Com. MefMBBS - CONTROL OF AIR POLLUTION.pptx

CONTROL OF AIR POLLUTION
DR. CHIJIOKE EZENYEAKU
DEPARTMENT OF COMMUNITY MEDICINE
NNAMDI AZIKIWE UNVERSITY

INTRODUCTION
• Air is the invisible mixture of gases that surround the Earth.
• Air in its pure form is made up of approximately the following -
 78.1% of Nitrogen,
 20.93% of oxygen,
 0.03% of carbon dioxide
 Traces of other gases like argon, neon, krypton, xenon, methane, helium and water vapour.

INTRODUCTION
• The ambient or prevailing local air can also contain natural substances from various biotic and abiotic sources
including organic vapours, spores and pollens, particulate matter and vapours, dust and industrial effluents
and emissions, etc.
• These additions to the ambient air are mainly due to –
1. Respiration of men and animals
2. Combustion of coal, gas, oil, etc
3. Decomposition of organic matter
4. Trade, traffic and manufacturing processes which give off dust, fumes, vapours and gases
• These additions may render the air impure.

INTRODUCTION
• The composition of outdoor air is remarkably constant under normal circumstances due to the
following self-cleansing mechanisms that operate in nature –
1. Wind – Dilutes and sweeps away impurities by its movement thereby preventing the impurities
from accumulating in one place
2. Sunlight – The atmospheric temperature and sunlight act by oxidizing impurities and killing
bacteria
3. Rain - Cleanses the atmosphere by removing the suspended and gaseous impurities
4. Plant life – The green plants utilize carbon dioxide and generate oxygen during the day. The
process is reversed during the night.

INTRODUCTION
• Harmful substances will accumulate in the ambient air and cause air pollution when the following
prevailing environmental conditions prevent their dispersion or dilution –
1. Temperature inversion which prevents the ascent of hot contaminated air and the descent of cold
cleaner air
2. Poorly ventilated houses which prevent the dispersal of pollutants
3. Mountains and high-rise buildings which can block the circulation of air

INTRODUCTION
• Air pollution is said to occur when the substances in the ambient air
attain concentrations that can adversely affect human health or are
capable of causing damage to property, plant or animal life.
• Air pollution is usually due to the release of pollutants that are
detrimental to human health and plant life into the air.
• The pollutants may result from the indiscriminate disposal of gaseous
refuse or it can be due to solid and liquid refuse.

SOURCES OF AIR POLLUTION
• Air pollution is mainly due to the various activities of man and some natural occurrences.
• Human activities resulting in air pollution -
1. Specific industrial processes – Examples –
i. Industries and manufacturing plants emitting a lot of sulphur dioxide, and carbon dioxide as well as other
organic compounds and chemicals into the atmosphere,
ii. Petroleum refinery releasing a lot of hydrocarbons
iii. Rayon, canning and dye-making industries emitting hydrogen sulphide

iv. Aluminium and fertilizer industries which discharge hydrogen fluoride as well as
other carcinogenic hydrocarbons discharged from organic chemical industries
v. Combustion from automobile exhausts discharging carcinogenic hydrocarbons,
oxides of nitrogen, carbon monoxide, organic lead, some hydroarbons and other
particulates
vi. Steel heat blast furnaces discharging carbon monoxide
vii. Gas flaring

2. Personal habits – These result from household and farming chemicals. Examples -
i. Fumigation or spraying with insecticides, herbicides and other chemicals eg paints
ii. Smoking which may lead to the discharge of carbon monoxide and hydrocarbons
iii. Burning oils discharging sulphur dioxide, etc

• Natural causes / events resulting in air pollution –
1. Volcanic eruptions
2. Natural radioactivity
3. Wind erosions
4. Pollen grains, dusts, mould spores, vegetable fibres, dispersals from plants, including micro organisms
5. Carbon monoxide and other gases discharged from coal mines, etc

