Air pollution and Air quality Measures

Air pollution and Air quality Measures in India (Environment) GS Paper-3 P-M-P

Air pollution may be defined as the presence of any solid, liquid or gaseous substance including noise and radioactive radiation in the atmosphere in such concentration that may be directly and/or indirectly injurious to humans or other living organisms, property or interferes with the normal environmental processes.

• An ever-increasing use of fossil fuels in power plants, industries, transportation, mining, construction of buildings, stone quarries had led to air pollution.
• Fossil fuels contain small amounts of nitrogen and sulphur.
• Burning of fossil fuels like coal (thermal power plants) and petroleum release different oxides of nitrogen and sulphur into the atmosphere.
• These gases react with the water vapour present in the atmosphere to form sulphuric acid and nitric acid. The acids drop down with rain, making the rain acidic. This is called acid rain.
• Acid rain corrodes the marble monuments like Taj Mahal. This phenomenon is called as Marble cancer.
• Other kinds of pollutants are chlorofluorocarbons (CFCs) which are used in refrigerators, air conditioners and as pressurising agents in aerosol sprays. CFCs damage the ozone layer of the atmosphere.
• The combustion of fossil fuels also increases the number of suspended particles in the air. These suspended particles could be unburnt carbon particles or substances called hydrocarbons.
• Presence of high levels of all these pollutants causes visibility to be lowered, especially in cold weather when water also condenses out of the air. This is known as smog and is a visible indication of air pollution.

Classification of Pollutants

According to the form in which they persist after release into the environment.

• Primary pollutants: These are persistent in the form in which they are added to the environment, e.g. DDT, plastic, CO, CO₂, oxides of nitrogen and sulphur, etc.
• Secondary Pollutants: These are formed by interaction among the primary pollutants. For example, peroxyacetyl nitrate (PAN) is formed by the interaction of nitrogen oxides and hydrocarbons.

According to their existence in nature

• Quantitative Pollutants: These occur in nature and become pollutant when their concentration reaches beyond a threshold level. E.g. carbon dioxide, nitrogen oxide.
• Qualitative Pollutants: These do not occur in nature and are human-made. E.g. fungicides, herbicides, DDT etc.

Particulate pollutants

• Particulate pollutants are matter suspended in air such as dust and soot.
• Major source of SPM (suspended particulate matter) are industries, vehicles, power plants, construction activities, oil refinery, railway yard, market place, industries, etc.
• Their size ranges from 0.001 to 500 micrometres (µm) in diameter.
• Particles less than 10 µm float and move freely with the air current.
• Particles which are more than 10 µm in diameter settle down.
• Particles less than 0.02 µm form persistent aerosols.
• According to the Central Pollution Control Board (CPCB), particulate size 2.5 µm or less in diameter (PM 2.5) are responsible for causing the greatest harm to human health.
• These fine particulates can be inhaled deep into the lungs and can cause breathing and respiratory symptoms, irritation, inflammations and pneumoconiosis (disease of the lungs caused due to inhalation of dust. It is characterised by inflammation, coughing, and fibrosis – excess deposition of fibrous tissue).

Fly ash

• Fly ash is ejected mostly by thermal power plants as by-products of coal burning operations.
• Fly ash pollutes air and water and may cause heavy metal pollution in water bodies.
• Fly ash affects crops and vegetation as a result of its direct deposition on leaf surfaces.

Composition

• Fly ash particles are oxide rich and consist of silica, alumina, oxides of iron, calcium, and magnesium and toxic heavy metals like lead, arsenic, cobalt, and copper.
• Major oxides are present are aluminium silicate (in large amounts), silicon dioxide (SiO₂) and calcium oxide (CaO).

Uses

• Cement can be replaced by fly ash up to 35%, thus reducing the cost of construction, making roads, etc.
• Fly ash bricks are light in weight and offer high strength and durability.
• Fly ash is a better fill material for road embankments and in concrete roads.
• Fly ash can be used in the reclamation of wastelands.
• Abandoned mines can be filled up with fly ash.
• Fly ash can increase crop yield when added to the soil. But if it gets deposited on the leaf, it will reduce photosynthesis.
• It also enhances the water holding capacity of the land.

