2- What is air pollution?
Many types of pollutants enter the atmosphere as a result of natural and artificial activities caused by human activities on earth, so air pollution generally means the presence of a foreign substance in the air. According to one definition, air pollution is defined as:
Air pollution is the presence of any type of pollutant, including solid, liquid, gas or radioactive and non-radioactive radiation in the air in the number and duration of quality of life for humans and other living things Endanger or damage antiquities and property.
3- Air pollution sources:
For ease of studying different sources of air pollution are classified as follows:
Natural resources and artificial resources (domestic, industrial, transportation)
1-3- Natural resources:
Natural sources of air pollution such as dust storms, forest fires, volcanoes, plant pollen and natural gas leaks are a permanent phenomenon that is more or less constant due to the circulation of natural processes. The amount of natural pollution is much higher and more significant than artificial pollution. But in nature there are several self-purification mechanisms that make the earth’s surface suitable and tolerable for the life of living things. The role of humans in controlling pollution from natural resources is very small. But humans can worsen the situation and add to natural pollution by upsetting the ecological and natural balance caused by artificial pollution.

2-3- Artificial resources
1-2-3- Household pollution: Household
pollution is caused by household activities or cleaning the house or using insecticides to clean and maintain the house. Although the amount of this pollution is not high compared to other sources, but the same amount helps to change the quality of the urban environment. Proper home maintenance practices will help reduce pollution.

2-2-3- Industrial pollution:
Pollution from industries is the main source of pollution caused by artificial activities. Among the thermal power plant industries, chemical plants, cement factories, paper mills, textiles, tanners, etc. are the main sources of air pollution. Applying appropriate pollution control methods will help reduce resource pollution.

3-2-3- Traffic pollution (transportation):
Pollution caused by transportation is as important as industrial pollution due to rapid urbanization. Pollution from transportation and vehicles is in the form of exhaust fumes, particulate matter, noise, and so on. This pollution is minimized by adopting national, regional and urban planning methods and the use of appropriate cars and fuels along with the application of pollution control technology.
However, the EPA has classified major sources of air pollution as follows:
a) Transportation such as ships, airplanes, trains and cars
b) Combustion of fuel from fixed sources such as power plants etc.
c) Industrial processes such as steel mills, textiles And paper making
D: Disposal of solid waste such as: outdoor waste incineration, sanitary landfill and waste incineration with incinerator
Miscellaneous processes such as household activities such as: application of insecticides and cleaning of insecticides

4- Factors affecting air pollution The
factors that affect air pollution are as follows.

1-4- Meteorological characteristics Atmospheric
parameters such as wind size and direction, atmospheric drop rates, relative humidity, etc. of an area will affect air pollution. The wind will move the pollutant horizontally.
Pollution carried by downward wind speeds. The concentration of pollutants on the earth’s surface mainly depends on the size and direction of the wind and the amount of drop. Changing the air temperature with increasing altitude causes the pollutants to move relatively fast.

2-4- ‌ The topographic shape of the
rugged terrain and obstacles such as mountains, etc. affect the release of pollutants. Depending on the local situation, topography may be beneficial or harmful.

3-4-‌ Characteristics of pollutants The
importance of air pollution issues depends on the type and size of the pollutant, whether it is solid or liquid or gaseous. It also depends on energy or sound or heat or radioactivity or a combination of these factors. Reactions between pollutants in the atmosphere may increase or decrease the amount of pollutants in the atmosphere, depending on the characteristics of the pollutants.

4.4-‌ Pollutant release method
How pollutants enter as well as the rate of release of pollutants into the atmosphere affect air pollution. Contaminants may be released intermittently or continuously or periodically, or from a single source or from multiple sources, or from point and non-point sources. The distribution of pollutants also depends on how they enter the atmosphere.

Classification of Pollutants
The American Environmental Protection Agency (EPA) has selected six major pollutants as criteria and divided them into primary and secondary categories. Primary pollutants are substances that enter the air directly from sources and include five pollutants: carbon monoxide (CO), nitrogen dioxide (NO2), sulfur dioxide (SO2), particulate matter less than 10 microns in diameter (PM-10) and lead (pb). is. Secondary pollutants are substances that are formed due to interactions in the air around the earth and in this group can be named ozone (O3).

