Ozone (O3) is found throughout the entire atmosphere, although its concentration peaks are found in the stratosphere (15–50 km) and troposphere (0–15 km), with the stratospheric O3 layer having the highest percentage and concentrations. Even at relatively low quantities, ozone has an impact on both plants and animals. By harming the leaf, it prevents plant growth. Animals and humans may sustain damage to their respiratory systems. Reduced air pollution, especially nitrogen oxide and hydrocarbon emissions, is required to prevent an increase in ozone concentrations. This article will explain to you about Ozone which will be helpful in Environment Subject preparation for the UPSC Civil Service Exam.

Ozone

• Ozone (O3) is a colorless, reactive oxidant gas that is a major constituent of atmospheric smog.
• Both the upper atmosphere of the Earth and its surface are home to ozone, a gas made up of three oxygen atoms.
• Depending on where it is in the atmosphere, ozone can either be "good" or "bad" for the environment and your health.
• Even at low concentrations, the unpleasant, pale blue gas known as ozone is explosive and dangerous.
• In India, the ozone problem is essentially a "sunny weather concern," as sunlight directly affects the development of ground-level ozone.
• Photochemical processes are aided by the catalytic effect of heat. As a result, summertime is when ozone concentrations are at their highest.

Ozone Formed

• Ozone (O3) at the ground level is not directly emitted by human activity.
• It is a "secondary" pollutant that develops as a result of a complex series of chemical reactions when sunlight is present.
• The amount of ground-level O3 in the atmosphere is controlled by photochemical reactions of NOx and VOCs, which are mostly produced during combustion activities.
• Three reactions attain equilibrium and no net chemistry takes place under typical daytime conditions with a well-mixed environment.

What is good and bad ozone?

Good Ozone: Ozone is a good thing because it naturally occurs in the stratosphere, the highest atmosphere of the Earth, where it creates a barrier that protects us from the sun's harmful ultraviolet rays.

This protective barrier is destroyed and an ozone hole is created by ozone-depleting chemicals such as chlorofluorocarbons (CFCs), HCFCs, and halons.

The Kigali Amendment had been adopted by India (aims to phase-down hydrofluorocarbons).

Bad Ozone: When pollutants generated by vehicles, power plants, industrial boilers, refineries, chemical plants, and other sources react chemically in the presence of sunlight, ozone is formed in the lower atmosphere (troposphere) of the Earth, close to the ground.

Ozone at surface levels is a dangerous air contaminant.

How Ozone is an Air Pollutant?

• Ozone has negative effects on both people and the environment, ozone is a dangerous air pollutant at ground level and the primary component of "smog."
• In the atmosphere, ozone naturally forms. It exists because oxygen (O2) gets photo-dissociated into two oxygen atoms, one of which is energetically excited and can start a chain reaction that also involves nitrogen oxides and hydrocarbons.
• Before the industrial revolution, it only reached 0.02 ppmv or less in the lower troposphere (also known as surface ozone).
• Due to accelerated photo-oxidation brought on by rising NOx levels in the air, it has risen since the latter part of the 19th century, especially in industrialised areas.
• Concentrations in industrial locations are currently more or less 0.04 ppmv and in severely contaminated areas, they may briefly exceed 0.1 ppmv.
• Even at relatively low quantities, ozone has an impact on both plants and animals.
• By harming the leaf, it prevents plant growth. Animals and humans may sustain damage to their respiratory systems.
• Reduced air pollution, especially nitrogen oxide and hydrocarbon emissions, is required to prevent an increase in ozone concentrations.
• In affluent nations, this has had some success, but in many developing nations, high ozone concentrations are now also seen in areas with a lot of people.
• Although it fluctuates greatly in both location and time, the ozone concentration rises with height and reaches a maximum of roughly 1 ppmv in the stratosphere at elevations between 20 and 25 km.

Ozone Layer

• A natural gas barrier in the upper atmosphere called the ozone layer shields people and other living things from the sun's harmful ultraviolet (UV) radiation.
• Ozone (O3) exists in modest amounts throughout the atmosphere, but the majority of it (about 90%) is found in the stratosphere, a layer between 10 and 50 km above the earth's surface.
• The majority of the sun's biologically hazardous UV radiation is filtered away by this ozone layer, which serves a crucial function.

What Causes Ozone Layer to Deplete?

