Smog is an air pollution phenomenon that reduces visibility. Early in the 20th century, a mixture of smoke and fog was originally referred to as "smog." Usually, burning coal was the source of the smoke. Industrial locations and modern cities have frequent smog formation. Photochemical haze is the predominant type of smog today. When sunlight combines with nitrogen oxides and at least one other substance, it creates a photochemical haze. This article will explain to you 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 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.
• It was coined in the early twentieth century.
• 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 cause 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.

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

Types of Smog

Different factors contribute to the production of smog. As a result, they are divided into two categories:

• Photochemical smog (Also called Los Angeles Smog)
• Sulphurous smog (Also called London Smog)

Photochemical Smog

• When sunlight reacts with nitrogen oxides and at least one volatile organic compound (VOC) in the atmosphere, photochemical smog is formed.
• The chemical formation of airborne particles and ground-level ozone occurs in the presence of sunlight.
• This type of smog does not require smoke or fog.
• Automobiles, power plants, and industrial pollutants all release nitrogen oxides into the environment.
• VOCs are released into the atmosphere by paints, gasoline, and many cleaning solvents.
• Aromatic compounds such as benzene, toluene, and xylene are carcinogenic and have been linked to leukaemia.
• VOCs have been found to indirectly contribute to respiratory and other ozone-related problems.

Causes of Photochemical smog

• Stubble burning – The states of Punjab and Haryana are thought to be responsible for setting 35 million tonnes of crop on fire each year. All of the airborne contaminants and dust particles are carried by the wind.
• Increase in the number of vehicles on the road - The National Environmental Engineering Research Institute (NEERI) and the Central Pollution Control Board (CPCB) have identified vehicular emissions as a major cause of Delhi's rising air pollution, which in turn fuels the growth of photochemical smog.
• Seasonal changes - As the winter months approach, airborne dust and contaminants become immobile.
  • Smog develops as a result of these pollutants becoming trapped in the atmosphere by ineffective winds, which also impact weather patterns.
• Dust Pollution - Another factor contributing to the increase in dust and pollution in the air is large-scale buildings and construction.

Impact of Photochemical Smog

• Plants and animal life are negatively impacted by the collection of chemicals contained in a 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.

Sulphurous Smog

• "London smog" is another name for sulphurous haze (first formed in London).
• The usage of sulphur-containing fossil fuels, notably coal (which was the primary source of energy in London throughout the nineteenth century), results in sulphurous smog.
• It is characterised by a high concentration of sulphur oxides in the atmosphere.
• Wetness and a high level of suspended particulate matter in the air exacerbate this type of smog.
• This gas is a serious air pollutant that irritates the eyes, nose, and lungs of humans.
• It is emitted into the atmosphere by sulfur-containing fossil fuels such as coal. Volcanoes release sulphur dioxide into the atmosphere as well.
• Natural sources are estimated to contribute 24% of sulphur dioxide emissions, while anthropogenic sources contribute the remaining 76%.

Effects of Smog

• They can also cause allergies and irritation of the eyes, chest, nose, and throat.
• Smog exposure increases the risk of developing cancer and developing respiratory disorders.
• Birth abnormalities and low birth weight are strongly associated with smog.
• It reduces visibility and has a negative impact on the environment.
• Smog causes a decline in natural vitamin D production, which leads to an increase in rickets instances.
• Smog reduces UV radiation significantly.
• Other health issues like lung issues, bronchial disease-related deaths are also effects of smog.
• Plants and animal life are negatively impacted by the collection of chemicals contained in photochemical haze.

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

Measures to Counter Smog Pollution

• The MoEFCC launched the National Clean Air Programme (NCAP) in April 2018.
  • The programme is an effort to manage pollution, and one of its main objectives is to lower the amount of coarse and fine particulate matter in the atmosphere by at least 20% by the year 2024.
  • The program's objective is to strengthen the system for tracking national air quality.
• It was preceded by the Clean Air Programme in Delhi in February 2018.
• In Delhi and the NCR, significant measures have been taken, including the creation of the Graded Response Action Plan (GRAP) by the CPCB.
• The air quality monitoring stations in Delhi and NCR, the upgrading of the Central Control Room at the CPCB, the integration of data on air quality from stations operated by the Indian Meteorological Department (IMD), strict surveillance over coal-fired plants, strict action against construction activities, and other measures contribute to greater reduction of Smog formation.
• Introducing the SAMEER mobile app for grievance resolution.
• Moving up from BS-IV to BS-VI are some of the measures taken to counter Air pollution.

