Today, air pollution has emerged as a global public health problem and is identified as a major environmental health hazard by agencies such as the World Health Organization (WHO) and governments around the world.

A study published by the World Bank in 2016 revealed that air pollution cost India approximately 8% of its GDP or $560 billion, as a result of lost productivity due to premature mortality and morbidity.

In recent years, air pollution has acquired critical dimensions and the air quality in most Indian cities that monitor outdoor air pollution fail to meet WHO guidelines for safe levels.

The levels of PM2.5 and PM10 (Air-borne particles smaller than 2.5 micrometres in diameter and 10 micrometres in diameter) as well as concentration of dangerous carcinogenic substances such as Sulphur Dioxide (SO2) and Nitrogen Dioxide (NO2) have reached alarming proportions in most Indian cities, putting people at additional risk of respiratory diseases and other health problems. Furthermore, the issue of indoor air pollution has put women and children at high risk.

There are five key sources of pollution:

a. Vehicles – grossly polluting vehicles like trucks and diesel vehicles as well as growing numbers that negates the impact of cleaner fuel and emission technology;

b. Combustion in power plants and industries using dirty fuels, like pet coke, FO (and its variants), coal and biomass

c. Garbage burning, both in landfills and other places where there is no collection, processing or disposal;

d. Dust management on roads, construction sites etc, which adds to the particulate pollution.

e. Crop residue burning because farmers do not have alternatives for use of straw.

Indoor air pollution: 

Individuals spend close to three-fourths of their day (around 18 hours) in indoor environments, which include residences and workplaces. Indoor activities such as cooking, heating, cleaning, incense burning, tobacco smoking, refrigeration, and air conditioning are significant contributors of air pollutants emissions.

The infiltration of ambient air into indoor environments through ventilation intakes, doors and windows also result in household air pollution (HAP).

Fine and ultrafine particulates, biological aerosols, volatile organic compounds (VOCs), poly aromatic hydrocarbons (PAHs), carbon monoxide (CO), oxides of sulphur and nitrogen (SOx and NOx) are typically found indoors in households where biomass is used for cooking or heating.

 Close to 60% of Indian households use biomass (in the form of firewood, charcoal, manure, and crop residues) as their main energy source for cooking. Biomass combustion, involved in cooking and heating practices, is the principal source of HAP in India.

Over the years, a strong body of evidence has been established linking HAP with three broad categories of health outcomes in India – acute lower respiratory infections in children under five years of age, chronic obstructive pulmonary disease in women, and lung cancer (especially in users of coal).Poverty, inaccessibility to improved cooking fuel, and lack of awareness about harms of biomass emissions are among the major factors that drive their widespread use.

Major Pollutants:

Particulate matter (PM10, PM2.5)

Particulate matter (PM) is made up of small airborne particles like dust, soot and drops of liquids. The majority of PM in urban areas is formed directly from burning of fossil fuels by power plants, automobiles, non-road equipment and industrial facilities.

Other sources are dust, diesel emissions and secondary particle formation from gases and vapours.

Coarse particulate matter (PM10, particles less than 10 microns in diameter) is known to cause nasal and upper respiratory tract health problems.

Fine particles (PM2.5, particles less than 2.5 microns in diameter) penetrate deeper into the lungs and cause heart attacks, strokes, asthma, and bronchitis, as well as premature death from heart ailments, lung disease and cancer. Studies show that higher PM2.5 exposure can impair brain development in children.

Black carbon (BC)

Black carbon is one of the components of particulate matter and comes from burning fuel (especially diesel, wood, and coal). Most air pollution regulations focus on PM2.5, but exposure to black carbon is a serious health threat as well.

Populations with higher exposures to black carbon over a long period are at a higher risk for heart attacks and stroke. In addition, black carbon is associated with hypertension, asthma, chronic obstructive pulmonary disease, bronchitis, and a variety of types of cancer.

