Smog is one of the main reasons for air pollution in major cities. It is a collection of dangerous pollutants that are released into the atmosphere by both natural and human-induced processes, and it frequently appears quite low to the ground as a yellow-brown haze. Smog is very harmful to humans and the environment. This article will explain to you the Formation of Smog which will be helpful in Environment Subject preparation for the UPSC Civil Service Exam.

What is Smog?

• Dr H A Des Voeux coined the term "smog" in 1905.
• Smog was created by combining the words fog and smoke. Smog is a type of fog that contains soot or smoke.
• Smog is a type of air pollution that makes it difficult to see. Smog means smoke and fog that refers to smoky fog due to its opacity and odour.
• The term was originally intended to relate to pea soup fog, which was a common and major phenomenon in London from the 19th century to the mid-20th century.
• Nitrogen oxides, sulphur oxides, ozone, smoke, and other particles make up this type of visual air pollution.
• Coal combustion emissions, automotive emissions, industrial emissions, forest and agricultural fires, and photochemical reactions of these emissions all contribute to man-made events.
• The reaction of pollutants from automobiles, factories, and industries with sunlight and the environment causes smog.

Formation of Smog

• Smog is formed when contaminants are discharged into the atmosphere.
• The pollutants released into the atmosphere are due to natural and manmade factors.
• Manmade pollutants pose severe threats to humans and the environment.
• Example: burning of fossil fuel from industries releases significant NOX, SOX and other pollutants into the atmosphere.
• These human induced pollutants have greater impacts on human health.
• A significant fraction of smog is produced in cities, where a sizable portion of the population resides, the location of smog creation is also a major problem, particularly for human health.
• Ozone, one of the main components, is produced by chemical interactions between sunlight and certain contaminants.
• While ozone in the stratosphere shields the earth from harmful UV radiation, ozone on the ground is toxic to humans.
• When nitrogen oxides (primarily from vehicle exhaust) and volatile organic compounds (from paints, solvents, printing inks, petroleum products, vehicles, and so on) interact in the presence of sunlight, ground-level ozone is formed.
• Particulate matter, the other main component, can similarly be formed by chemical processes but is also added to the atmosphere in other ways.
• These particles may be dispersed by wind throughout the land, reducing their concentration in a particular region.
• Rainfall may also remove these pollutants from the local atmosphere, however doing so may also cause unintended consequences like acid rain.
• People are exposed to the impacts of smog for a longer amount of time when it forms an inversion layer over a place due to warm areas in the upper atmosphere.
• Smog is defined as hazy air that makes breathing difficult. It is a mixture of various gases, water vapour, and dust.
• Its occurrence is frequently associated with heavy traffic, high temperatures, and calm winds. During the winter, wind speeds are low, causing smoke and fog to congregate near the ground, increasing pollution levels.
• The trapped smoke particles in the fog give it a yellow/black colour, and this smog often settles over cities for several days.

Sulphuric Smog vs Photochemical Smog

Formation of Photochemical Smog

Haze

• Haze is often an atmospheric condition where dry particles like dust, smoke, and other materials obstruct the sky's transparency (no condensation).
• Smog and haze are similar, but smog contains condensation.
• Agriculture (especially ploughing in dry weather), traffic, industry, and wildfires are all sources of haze particles.

Effects of Smog

• It reduces visibility and is harmful to the environment.
• It causes respiratory problems and Bronchial disease-related deaths.
• Smog significantly reduces ultraviolet radiation.
• Heavy smog reduces natural vitamin D production, leading to an increase in rickets cases.
• Plants and animal life are negatively impacted by the collection of chemicals contained in photochemical haze.
• Photochemical pollution can completely destroy these delicate crops, trees, and other vegetation because some plants, including tobacco, tomato, and spinach, are especially vulnerable to ozone.
• On the upper surfaces of tree leaves, ozone creates necrotic (dead) patterns.
• The development and production of trees can also be hampered by ground-level ozone.
• Smog has similar effects on animals as it does on people, including a reduction in lung function and elasticity.

*For detailed notes of this topic, check this link Effects of Smog

Conclusion

Smog has a significant impact on the surrounding physical environment in addition to the lives of people. Smog and its components can have serious negative impacts on health, and these effects can vary widely. When inhaled, smog is dangerous, and the degree to which it is detrimental depends on the amount inhaled, the types of pollutants it contains, the person's age, weight, level of activity, and general well-being.