TYPES OF AIR POLLUTANTS
• These are varied and are classified based on the following -
1. Based on the mode of formation -
a. Primary pollutants – These are formed and emitted directly from a particular source into the air. Eg - Particulates,
carbon monoxide, nitrogen oxide, and sulfur oxide smokestacks from a point source or specific locations of highly
concentrated discharge
b. Secondary pollutant – These are pollutants that become hazardous after reactions in the air. Eg – photochemical
oxidants, atmospheric acids, etc

2. Based on the emission from burning conventional and alternative fuels
a. Conventional or criteria pollutants – These are a group of seven major pollutants that contribute the largest
volume of air quality degradation and is the most serious threat of all air pollutants to human health. The
Environmental protection agency is therefore required to set standards for them based on certain health and
environmental "criteria." Eg - Sulphur dioxide, carbon monoxide, particulates, volatile organic compounds,
nitrogen oxides, ozone and lead.
b. Unconventional or non - criteria pollutants – These are produced in less volumes than the conventional ones
but are also toxic or hazardous. They are not regulated by the Environmental protection agency. Most of
these pollutants are anthropogenic in origin ie have no natural source in the environment to a great extent.
Eg – Asbestos, benzene, beryllium, mercury, polychlorinated biphenyls and vinyl chloride.

3. Based on the environment where they are generated
a. Indoor air pollution - Indoor air pollution refers to the contamination of the air inside buildings. It is a common
problem globally since many people spend most of their time indoors. It is mainly due to the use of biomass
fuels, and environmental tobacco smoke. Air pollution from the fireplace affects mainly the women who are
traditionally responsible for food preparation and cooking, and the infants/young children who are usually with
their mothers near the cooking area while ETS affects both the smoker and non-smoker.
• Outdoor air pollution - Outdoor air pollution is a complex mixture of pollutants in the air originating from natural
and anthropogenic sources, the mix of which varies widely in space and time depending on the diversity of the
sources and the influence of atmospheric processes. Eg. vehicle emissions, industrial activities, and natural events
like wildfires.

EFFECTS OF AIR POLLUTION
• These are varied and include the following -
Health effects - Determined by the level of pollution and the amount of time spent breathing the polluted air. Egs -
1. Acute lower respiratory infection in children, particularly pneumonia – Exposure to solid fuel smoke is responsible for up
to 35% of all ALRI.
2. Chronic obstructive pulmonary disease – Exposure to indoor smoke from biomass is responsible for about 22% of all
COPD
3. Lung cancer particularly from exposure to coal smoke in the house – Cooking with the traditional fireplace is equivalent to
smoking several sticks of cigarrete per day. Cooking for 3 hours is equivalent to smoking 2 packets of cigarettes.
4. Low birth weight – Women that cook with firewood have babies that are an average of 63g less than those that use cleaner
fuel due to prolonged exposure to carbon monoxide poisoning

5. Asthma – Wood smoke pollution can exacerbate and or trigger asthmatic attack
6. Tuberculosis – People in homes that use wood for cooking are 2.5 times more
likely to develop active tuberculosis due to reduced resistance to infection
7. Naso-pharyngeal and laryngeal cancer – Due to known carcinogens like
benzene found in wood smoke
8. Cataract in adults – Wood smoke, like cigarette smoke, causes damage to the
lens causing discolouration, opacities and particulate debris.

Other Health Effects –
1. Heart diseases - heart attacks, strokes
2. Neurological problems - Cognitive impairment, neurodegenerative diseases
3. Other effects - Birth defects, cancers, Irritation eg of the eyes

Effects on the vegetation – Fumes from furnaces, smelters, refineries and chemical plants destroy the
vegetation and create desolate and baren landscapes around mining and manufacturing areas.
Effects on the ecosystem – Air pollution creates smog which affects visibility, and acid rain as well as depletes
the ozone layer thereby contributing to global warming. These changes are referred to as climate change.
Climate change is becoming a constantly increasing problem due to air pollution.

