Why in the news? 

Recently, Delhi, Mumbai, and Kolkata were among the world’s 10 most polluted cities, according to a Swiss air quality technology company, IQAir.

 Causes of air pollution in cities 
☆ Burning of Fossile Fuels:   Most air pollution occurs due to the incomplete burning of fossil fuels. These include coal, oil, and gasoline to produce energy for electricity or transportation. 
☆ Industrial  Emission: Particulate Matter (PM) 2.5 and 10, NO2, SO2, and CO are key pollutants that are emitted from industries.
☆ Open Burning  of Garbage Waste: Open-air garbage burning releases toxins such as black carbon, soot, and carcinogens.   It actively contributes to pollution and in turn to the greenhouse effect. 

  ☆ Construction and Demolition:Construction and demolition sites are a rich source of PM and other air pollutants including Volatile Organic Compounds (VOCs) etc. 

 ☆ Indoor Air Pollution  :Use of toxic products also called VOCs, inadequate ventilation, uneven temperature, and humidity level can cause indoor air pollution.  

  ☆ Some Agriculture Practices :Like stubble burning and use of fertilizers and pesticides in agriculture can release ammonia.  Also, Livestock farming is one of the major contributors to methane emissions. 

 Variations due to geographic processes:  

Change in weather patterns. For example, a dip in La Nina (cooling of the ocean surface and change in wind patterns) partially caused the recent spike in PM in coastal cities (including Mumbai). 

 ♧  Dust storms, wildfires, and natural sources of pollution also impact air quality in various regions of India. E.g., the temperature difference between the city and nearby hills draws winds and dust from areas like Navi Mumbai towards the city.  Impacts of urban air pollution 

☆ Adverse health outcomes :  It increases the risk of respiratory infections, heart disease and lung cancer.  
♧  Children, elderly, and poor people are more susceptible. 
  Climate Change : Certain air pollutants, such as black carbon (soot) and methane, contribute to climate change.   Methane is a potent greenhouse gas, contributing to global warming. 

 Environmental Damage : pollution contributes to environmental degradation, including damage to ecosystems, soil, and water bodies.  For instance, Acid rain, resulting from the release of sulphur dioxide and nitrogen oxides, can harm forests, aquatic systems, and soil quality. 

 Reduced  Agricultural  Productivity  : Ground-level ozone damages plant tissues, affecting photosynthesis and reducing crop productivity.  Particulate matter can also get deposited on crops, affecting their growth. 

 Economic Costs : Health impacts of air pollution result in significant economic costs, including healthcare expenses, lost productivity due to illness, and the cost of premature mortality.   Environmental damage and reduced agricultural productivity can impact various sectors of the economy.

Regulatory measures taken to improve air quality 

  Vehicular Emission:  

     BS_ IV to BS _ VI norms and introduction of cleaner/alternate fuels like CNG, LPG, and ethanol blending in petrol. 

  Faster Adoption and Manufacturing  of Electric Vehicle  ( FAME) _ 2 scheme has been rolled out. 

 ● Industrial  Emissions  : Ban on the use of  pet coke and furnace oil in NCR,  use of pet coke in processes in cement plants, lime kilns and ement  plants, lime kilns and calcium carbide manufacturing units. 

   Shifting of brick kilns in Selhi _ NCR to zig_ zag technology (zigzagging the air flow in brick kilns) for reduction of pollution. 

 Air Pollution  due to dust and burning  of waste : Extended Producer Responsibility (EPR) framework for plastic packaging, battery waste, tire waste and e-waste have been implemented. 

 Monitoring  of Ambient Air Quality  : System of Air Quality and Weather Forecasting And Research (SAFAR) was launched to know the Air Quality and Overall city pollution and Location-specific Air Quality through AQI.

  National  Clean Air Programme  ( NCAP): Envisages to achieve reductions up to 40% or achievement of National Ambient Air Quality Standards for PM 10 concentrations by 2025-26. 

