Download Sources of air pollution

Dr. Jinan Abdul-Amir S. Al-Hussaini
Toxicology//Lect.NO.(
)
Environmental toxicity
1- Air pollution
Introduction:
The presence of noxious gases, metals, non-metals, organic or inorganic volatile
and nonvolatile compounds and other suspended particulates which pose
deleterious effects on the well being of the plants and animals is referred as air
pollution. The major air pollutants includes gases such as carbon monoxide (CO),
carbon dioxide (CO2), sulphur dioxide (SO2) and nitrogen oxides (NO and NO2);
organic compounds such as mixture of hydrocarbons such as olefins, dienes,
polycyclic aromatic hydrocarbons (PAH); metals such as mercury, lead,
chromium, berrylium, nickel, cadmium, etc.; nonmetals such as carbon, sulphur
etc. and particulates of fly ash, smoke, dust etc. These air pollutants are absorbed
into blood circulation from lungs after inhalation or retained in alveolar tissues and
produce acute, subacute, or chronic diseases depending upon the amount and type
of the pollutant.
Sources of air pollution:
Air pollution occurs due to gaseous pollutants, odour, and SPM (suspended
particulate matter) such as dust, fumes, mist, and smoke. The concentration of
theses in and near the urban areas causes severe pollution to the surrounding. The
largest sources of human-created air pollution are energy generation,
transportation, and industries that use a great deal of energy sources. Depending on
their source and interactions with other components of the air, they can have
different chemical compositions and health impacts (see the table below):
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Table (1): Various sources of air pollution
Common atmospheric pollution sources and their pollutants
Sr.No. Category
Argiculture
1
2
Mining and
Quarrying
3
Industrial
4
Power
generation
5
Transport
ion
Community
service
Livestock
6
7
Source
Emitting pollutants
Open burning of
SPM, CO, CO2, smoke, volatile organic
household wood and other
compounds
fuels
Coal mining; crude oil and SPM, sulphur dioxide, oxides of nitrogen,
gas production; stone
metals, nonmetals, volatile organic
quarrying
compounds
Sugar, paper, smelter, kiln SPM, CO, CO2, SO2, sulphur, mercury,
and other industries
lead, smoke, carbon, volatile organic
compounds
Electricity, gas, steam
SPM, oxides of nitrogen, SO2, CO, CO2,
volatile organic compounds, lead, sulphur
trioxide
Automobile exhausts
SPM, CO, CO2, SO2, oxides of nitrogen,
volatile organic compounds, lead
Municipal incinerators
SPM, CO, CO2, SO2, oxides of nitrogen
Cattle dung cake, gobar
gas plants, SPM
SPM, methane, CO, CO2, smoke
Fires are another major source of air pollution and can lead to severe problems
if the smoke is inhaled for a period of time. These fires can either be forest fires,
oil well fires, burning of leaves in the backyard or as in the case of rural areas,
large-scale burning of agricultural waste. Other sources include industries and
power plants located in these areas.
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Forms of air pollution:
1- Indoor and outdoor air pollution:
Indoor air pollution can be particularly hazardous to health as it is released in
close proximity to people. Open fires used for cocking and heating are commonly
found in the household both in the rural and urban areas. In addition, they are often
not fitted with a chimney to remove the pollutants. In such households the children,
women and animals, pets in particular, are most likely to be affected. The main
pollutant in this environment is the SPM.
2- Fly ash:
Thermal power generation through coal combustion produces minute particles
of ash called fly ash, which cause serious environmental and health problems.
These ash particles consist of silica, alumina, oxides of iron, calcium, magnesium,
and toxic heavy metals like lead, arsenic, cobalt, and copper. Fly ash tends to
remain air borne for a very long period causing serious health problems like
irritation to eyes, skin, nose, throat, and respiratory tract. Repeated inhalation of fly
ash dust containing crystalline silica can cause bronchitis and lung cancer.
3- Smog:
The word smog has been coined from a combination of the words “fog” and
“smoke” and refers to hazy air that causes difficult breathing conditions. The term
smog describes the conditions of fog mixed with smoke in it. Smog is a
combination of various gases with water vapour and dust. It is produced when
fuels are burnt and sunlight reacts with these gases and fine smoke particles in the
air.
4- Carbon pollution:
Carbon pollution is the release of tiny particles into the air from burning fuel for
energy. Air pollution caused by such particulates has been a major problem since
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the beginning of the industrial revolution and the development of the internal
combustion engine.
