Pollution may be defined as unfavourable alternations of surroundings wholly or largely as a by-product of man’s actions through direct or indirect effects of changes in energy flow radiation level, physical or chemical constituents and abundance of organisms. These changes may affect man directly or through his supplies of water and of agricultural and their biological products, his physical objects or his opportunities for recreation and appreciation of nature.

Pollutants:

Pollutant is anything including a chemical geochemical substance or a biological product that deteriorates natural environment by changing the growth rate of species, interferes with the food chain, is toxic or interferes with the health, comfort, amenities or property value of people. The pollutants are of two types.

Non degradable pollutants: They are the materials and poisons such as heavy metals, long chain, phenolic compounds and pesticides, which do not degrade or degrade extremely slowly in the natural environment. Most of the non degradable pollutants combine with other compounds in the environment to produce additional toxicity and toxin.

Biodegradable pollutants: They are domestic sewage and wastes of several industries that rapidly decomposed by the natural processes by the action of micro organisms such as the bacteria, fungi and protozoa or by some artificial systems.

Primary air pollutants - Materials that when released pose health risks in their unmodified forms or those emitted directly from identifiable sources.

Secondary air pollutants - Primary pollutants interact with one another, sunlight, or natural gases to produce new, harmful compounds. Pollution is of various types e.g.

• The air pollution may be defined as a release or occurrence of any foreign materials or gases in the atmosphere, which may be harmful to man, animals and vegetation etc.
• Air pollution is aggravated because of four developments: increasing traffic, growing cities, rapid economic development, and industrialization.
• ‘The presence in the atmosphere of one or more con-taminants in such quality and for such duration as it is injurious, or tends to be injurious, to human health or welfare, animal or plant life.’
• It is the contamination of air by the discharge of harm-ful substances.
• Air pollution can cause health problems, damage the environment, property and climate change.

Major air pollutants and their sources

Carbon monoxide (CO)

• It is a colourless, odourless gas that is produced by the incomplete burning of carbon-based fuels including petrol, diesel, and wood.
• It is also produced from the combustion of natural and synthetic products such as cigarettes.
• It lowers the amount of oxygen that enters our blood.
• It can slow our reflexes and make us confused and sleepy.

Carbon dioxide (CO2)

• It is the principle greenhouse gas emitted as a result of human activities such as the burning of coal, oil, and natural gases.

Chlorofluorocarbons (CFC)

• These are gases that are released mainly from air-con-ditioning systems and refrigeration.

When released into the air, CFCs rise to the stratosphere, where they come in contact with few other gases, which lead to a reduction of the ozone layer that protects the earth from the harmful ultraviolet rays of the sun.

Lead

• It is present in petrol, diesel, lead batteries, paints, hair dye products, etc. Lead affects children in particular.
• It can cause nervous system damage and digestive problems and, in some cases, cause cancer.

Ozone

• It occurs naturally in the upper layers of the atmosphere.
• This important gas shields the earth from the harmful ultraviolet rays of the sun.
• However, at the ground level, it is a pollutant with highly toxic effects.
• Vehicles and industries are the major source of ground-level ozone emissions.
• Ozone makes our eyes itch, burn, and water. It lowers our resistance to cold and pneumonia.
• Nitrogen oxide (Nox)
• It causes smog and acid rain. It is produced from burning fuels including petrol, diesel, and coal.
• Nitrogen oxide can make children susceptible to respiratory diseases in winters.

Suspended particulate matter (SPM)

• It consists of solids in the air in the form of smoke, dust, and vapour that can remain suspended for extended periods and is also the main source of haze which reduces visibility.
• The finer of these particles, when breathed in can lodge in our lungs and cause lung damage and respiratory problems.

Sulphur dioxide (SO2)

• It is a gas produced from burning coal, mainly in thermal power plants.
• Some industrial processes, such as production of paper and smelting of metals, produce sulphur dioxide.
• It is a major contributor to smog and acid rain. Sulfur dioxide can lead to lung diseases.