Nitrogen oxides (NO and NO2)

Nitrogen oxide (NO) and nitrogen dioxide (NO2) are produced primarily by the transportation sector. NO is rapidly converted to NO2 in sunlight. NOx (a combination of NO and NO2) is formed in high concentrations around roadways and can result in development and exacerbations of asthma and bronchitis, and can lead to a higher risk of heart disease.

Ozone (O3)

Ozone high in the atmosphere can protect us from ultraviolet radiation. But ozone at ground level (where it is part of what is commonly called smog) is a well-established respiratory irritant. Ozone is formed in the atmosphere through reactions of volatile organic compounds and nitrogen oxides, both of which are formed as a result of combustion of fossil fuels.

Short-term exposure to ozone can cause chest pain, coughing and throat irritation, while long term exposure can lead to decreased lung function and cause chronic obstructive pulmonary disease. In addition, ozone exposure can aggravate existing lung diseases.

Sulphur dioxide (SO2)

SO2 is emitted into the air by the burning of fossil fuels that contain sulphur. Coal, metal extraction and smelting, ship engines, and heavy equipment diesel equipment burn fuels that contain sulphur.

Sulphur dioxide causes eye irritation, worsens asthma, increases susceptibility to respiratory infections and impacts the cardiovascular system. When SO2 combines with water, it forms sulfuric acid; this is the main component of acid rain, a known contributor to deforestation.

Government Initiatives:

Amid growing concerns pertaining to rising air pollution, government of India has taken various initiatives as well as introduced policies to address the issue. In order to prevent and control air pollution, the Parliament of India enacted the Air (Prevention and Control of Pollution) Act, 1981. Salient features of the Act are given below:

AQI and health index

CPCB in association with various State Pollution Control Boards (SPCBs) monitors the ambient air quality according to the National Ambient Air Quality Standards (NAAQS).

The National Air Quality Monitoring Programme (NAMP) set up 629 stations in 264 cities and towns, across the country, to regularly monitor PM10, NOx, and SO2.

The data suggests that about 80% of Indian cities do not meet the prescribed national standards of PM10, while NOx is exceeded in only 8% of cities.

National Air Quality Index notified by the government which classifies air quality of a day considering criteria pollutants through colour codes, air quality descriptor along with health advisory which is as follows.

On a positive note, SO2 concentrations have been reduced, and now just 1% of the cities violate the national standards. 

Steps to curb vehicular emission: With the increase in number of vehicles on Indian roads, air pollution resulting from vehicular emissions has become the main source of air pollution in the urban centres of the country. Government has notified early implementation of BS-VI norm from 2020 to reduce emission from vehicles.

National Urban Transport Policy: Most Indian cities are increasingly relying on motorized personal transport. With this in mind, the National Urban Transport Policy launched to prioritize the use of public transport running on cleaner fuel and technology and develop a people-centric sustainable multi-modal urban transport network.

Faster Adoption and Manufacturing of (Hybrid &) Electric Vehicles (FAME-India) Scheme, which was launched in 2015 under the National Electric Mobility Mission Plan (NEMMP) aims to create the infrastructure for and promote e-mobility.

The purpose of Atal Mission for Rejuvenation and Urban Transformation (AMRUT) is to (iii) reduce pollution by switching to public transport or constructing facilities for non-motorized transport. 

National Mission for a Green India is aimed at protecting, restoring and enhancing India’s diminishing forest cover and responding to climate change by a combination of adaptation and mitigation measures.

National Biomass Cookstoves Programme: The National Biomass Cookstoves Programme (NBCP) was launched by the Ministry of New and Renewable Energy to promote the use of improved cookstoves, which would result in reduced emissions and offer cleaner cooking energy solutions.  Initiative to design, develop an efficient and cost-effective device and assess the status of improved chulhas.