Policy measures of MoEF

• The Ministry of Environment and Forests has made it mandatory to use Fly Ash-based products in all construction projects, road embankment works, and low lying landfilling works within 100 km radius of Thermal Power Station and mine filling activities within 50 km radius of Thermal Power Station.

Lead

• It is present in petrol, diesel, lead batteries, paints, hair dye products, etc.
• It can cause nervous system damage and digestive problems and, in some cases, cause cancer.
• Lead affects children in particular.
• Tetraethyl lead (TEL) is used as an anti-knock agent in petrol for a smooth and easy running of vehicles.
• The lead particles coming out from the exhaust pipes of vehicles is mixed with air.
• It produces injurious effects on kidney and liver and interferes with the development of red blood cells.
• Lead mixed with water and food can create cumulative poisoning.
• It has long term effects on children as it lowers intelligence.

Metallic Oxides

• Oxides of iron, aluminium, manganese, magnesium, zinc and other metals have an adverse effect due to deposition of dust on plants during mining operations and metallurgical processes.
• They create physiological, biochemical and developmental disorders in plants and also contribute towards reproductive failure in plants.

Nanoparticles (NPs)

• Nanoparticles are particles with dimensions comparable to 1/10⁹ of a meter (1 divided by 100 crores).
• Major natural processes that release NPs in the atmosphere are forest fires, volcanic eruptions, weathering, dust storms from desert etc.
• Naturally occurring NPs are quite heterogeneous in size and can be transported over thousands of kilometres and remain suspended in the air for several days.
• Nanotechnology has a global socioeconomic value, with applications ranging from electronics to biomedical uses (delivering drugs to target sites).
• Man-made NPs are unknowingly or purposely released in the environment during various industrial and mechanical processes.

Effects of Nanoparticles on the environment

• After releasing in the environment, NPs will accumulate in various environmental matrices such as air, water, soil and sediments including wastewater sludge.
• NPs in the environment influences dust cloud formation, environmental hydroxyl radical concentration, ozone depletion, or stratospheric temperature change.

Effect of NPs on dust cloud formation

• NPs in environment coagulate and form dust cloud.
• Dust cloud formation decreases sunlight intensity.

Asian brown clouds impact on Himalayan glaciers

• Asian brown clouds carry large amounts of soot and black carbon (NPs) and deposit them on the Himalayan glaciers.
• This could lead to higher absorption of the sun’s heat (reduced albedo) and potentially contributing to the increased melting of glaciers.

Carbon monoxide (CO)

• Carbon monoxide (CO) is a colourless, odourless, tasteless and highly toxic gas that is slightly less dense than air. It is short-lived (stay only a few months) in the atmosphere.
• Carbon monoxide is produced from the exhaust of internal combustion engines and incomplete combustion of various other fuels. Iron smelting also produces carbon monoxide as a by-product.
• It forms when there is not enough oxygen to produce carbon dioxide (CO₂).
• In the presence of oxygen, carbon monoxide burns with a blue flame, producing carbon dioxide.
• Worldwide, the largest source of carbon monoxide is natural in origin, due to photochemical reactions in the troposphere.
• Other natural sources of CO include volcanoes, forest fires, and other forms of combustion.

Health Effects

• Carbon monoxide poisoning is the most common type of fatal air poisoning (poor ventilation and heat management in laptops and other electrons can cause the release of CO).
• It is toxic to haemoglobin animals (including humans) when encountered in concentrations above about 35 ppm.
• It combines with haemoglobin to produce carboxyhaemoglobin, which usurps the space in haemoglobin that normally carries oxygen.

Environmental Effects

• Carbon monoxide (CO) is not considered a direct greenhouse gas (GHG).
• In the atmosphere, it is spatially variable and short-lived, having a role in the formation of ground-level ozone (tropospheric ozone) and can elevate concentrations of methane (a strong GHG).

• Carbon monoxide reacts with hydroxyl radical (-OH) to produce peroxy radical.
• Peroxy radical reacts with nitrogen oxide (NO) to form nitrogen dioxide (NO₂) and hydroxyl radical.
• NO₂ gives O₃ via photolysis (separation of molecules by the action of light).

Carbon dioxide (CO₂)

• Colourless and odourless gas. It is heavier than air.
• Natural sources include volcanoes, hot springs and geysers, and it is freed from carbonate rocks by dissolution in water and acids.
• Because carbon dioxide is soluble in water, it occurs naturally in groundwater, rivers and lakes, in ice caps and glaciers and also in seawater.