Global success stories to combat air pollution

  Seoul, Republic  of Korea : 5G-enabled autonomous robots scan industrial complexes to monitor air quality, while a satellite monitoring system offers real-time air quality data to the public. 
 Bogota, Colombia : Strict emissions standards on trucks and other heavypolluting vehicles; a fully electric metro rail system etc. 
  Spain : Four-day work week trial in Spain leads to healthier workers, less pollution. 

  Southern California : Electric cars, ship atport electrification, cleaner fuel for trucks, ships and trains and mandatory installation of newer and cleaner engines. 

Way ahead

 Reduce Emissions  by Optimizing  Power Sector : Inefficient power plant systems could be replaced by efficient super-thermal plants or with power generators that are based on renewable energy. 

 Implementing  a National  Emissions  Trads System  : A marketbased instrument within a regulatory framework based on the concept of ‘polluters pay’ could be implemented.

  Similar models exist in the European Union  ( Emissions  Trading  System ). 

  Implementation  of a Business  Model  to Utilize  Crop Residue : Direct procurement of crop residue by large agro-waste management companies, inter-state trading for paddy stubble. 

 Trackle City Dust through  ULBs:  Undertaking reforestation and afforestation drive along roadsides, covering landfills with vegetation.

  Decarbonization of the transport sector :  Declaring some expressways and national highways as green freight corridors.  


Why in the news? 

Supreme Court directed Punjab, Haryana, Uttar Pradesh, Rajasthan, and Delhi to stop stubble burning immediately which is considered a major cause of air pollution in Delhi. 

About Stubble (Parali) burning 

 Stubble burning is a process of setting on fire the straw stubble, left after the harvesting of grains, like paddy, wheat, etc. It is usually required in areas that use the combined harvesting method which leaves crop residue behind.  

Reasons why farmers burn the stubble 

 Time Constraints  : In many agricultural regions, there is a narrow window between the harvest of one crop and the sowing of the next. Stubble burning is seen as a quick and efficient way to clear fields. 

 For example, in Punjab and Haryana, there is only a two to three-week time between cropping cycles.

  Increased  mechanization  of harvesting  : Use of mechanized harvesters leaves stubble of 10 – 30 cm in the field, depending on the type of crop, which was not the case earlier with manual harvesting. 

Labour shortage  : Use of expensive labour for stubble extraction is not feasible. Costs are high, especially in Punjab and Haryana, where farm sizes are large, and the use of mechanized harvesters is common. 

 No market for crop residue :  Low commercial and economic value of crop residue, coupled with the high costs of processing, reduces its value for farmers.

  Tradition and Conventional Practices  : Stubble burning has been a long-standing practice in some agricultural communities and is considered a traditional approach passed down through generations.

  Pest and Disease  Management  : Farmers view burning the stubble can help eliminate pests, diseases, and weed seeds that may be present in the crop residue.

  Access to Resources : Limited access to resources such as equipment for residue management also indirectly encourages stubble burning.  Impact of stubble burning 

Pollution  :Stubble burning emits toxic pollutants in the atmosphere containing harmful gases like Carbon Monoxide (CO), methane (CH4), carcinogenic polycyclic aromatic hydrocarbons, and volatile organic compounds (VOC). These pollutants disperse in the surroundings and eventually affect air quality and people's health by forming a thick blanket of smog. 

  Soil fertility : Soil becomes less fertile, and its nutrients are destroyed when the husk is burned on the ground. Burning paddy straw radiates heat that kills fungus and bacteria which are essential for soil fertility. 

 Heat penetration  : Stubble burning generates heat that penetrates the soil, causing an increase in erosion and loss of useful microbes and moisture.

   Impact on Biodiversity  :Fires can destroy habitats for various wildlife species, such as insects, birds, and small mammals, which may rely on crop residues for shelter or food.

