AIR POLLUTION

 

Introduction

 

           Air pollution is contamination of the indoor or outdoor environment by any chemical, physical or biological agent that modifies the natural characteristics of the atmosphere. Stratospheric ozone depletion due to air pollution has long been recognized as a threat to human health as well as to the Earth's ecosystems.

 

 

            Air quality is closely linked to the earth’s climate and ecosystems globally. Many of the drivers of air pollution (i.e. combustion of fossil fuels) are also sources of greenhouse gas emissions. Policies to reduce air pollution.

  

            Pollutants can be classified as either primary or secondary. Air pollutants are emitted from anthropogenic and natural sources, both either emitted directly (primary pollutants) or formed in the atmosphere (as secondary pollutants). They are produced on a local scale and it can be transported or formed over long distances and it affects ecosystems, climate and health at small or large areas.

 

1.Primarily Pollutants

 

            Primary pollutants are substances that produce pollution levels in the state in which they have been discharged at the source and are therefore considered to be harmful to human health and the environment. The chemical reactions that occur between certain primary pollutants and some other elements produce new substances, which are referred to as secondary pollutants. Primary pollutants pollute the environment because they are released directly into the ecosystem. It is possible that the substance discharged was previously present in certain amounts, but it is deemed the main pollutant if the extra release increases the overall physical quantity to levels that are considered harmful to human health.

 

 

 

2. Secondary Pollutants:

   

Secondary pollutants are concerning as they can be formed from many different compounds. The phenomena of photochemical smog is a result of the interactions of primary pollutants with other molecules in the air such as molecular oxygen,  water and hydrocarbons. These combine to form yellow clouds that are harmful to humans. Photochemical smog is made up of various secondary pollutants like ozone, peroxyacyl nitrates (PANs), and nitric acid.

 

 

  

 

Causes of pollution:

 

           There are various activities or factors which are responsible for releasing pollutants into the atmosphere.  These sources can be classified into two major categories.

 

i.  Anthropogenic (man-made) sources

ii. Natural sources

  

 

i. Anthropogenic (man-made) sources

 

 

 

These are mostly due to the burning of multiple types of fuel. Anthropogenic sources include the following:

 

• Stationary sources include stacks of power plants, manufacturing Factories, waste incinerators, furnaces and other types of fuel-burning devices.
• In less developed countries traditional biomass burning is the major source of air pollutants; Traditional biomass includes wood, crop waste and Cow-dung.
• Mobile Sources include vehicles, marine vessels, and aircrafts. Fumes from paint, hairspray, varnish, aerosol sprays and other solvents also contribute   towards air pollution.
• Waste deposition in landfills; generate methane during the breakdown of compounds.  Methane being highly flammable and forms explosive mixtures with air.
• Methane is also an asphyxiant and displaces oxygen in an enclosed space.  Military resources, such as nuclear weapons and toxic gases are also key source of air pollution. 

 

 

 

ii. Natural sources

 

• Dust from natural sources, mostly large areas of land with few or no vegetation.  Radon gas from radioactive decay within the Earth's crust. Radon is a naturally occurring, radioactive noble gas that is formed from the decay of radium. It is considered to be a health hazard.  
•  Radon gas from natural sources can accumulate in buildings; especially in confined areas is the one of the most frequent cause of lung cancer. Smoke and carbon monoxide from wildfires volcanic activity, produces sulfur, chlorine, and ash particulates.
• A pollutant can be of natural origin or man-made. Pollutants are classified as primary or secondary Primary pollutants are usually produced from a process, such as ash from a volcanic eruption.
• Other examples include carbon monoxide gas from motor vehicle exhaust, or the sulfur dioxide released from factories secondary pollutants are not emitted directly. 
• Rather, they form in the air when primary pollutants react or interact. Ground level ozone is a prominent example of a secondary pollutant. Some pollutants may be both primary and secondary: they are both emitted directly and formed from other primary pollutants. 
•  In India the Major source of air pollution include Fuel wood and biomass burning in rural and urban India, Most of India uses Fuel wood and biomass cakes for cooking and general heating needs.
• Cook stoves using biomass are present in over 100 million Indian households and used two to three times a day. Majority of Indians still use traditional fuels such as dried cow dung, agricultural wastes, and firewood as cooking fuel.