Effects on Health

• CO₂ is an asphyxiant gas (asphyxia: a condition arising when the body is deprived of oxygen, causing unconsciousness or death.).
• Concentrations of 7% may cause suffocation, even in the presence of sufficient oxygen, manifesting as dizziness, headache, and unconsciousness.

Effects on Environment

• Carbon dioxide is an important greenhouse gas.
• Burning of carbon-based fuels since the industrial revolution has led to global warming.
• It is also a major cause of ocean acidification because it dissolves in water to form carbonic acid.

Chlorofluorocarbons (CFCs)

• Chlorofluorocarbons (CFCs) are used in refrigerators, air conditioners and aerosol sprays.
• Since the late 1970s, the use of CFCs has been heavily regulated because of their destructive effects on the ozone layer. (Explained in Geography > Climatology > Polar Vortex > Ozone Depletion)
• The Montreal Protocol on Substances that Deplete the Ozone Layer (a protocol to the Vienna Convention for the Protection of the Ozone Layer) is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances including CFCs which are responsible for ozone depletion.

Ozone (O₃)

• It occurs naturally in the stratosphere and absorbs harmful ultraviolet rays of the sun.
• However, at the ground level, it is a pollutant (Greenhouse gas) with highly toxic effects.
• Vehicles and industries are the major sources of ground-level ozone emissions.
• Carbon monoxide, Nitrogen dioxide play a major role in converting O₂ to O₃.
• Ozone makes our eyes itchy, and watery. It lowers our resistance to cold and pneumonia.

Nitrogen oxide (NO_x)

• NO_x is a generic term for the various nitrogen oxides produced during combustion.
• They are produced mainly in internal combustion engines and coal-burning power plants.
• They are also produced naturally by lightning.

Oxygen and nitrogen do not react at ambient temperatures. But at high temperatures, they produce various oxides of nitrogen. Such temperatures arise inside an internal combustion engine or a power station boiler.

• Agricultural fertilisation and the use of nitrogen-fixing plants also contribute to atmospheric NO_x, by promoting nitrogen fixation by microorganisms.
• NO and NO₂ (contribute to global cooling) should not be confused with nitrous oxide (N₂O – GHG), which is a greenhouse gas and has many uses as an oxidiser.

Effects on Health and Environment

• They are believed to aggravate asthmatic conditions and create many respiratory health issues.
• The reduction of NO_x emissions is one of the most important technical challenges facing biodiesel.
• NO_x gases react to form smog and acid rain as well as being central to the formation of tropospheric ozone.
• When NO_x and volatile organic compounds (VOCs) react in the presence of sunlight, they form photochemical smog.
• Mono-nitrogen oxides eventually form nitric acid when dissolved in atmospheric moisture, forming a component of acid rain.
• NO and NO₂ emissions cause global cooling through the formation of -OH radicals that destroy methane molecules, countering the effect of greenhouse gases.

Sulphur dioxide (SO₂)

• It is a toxic gas with a pungent, irritating smell. It contributes to acid rain.
• It is released naturally by volcanic activity. It is abundantly available in the atmosphere of Venus.
• Sulphur dioxide is primarily produced for sulfuric acid manufacture.
• Inhaling sulphur dioxide is associated with increased respiratory symptoms and premature death.
• It also weakens the functioning of certain nerves.
• It is also produced by
  • burning coal in thermal power plants and diesel fuels.
  • some industrial processes, such as the production of paper and smelting of metals.
  • reactions involving Hydrogen Sulphide (H₂S) and oxygen.
  • The roasting of sulphide ores such as pyrite, sphalerite, and cinnabar (mercury sulphide).

Volatile organic compounds (VOCs)

• Volatile Organic Compounds (VOCs) are a large group of carbon-based chemicals that easily evaporate at room temperature.
• For example, formaldehyde, which evaporates from paint, has a boiling point of only –19 °C.
• Formaldehyde causes irritation to the eyes and nose and allergies.
• The main indoor sources are perfumes, hair sprays, furniture polish, glues, air fresheners, moth repellents, wood preservatives, and other products.
• Health effects: irritation of the eye, nose and throat, headaches, nausea and loss of coordination.
• Long term health effects: suspected to damage the liver and other parts of the body.