 Smog

• The term smog was first used (1905) by Dr H A Des Voeux
• Smog has been coined from a combination of the words fog and smoke. Smog is a condition of fog that had soot or smoke in it. The Formation of Smog
• Photochemical smog (smog) is a term used to describe air pollution that is a result of the interaction of sunlight with certain chemicals in the atmosphere.
• One of the primary components of photochemical smog is ozone.
• While ozone in the stratosphere protects earth from harmful UV radiation, ozone on the ground is hazardous to human health.
• Ground-level ozone is formed when vehicle emissions containing nitrogen oxides (primarily from vehicle exhaust) and volatile organic compounds (from paints, solvents, printing inks, petroleum products, vehicles, etc.) interact in the presence of sunlight.
• Smog refers to hazy air that causes difficult breathing conditions. It is a combination of various gases with water vapour and dust.
• Its occurrences are often linked to heavy traffic, high temperatures, and calm winds. During the winter, wind speeds are low and cause the smoke and fog to stagnate near the ground; hence pollution levels can increase near ground level.
• Smoke particles trapped in the fog gives it a yellow/black colour and this smog often settled over cities for many days.

The effects of smog

• It hampers visibility and harms the environment.
• Respiratory problems
• Deaths relating to bronchial diseases.
• Heavy smog greatly decreases ultraviolet radiation.
• Heavy smog results in the decrease of natural vitamin D production leading to a rise in the cases of rickets.

Air forms nearly 80% of man’s daily intake by weight. A normal man breathes nearly 22,000 times a day inhaling about 16 kg airs. Many of the long known effects of air pollution are reduction in sunshine, morbidity, mortality from respiratory ailments dust, fall corrosion of metals and so on.

Industrial and powerhouses, burning of fuels, auto exhausts etc. emit such pollutants into the atmosphere as suspended matters like smoke dust and sprays. SO2, CO, nitrogen oxides, fluorides and silicon, tetra fluoride and foul odours. Motor vehicles alone contribute about 60% of air pollution; carbon monoxide causes difficulty in breathing, cause irritation in mucous membranes, combines with blood haemoglobin reducing its oxygen carrying capacity and causes. Benzyprene a fatal hydrocarbon released due to incomplete combustion is responsible for causing lung cancer. Hydrocarbons and nitrogen oxides when mixed in the atmosphere form ozone and complex organic gases in the presence of UV radiation in sunlight. This in turn causes photochemical smog, which is responsible for causing, eye watering, and respiratory distress in human beings.

Government Initiatives Air pollution:

(1) National Air Quality Monitoring Programme

• In India, the Central Pollution Control Board (CPCB) has been executing a nationwide programme of ambient air quality monitoring known as National Air Quality Monitoring Programme (NAMP).
• The National Air Quality Monitoring Programme (NAMP) is undertaken in India

(i) To determine status and trends of ambient air quality;

(ii) To ascertain the compliance of NAAQS;

(iii) To identify non-attainment cities;

(iv) To understand the natural process of cleaning in the atmosphere

(v) To undertake preventive and corrective measures.

• Annual average concentration of SOx levels are within the prescribed National Ambient Air Quality Standards

(NAAQS).

• This reduction from earlier levels is due to various measures taken, including the use of CNG in public transport in Delhi, the reduction of sulphur in diesel and use of LPG instead of coal as a domestic fuel.
• A mixed trend is observed in NO2 levels due to various measures taken for vehicular pollution control, such as stricter vehicular emission norms being partially offset by increased NOx levels due to the use of CNG in urban transport.
• Total suspended particulates, however, are still a matter of concern in several urban and semi urban areas.