5- Acid rain:
This phenomenon occur when sulphur dioxide and nitrogen oxides from the
burning of fossil fuels such as petrol, diesel, and coal combine with water vapour
to form sulphuric and nitric acid in the atmosphere and fall as rain, snow, or fog.
These gases can also be emitted from natural sources like volcanoes.
6- Ozone depletion:
There has been a slow and steady decline of about 4 percent per decade in the
total amount of ozone in earth’s stratosphere particularly a much larger, but
seasonal, decrease in stratospheric ozone over earth’s polar regions since around
1980. The later phenomenon referred to as the “ozone hole”.
Toxic effects of major air pollutants:
These effects can be summarized in the following table:
Table (2): toxic effects of major air pollutants
Name of air
Toxic effects
pollutant
Respiratory illness including; chronic bronchitis, pneumoniosis, restrictive lung
SPM
SO2
NO2
Benzene
Ozone
CO
Lead
disease, asthma, cancer and heart disease.
Heart disease, respiratory problems including pulmonary emphysema, cancer,
eye burning, headache, etc.
Lung irritation, viral infection, airway resistance, chest tightness, etc.
It cause immunotixicity, carcinogenicity, asthma, anemia, unconsciousness, etc.
Impaired lung function, chest pains, coughing, irritation of eyes and nose, etc.
CO poisoning cause cherry lips, unconsciousness, death by asphyxiation, etc.
It causes decrease hemoglobin synthesis, anemia, damage the nervous and renal
system, etc.
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2- Water pollution:
When water is unfit for its intended use, it is considered polluted. Water
pollution is defined as the addition of any substance or material to a body of water
making it foul or unclean and dirty and unfit for health of man and animals.
Sources of water pollution:
Water may be polluted in two ways:
A) Point source of pollution which occurs when harmful substances are emitted
directly into a body of water. Release of industrial effluents into water is an
example of point source of water pollution.
B) Non-point source in which pollutants are added to water indirectly through
environmental changes. An example of non-point type of water pollution is
when fertilizer from field is carried into a stream by rain in the form of
runoff affecting aquatic life.
Causes of water pollution:
Sewage as leaves and grass clippings, or as runoff from livestock feedlots and
pastures and fertilizers released into water contain nutrients such as nitrates and
phosphates in excess levels which over stimulate the growth of bacteria, protozoa,
plants, and algae. Excessive growth of these types of organisms use up dissolved
oxygen and block light to deeper water and proves very harmful to aquatic
organisms as it affects the respiration ability of aquatic flora and fauna. Many
types of fish and other animals cannot survive in levels of dissolved oxygen below
2-5 ppm, consequently, death of aquatic organisms in large numbers leads to
disruption in the food chain.
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3- Radiation hazards:
Radiation is defined as energy travelling through space. Non-ionizing radiation
is essential to life, but excessive exposures will cause tissue damage. All forms of
ionizing radiation have sufficient energy to ionize atoms that may destabilize
molecules within cells and lead to tissue damage.
Sources of radiation hazards:
(A)
Ionizing or nuclear radiation:
Ionizing or nuclear radiation differs from heat and other types of radiation in
that each particle or photon has a sufficiently high energy to cause ionization.
Radioactive particles are alpha, beta (electrons) and neotrons.
(B)
Non-ionizing radiation:
Non-ionizing radiation is described as a series of energy waves composed of
oscillating electric and magnetic fields travelling at the speed of light. It includes
the followings:
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Electromagnetic radiation
Extremely low frequency radiation (ELF)
Radio frequency and microwave radiation
Infrared radiation
Visible light radiation
Ultraviolet radiation
Laser hazards
Ultrasonic radiation
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Mechanism of radiation toxicity:
Ionizing radiation comprising alpha and beta particles and gamma rays loses
energy when passing through organic matter by releasing ion pairs of an electron
and a positively charged atoms. Ionization can break the bonds in the DNA and
subsequently damage DNA. These ion pairs rapidly interact with organic
molecules in the tissues and produce free highly reactive oxidative species (ROS)
radicals by forming super oxide O2. anion which subsequently converted to a
strong oxidizing agent hydrogen peroxide. Free radicals or H2O2 cause cellular
damage by interacting and disrupting structure and function of proteins, amino
acids, carbohydrates, nucleic acids, lipids, thiols, etc. damage to DNA results in
mutation, chromosomal aberrations and loss of genes subsequently leading to cell
death. The extent and rate of chromosomal aberrations is directly related to
radiation dose.
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