Benzene

• Benzene is a natural constituent of crude oil and is one of the elementary petrochemicals.
• Because benzene has a high octane number, it is an important component of gasoline (petrol).
• Benzene increases the risk of cancer and other illnesses.
• Benzene is a notorious cause of bone marrow failure.

Ethylene

• Ethylene is widely used in the chemical industry.
• Much of this production goes toward polyethylene, a widely used plastic containing polymer chains of ethylene units in various chain lengths.
• Ethylene is also an important natural plant hormone, used in agriculture to force the ripening of fruits.
• Ethylene is of low toxicity to humans and exposure to excess ethylene cause adverse health effects like headache, drowsiness, dizziness and unconsciousness.
• Ethylene is not but ethylene oxide is a carcinogen (cancer-causing agent).

Biological pollutants

• It includes pollen from plants, mite, and hair from pets, fungi, parasites, and some bacteria.
• Most of them are allergens and can cause asthma, hay fever, and other allergic diseases.

Asbestos

• Asbestos refers to a set of six naturally occurring silicate fibrous minerals –– chrysotile, crocidolite, amosite, anthophyllite, tremolite, and actinolite.
• It is now known that prolonged inhalation of asbestos fibres can cause serious and fatal illnesses including lung cancer, mesothelioma, and asbestosis (a type of pneumoconiosis).

Radon

• It is a gas that is emitted naturally by the soil.
• Due to modern houses having poor ventilation, it is confined inside the house and causes lung cancers.

In 2023, India stood as the third most polluted nation globally, recording an average population-weighted fine particulate matter (PM) 2.5 concentration of 54.4 micrograms per cubic metre (μg/m³), found a new global report by IQAir. The economic impact of air pollution is staggering. Annual deaths attributable to air pollution translate to an economic loss of Rs 2.7 lakh crore, which accounts for 1.36% of India's GDP. Furthermore, a recent survey revealed that India's GDP could have been 4.5% higher if air pollution had grown 50% slower each year.

Major Driving Factors of Air Pollution:

1. Vehicular and Industrial Emissions: Carbon monoxide (CO), nitrogen oxides (NOx), and non-methane volatile organic compounds (NMVOCs) are the primary pollutants from vehicles (>80%).

Industries like iron and steel, sugar, paper, cement, fertiliser, copper, and aluminum contribute to suspended particulate matter (SPM), sulfur oxides (SOx), nitrogen oxides (NOx), and carbon dioxide (CO2). Road transport presently accounts for 12% of India's energy-related CO₂ emissions and is a key contributor to urban air pollution (International Energy Agency)

2. Solid Waste Burning: According to a report by The Energy and Resources Institute (TERI), India generates over 62 million tons (MT) of waste in a year, a significant portion of which is burned openly or in informal dump sites. Open burning of solid waste contributes to the release of various pollutants, including PM, dioxins, and furans.
3. Stubble Burning and Other Agricultural Activities: Intentional burning of straw stubble after harvesting grains like paddy and wheat, particularly in Punjab, Haryana, and UP, contributes significantly to air pollution, especially in the NCR region during winter. The Supreme Court in 2023 proposed excluding stubble-burning farmers from minimum support price (MSP) as part of efforts to discourage this practice in Punjab and neighboring states near Delhi. In addition to crop residue burning, other agricultural activities like tilling, fertilizer and pesticide application, and improper livestock farming contribute to air pollution. These activities release ammonia, methane, and particulate matter into the air.
4. Domestic Cooking and Heating: Around 62-65% of India's rural households rely on solid fuels, such as biomass, coal, and kerosene, for cooking and heating purposes. The incomplete combustion of these fuels releases harmful pollutants, including PM, carbon monoxide (CO), and volatile organic compounds (VOCs).
5. Coal Based Power Plants: Coal-based thermal power stations with no pollution control technology are responsible for over half sulfur dioxide (SO2), 30% oxides of nitrogen (NOx), about 20% particulate matter (PM), among other man-made emissions in India (International Energy Agency).
6. Improper Use of Pyrolysis: Pyrolysis, a technique to break down synthetic material, leaves fine carbon matter and residue like pyro gas and oil, contributing to pollution. The National Green Tribunal, in 2014, prohibited used tyres from being burnt in the open or used as fuel in brick kilns.

Key Government Initiatives for Controlling Air Pollution?