(b) National Ambient Air Quality Standards (NAAQS)

• National Ambient Air Quality Standards (NAAQS) were notified in the year 1982, duly revised in 1994 based on health criteria and land uses.
• The NAAQS have been revisited and revised in November 2009 for 12 pollutants, which include

1. Sulphur dioxide (SO2),

2. Nitrogen dioxide (NO2),

3. Particulate matter having size less than 10 micron.

4. Particulate matter having size less than 2.5 micron (PM2.5),

5. Ozone,

6. Lead,

7. Carbon monoxide (CO),

8. Arsenic,

9. Nickel,

10. Benzene,

11. Ammonia, and

12. Benzopyrene.

(c) National Air Quality Index

• National Air Quality Index was launched by the Prime Minister in April, 2015 starting with 14 cities to disseminate air quality information. The AQI has six categories of air quality, viz Good, Satisfactory, Moderately Polluted, Poor, Very Poor and Severe with distinct colour
• scheme. Each of these categories is associated with likely health impacts. AQI considers eight pollutants (PM10, PM 2.5, NO2, SO2, CO, O3, NH3 and Pb) for which (up to 24-hourly averaging period) National Ambient Air Quality Standards are prescribed.

Air Pollution in India:

• India’s air pollution, ranked among the worst in the world is adversely impacting the lifespan of its citizens, reducing most Indian lives by over three years - WHO.
• Over half of India’s population – 660 million people live in areas where fine particulate matter pollution is above India’s standards for what is considered safe.
• Of the world’s top 20 polluted cities, 13 are in India. Air pollution slashes life expectancy by 3.2 years for the 660 million Indians who live in cities.
• 2014 global analysis of how nations tackle environmental challenges has ranked India 155 among 177 nations and labelled the country’s air quality among the worst in the world.
• India is placed as the “bottom performer” on several indicators such as environmental health impact, air quality, water and sanitation and india’s environment health severely lags behind the BRICS nations - Environmental Performance Index 2014.
• The Ganga and Yamuna are ranked among the world’s 10 most polluted rivers.
• Despite the directives of the National Green Tribunal, civic agencies continue to allow concretisation in green belts. Booming real estate and demand for housing units is leading to change of land use and shrinkage of natural conservation zones such as forests, water bodies, wastelands, sanctuaries, groundwater rechargeable areas.
• Mindless concretisation of ground and green belts and booming real estate has led to heat island effect - shortwave radiations emanate from concrete surfaces at night time. Concretisation prevents ground water recharge thus depleting green cover. Tall buildings also block winds thereby reducing their cooling effect. Excessive concretisation also leads to weakening of trees.
• The environmental crisis in India is many-sided and multi-faceted which has to be addressed on different fronts and by a variety of different actors. We need to harness scientific and social-scientific expertise to develop and promote eco-friendly technologies in construction, energy, water management, industrial production and transportation. Scientific innovation needs to be complemented by legislative change as well as by changes in social behaviour.

Vehicular pollution

The following are the major pollutants associated with motor vehicles:

Ozone (O 3 ). The primary ingredient in urban smog, ozone is created when hydrocarbons and nitrogen oxides (NO x )—both of which are chemicals released by automobile fuel combustion—react with sunlight. Though beneficial in the upper atmosphere, at the ground level ozone can irritate the respiratory system, causing coughing, choking, and reduced lung capacity.

Particulate matter (PM). These particles of soot, metals, and pollen give smog its murky color. Among vehicular pollution, fine particles (those less than one-tenth the diameter of a human hair) pose the most serious threat to human health by penetrating deep into lungs. In addition to direct emissions of fine particles, automobiles release nitrogen oxides, hydrocarbons, and sulfur dioxide, which generate additional fine particles as secondary pollution.

Nitrogen oxides (NO x ). These vehicular pollutants can cause lung irritation and weaken the body's defenses against respiratory infections such as pneumonia and influenza. In addition, they assist in the formation of ozone and particulate matter. In many cities, NO x pollution accounts for one-third of the fine particulate pollution in the air.