1-5-‌ Carbon monoxide (CO)
is a colorless, odorless but highly toxic gas. The main source of this gas is cars. Carbon monoxide gas in the open air in small quantities endangers the lives of heart and lung patients and causes headaches, dizziness, fatigue and nerve irritation in healthy people. Inhalation of this gas in closed and roofed environments causes suffocation and death.
Carbon monoxide combines 200 times faster than oxygen with hemoglobin in the blood to form carboxyhemoglobin. This gas not only binds to hemoglobin to prevent oxygen from sticking to it, but also prevents the release of oxygen from oxyhemoglobin between residues.
In this way, the body’s tissues are deprived of oxygen and the vital organs, especially the heart, are damaged. In addition to this, carbon monoxide itself directly damages the heart cells and accelerates the process of narrowing of the arteries.

2-5  Suspended particles (PM-10)
Suspended particles with a diameter of less than 10 micrometers are introduced as the main indicator of airborne substances due to their passage to the lower respiratory system. According to studies, suspended particles are more hazardous to health than sulfur oxides and nitrogen oxides, and the value of 10-PM in the exacerbation of cardiovascular disease, reduced immune system resistance to disease, lung tissue loss, pediatric asthma, mortality Premature and cancer play a major role.

Nitrogen Oxides (NOX) Nitrogen
dioxide, which is released into the air more than any other nitrogen oxide, is a brown, foul-smelling gas that is released into the air by motor vehicles and factories that use internal combustion engines. It also affects the deep parts of the lungs, causing extreme fatigue and increased disease, as well as damaging plants.

4-5 ‌ Sulfur Oxides (SOX)
Sulfur dioxide (SO2), which is released more into the air than other sulfur oxides, is a colorless and foul-smelling gas that irritates the airways, especially the throat, nose and larynx, causing chronic bronchitis, asthma and It emphysema. The main source of this gas is the combustion of diesel and fuel oil in homes, factories and motor vehicles.
Sulfur dioxide, when combined with water vapor in the air, is converted to acid, and precipitation in the form of acid rain causes corrosion of metals, rocks, and fabrics. This gas, like nitrogen dioxide, affects plants and causes them to die.

5-5 ‌ Ozone (O3)
Ozone is produced by photochemical reactions in the atmosphere due to hydrocarbons emitted by car exhaust and nitrogen oxides, and thus is considered a secondary pollutant.
Harmful effects of this pollutant on human health include burning eyes and lungs. Statistics show that asthma attacks have significantly increased on days when high concentrations of this pollutant are observed. Ozone in the air can cause serious harm to children, the elderly and people with respiratory problems. Ozone also reduces crop yields and destroys forests and plant ecosystems.

6.5  Volatile hydrocarbons (VOCs)
Some hydrocarbon vapors in the atmosphere have a potential role in degrading human health. Benzene as one of the most important volatile hydrocarbons, although due to its high solubility, plays a major role in industry, but its inhalation prevents the formation of red blood cells in the bone marrow. The main source of gasoline production is gasoline used in cars. In a few cases, leukemia has been reported in people who have been exposed to benzene fumes for a long time due to occupational problems.

6.
Pollutant Standard Index (PSI) The Pollutant Standard Index (PSI) is a standard used to report daily air quality and typically uses five pollutants: carbon monoxide, ozone, nitrogen dioxide, sulfur dioxide, and particulate matter. Contaminant concentrations are converted to a numerical scale between zero and five hundred PSI, according to the Environmental Protection Agency (EPA).
PSI is preferred in that it measures the concentration of pollutants on a single scale.
7. Environmental effects of air pollution

1-7-
Diseases caused by air pollution:

1-1-7-‌ Emphysema
This disease is caused by the contraction of the bonschial tubes and the destruction of air sacs by pollutants and causes shortness of breath in the patient.

2.1.7.1 Chronic bronchitis is
characterized by recurrent coughing and continuous sputum flow in the affected person. Contaminants destroy the lashes of the airways – which expel irritants from the lungs – and coughing will be the only way to get the particles out of the lungs. If left untreated, chronic bronchitis can lead to death.

3-1-7- ‌ Sensitivity
to contaminants can cause various allergic reactions including runny nose, shortness of breath, itchy skin, tears and recurrent sneezing.

4-1-7-‌ Asthma
is the resistance of the airway to the passage of air, in an asthma attack, the airways are narrowed and the passage of air is minimized, resulting in shortness of breath.
It can cause heart attacks or heart attacks, which are mainly manifested as chest pain, palpitations, shortness of breath and disorders of the heart system.

5-1-7- ‌ Lung, stomach and heart diseases
Although these diseases are not directly and exclusively related to air pollution, but air pollution is one of the important factors that cause and aggravate them.