• National Clean Air Programme
• System of Air Quality and Weather Forecasting and Research (SAFAR) Portal.
• New Commission for Air Quality Management
• Graded Response Action Plan (for Delhi).
• For Reducing Vehicular Pollution:
• BS-VI Vehicles,
• National Electric Mobility Mission Plan

Note: In M.C. Mehta vs. Union of India, the Supreme Court treated the right to live in pollution free environment as a part of fundamental right to life under Article 21 of the Constitution.

Reasons of Winter Pollution in Delhi: Apart from the other pollution which are due to overpopulation, vehicular emissions and industries, following are the factors that make winter pollution severe: Stubble Burning: It is a traditional practice in Punjab and Haryana to clean off the rice chaff to prepare the fields for winter sowing. Shifting of Jet Stream: The southward shift of subtropical jet stream happens causing a westward wind pattern in the northern part of India and thus spread of pollutants. Stagnant Lower Level Winds: As the winter season sets in, dust particles and pollutants in the air become unable to move. Due to stagnant lower level winds, pollutants get locked in the air and affect weather conditions, resulting in smog.

Major programmes to control Air Pollution

National Clean Air Programme?

• It was launched by the Ministry of Environment, Forests and Climate Change (MoEFCC) in January 2019.
• It is the first-ever effort in the country to frame a national framework for air quality management with a time-bound reduction target.
• The NCAP's goal is to reduce average particulate matter (PM) concentrations by 40% by 2026 in 131 cities. Initially aimed for a 20-40% reduction by 2024, the target was later extended to 2026

It covers 131 non-attainment cities which were identified by the Central Pollution Control Board (CPCB).

Non-attainment cities are those that have fallen short of the National Ambient Air Quality Standards (NAAQS) for over five years.

• • • NAAQs are the standards for ambient air quality with reference to various identified pollutant notified by the CPCB under the Air (Prevention and Control of Pollution) Act, 1981.
    • List of pollutants under NAAQS: PM10, PM2.5, SO2, NO2, CO, NH3, Ozone, Lead, Benzene, Benzo-Pyrene, Arsenic and Nickel.

PRANA ( Portal for Regulation of Air-pollution in Non-Attainment cities), is a portal for monitoring of implementation of NCAP.

Graded Response Action Plan: The action plan which was formulated in 2016 and notified in 2017 for Delhi and the National Capital Region (NCR).

• The plan was formulated after several meetings were held by Environment Pollution (Prevention and Control) Authority (EPCA) with state government representatives and experts.
• These are institutionalized measures to be taken when air quality deteriorates, hence works only as an emergency measure.
• GRAP includes the measures which will be taken by different government agencies to prevent worsening of Air Quality of Delhi-NCR and prevent PM10 and PM2.5 levels to go beyond the ‘moderate’ national Air Quality Index (AQI) category.
• If air quality reaches the severe+ stage, GRAP talks about shutting down schools and implementing the odd-even road-space rationing scheme.

Environment Pollution Control Authority

It was notified in 1998 under the Environment Protection Act, 1986. EPCA is a Supreme Court mandated body tasked with taking various measures to tackle air pollution in the National Capital Region.

New Commission for Air Quality Management

Tne new bill, provides for the constitution of a Commission for better coordination, research, identification, and resolution of problems related to air quality in the National Capital Region (NCR) and adjoining areas.

Adjoining areas have been defined as areas in the states of Haryana, Punjab, Rajasthan, and Uttar Pradesh adjoining the NCR where any source of pollution may cause adverse impact on air quality in the NCR.

It also dissolves the Environment Pollution Prevention and Control Authority established in the NCR in 1998.

Composition:

The Commission will be headed by a full-time chairperson who has been a Secretary to the Government of India, or a Chief Secretary to a State government. The chairperson will hold the post for three years or until s/he attains the age of 70 years.

It will have members from several Ministries as well as representatives from the stakeholder States.

It will have experts from the Central Pollution Control Board (CPCB), Indian Space Research Organisation (ISRO) and Civil Society.

Functions:

• • Coordinating actions taken by concerned state governments (Delhi, Haryana, Punjab, Rajasthan, and Uttar Pradesh).
  • Planning and executing plans to prevent and control air pollution in the NCR.
  • Providing a framework for identification of air pollutants.
  • Conducting research and development through networking with technical institutions.
  • Training and creating a special workforce to deal with issues related to air pollution.
  • Preparing various action plans such as increasing plantation and addressing stubble burning.