Behavioural Changes to Reduce Smog

• Reduce your driving. Whenever possible, walk, bike, carpool, or take public transportation.
• Regular tune-ups, regular oil changes, and properly inflated tyres can improve gas mileage and lower emissions.
• Fill up during the cooler hours of the day, such as at night or early in the morning. This keeps gas fumes from heating up and creating ozone.
• Avoid products that emit a lot of VOCs.
• Avoid using gas-powered equipment. Instead, use electric appliances.

Conclusion

It is clear that the majority of the actions done to combat smog and pollution are punitive and ad hoc in character, focusing on the symptoms rather than the underlying source of the issue. A coordinated effort by the Center, the National Green Tribunal, the judiciary, expert agencies, and most crucially the general public is required to develop a long-term and sustainable solution to air pollution and smog.

FAQs

MCQs

1. Which of the following is a primary component of photochemical smog?

A) Sulfur dioxide
B) Carbon monoxide
C) Ground-level ozone
D) Particulate matter

2. Which city experienced the "Great Smog" of 1952?

A) New York
B) London
C) Beijing
D) Tokyo

3. What is the primary cause of classical smog?

A) Vehicle emissions
B) Industrial solvents
C) Coal combustion
D) Agricultural activities

4. Which of the following pollutants is most associated with photochemical smog?

A) Lead
B) Nitrogen oxides
C) Chlorofluorocarbons
D) Methane

5. Which health condition is commonly exacerbated by smog exposure?

A) Diabetes
B) Asthma
C) Hypertension
D) Arthritis

GS Mains Questions and Model Answers

Q1: Discuss the formation and effects of photochemical smog in urban areas.

Answer: Photochemical smog forms when sunlight reacts with nitrogen oxides and volatile organic compounds in the atmosphere, leading to the production of ground-level ozone and other pollutants. This type of smog is common in urban areas with high vehicular and industrial emissions. The effects include respiratory problems, eye irritation, reduced visibility, and environmental damage such as harm to crops and vegetation. Mitigation strategies involve reducing emissions through stricter regulations, promoting public transportation, and encouraging the use of cleaner energy sources.

Q2: Explain the historical significance and impact of the "Great Smog" of 1952 in London.

Answer: The "Great Smog" of 1952 in London was a severe air pollution event caused primarily by the burning of coal. It resulted in a thick, choking fog that enveloped the city for several days, leading to respiratory illnesses and the deaths of thousands of people. This event highlighted the dangers of industrial air pollution and led to significant changes in environmental policy, including the Clean Air Act of 1956 in the United Kingdom. It serves as a historical example of the need for effective air quality management and regulation.

Q3: Evaluate the measures taken to reduce smog in major cities and their effectiveness.

Answer: Measures to reduce smog in major cities include implementing stringent emissions standards for vehicles and industries, promoting public transportation, and encouraging the adoption of renewable energy sources. Cities like Los Angeles have seen improvements in air quality due to such regulations. However, challenges remain, particularly in rapidly growing urban areas with increasing vehicular use and industrial activity. Effective measures require a combination of regulatory enforcement, public awareness campaigns, and international cooperation to address transboundary air pollution.

Previous Year Questions on Smog

1. UPSC CSE Prelims 2020:

Question: Which of the following is a key component of photochemical smog?

A) Particulate matter
B) Ground-level ozone
C) Sulfur dioxide
D) Carbon monoxide

Answer: (B)

Explanation: Ground-level ozone is a major component of photochemical smog, formed when sunlight reacts with nitrogen oxides and volatile organic compounds.

2. UPSC CSE Mains 2019 (GS Paper 3):

Question: "Examine the causes and consequences of smog formation in urban centers. Suggest measures to mitigate its impact."

Answer: Smog formation in urban centers is primarily caused by vehicular emissions, industrial activities, and the burning of fossil fuels. Photochemical smog forms when pollutants like nitrogen oxides and volatile organic compounds react with sunlight, while classical smog results from burning coal. Consequences include respiratory and cardiovascular issues, reduced visibility, and environmental damage. Mitigation measures include implementing stricter emission norms, promoting public transportation, using cleaner fuels, and raising public awareness. Effective regulation and technological innovations are essential to reduce smog levels and their associated health and environmental impacts.