What Are the Key Sources and Effects of Smog in Our Atmosphere?
Atmospheric pollution is highly harmful to life; when it comes to the survival of all living organisms, the air has more importance than food. Atmospheric pollution is thus a matter of great concern on this planet for life to survive. The most common type of air pollutant that affects a large portion of the globe is smog. The blend of two words, smoke, and fog, contributes to the development of the word smog.
It lowers visibility and creates breathing troubles. As it is made of very minute particles, smog comes under particulate pollutants. The types of smog are discussed briefly below.
Air Pollutants
Carbon monoxide is an invisible, odourless gas produced as a result of incomplete combustion. The primary source is gasoline-powered highway vehicles, while large quantities of this gas are also emitted by residential heating systems and some industrial processes. Power plants produce very little carbon monoxide because, to optimize combustion efficiency, they are carefully engineered and controlled. As it quickly displaces oxygen in the bloodstream, exposure to carbon monoxide can be acutely detrimental, leading to asphyxiation at sufficiently high concentrations and exposure periods.
Sulfur dioxide: During the combustion of coal or oil containing sulfur as an impurity, a colourless gas with a strong, choking odour, sulfur dioxide, is produced. Much of the emissions of sulfur dioxide come from plants that produce power; very little comes from mobile sources. This pungent gas, when inhaled, can cause irritation of the eye and throat and damage lung tissue.
Sulfur dioxide also reacts in the air with oxygen and water vapour, creating a sulfuric acid mist that reaches the ground as an acid rain portion.
Nitrogen dioxide, a pungent, unpleasant gas, is of most concern among the other types of nitrogen oxides. In the atmosphere, nitrogen dioxide also reacts to form nitric acid, leading to the acid rain crisis. Nitrogen dioxide also plays a role in the creation of photochemical smog, a reddish-brown haze that is frequently seen in many urban areas and formed in the lower atmosphere by sunlight-promoted reactions.
Ozone: In the presence of sunlight, ozone is a key component of photochemical smog, created by a complex reaction between nitrogen dioxide and hydrocarbons. It is known to be a tropospheric pollutant, i.e., in the lowest layer of the atmosphere, but not in the upper layers of the atmosphere, where it occurs naturally and is used to block the Sun's harmful ultraviolet rays.
How Is the Smog Formed?
Smog is produced when certain chemicals interfere with the sunlight in our atmosphere, which in turn contributes to visible air pollution that we call smog. It is primarily produced by the emission of vehicle nitrogen oxides, but also by the use of solvents or paints to release volatile organic compounds.
Causes of Smog
Overpopulation
Fossil fuels
Private cars
Long transportation distances
Industrial processes
Excessive consumption
Excessive waste production
Fireworks
Burning of agricultural material
Construction activities
Volcanoes
Smog and Its Type
We have two major types of smog and they are as follows
Classical Smog
When there is a high concentration of sulfur dioxide and particulate matter produced due to fuel combustion, classical smog is created. This happens in humid and cold climates. It is also known as Sulphurous smog, or London smog, and causes the atmosphere to be dark brownish in colour. This smog has a high reducing agent concentration, so it is also known as reducing smog.
Photochemical Smog
In dry and sunny areas of the world, this form of smog is prevalent. Automobiles and factories emit smoke containing hydrocarbons and nitrogen dioxide, which becomes the main component of photochemical smog under the action of sunlight. This smog has a high oxidizing agent concentration, so it is also known as oxidizing smog.
Effects of Photochemical Smog in Points:
There are various harmful effects of photochemical smog.
The harmful effects of photochemical smog are discussed below.
Pulmonary Health Issues: It can contribute to many different respiratory diseases because smog is made up of many particles and elements that are detrimental to our health. This may include health conditions including COPD or bronchitis. The greater the concentration of toxic compounds in the air, the greater the risk of problems with lung health.
Lung Damage: Due to smog, our lungs can also be impaired. For example, these substances can remain in our lungs for quite a long time if we breathe air that is highly polluted with particles and other harmful substances. These substances can cause many physical problems in the lungs during this period of time.
Lung Cancer: When it comes to the consequences of smog, lung cancer is another key concern. Lung cancer is a major problem, particularly in countries where high concentrations of toxic gases and particles can enter the air due to inadequate regulations, because people have no choice but to breathe polluted air. Many of these individuals, which further exacerbates the problem, do not even wear masks or other protection.
Long-Term Health Issues: A variety of chronic diseases related to damage to our lungs can also be caused by smog. When it comes to contamination with toxic chemicals, our lungs are normally very susceptible. Thus, if our lungs are contaminated with smog-related pollutants, the risks of long-term complications grow significantly.
Allergies: While it is difficult to verify, several scientists have also concluded that the probability of allergies can also be increased by a substantial level of air pollution and smog. Researchers have found that allergies are more prevalent in these areas, especially in regions with high smog concentrations.
Irritation of Eyes: These individuals can also suffer from eye irritations, particularly for individuals who respond very sensitive to environmental conditions, as smog contains tiny particles that could irritate our body's mucosae.
Birth Defects: This is especially true in countries where people do not wear protective masks against smog and where air cleaning systems are not sophisticated enough to filter out harmful particles. Therefore, unborn children may suffer or die due to smog and related adverse issues.
Effect on Flora and Fauna: Animals can suffer because smog can contaminate their respiratory systems, which can in turn lead to many kinds of diseases and even death.