 

 a)    Sulphur oxides (SO_x)

        

    Sulphur dioxide is the pollutant gas most commonly found in the atmosphere and is usually present in high concentrations in urban and industrial locations. In combination with other pollutants and moisture (e.g. humidity) sulphur dioxide is responsible for the formation of high resistance, visible corrosion layers on all but the most noble metals (e.g. silver and gold) and alloys. Whilst sulphur dioxide also occurs in volcanic emissions, it originates from both natural and man-made sources.

 

 

 b)    Nitrogen oxides (NO_x)

 

    Nitrogen Oxide describes a mixture of nitric oxide (NO) and nitrogen dioxide (NO₂), which are gases produced from natural sources, motor vehicles and other fuel burning processes. Nitric oxide is colourless and is oxidised in the atmosphere to form nitrogen dioxide. Nitrogen dioxide has an odour, and is an acidic and highly corrosive gas that can affect our health and environment. Nitrogen oxides are critical components of photochemical smog. They produce the yellowish-brown colour of the smog. In poorly ventilated situations, indoor domestic appliances such as gas stoves and gas or wood heaters can be significant sources of nitrogen oxides.

  

c)   Carbon monoxide (CO)

 

            CO is a colorless, odorless gas that can be harmful when inhaled in large amounts. CO is released when something is burned. The greatest sources of CO to outdoor air are cars, trucks and other vehicles or machinery that burn fossil fuels. A variety of items in your home such as unvented kerosene and gas space heaters, leaking chimneys and furnaces, and gas stoves also release CO and can affect air quality indoors.

 

d)    Volatile organic compounds 

 

            Volatile organic compounds, or VOCs, are gases that are emitted into the air from products or processes. Some are harmful by themselves, including some that cause cancer. In addition, some can react with other gases and form other air pollutants after they are in the air. VOCs are a well-known outdoor air pollutant. They are categorized as either methane (CH₄) or non-methane (NMVOCs).

  

e)   Particulate Matter

 

            PM stands for particulate matter (also called particle pollution): the term for a mixture of solid particles and liquid droplets found in the air. Some particles, such as dust, dirt, soot, or smoke, are large or dark enough to be seen with the naked eye. Others are so small they can only be detected using an electron microscope.

 

f)  Chlorofluorocarbons (CFCs)

 

            Chlorofluorocarbons (CFC) are gases used for various purposes including solvents, refrigerants and aerosol sprays. They are organic chemicals and contain carbon, (sometimes hydrogen,) chlorine, and fluorine. They were much used in the middle 20th century, replacing chemicals that were toxic or flammable or had traits that were generally harmful to human health. Chlorofluorocarbons have a direct impact on the environment as a whole.

 

Secondary Pollutants Include:

 

            Particulates created from gaseous primary pollutants are called secondary pollutants. Smog is a kind of secondary air pollution. Smog results from large amounts of coal burning in an area caused by a mixture of smoke and sulfur dioxide. Smog also comes from vehicular and industrial emissions that are acted on in the atmosphere by ultraviolet light from the sun to form secondary pollutants that also combine with the primary emissions to form photochemical smog. 

 

 

  a) Photochemical Smog

 

            When ultraviolet light from the sun reacts with nitrogen oxides in the atmosphere, photochemical smog is produced. Brown haze is commonly seen, and is most prominent during the morning and afternoon, especially in densely populated, warm cities. This fog forms in the morning when a large number of people are driving their vehicles to work. Nitrogen oxides emitting from the car engine come into the atmosphere, which may combine with water to form nitric acid or react with sunlight to produce singular oxygen atoms.