Carbon monoxide (CO). This odorless, colorless gas is formed by the combustion of fossil fuels such as gasoline. Cars and trucks are the source of nearly two-thirds of this pollutant. When inhaled, CO blocks the transport of oxygen to the brain, heart, and other vital organs in the human body. Newborn children and people with chronic illnesses are especially susceptible to the effects of CO.

Sulfur dioxide (SO 2 ). Motor vehicles create this pollutant by burning sulfur-containing fuels, especially diesel. It can react in the atmosphere to form fine particles and can pose a health risk to young children and asthmatics.

Hazardous air pollutants (toxics). These chemical compounds, which are emitted by cars, trucks, refineries, gas pumps, and related sources, have been linked to birth defects, cancer, and other serious illnesses. The EPA estimates that the air toxics emitted from cars and trucks account for half of all cancers caused by air pollution.

Government Measures taken to Reduce Vehicular Pollution

• Automobile Pollution Control initiatives marks enforcement of a variety of control measures ranging from notification of advanced Euro-IV equivalent emission norms and commensurate fuel for new vehicles to stricter exhaust emission limits for in-use vehicles, augmentation of infrastructures for alternative fuels and mass transits and other urban planning and management options.
• The vehicular pollution control framework in the country has now shifted its focus towards integrated control and management options and has extended its domain to cover all major metro cities and now it is no more restricted only to capital of India.
• Motor Vehicle Act, 1988, and the Central Motor Vehicles Rules (CMVR), 1989, are the principal instruments for regulation of motor vehicular traffic /emissions throughout the country. The implementation of various provisions of this Act rests with the state governments. The Ministry of Road Transport and Highways (MRTH) acts as a nodal agency for the formulation and implementation of various provisions of the Motor Vehicle Act and CMVR.
• Mass Emission Standards (Bharat Stage IV) have been notified for all categories of new vehicles (except two and three wheelers) in 11 mega cities, to be implemented on or after the 1st April, 2010.

Fuel Quality Specifications

• Auto-Fuels commensurate to Euro III (whole country) and Euro IV (for 11 cities) specifications is proposed to be made available in the respective cities from 01.04.2010.
• The Research Octane Number (RON) for premium petrol available in 11 mega cities has been boosted to 95 with lead content being reduced to 0.005 g/l and benzene content of maximum 1%. From 01.04.2010, the content of sulphur in gasoline is proposed to be reduced to 0.005% (50 mg/kg) from existing 0.015% (150 mg/kg
• The amount of sulphur in diesel is proposed to be 0.035% (350 mg/kg) all over the country

BS Emission Norms

The BS — or Bharat Stage — emission standards are norms instituted by the government to regulate the output of air pollutants from internal combustion engine equipment, including motor vehicles. India has been following the European (Euro) emission norms, though with a time lag of five years. BS-IV norms are currently applicable in 33 cities in which the required grade of fuel is available; the rest of India still conforms to BS-III standards.

India introduced emission norms first in 1991, and tightened them in 1996, when most vehicle manufacturers had to incorporate technology upgrades like catalytic converters to cut exhaust emissions. Fuel specifications based on environmental considerations were notified first in April 1996 — to be implemented by 2000, and incorporated in BIS 2000 standards. Following the landmark Supreme Court order of April 1999, the Centre notified Bharat Stage-I (BIS 2000) and Bharat Stage-II norms, broadly equivalent to Euro I and Euro II respectively. BS-II was for the NCR and other metros; BS-I for the rest of India. From April 2005, in line with the Auto Fuel Policy of 2003, BS-III and BS-II fuel quality norms came into existence for 13 major cities, and for the rest of the country respectively.

Subsequently, BS-IV and BS-III fuel quality norms were introduced from April 2010 in 13 major cities and the rest of India respectively. As per the roadmap in the auto fuel policy, BS­V and BS-VI norms were to be implemented from April 1, 2022, and April 1, 2024, respectively. But in November 2015, the Ministry of Road Transport issued a draft notification, advancing the implementation of BS­V norms for new four-wheel vehicle models to April 1, 2019, and for existing models to April 1, 2020. The corresponding dates for BS-VI norms were brought forward to April 1, 2021, and April 1, 2022, respectively.