2-7-‌ The effect of air pollution on plants
Air pollution also has a negative effect on the metabolism of plants and while weakening the plant, it causes various diseases and pests in them. This is especially the case with the increasing expansion of cities and the transformation of rural and agricultural areas into industrial areas. In general, the effect of air pollution on the plant can be manifested in the form of the appearance of dried spots on the leaves, loss of color, reduced plant growth, reduced crop and even plant loss.
Attention to the important role of plants in clean air has led to serious measures to maintain and increase green spaces. However, air pollution is a serious threat to plants and threatens to destroy green spaces. Therefore, it is vital to inform the people and take serious and rapid measures to prevent the further destruction of forests and natural resources and the creation of green spaces.

3-7- Atmospheric effects
1-3-7-  Atmospheric inversion
Usually in the lower layer of the atmosphere, the air temperature decreases with increasing altitude, so it is natural that there is an upward movement of air and pollution with the upper floors of the atmosphere Enslaves and keeps away from the place of breathing. But in certain geographical conditions – such as a city surrounded by mountains – a layer of warm air, such as a glass roof covering the top of the city, traps the cold air below and prevents pollution from rising and moving away from the city. In this case, the air flow is reversed and causes more air stability and condensation of pollutant gases to a very dangerous level, which is called atmospheric inversion. Unfortunately, Tehran is facing the phenomenon of atmospheric inversion for more than two thirds of the days of the year (about 250 days). This condition is more common in autumn and winter.

2-3-7-‌ Green House Effect The
activity and mobility of the Earth’s atmosphere is the result of the constant flow of energy from the sun to the earth and from the earth to space. About 3 percent of the sun’s energy is reflected back into space, and some of that reflected energy is reflected back to Earth by gases known as greenhouse gases – including carbon dioxide, methane and nitrous oxide. This phenomenon, known as the greenhouse effect, causes the temperature in the infected areas to rise. In confined air, the level of pollution has increased more than before, and as a result, the dangers of pollution have risen significantly and seriously threaten the urban population. Obviously, in the case of reducing greenhouse gases by eliminating or limiting the sources of its production, the greenhouse effect and its dangers can be prevented.

3-3-7- Acid precipitation Acid
precipitation refers to rain that is more acidic than normal rain (PH 5.6). Usually the acidic properties of water are measured by PH, the natural range of which is between 6.5 to 8.5. . If the pH of the rain is less than 6, it is considered as acid rain. The highly acidic nature of water is due to the widespread air pollution caused by industrialization. Therefore, in order to avoid acid rain, proper planning is necessary.
At the same time, the location of industries in a region or a country also requires careful and calculated studies.
Due to the lack of planning and forecasting of the weather around acid rain, several developed countries are now facing problems with acid rain. Lakes and forests in the fertile (rainy) regions of Europe, Canada, the United States, and the forests of West Germany are affected by the effects of acid rain. In India, acid rain has also been reported in Mumbai.
Sulfur oxides, nitrogen and hydrocarbons are the main parameters contributing to acid rain. Huge amounts of sulfur and nitrogen oxides enter the atmosphere from the chimneys of industrial units as well as from car exhaust. Incineration of fossil fuels for energy production is the main factor (60-70%) of sulfur oxides entering the atmosphere. Melting of sulfur ores, especially lead, zinc and copper, is also a factor in increasing the amount of atmospheric sulfur oxides. The main causes of nitrogen oxides are pollutants emitted from car exhausts, power plants and smelters. When these contaminants react in the presence of moisture. They constitute secondary pollutants. Most secondary pollutants from photochemical reactions receive their required energy from solar waves. Acid rain causes the following effects:

A: Acid rain reduces the pH of rivers and lakes, which in turn leads to the destruction of aquatic organisms (fish, etc.) and leads to reduced growth of plankton and reproduction of fish. A change in pH prevents the fish from hatching. Green algae and several types of bacteria, which are essential for the survival of aquatic organisms, are unable to survive in an acidic environment.
B: Acid rain is harmful to forests and pastures. Acid rain damages tree leaves and accelerates leaf surface erosion. Leaf growth is reduced due to high acidity. When the growth of the leaves is affected by acid rain, the destruction of green plants also occurs.
A: Acidity affects the soil. A plant nutrient such as potassium is gradually leached from the soil. Under acidic conditions, toxic metals for the plant accumulate in the soil.
D: Acid rain also disrupts the activity of microbes that convert soil organic matter into nutrients needed by the plant. When the microbial population decreases, the microbes are less able to tolerate the acidic environment of the soil due to acid rain.