 

These atoms combine with molecular oxygen to produce ozone. As the nitrogen oxide directly comes from the vehicles, the smog forms over cities where many people may encounter adverse health effects.

 

b) Ground level ozone (O₃) 

 

     It is a highly reactive secondary pollutant. This formation occurs when primary pollutants, like hydrocarbons and nitrogen oxides, react with sunlight. Ozone irritates people’s lungs. High temperatures and sun both act as catalysts to this reaction. Ground-level ozone has adverse effects on people.

 

   The effects are breathing problems, coughing, and irritation to the eyes, nose, and throat. Ground-level ozone causes aggravated symptoms to people with asthma, bronchitis, emphysema when they were exposed to that. It also reduces the body’s immune system, increasing the tendency for more colds and flu.

 

Acid Deposition:

 

            It is a type of precipitation – rain, snow, sleet, hail, or fog – that has a lower pH (and is, therefore, more acidic) than normal. This higher acidity causes problems in ecosystems and the environment and remains one of the major environmental concerns.

 

            Acid rain forms when water in the air combines with nitrogen oxides and sulfur dioxide (two types of pollutants) and then falls down the surface of the Earth. It has many damaging effects on vegetation, lakes, fish, buildings and other structures. It also causes respiratory diseases in humans, especially those that have bad health.

 

 

Air Pollution in Tamil Nadu Scenario:

 

 Air quality is being monitored by the Tamil Nadu Pollution Control Board (TNPCB) to assess the concentration of air pollutants arising out of emissions from industries as well as increasing vehicular population. In Chennai alone, ambient air quality is being monitored at three locations under National Air Quality Monitoring Programme (NAMP) and at five locations under Chennai Ambient Air Quality Monitoring Programme (CAAQM). Apart from Chennai, monitoring of ambient air quality is carried out at Thoothukudi, Coimbatore, Madurai, Salem and Tiruchirapalli. Besides, six continuous ambient air quality monitoring stations are established at Cuddalore, Tuticorin, Ranipet, Manali-Chennai, Tamil Nadu Scenario. Royapuram- Chennai, Kottivakkam - Chennai to evaluate the levels of pollution. There has been a rapid increase in the number of vehicles, as a result of urbanization, economic growth and easy availability of finance. Apart from new vehicles, old vehicles also exist often with outdated technology and nonobservance of emission norms. The quality of fuel supplied has also compounded the problem of vehicular pollution. The Board is monitoring vehicular emission since 1992. In Chennai city, three vehicular monitoring stations located at Alandur, Ambattur and Vyasarpadi for monitoring of the vehicular emission from goods and transport vehicles on a continuous basis. In addition to this, vehicular emission is being monitored at Dindigul, Palani, Ooty, Chengalpattu and Katteri.

 

 

 

Strategies and Actions taken for controlling Air Pollution in Tamil Nadu

 

             Government of Tamil Nadu faces to deterioration of air quality in view of it being a rapidly industrialising State which is also the most urbanized State in the country. There are several industrial clusters within the State in which air pollution is emerging as a concern, even as growth in personalized transportation contributes to degradation of air quality in urban areas. Along with these challenges, the expected increase in thermal power generation to meet the growing power demand makes it necessary to accord greater focus and thrust on minimizing risks of air pollution.

  

           Government of Tamil Nadu would undertake the following actions in Air pollution Strengthen systems for monitoring air quality Continuous Emission Monitoring Systems (CEMS) shall be implemented in all industry clusters, thermal power plants and urban areas.

  

 

Urban air quality monitoring

 

            a) The Tamil Nadu Pollution Control Board (TNPCB) monitors ambient air quality at 28 stations in major cities and towns under National Ambient Air Quality Monitoring Programme (NAAQMP) Tamil Nadu. These cities include Chennai (Eight stations), Coimbatore (Three stations), Thoothukudi (Three stations), Madurai (Three stations), Salem (One station), Trichy (Five stations), Cuddalore (Three stations) and Mettur (Two stations). This network shall be expanded to monitor air quality in all large urban agglomerations with population greater than 5,00,000.