Also, plants may suffer because they are typically very sensitive to their natural conditions and their growth actions, and because of smog, crop yields may also be adversely affected.
It also causes Asthma, Lower life expectancy, Accidents due to bad visibility, Breathing issues, Lower quality of life, and Accidents due to bad visibility.
Do You Know?
92% of people across the world do not breathe fresh air.
The cost of atmospheric pollution to the global economy is around USD 5 trillion every year.
Approximately 7 million people die prematurely every year from atmospheric pollution, with maximum deaths taking place in Asia- Pacific.
Solved Examples
Example 1: What Are the Smog Solutions?
By modifying a few habits, such as: Driving less, everyone can do their part to minimize smog. Whenever possible, walk, ride, carpool, and use public transit. Take control of equipment.
Example 2: Why Will Smog Be Dangerous?
Smog irritates our airways when inhaled, raising our risk of severe heart and lung diseases. Such health threats are why smog levels are tracked by many cities. On a high ozone-alert day, for example, eyes and throat may burn, and may cause cough and wheeze.
FAQs on Smog: Main Causes of Atmospheric Pollution Explained
1. What is smog and how is it generally formed?
Smog is a type of intense air pollution that reduces visibility. The word is a combination of "smoke" and "fog". It is formed when a mixture of pollutants, primarily from industrial and vehicular emissions, accumulate in the lower atmosphere. The formation process differs based on the type of smog, with classical smog forming in cool, humid conditions and photochemical smog forming in warm, sunny conditions.
2. What are the main causes of atmospheric pollution that lead to smog?
The primary causes of smog are pollutants released into the atmosphere from various sources. The main contributors include:
- Vehicular Emissions: Cars and trucks release nitrogen oxides (NOx) and volatile organic compounds (VOCs).
- Industrial Activity: Factories and power plants release sulphur dioxide (SO₂) and other particulate matter.
- Coal Combustion: Burning coal for energy and heat is a major source of sulphur dioxide, a key component of classical smog.
- Natural Sources: Forest fires and volcanic eruptions can also release pollutants that contribute to smog formation.
3. What is the difference between classical smog and photochemical smog?
Classical and photochemical smog are two distinct types of air pollution. The key differences are:
- Composition: Classical smog is a mixture of smoke, fog, and sulphur dioxide. Photochemical smog is primarily composed of ground-level ozone, nitrogen oxides, and PAN (Peroxyacetyl nitrate).
- Climate: Classical smog occurs in cool, humid climates, often in winter. Photochemical smog occurs in warm, dry, and sunny climates.
- Chemical Nature: Classical smog has a reducing character due to high concentrations of SO₂. Photochemical smog has an oxidising character due to high concentrations of oxidants like ozone.
- Common Name: Classical smog is also known as "London Smog," while photochemical smog is called "Los Angeles Smog."
4. What are the primary chemical components of photochemical smog?
Photochemical smog is a complex mixture of pollutants formed by chemical reactions in the presence of sunlight. Its main components are:
- Ground-level Ozone (O₃): A highly reactive and toxic gas that is the main component of this type of smog.
- Nitrogen Oxides (NOx): Primarily nitric oxide (NO) and nitrogen dioxide (NO₂), which are precursors to ozone formation.
- Volatile Organic Compounds (VOCs): Carbon-based chemicals that easily evaporate and react with NOx to form ozone.
- Peroxyacetyl Nitrate (PAN): A secondary pollutant that causes eye irritation and is toxic to plants.
5. What are the harmful effects of smog on human health and the environment?
Smog has severe negative effects on both health and the environment. For humans, it can cause respiratory problems like asthma and bronchitis, lead to severe eye irritation, and increase the risk of heart disease. Environmentally, smog damages plant life, including agricultural crops, by inhibiting photosynthesis. It can also corrode building materials and significantly reduce visibility.
6. Why is photochemical smog more common in warm, sunny, urban areas?
Photochemical smog formation is heavily dependent on sunlight and temperature. The chemical reactions that create its key components, such as ozone (O₃) and PAN, are photochemical, meaning they are driven by the energy from sunlight. Warm temperatures accelerate the rate of these reactions. Urban areas have high concentrations of the necessary precursor pollutants—nitrogen oxides (NOx) and VOCs—from heavy traffic and industrial activity, creating the perfect conditions for smog formation on a sunny day.
7. What are the key chemical reactions involved in the formation of photochemical smog?
The formation of photochemical smog involves a cycle of reactions initiated by sunlight. First, nitrogen dioxide (NO₂) from vehicle emissions is split by sunlight into nitric oxide (NO) and a free oxygen atom (O). This highly reactive oxygen atom then combines with an oxygen molecule (O₂) to form ozone (O₃). Normally, this ozone would react with NO and break down. However, in the presence of Volatile Organic Compounds (VOCs), the NO is consumed in other reactions, allowing ozone to accumulate to harmful levels.
8. How do primary pollutants lead to the creation of secondary pollutants in smog?
This distinction is key to understanding smog. Primary pollutants, such as nitrogen oxides (NOx) from car exhaust and sulphur dioxide (SO₂) from factories, are emitted directly into the atmosphere. They are the initial ingredients. Secondary pollutants, such as ground-level ozone (O₃), sulphuric acid, and PAN, are not emitted directly. Instead, they are formed in the air when primary pollutants undergo chemical reactions with each other and with other atmospheric components, often triggered by sunlight. Thus, smog is largely a problem of secondary pollutants created from primary ones.