FAQs

Question: What is smog and how is it formed?

Question: What are the main causes of smog?

Question: What are the health effects of exposure to smog?

Question: How can smog be controlled or reduced?

Question: What is the role of weather in smog formation?

MCQs 

1. Which of the following is the primary cause of the formation of smog?

A) High humidity

B) Sulfur dioxide emissions from coal plants

C) Interaction of sunlight with pollutants in the atmosphere

D) Depletion of the ozone layer

2. Which of the following is NOT a major constituent of smog?

A) Carbon monoxide

B) Ground-level ozone

C) Nitrogen dioxide

D) Carbon dioxide

3. What is a temperature inversion and how does it contribute to smog?

A) A rise in temperature near the Earth's surface

B) A layer of warmer air traps cooler air near the ground

C) A natural cooling phenomenon in urban areas

D) A meteorological event that disperses pollutants

4. Which of the following groups is most vulnerable to the effects of smog?

A) Young adults

B) Healthy individuals

C) Children, the elderly, and people with pre-existing respiratory conditions

D) None of the above

5. What is the role of vehicular emissions in the formation of smog?

A) They release only water vapor

B) They provide sulfur dioxide, which reacts with sunlight

C) They emit nitrogen oxides and VOCs, which contribute to smog formation

D) They help disperse smog

GS Mains Questions and Model Answers

Q1: Discuss the environmental and health impacts of smog in urban areas.

Answer: Smog, a dangerous air pollution phenomenon, has both environmental and health consequences in urban areas. Environmentally, smog can impair visibility, harm ecosystems, and damage vegetation by reducing photosynthesis, impacting agricultural productivity. Health-wise, smog is associated with respiratory issues like asthma, bronchitis, and chronic obstructive pulmonary diseases (COPD). Long-term exposure increases the risk of cardiovascular diseases and aggravates pre-existing conditions, especially among vulnerable groups such as children, the elderly, and individuals with compromised immune systems. Smog also contributes to ground-level ozone formation, a potent greenhouse gas, which accelerates climate change by trapping heat in the atmosphere.

Q2: Evaluate the effectiveness of current strategies used to combat smog in major cities.

Answer: Strategies to combat smog in major cities include reducing vehicular emissions, promoting cleaner industrial processes, and increasing green spaces. Governments have implemented stricter vehicle emission standards, encouraged the use of public transport, and invested in renewable energy sources. However, challenges remain. Increasing vehicle numbers and industrial activity continue to release large amounts of pollutants, outpacing efforts to curb smog. In cities like Delhi and Beijing, initiatives such as stricter fuel standards, promotion of electric vehicles, and regulation of construction dust have shown progress, but sustained commitment and international cooperation are essential for long-term reduction in smog.

Q3: Analyze the role of meteorological factors in the formation and persistence of smog.

Answer: Meteorological factors are critical in smog formation and persistence. Temperature inversions trap cooler air and pollutants close to the ground, preventing their dispersion, which exacerbates smog, especially during winter. Low wind speeds further prevent the dispersion of pollutants, causing them to concentrate in urban areas. High humidity can contribute to particulate matter formation, worsening smog. In contrast, strong winds can help disperse pollutants, improving air quality. Understanding these meteorological conditions is vital for forecasting and mitigating smog in urban environments.

Previous Year Questions on  Formation of Smog

1. UPSC CSE (2022) – General Studies Paper II

Question: Discuss the various factors contributing to the deteriorating air quality in Indian cities. What measures can be adopted to address this issue effectively?

Answer: Major factors contributing to deteriorating air quality in Indian cities include vehicular emissions, industrial pollutants, construction dust, burning of crop residues, and the use of low-quality fuels. Meteorological conditions such as temperature inversions further exacerbate the situation. Measures to combat this issue include implementing stricter vehicle emission standards, transitioning to cleaner technologies in industries, promoting renewable energy sources, improving waste management, and incentivizing better public transportation. A coordinated effort among government, citizens, and organizations is necessary to effectively improve air quality.

2. UPSC CSE (2021) – General Studies Paper III

Question: What are the environmental and health impacts of smog formation? Discuss the measures needed to reduce its occurrence in urban areas.

Answer: Smog formation has significant environmental and health impacts, including reduced visibility, damage to plant life, and respiratory and cardiovascular diseases. To reduce its occurrence, stringent pollution control regulations for vehicles and industries