Powers:

• • The new body will have the power to issue directions and entertain complaints as it deems necessary for the purpose of protecting and improving the quality of the air in the NCR and adjoining areas.
  • It will also lay down parameters for control of air pollution (such as permissible levels of emissions and discharge of pollutants).
  • It will also be in charge of identifying violators, monitoring factories and industries and any other polluting unit in the region, and will have the powers to shut down such units.
  • It will also have the powers to overrule directives issued by the state governments in the region, that may be in violation of pollution norms.

SAFAR: System of Air Quality and Weather Forecasting and Research, known as "SAFAR", for greater metropolitan cities of India to provide location specific information on air quality in near real time. It was introduced by the Ministry of Earth Science.

AQI: Air Quality Index (AQI) is a tool for effective communication of air quality status to people in terms, which are easy to understand. There are six AQI categories, namely Good, Satisfactory, Moderately polluted, Poor, Very Poor, and Severe. AQ sub-index has been evolved for eight pollutants (PM10, PM2.5, NO₂, SO₂, CO, O₃, NH₃, and Pb) for which short-term (upto 24-hours) National Ambient Air Quality Standards are prescribed.

National Air Quality Monitoring Programme (NAMP) based dashboard, built on data from the Central Pollution Control Board’s National Ambient Air Quality Monitoring (NAAQM) Network which was started in 1984-85 and covers 344 cities/towns in 29 states and 6 UTs. Under the NAMP, each station records about 104 observations a year covering four pollutants– Sulphur dioxide (SO2), nitrogen dioxide (NO2), suspended particulate matter (SPM), and respirable suspended particulate matter (RSPM).

State pollution control boards and the National Environmental Engineering Research Institute (NEERI), Nagpur carry out the monitoring, and the Union Ministry of Environment, Forest and Climate Change oversees the operation under the NCAP.

What to do more to prevent Air Pollution

Introduce Air Quality Bonds: Mandate industries and other major polluters to purchase Air Quality Bonds, where the bond amount is proportional to their emissions.

• • The funds collected can be used for remediation efforts, public awareness campaigns, and subsidies for clean technologies.
  • Non-compliance would lead to penalties or loss of the bond amount.

Biochar Brigade: Empowering rural communities, particularly women's self-help groups, to create and distribute biochar, a charcoal-like substance produced by burning organic waste in a controlled environment.

• • Biochar can be mixed with soil to improve fertility and sequester carbon. It can also be used as a fuel source, reducing dependence on polluting firewood.
  • The Pradhan Mantri Ujjwala Yojana distributes LPG cylinders to rural households, reducing firewood use. A similar program could promote biochar production and utilization.

Increasing Urban Forest Canopy Cover: Launching a national competition among cities to increase their urban forest canopy cover.

• • Cities with the most significant increase in green spaces within a set timeframe win grants for further greening initiatives.
  • Curitiba, Brazil, is known for its innovative urban planning with a focus on green spaces. India could adapt similar strategies specific to its climate and urban environments.

Air Quality-Based Tolling: Implementing dynamic toll pricing on highways and bridges based on real-time air quality data.

• • This strategy can regulate traffic flow and reduce emissions during high-pollution days. Revenue generated can be used for public transport improvement or clean air initiatives.
  • Stockholm, Sweden, has implemented a similar system to manage traffic congestion. India can adapt this concept with a focus on air quality management.

National Air Quality Awareness Corps: Create a dedicated National Air Quality Awareness Corps comprising trained volunteers and professionals who can conduct grassroots awareness campaigns, educate communities, and promote citizen engagement in air pollution mitigation efforts.

Building with Biomimicry: Building construction can be revolutionized through biomimicry. For instance, incorporating natural ventilation systems modeled after termite mounds or developing facades with microstructures inspired by leaves can enhance airflow naturally.

• • Integrating greenery such as vertical gardens and rooftop plantings not only adds aesthetic value but also acts as natural air purifiers, absorbing harmful gases and particulate matter.
  • Green City Solutions from Europe that has introduced tree benches across major city landmarks is a significant example. These benches, coated with moss, effectively absorb pollutants from the air, offering a unique solution to combat pollution.