• Concentrations of ozone in the atmosphere vary naturally according to temperature, weather, latitude and altitude.
• Furthermore, substances ejected by natural events such as volcanic eruptions can have measurable impacts on ozone levels.
• However, natural phenomena cannot explain the current levels of ozone depletion.
• The scientific evidence shows that certain man-made chemicals are responsible for the creation of the Antarctic ozone hole and the global ozone losses.
• These chemicals are industrial gases which have been used for many years in a range of products and applications including aerosol sprays, refrigerators, air conditioners, fire extinguishers and crop fumigation.
• ODS(Ozone Depleting substances) are broken down by sunlight in the stratosphere, producing halogen (e.g. chlorine or bromine) atoms, which subsequently destroy ozone through a complex catalytic cycle.
• At the South Pole, where extremely low stratospheric temperatures throughout the winter form polar stratospheric clouds, ozone degradation is at its highest.
• These clouds' ice crystals increase the surface area available for chemical reactions, speeding up catalytic cycles.
• Since sunlight is used to destroy ozone, the process is accelerated during spring, when solar radiation levels at the pole are at their peak and polar stratospheric clouds are continuously present.

Ground Level Ozone

• Tropospheric ozone is produced by chemical interactions between nitrogen oxides (NOx) and volatile organic molecules (VOC).
• They are not directly released into the atmosphere.
• When sunlight is present, pollutants released from factories, power plants, industrial boilers, refineries, and other sources undergo chemical reactions.
• Ozone can still reach high levels throughout the colder months, although it is most likely to do so on hot, bright days in urban areas.
• Even in rural places, high ozone levels are possible due to the wind's ability to spread ozone across great distances.

Effects of Ground Level Ozone

• Inhaling ozone can result in a number of health issues, such as congestion, coughing, throat discomfort, and chest pain. It can make asthma, emphysema, and bronchitis worse.
• Ozone at ground level also impairs lung function and irritates the linings of the lungs. Repeated exposure may leave lung tissue irreversibly scarred.
• When exposed to ozone pollution, healthy people also have trouble breathing.
• Ground-level ozone harms ecosystems and vegetation, as well.
• Reduced development and survival of tree seedlings, decreased yields from agricultural crops and commercial forests, and greater susceptibility to diseases, pests, and other pressures like extreme weather are all results of it.

Measures to Counter Ground Ozone Depletion

Surface ozone concentrations in India are higher than the recommended limit of an 8-hour average of 100 g/m3, which is used to monitor air quality at various sites. Numerous health issues are brought on by surface ozone exposure at high levels.

The following are some of the actions the government has done to lessen ozone pollution:

• Switching from BS-IV to BS-VI certified automobiles.
• Burning of trash is forbidden.
• Action Plan for Graded Response (GRAP).
• The National Clean Air Programme has begun (NCAP).
• the establishment of a monitoring network to evaluate the ambient air quality at 779 sites, including 339 cities in 29 states and six union territories.

Stratospheric Ozone Layer

• The stratosphere produces ozone naturally. However, ozone-depleting substances (ODS) generated by humans, such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), halons, methyl bromide, carbon tetrachloride, and methyl chloroform, are slowly destroying this "good" ozone.
• Coolants, foaming agents, fire extinguishers, solvents, insecticides, and aerosol propellants all once employed these compounds also depletes the Layer.
• These ozone-depleting chemicals decay very slowly after being discharged into the atmosphere.
• They can endure the transition through the troposphere and into the stratosphere unharmed for years.
• The UV radiation from the sun breaks them down, releasing chlorine and bromine molecules that deplete the stratospheric ozone.
• One chlorine atom is thought to be capable of obliterating 100,000 molecules of ozone in the stratosphere.
• Even though we no longer use many ODS( Ozone Depleting Substances) , their historical use can still have an impact on the ozone layer's protective layer.
• According to research, there is a global decline in stratospheric ozone layer thinning. Satellite observations also detect ozone layer thinning over the Polar Regions.

Impacts on Stratospheric Ozone depletion

• Ozone depletion can increase the quantity of UV radiation that reaches Earth, which can raise the incidence of cataracts, skin cancer, and immune system impairment.
• Melanoma, the most lethal of all skin cancers, is thought to be on the rise as a result of excessive UV exposure. The likelihood of getting melanoma has more than doubled since 1990.
• UV exposure can also lower crop production and harm delicate crops like soybeans. According to some scientists, UV radiation is already stressing marine phytoplankton, the foundation of the ocean food chain.
• The human food supply that comes from the oceans may suffer as a result of this stress.