Pradhan Mantri Ujjwala Yojana (PMUY) aims to safeguard the health of women & children by providing them with a clean cooking fuel – LPG, so that they don’t have to compromise their health in smoky kitchens or wander in unsafe areas collecting firewood. Renewable Energy: the new area of focus to reduce dependency on coal India is extremely rich in renewable energy (RE) sources, such as wind, solar and small hydro, however, green energy accounts for only 12.14% of India’s total installed power capacity. It is imperative that the country alters its existing energy mix and reduce its reliance on coal and shift to greener modes of energy.

It is in line with this idea that the government has set an ambitious target to achieve 175,000 MW of green energy by 2022.

Solar Power:  Solar power is to become a crucial component of India’s power portfolio The Jawaharlal Nehru National Solar Mission (JNNSM), part of the missions launched as part of the National Action Plan on Climate Change seeks to tap the immense potential of solar power as a future energy source in the country.

As part of the mission, it is envisaged that the installed capacity of solar power – both solar thermal and solar photovoltaic – should be ramped up to 20 GW by 2022 in three phases. This mission has been largely successful and the government has revised the target to 100 GW by 2022.

National ‘Air Quality Index’ to enable common man to understand Air Quality Announced in October 2014 by the Ministry of Environment, Forests and Climate Change, the National Air Quality Index (AQI) is a measurement index consisting of 8 parameters, which would disseminate information in a simple and effective manner to the common man as characterized by its slogan “One Colour, One Number and One Description”. 


  • Several control measures have been introduced from time to time to combat the pollution levels, but the pace at which the emission levels have increased is very high compared to that of control measures.
  • Barriers for this controlled pace of introduction of air pollution control equipment (APCE) are varied ranging from financial constraints to lack of awareness levels.
  • Every investment under the umbrella of environmental protection demands for financial support by the government. While India being a developing country, the main priority is firstly the investment in development sector and provide basic amenities to the burgeoning population. Thus, allocation of funds for this sector comes as a second priority.
  • In few sectors like power lack of capacity of vigilance authorities is a major reason behind control of emissions. APCEs (electrostatic precipitators) have been made compulsory for all the power plants by the government. But proper inspection and maintenance system is missing in terms of regular check on efficiencies of these APCEs.
  • In case of residential sector, traditional chulhas and traditional fuel are the main cause of emissions. Despite of information regarding better available technologies around the world, dissemination of the same across the entire country becomes a big challenge.
  • Rajiv Gandhi Gramin LPG Vitaran Yojana – RGGLVY started by the government is active since 2009. But to reach each remote village is a challenge. Since all the villages are still not electrified, villagers still rely on kerosene for lighting purpose which lead to increased emission of pollutants.
  • Similarly, though improved cookstoves have been introduced by the government through different programs but the scale of these programs is not sufficient to cater the needs of the entire country. Also, complete awareness regarding the importance of protecting environment is still low among rural communities.
  • Shift freight transport from road to lower-emission modes such as rail, inland waterways, and coastal shipping.
  • Provide cleaner fuels (LPG, Electricity) and biomass stoves with an efficiency of 50% or more and with a forced draft fan to those who cannot afford LPG.
  • Develop business models for collection, transport, and storage of agriculture residues and farm manure. Convert agriculture residues and farm manure to electricity for rural power and biomass pellets for women who depend on biomass stoves.
  • Adopt cleaner and efficient production technologies such as supercritical technologies in power sector, vertical shaft kilns, hoffman kilns, and tunnel kilns for brick manufacturing.

Technology specific initiatives for the way forward are given in the table below:

  • Deploy National Emission Trading Schemes (ETS) with cap and trade for power generation and other large polluting industries.
  • Implement stringent emission standards to control gaseous pollutants
  • (NOx, SO2) and fine particulate (black carbon and fly ash) emissions from both power plants and big industries.
  • Implement wall-to-wall paving of streets and vacuum cleaning of roads; enforce ban on open burning of solid waste; manage waste and recovery of methane from landfills.