Alternate Fuels – Initiatives:

• biodiesel from Jatropa
• supply of CNG as automotive fuel
• Bus Rapid Transit System (BRTS) aims at segregation of traffic in various lanes according to type of vehicles.
• Catalytic converter is a device, fitted on to the exhaust pipes of petrol-driven automobiles which helps reduce the emission of environmentally damaging gases from the automobiles

Pollution is a one of biggest threat to the humanity and India as responsible nation is trying to move toward green development in sink with the SDG and Paris climate agreement.

DELHI AIR POLUTION- A CASE STUDY

In India, air pollution is referred to as the silent and fifth largest killer in India.  According to the WHO, the country has the highest death rate from asthma and chronic respiratory ailments in the world, as air pollution does irreversible lung damage to more than 50 per cent of children.

Delhi Air Quality Index generally hovers from moderate to worse. It is rarely satisfactory and never ‘good.’ During December to March- the months of winters when Sun is hard to spot, it is the smog that affects the visibility to a great extent, and the quality reduces to very poor, severe and eventually hazardous. From October to December, the pollution level worsens exorbitantly due to stubble burning, dust storms, vehicle pollution, and gradually changing weather.

Causes of sever air pollution in Delhi

• Growing population of the city and highly haphazard and unplanned development of industries and factor Studies have revealed that only about 20% of the industrial units are set up in the approved industrial areas whereas the rest of them are in residential and commercial areas. -The pressure and haphazard growth of the population is deteriorating the environment.
• There has been a huge rise in the vehicular in the Delhi NCR region, despite the metro railways, aggravating traffic congestion and increasing air and noise pollution. It has also been reported that the number of vehicles plying on the roads of Delhi is more than that of the three metropolitan cities of Mumbai, Kolkata and Chennai taken together.
• There has also been an ever-increasing number of diesel vehicles plying on the roads, which are largely responsible for the air pollution.
• It has been reported by the National Environmental Engineering Research Institute (NEERI) that everyday almost 8,000 m tonnes of solid waste is being generated in Delhi. Plus, we also have the industrial hazardous and non-hazardous waste. On an average, every day, the MCDs and the NDMC manage to clear about 5,000-5,500 m tonnes of garbage. This results in the accumulation of more and more garbage in the city.
• There has been no proper technology or methods to treat solid and directly dumping in on landfills, liquid, waste water, industrial and hospital wastes in the city.
• There has been too much dependence on fossil fuels like coal-fired power plants, improper use of energy in buildings and the excessive use of biomass for cooking and heating, etc.

Major reasons for extremely poor Delhi air in winters

• Stubble Burning – Burning of crop residue by farmers in Northern states of Punjab, Haryana and Uttar Pradesh is considered as the prime reason for a spike in air pollution during the winter months in Delhi and NCR. This is a traditional practice followed by farmers in these states to prepare their fields for sowing crops after harvesting their fields.
• Winter season - As the winter season sets in, dust particles and pollutants in the air become unable to move. Due to stagnant winds, these pollutants get locked in the air and affect weather conditions, resulting in smog.
• Burning crackers during the Diwali season - Despite the ban on cracker sales, firecrackers are usually a common sight every Diwali. It may not be the top reason for this smog, but it contributes to its build up.