Measures to Counter Stratospheric Ozone Depletion

• A convention known as the Montreal Protocol was adopted in 1987 by more than 180 nations in order to gradually phase out the manufacture and use of ozone-depleting chemicals in response to the concerns posed by ozone depletion.
• Following this, negotiations were on to regulate anthropogenic (ODSs) and certain hydrofluorocarbon production and consumption through the 1987 Montreal Protocol on Substances that Deplete the Ozone Layer and its ensuing amendments (HFCs).
• Hydrochlorofluorocarbons (HCFCs) and afterwards HFCs are two compounds that need to be replaced, according to the Montreal Protocol, in a variety of industrial sectors.
• HFCs have a little impact on stratospheric ozone, yet some of them are potent greenhouse gasses (GHGs).
• India is one of the few nations in the world and, in some circumstances, a pioneer in the adoption of technology that does not deplete the ozone layer and has minimal global warming potential (GWP).
• India has actively opted to transition away from ozone depleting substances and toward environmentally and energy-friendly technologies (ODSs).
• Hydrochlorofluorocarbon (HCFC)-141 b, one of the most potent ozone depleting chemicals after Chlorofluorocarbons (CFCs) (HCFC)-141 b is used primarily as a blowing agent in the production of stiff polyurethane (PU) foams, has been completely phased out in India with success.

Ozone pollution effects

Health

• The respiratory system may become irritated, which can cause coughing and an uneasy feeling in the chest.
• Ozone worsens bronchitis, emphysema, asthma, and other conditions, raises the likelihood of lung inflammation, such as Chronic Obstructive Pulmonary Disease, and increases susceptibility to it (COPD).
• It could weaken lung capacity and make breathing challenging.

Environment

• UV alterations development, food chains, and metabolic processes in terrestrial and aquatic environments.
• High UV radiation has a negative impact on aquatic life, especially that which is found just below the water's surface and is the foundation of the food chain.
• Additionally, UV rays have a negative impact on plant growth, which lowers agricultural productivity.
• Additionally, as stratospheric ozone is lost, the temperature of the atmosphere changes, having a range of environmental and climatic effects.

Economic Impacts

• The most significant direct economic impact of increased UV radiation is an increase in health care expenses.
• Health care systems, particularly in less developed nations, are challenged by the costs of treating millions of cases of skin cancer and cataracts.
• The lifespan and tensile characteristics of some polymers and fibers are also decreased by increased UV light.
• Additional expenses, such as those incurred in the fight against climate change or as a result of depleted fish stocks, are examples of indirect economic impacts.

Montreal Protocol on Ozone Depleting substances

• A global agreement called the Montreal Protocol on Substances that Deplete the Ozone Layer aims to protect the ozone layer of the Earth by gradually banning the substances that damage it.
• The production and consumption of ozone-depleting chemicals are both covered by this phase-out strategy.
• The historic pact was signed in 1987 and came into effect in 1989.
• Once a year, the parties to the Protocol get together to make decisions that will help the agreement be carried out successfully.
• Adjusting or revising the Protocol, which has been done six times since its inception, is one of them.
• Hydrofluorocarbons (HFCs) were to be phased down starting in 2016 according to the most recent revision, the Kigali Amendment.

Conclusion

In order to reduce ozone pollution, we must reduce overall pollution through interventions like the implementation of BS-VI standards for vehicles, the expansion of public transportation, the switch to cleaner fuel in industries, and the promotion of activities like cycling and walking.

FAQs

Question. What is ozone?

Question. What is the importance of the ozone layer?

Question. What causes ozone depletion?

Question. What measures have been taken to protect the ozone layer?

Question. How does ozone at ground level affect human health?