Effects of air pollution on the stratosphere: The upper stratosphere consists of considerable amounts of ozone, which works as an effective screen for ultraviolet light. This region called the ozone layer extends up to 60 kms above the surface of the earth. Though the ozone is present upto 60 kms its greatest density remains in the region between 20 to 25 kms.

The ozone layer does not consist of solely ozone but a mixture of other common atmospheric gases. In the densest ozone layer, there will be only one ozone molecule in 100,000 gas molecules. Therefore, even small changes in the ozone concentration can produce dramatic effects on life on earth.

Ozone is a form of oxygen with three atoms instead of two. It is produced naturally from the photodissociation of oxygen gas molecules in the atmosphere. The ozone thus formed is constantly broken down by naturally occurring processes that maintain its balance in the ozone layer.

The total amount of ozone in a ‘column’ of air from the earth’s surface up to an altitude of 50 km is the total column ozone. This is recorded in Dobson Units (DU), a measure of the thickness of the ozone layer by an equivalent layer of pure ozone gas at normal temperature and pressure at sea level. This means that 100 DU=1mm of pure ozone gas at normal temperature and pressure at sea level.

In the absence of pollutants, the creation and breakdown of ozone are purely governed by natural forces, but the presence of certain pollutants can accelerate the breakdown of ozone. Though it was known earlier that ozone shows fluctuations in its concentrations which may be accompanied sometimes with a little ozone depletion, it was only in 1985 that the large-scale destruction of the ozone also called the Ozone Hole came into limelight when some British researchers published measurements about the ozone layer.

Soon after these findings a greater impetus was given to research on the ozone layer, which convincingly established that CFC’s were leading to its depletion. These CFCs (chloro-flurocarbons) are extremely stable, non-flammable, non-toxic and harmless to handle. This makes them ideal for many industrial applications like aerosols, air conditioners, refrigerators and fire extinguishers.

Many cans, which give out foams and sprays, use CFCs. (eg: perfumes, room fresheners, etc.) CFCs are also used in making foams for mattresses and cushions, disposable Styrofoam cups, glasses, packaging material for insulation, cold storage etc.

However, their stability also gives them a long-life span in the atmosphere. Halons are similar in structure to the CFCs but contain bromine atoms instead of chlorine. They are more dangerous to the ozone layer than CFCs.

Halons are used as fire extinguishing agents as they do not pose a harm to people and equipment exposed to them during firefighting. The CFCs and the halons migrate into the upper atmosphere after they are released. As they are heavier than air, they have to be carried by air currents up to just above the lower atmosphere and then they slowly diffuse into the upper atmosphere. This is a slow process and can take as long as five to fifteen years.

In the stratosphere unfiltered UV-radiation severs the chemical bonds releasing chlorine from the rest of the CFC. This attacks the ozone molecule resulting in its splitting into an oxygen molecule and an oxygen atom. Despite the fact that CFCs are evenly distribute over the globe, the ozone depletion is especially pronounced over the South Pole due to the extreme weather conditions in the Antarctic atmosphere. The presence of the ice crystals makes the Cl-O bonding easier.India has signed the Montreal Protocol in 1992, which aims to control the production and consumption of Ozone Depleting Substances.

Montreal Protocol:

In 1985 the Vienna Convention established mechanisms for international co-operation in research into the ozone layer and the effects of ozone depleting chemicals (ODCs). The Protocol called for the Parties to phase down the use of CFCs, halons and other man-made ODCs.

The Montreal Protocol represented a landmark in the international environmentalist movement. For the first time whole countries were legally bound to reducing and eventually phasing out altogether the use of CFCs and other ODCs. Failure to comply was accompanied by stiff penalties.

Using CFC compounds in devices would be cheaper than using replacement compounds harmless to ozone. An international fund was therefore established to help developing countries introduce new and more environmentally friendly technologies and chemicals. The depletion of the ozone layer is a worldwide problem which does not respect the frontiers between different countries. It can only be affected through determined international co-operation. 