 Regulatory Measures and Policies 

    National Policy for Management  of  crop  Residue ( NPMCR ) 2014 : Envisages adoption of technical measures including diversified uses of crop residue, capacity building & training along with formulation of suitable law/legislation. 

National Green Tribunal (NGT) had issued the following directions in 2015: 

 Mechanism for  collection of crop  residue, transportation, and utilization to be evolved.  

■ For persistent defaulters of crop  residue burning, appropriate coercive and punitive action could be taken.

   Every state must provide machines,  mechanisms and equipment or cost to the farmers to remove, collect and store straws.

  Commission on Air  Quality  Management  in NCR and Adjoining  Areas  ( CAQM) developed an action plan for effective prevention and control of Stubble Burning.

  In_ situe Crop Residue Management  : Setting up of Custom Hiring Centers, high yield, and short duration paddy varieties, staggering of harvesting schedule, extensive use of bio-decomposer. 

Ex_ situe Crop Residue Management  : Alternative usage of paddy straw viz. Biomass Power Projects, Co-firing in Thermal Power Plants, Feed stock for 2G Ethanol plants, Feed stock in Compressed Biogas plants, fuel in industrial boilers, WTE plants, packaging materials etc

  Crop Diversification  Programme  ( CDP): A sub-scheme of Rashtriya Krishi Vikas Yojana (RKVY) in Haryana, Punjab & Western Uttar Pradesh since 2013-14 to divert the area of water-intensive paddy crop to alternative crops like pulses, oilseeds etc. 

Government is implementing a Scheme for the Promotion of Agricultural Mechanization for In-Situ Management of Crop Residue in the States of Punjab, Haryana, Uttar Pradesh and the National Capital Territory (NCT) of Delhi

Way forward 

 New and Improved  Seed Varieties  : Recently, the Indian Agricultural Research Institute has developed a high-yielding short-duration variety namely Pusa-2090.

 1)  The Pusa-2090 variety matures in only 120 to 125 days as compared to currently Pusa-44 which takes 155 to 160 days to mature. 

 2) New paddy variety will give around 30 days time to farmers to ready their fields for the next crop. 

 Innovative  farm technologies  :Employing agricultural machines like Happy Seeder, Rotavator, Baler, Paddy straw chopper etc.

1)  As these machines are cost-intensive, the Government could provide adequate subsidies to make these machinery affordable for farmers. 

 Biogas plants can curb crop burning  :These plants are installed by the government under ‘waste to energy mission’ and they generate bio-gas by utilising crop waste such as rice straw through bio-methanation technology. 

 Pusa _ bio_ decomposer :  Developed by scientists at the Indian Agricultural Research Institute, which turns crop residue into manure in 15-20 days by accelerating the decomposition process. 

Educating  and empowering  the stakeholders  : Educating and empowering the farming community could be an important step to making a significant impact.  

• Encouraging Sustainable Alternatives to Crop Residue Management:

Mulching:   Mulching involves spreading crop residues on the soil surface as a protective layer.  

Zero _ Till Farming  : It minimizes soil disturbance and relies on the direct planting of seeds into crop residues.  

 Residue Incorporation : Instead of burning crop residues, farmers can incorporate them into the soil. Techniques like chiseling and ploughing help bury crop residues, enriching the soil with organic matter and nutrients.  


Why in the news? 

Researchers discussed the possibility of using cloud seeding to tackle Delhi's air pollution. About Cloud Seeding
  Cloud Seeding  : It is a weather modification technique to enhance precipitation by dispersing substances into the air that help to saturate the clouds. 

• The Process:  

1)  It starts with identifying suitable clouds through weather analysis using aircraft or ground-based generators.  
2)  Following this, seeding agents are released into the targeted clouds.  
3)  Seeding particles help in the formation of larger water droplets, which leads to increased rainfall. 

  Chemicals used : To initiate cloud seeding, clouds are injected with salts such as silver iodide, potassium iodide, sodium chloride, or dry ice (solid carbon dioxide), which acts as the seed.  