• Visibility problems – Gases, particles and other pollutants in the air can combine to form smog which affects
visibility. Particulates in the air can also cause visual impairment.
• Acid rain – Chemical and toxic pollutants like nitrogen oxide, sulphur dioxide and carbon dioxide react with
water molecules in the atmosphere to produce aid rain which can damage crops and induce corrosion of
metals as well as cause harmful effects to living things including aquatic animals and fauna. Acid rain also
damages buildings.

Ozone depletion –
• The ozone-depleting substances such as chlorofluorocarbon (CF), hydrofluorocarbon
(HCFC), methyl bromide, halon, methyl-chloroform, etc, which are mainly bye-products of
manufacturing processes in the atmosphere can react with the ultra-violet rays in the sun to
produce chlorine and bromine atoms.
• These compounds (Chlorine and bromine) react with the ozone molecules in the ozone layer
by binding to the oxygen atoms of ozone, thereby destroying the ozone and leading to the
degradation or depletion of the ozone layer.
• The ozone layer filters the sun’s ultraviolet radiation and shields man from its harmful
effects.
• A diminished ozone layer therefore allows more radiation to reach the earth’s surface and
leads to harmful effects such as skin cancer, cataract and weakened immunity in man as well
as a reduction in crop yield and disruption of marine food chain.

Global warming –
• A number of human activities, eg combustion of fossil fuels in cars, factories and electricity
production, lead to the emission of excessive amounts of green house gases to the atmosphere.
• These gases such as water vapour, carbon dioxide, nitrous oxide, methane, chlorofluorocarbon,
etc., slow the escape of heat that would normally escape into the outer space.
• They trap the heat which reflects back to the earth’s surface where it builds up, causing a rise in
global temperature.
• The progressive warming up of the earth’s surface due to the blanketing effect of the green
house gases is known as global warming.
• The consequences of global warming include heat waves, breeding of mosquitoes and other
insects, flooding due to the melting of polar ice, dangerous weather events such as hurricanes,
reduced crop production, increased infectious diseases and vector-borne diseases, food and
water-borne diseases, poverty, hunger, death, etc.

• Control of air pollution involves a combination of government policies, technological innovations, and
individual actions such as -
• Site selection – Careful planning of the residential areas, industrial zones and highways to ensure that air
pollution is minimized and reduced. The government can also designate and map out national air control
zones and urban green spaces and declare the air quality objectives for each these designated zones.

• Legislation and health education – Through effective legislation backed up by health education, the
government can set emission and air quality standards and compel all, especially the major industrial air
pollutants, to meet the set standards. Penalties are then extracted from defaulters. The polluter is also
responsible for the mitigation and remediation of the effects of the pollution, including paying compensation
to individuals that suffered significantly from the pollution.
• Monitoring – Through regular monitoring of industrial gases, fumes and vapours to ensure that they are at
low levels. There should be licensing and registration of all major industrial air polluters and the monitoring
of their compliance with the set standards. Air quality monitoring can be done using stations, sensors, satellite
remote sensing while Air quality modelling can be done through dispersion models and emission inventories.

• Process re-design and equipment modification – Through the use of tall chimneys, substitution of raw
materials, reduction of pollution at source, wet methods to reduce the dust and use of electrostatic precipitators to
capture particulate matter, scrubbers to remove pollutants from industrial emissions and catalytic converters to
convert toxic gases to less toxic ones.
• Mitigation of the use of fossil fuels - Mitigation involves measures such as tree planting to reduce carbon
dioxide, use of electric cars and bicycles which are emission free, trapping the sun for solar energy, use of solar
lanterns at homes and other measures that reduce the use of fossil fuels, E.g. - natural gas, electricity. Mitigation of
the use of fossil fuels will go a long way especially in reducing global warming and climate change in general.

Additional Measures -
• The use of advanced fuel technologies. Eg. cleaner diesel and biofuels.
• Using public transport, cycling, or walking.
• Reducing energy consumption by turning off appliances when not in use, and
using energy-efficient devices such as LED lights
• Avoiding burning waste, using eco-friendly products.

Com. MefMBBS - CONTROL OF AIR POLLUTION.pptx

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