Challenges due to Air Pollution

• There is concrete evidence that air pollution leads to low birth-weight, tuberculosis, ischemic heart disease, cataracts, asthma and nasopharyngeal and laryngeal cancers.
• New research has found that air pollution might also affect cognitive development. PM2.5 are so small that when inhaled they can enter the bloodstream, and recent medical research indicates that it can cause the degeneration of blood-brain barriers, leading to oxidative stress, neuro-inflammation and damage of neural tissue.
• Air pollution is linked to diseases and infections that kill around 600,000 children under five years of age per year.
• A study even shows that about 2.2 million school children in Delhi are growing up with irreversible lung damage which they will never recover.
• The number of premature deaths due to outdoor air pollution is projected to increase from three million people globally in 2010 to a global total of six to nine million people in 2060.
• The number of cases of bronchitis is projected to increase substantially, going from 12 to 36 million new cases per year for children aged six to twelve and from 3.5 to 10 million cases for adults.
• Total welfare costs of air pollution in the world is expected to increase from $3,160 billion in 2015 to $18,300 – $25,330 billion in 2060 (as per 2010 PPP exchange rates).
• Irritation in eyes and overall the tourism industry is affected due to the air pollution.

Government initiatives taken to control Delhi Pollution

• There are mobile enforcement teams deployed at various locations for monitoring polluting vehicles and vehicles not having PUC certificates.
• A Mass Rapid Transport System (MRTS) is being constructed with the aim of providing a non-polluting, useful and affordable rail-based mass rapid transit system for Delhi, integrated with other modes of transport. e.g Bus rapid transport system 
• With a view to reducing vehicular pollution, there has been a ban imposed on the plying of more than 15 years old commercial/transport vehicles, taxis and autos that run on conventional fuels, including diesel driven city buses.
• There has also been tightening of mass emission standards for new vehicles.
• The quality of the fuel being supplied in Delhi has been significantly improved over the years by the ban of selling leaded petrol, introduction of low sulphur diesel, reduction of sulphur and benzene content in petrol.
• There has been regular placement of dustbins, purchase of additional front-end loaders, mechanical sweepers, dumper placers, tipper trucks, to collect and dispose of garbage.
• The biggest positive step taken by the Delhi government was to permanently shut down the old, polluting Badarpur coal-fired power plant in the southeastern outskirts of Delhi. The plant, a major cause of the Capital Region’s air pollution, had been shut down every winter for the past three years to scale back pollution.
• The Centre constituted the Supreme Court-empowered Environment Pollution (Prevention and Control) Authority or the EPCA, which is tasked with taking various measures to tackle air pollution in the National Capital Region.
• Delhi government regularly comes up with emergency measures like Odd-Even formula for vehicles to control rising pollution.

Way forward

• Alternate Solutions to Burning Crop Stubble – Farmers need to be provided alternate options. Government agencies should provide shredder machines free of cost rather than just providing subsidy. Also, farmers should be educated and made aware of the harmful effects of crop burning. happy seeder etc
• Adopting Renewable Solar Power and promoting Solar Rooftops – A lot of government buildings in Delhi have rooftop solar installations which is praiseworthy. This should be further encouraged not just in government buildings but across all kinds of commercial buildings in the city and suburb towns of Delhi NCR. Government can also mandate residential plots measuring above a certain size to install solar rooftops.
• Public Transport – Improve public transport systems. Although metro has been a great success, the network is mostly concentrated in Delhi. Also, last mile connectivity and overcrowding remains an issue which prevents a lot of people from using the network. The various agencies involved in public transport infrastructure should work towards improving the efficiency of public transport networks.
• Promote CNG as fuel – The government should encourage CNG as a fuel for private vehicles. Most of public transport buses in the capital already use CNG as primary fuel. This should be encouraged for private vehicles as well by providing subsidies and increasing the number of CNG pumps
• Electric Vehicles and related infrastructure – There have been a thrust on electric vehicles in the past few years. The government should develop the necessary infrastructure – the most important of them being charging stations to help wide adoption of these vehicles. Subsidies should also be provided to people who want to buy electric vehicles.
• Sprinkling of Waste Water in Construction Sites – Waste water can be used to sprinkle construction sites so that pollutants emanating from these sites can be controlled
• Large Scale Afforestation Drives – The government should identify large tracks that can be planted with trees for green cover across the city. Also, hill ranges like the Aravallis should be preserved and they should be planted with trees.
• General awareness in public should be increased.