Ozone depletion-What does it do? Changes in the ozone layer have serious implications for mankind.

1. Effects on human health: Sunburn, cataract, aging of the skin and skin cancer are caused by increased ultra-violet radiation. It weakens the immune system by suppressing the resistance of the whole body to certain infections like measles, chicken pox and other viral diseases that elicit rash and parasitic diseases such as malaria introduced through the skin.

2. Food production: Ultra violet radiation affects the ability of plants to capture light energy during the process of photosynthesis. This reduces the nutrient content and the growth of plants. This is seen especially in legumes and cabbage. Plant and animal planktons are damaged by ultra-violet radiation.

In zooplanktons (microscopic animals) the breeding period is shortened by changes in radiation. As planktons form the basis of the marine food chain a change in their number and species composition influences fish and shell fish production. Effect on materials: Increased UV radiation damages paints and fabrics, causing them to fade faster.

3. Effect on climate: Atmospheric changes induced by pollution contribute to global warming, a phenomenon which is caused due to the increase in concentration of certain gases like carbon dioxide, nitrogen oxides, methane and CFCs.

Observations of the earth have shown beyond doubt that atmospheric constituents such as water vapour, carbon dioxide, methane, nitrogen oxides and Chloro Fluro Carbons trap heat in the form of infra-red radiation near the earth’s surface. This is known as the ‘Greenhouse Effect’.

The phenomenon is similar to what happens in a greenhouse. The glass in a greenhouse allows solar radiation to enter which is absorbed by the objects inside. These objects radiate heat in the form of terrestrial radiation, which does not pass out through the glass. The heat is therefore trapped in the greenhouse increasing the temperature inside and ensuring the luxuriant growth of plants.

  1. Effects on Bio-geo-chemical Cycles: Increased solar UV radiation could affect terrestrial and aquatic bio-geo-chemical cycles thus altering both sources and sinks of greenhouse and important trace gases, e.g. carbon dioxide (CO2), carbon monoxide (CO), carbonyl sulphide (COS), etc. These changes would contribute to biosphere-atmosphere feedbacks responsible for the atmosphere build-up of these gases.
  • Other effects of increased UV-B radiation include: changes in the production and decomposition of plant matter; reduction of primary production changes in the uptake and release of important atmospheric gases; reduction of bacterioplankton growth in the upper ocean; increased degradation of aquatic dissolved organic matter (DOM), etc.
  • Aquatic nitrogen cycling can be affected by enhanced UV-B through inhibition of nitrifying bacteria and photodecomposition of simple inorganic species such as nitrate. The marine sulphur cycle may also be affected resulting in possible changes in the sea-to-air emissions of COS and dimethylsulfied (DMS), two gases that are degraded to sulphate aerosols in the stratosphere and troposphere, respectively.
  • Effects on Air Quality: Reduction of stratospheric ozone and increased penetration of UV-B radiation result in higher photo dissociation rates of key trace gases that control the chemical reactivity of the troposphere. This can increase both production and destruction of ozone and related oxidants such as hydrogen peroxide which are known to have adverse effects on human health, terrestrial plants and outdoor materials.

Changes in the atmospheric concentrations of the hydroxyl radical (OH) may change the atmospheric lifetimes of important gases such as methane and substitutes of chlorofluoro carbons (CFCs). Increased troposphere reactivity could also lead to increased production of particulates such as cloud condensation nuclei from the oxidation and subsequent nucleation of sulphur of both anthropogenic and natural origin (e.g. COS and DMS).

  • Effects on Materials:  An increased level of solar UV radiation is known to have adverse effects on synthetic polymers, naturally occurring biopolymers and some other materials of commercial interest.

UV-B radiation accelerates the photo degradation rates of these materials thus limiting their lifetimes. Typical damages range from discoloration to loss of mechanical integrity. Such a situation would eventually demand substitution of the affected materials by more photo stable plastics and other materials in future.

Clean Air Mission for India – Ten Solutions