 

            b) Continuous air quality monitoring for industry areas and thermal power plants: In order to monitor source emissions and ambient air quality on a real-time basis, TNPCB has established a Centre for Accessing Real Time Air Quality Information Report (CARE AIR) at its Head office. A first-of-its-kind in the country initiative, CARE AIR is a continuous real-time emission monitoring system in which when emission levels exceed norms, an in-built alarm system is activated to inform concerned industry and environment officials.

 

 

Promote use of public transportation in urban areas

 

            Government of would initiate projects and programmes to increase the share of public transport in urban commuting. The Integration of Multi modal transport system including metro, mono-rail, bus rapid transit with cycle tracks and walk ways shall be implemented wherever necessary in the State. Government of Tamil Nadu had made necessary amendments in the Tamil Nadu Motor Vehicle Rules 1989 to get Pollution under Control (PUC) certificate for goods vehicles in Chennai from authorized private testing centres. This initiative will be launched in other large urban centres (with population greater than 500,000).

 

            Enforce legislation, policies, and rules to establish and meet air quality standards with focus on reducing Tamil Nadu industrial air pollution. Government of Tamil Nadu will ensure appropriate siting of industries and will strengthen enforcement mechanisms to control pollution from industries. Thrust shall be given to cleaner technologies, use of cleaner fuels and energy efficient devices.

  

 

Status of Air Pollution Tamil Nadu

 

          Tamil Nadu Pollution Control Board is operating eight ambient air quality monitoring stations in Chennai under two monitoring programmes.

  

              Table 1. Status of Monthly average of Air Quality of Chennai City of Tamil Nadu, Residential Report-April 2022 to March 2023

District	Location	Year	Month	SO2	NO2	SPM/ PM2.5	RSPM/ PM10
Chennai	Anna Nagar	2022	April	12	23	25	25
			May	11	22	24	24
			June	11	22	23	23
			July	10	22	23	23
			August	12	20	23	23
			September	11	20	21	21
			October	12	21	31	31
			November	10	21	23	23
			December	11	21	20	20
		2023	January	11	20	34	34
			February	11	22	20	20
			March	11	20	23	23
	Adyar	2022	April	9	19	19	49
			May	10	20	21	51
			June	10	20	19	49
			July	10	20	22	46
			August	10	20	20	44
			September	10	20	19	46
			October	9	17	24	60
			November	9	20	20	47
			December	10	21	20	46
		2023	January	11	21	27	71
			February	10	20	20	47
			March	10	19	20	49

(Source: ISBEID –TNPCB)

 

 

Action Taken to Prevent Air Pollution in Tamil Nadu

 

    The salient features of actions taken to control industrial pollution are as follows;-

• No new polluting units are permitted within the city.
• No new incinerators are permitted within the city, old incinerators being phased out.
• Common facilities are set up outside the city for incineration of Bio-medical Waste.
• The industries have been directed to develop a green belt of minimum 33% of the project area.
• Green belt is also being developed by industries on road sides as avenue    plantations.
• Renewal of the consent is based on compliance with this condition
• Periodic inspection of industrial units is to be fitted with online stack monitor connected to the pollution control board – CARE Air centre.

    

 

b)  Vehicular Pollution :

 

      The salient features of action taken  to control vehicular pollution are as follows:

• Bharat Stage –II norms have been implemented for the registration of new passenger car from 1-7-2011
• Emission norms for in-use vehicles in consultation with MoRTH & MoEF have been              implemented
• Ctalytic Converter fitted passenger car have been registered.   

 

 

Conclusion

 

          Air pollution can be prevented by avoiding the use of toxic substances from the outset. This would entail reducing all fossil fuel-burning processes, from industrial manufacturing to the home use of air conditioners, and promoting the use of alternative sources. Regulations should be designed to further decrease harmful emissions into the Earth's atmosphere.

 

 

Source:

1.     Tamil Nadu Pollution Control Board

2.     Policy Note 2024-2025