of
Nepal’s air quality ranked 176th out of 180 countries
and in Asia, Kathmandu is ranked one of the most
polluted cities. According to a report of World Health
Organization (WHO), the maximum status of fine
Particulate Matter (PM2.5) in urban areas of Nepal
was noted to be 140 µg/m3 which is 10 times higher
than the desirable value.
The Department of Environment is planning to
establish air quality monitoring stations throughout
the country. As of today, it is limited in nine places, 3
stations inside Kathmandu Valley and 6 stations
outside the valley.
• Due to vehicular emission, Kathmandu valley
is vulnerable to air pollution as number of
vehicle is increasing day by day.
• Rapid urbanization and exploding population
inflow and valley centric industrialization is
increasing air pollution in city area.
• Rural area is surrounded by heavy indoor air
pollution.