MCQs

1. What is the primary function of the ozone layer?

a) To trap heat in the atmosphere

b) To absorb harmful UV radiation from the Sun

c) To produce oxygen for breathing

d) To regulate Earth's temperature

2. What is the main cause of ozone depletion?

a) Greenhouse gases

b) Chlorofluorocarbons (CFCs)

c) Methane emissions

d) Excessive oxygen in the atmosphere

3. Which of the following is a major international agreement aimed at protecting the ozone layer?

a) Paris Agreement

b) Kyoto Protocol

c) Montreal Protocol

d) Stockholm Convention

4. What is ground-level ozone?

a) Ozone found in the stratosphere

b) Ozone found in the troposphere

c) Ozone found in the mesosphere

d) Ozone found on the Earth's surface

5. How does ozone depletion affect human health?

a) It causes respiratory diseases like asthma

b) It enhances immune system function

c) It helps with the healing of skin conditions

d) It has no significant effect on health

GS Mains Questions and Model Answers

Q1: Evaluate the impact of ozone depletion on human health and the environment.

Answer: Ozone depletion has far-reaching consequences for both human health and the environment. The ozone layer, which absorbs the majority of the Sun's harmful ultraviolet (UV) radiation, protects humans from conditions like skin cancer, cataracts, and immune system suppression. As the ozone layer thins, more UV-B rays reach the Earth's surface, increasing the risk of these health issues. Ozone depletion also harms the environment by damaging marine ecosystems, especially affecting phytoplankton, which form the base of the food chain. Additionally, higher UV levels can negatively impact terrestrial plants, disrupting agricultural production. To mitigate these effects, the international community has taken collective action through the Montreal Protocol, which aims to phase out ozone-depleting substances and promote the recovery of the ozone layer. While the ozone layer is gradually recovering due to these efforts, it remains crucial to continue these actions to protect global health and biodiversity.

Q2: Discuss the role of the Montreal Protocol in addressing ozone depletion.

Answer: The Montreal Protocol, adopted in 1987, is considered one of the most successful international environmental agreements. Its primary goal is to protect the ozone layer by phasing out the production and consumption of ozone-depleting substances (ODS), such as chlorofluorocarbons (CFCs), halons, and other chemicals. The protocol has been ratified by nearly every country, making it a universal effort to combat ozone depletion. Since its adoption, the Montreal Protocol has led to a significant reduction in the use of ODS, and scientific evidence suggests that the ozone layer is slowly recovering. The success of the Montreal Protocol has been attributed to the strong international cooperation, continuous amendments to phase out more harmful substances, and the support provided to developing countries to transition to safer alternatives. As a result, the protocol not only plays a key role in protecting human health and ecosystems but also serves as a model for global environmental cooperation.

Q3: Analyze the challenges in ensuring the complete recovery of the ozone layer.

Answer: While significant progress has been made in reducing ozone-depleting substances through the Montreal Protocol, there are still challenges in ensuring the complete recovery of the ozone layer. One major challenge is the persistence of certain chemicals in the atmosphere, such as CFCs, which have long lifespans and continue to impact the ozone layer for decades after their use is phased out. Additionally, the emergence of new chemicals that may contribute to ozone depletion, such as hydrochlorofluorocarbons (HCFCs), requires constant monitoring and regulation. The recovery of the ozone layer also depends on the cooperation of all countries, particularly developing nations, in adhering to the protocol's guidelines and implementing alternative technologies. Lastly, natural processes such as volcanic eruptions and solar activities can influence ozone levels, making it difficult to predict the exact timeline for complete recovery. Despite these challenges, continued international cooperation, research, and adaptation of the Montreal Protocol remain essential for the ozone layer's restoration.

Previous Year Questions on  Ozone

1. UPSC CSE (IAS) Prelims 2021

Question: What is the role of the ozone layer in protecting human health?

Answer: The ozone layer absorbs most of the Sun's harmful ultraviolet (UV) radiation, particularly UV-B rays, which can cause skin cancer, cataracts, and immune suppression. By filtering out these harmful rays, the ozone layer plays a critical role in protecting human health.

2. UPSC CSE (IAS) Mains 2020

Question: Evaluate the effectiveness of the Montreal Protocol in preventing ozone depletion and its impact on environmental protection.

Answer: The Montreal Protocol has been highly effective in reducing the use of ozone-depleting substances and slowing the depletion of the ozone layer. Its success lies in global cooperation, scientifically backed policies, and continuous amendments to phase out newer chemicals. The protocol has also been instrumental in environmental protection, as the recovery of the ozone layer helps mitigate risks to human health and ecosystems, ensuring long-term sustainability.