1)  These salts are dispersed to provide additional nuclei around which more cloud droplets can form.  

Conditions required for cloud seeding to be effective: 

  Cloud Type :  Not all clouds are suitable for seeding. Clouds should be deep enough and have a suitable temperature, typically between -10 and -12 degrees Celsius. 
o Cloudiness: Clouds should cover at least 50% of the target area. 

 Wind : Wind speeds should be below a certain level. 

Humidity :  Cloud seeding tends to be less effective when relative humidity is less than 75%. 

  Temperature : Clouds should be cold enough to contain supercooled liquid water.

Methods of cloud seeding

  Hygroscropic cloud seeding  : It involves dispersing salts through flares or explosives in lower portions of clouds. Following the dispersal, the salts grow in size. 

 (i) It has proved to have positive results in research conducted by countries such as South Africa and Mexico. 

Use of electrical  charges : Electrical charges work similarly to silver iodide by helping water droplets to merge and form precipitation.  

(a)  In 2010, researchers from the University of Geneva directed infrared to the air above Berlin.  

(b)  The experiment showed that infrared can help atmospheric sulphur dioxide and nitrogen dioxide form particles that act as seeds and cause rainfall. 

 How Artificial rain can help tackle pollution?

 Clearing  the atmosphere : Rainfall induced through cloud seeding can help remove particulate matter and pollutants from the air.  
 Reduction of airborne pollutants  : Artificial rain can assist in reducing concentration of pollutants, including dust, smoke, and chemicals, by washing them out of the atmosphere and depositing them on the ground.
  Mitigating   smog and haze : Cloud seeding can help disperse smog and haze, making the air clearer and more breathable. 

Applications of Artificial Rain (using Cloud Seeding) 

Agriculture  :  It helps to create rain, which can provide relief to drought-stricken areas. 

 For example, the Karnataka government, in 2017, launched "Project Varshadhari", under which an aircraft was used to spray chemicals to induce rainfall. 

  Power generation  : Cloud seeding method has been shown to augment the production of hydroelectricity (enhancing rainfall in catchment areas) in Tasmania, Australia, during the last 40 years. 

  Water pollution  control : The process of cloud seeding can maintain minimum river flows and dilute the impact of treated wastewater discharges from industries.  

(i) Minimum river flows refer to minimum quantity of water or ecological flow that various stretches of the river must necessarily have through the year.  

Fog dispersal and cyclone modifications  : During winters, cloud seeding is initiated to increase the mountain snowpack to ensure that additional runoff is received during the spring melt season. 

 For example, USA in 1962 launched "Project Sky Water", aimed at fog dispersal, hail suppression, and cyclone modification.


 Controlling  forest fires : In regions prone to wildfires, cloud seeding can be used to induce rainfall and help extinguish fires, preventing the release of smoke and pollutants into the atmosphere. 

 Research and Experimental Studies  : To better understand atmospheric processes, cloud physics, and potential impacts of weather modification. 

Issues with inducing Artificial Rains 

   Side _ effects  : The chemicals used in cloud seeding may cause harm to plants, animals, people, and even the environment.

  For example, silver iodide, the material used in cloud seeding, can be toxic to aquatic life.

  Abnormal Weather  patterns  : It may lead to changes in climatic patterns, interfering with local weather patterns. 

High cost :  Cloud seeding involves dispersing chemicals to the sky using aircraft or flare shots, which involves huge costs and logistic preparations. 

 Ethical and Legal Challenges  :  Issues related to water rights and environmental impact.  Also, ethical considerations regarding human intervention in natural processes raise questions about different communities' rights to natural resources. 


Collaborative efforts between scientists, policymakers, and the public are crucial to establish clear guidelines, ethical standards, and regulatory frameworks for the responsible implementation of cloud seeding projects. Also, dedicated research is necessary to understand the long-term impacts of Cloud Seeding on ecosystems, weather patterns, and human health. 


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