Category Archives: Air Pollution

Air Pollution Control measures – Top 9 Air pollution control devices

It’s the need of the hour to take measures for air pollution control and prevention since millions of Indians are constantly exposed to polluted air. For instance, they breathe up to 25 micrograms/cubic metre of the lethal, microscopic pollutant PM 2.5 on a 24-hour average. This is well above the World Health Organization’s (WHO) limit of 10 micrograms/cubic metre.

To begin with, let’s first look at the causes of air pollution.

Air Pollution Causes

Industrialisation and urbanisation have technologically upgraded our lives. But, they had some negative byproducts like degradation of the environment, air pollution etc. The air quality index in most of the metropolitan cities is alarmingly high. Let’s have a quick glimpse at some of the major causes of air pollution:

  • Emissions from Industries and Power Plants
  • Construction and Demolition
  • Mining
  • Vehicular Emissions
  • Burning of waste and stubble

If you wish to dig deeper into the causes of air pollution, please check our blog Air Pollution Causes – A Comprehensive Guide

 If we can prevent the release of toxic gases by removing them from the flue gas stream or converting it into harmless compounds, we can control air pollution to a great extent. Similarly, if we can collect the dust and dispose of it properly, we can avoid particulate pollution. 

Also read: Air Pollution Effects and Causes – A complete overview

Air Pollution Control Measures and Devices

Air pollution control equipment refers to devices and facilities used in industries to control and prevent the emission of particulate matter and toxic gases. Fans or blowers direct industrial emissions and pollutants into air pollution control equipment and systems. Subsequently, they eliminate or reduce air pollutants using one or more of the following procedures:

  • Combustion i.e., destroying the pollutant.
  • Conversion i.e., chemical conversion of the pollutant to a less harmful compound.
  • Collection i.e., removal of the pollutant from stack gas before releasing into the atmosphere.

Having understood the basic mechanism of pollution control devices, let’s have a closer look at each of the devices.


  • Scrubbers are the most widely used air pollution control devices in production and manufacturing facilities.
  • They use a physical process called scrubbing to remove particulates and gases from industrial emissions before releasing them into the atmosphere.
  • Scrubbers are of two types: dry scrubbers and wet scrubbers.
Industrial air scrubber- Air pollution control device
Industrial air scrubber- Air pollution control device

Dry Scrubbers

  • Dry scrubbers inject dry, neutralising chemical agents such as sodium bicarbonate into the exhaust stream.
  • Subsequently, the gaseous pollutants undergo a chemical reaction that either neutralises or transforms the pollutants into harmless compounds.
  • When the chemical reaction is finished, the expended agents are collected and removed from the cleansed emission gas by filters within the scrubber chamber.
  • Dry scrubbers are typically used to neutralise acid gas in oil refineries, wastewater treatment plants and metallurgical plants

Wet Scrubbers

  • Also known as wet adsorption scrubbers or wet collectors.
  • Wet scrubbers capture and remove water-soluble gas and particulate emissions from industrial emissions using liquid solutions—typically water.
  • A gas stream is passed through a liquid solution or a liquid solution is injected into a gas stream in the wet scrubbing process.
  • The solution on coming in contact with the gas stream absorbs the pollutant.
  • This process eliminates the pollutants from the gas and clean gas is released into the atmosphere.
  • The types of wet scrubbers include venturi, packed bed and bubbling scrubbers.
  • Flue gas desulphurisation employs wet scrubbing with a slurry of alkaline sorbent, usually limestone or lime.

Air Filters

  • Air filters are air pollution control systems that use a certain type of filtration media such as fabric, sintered metal, ceramic, etc.
  • They capture and remove dry particles and contaminants from air passing through them, such as dust, pollen, microorganisms, chemicals, and so on.
  • These devices remove pollutants from exhaust air and enhance the air quality in residential, commercial, and industrial buildings.
  • There are various types of air filters available for industrial purposes, including HEPA filters, fabric filters, and cartridge dust collectors.

Bag Filters

  • Also known as baghouses or fabric filters.
  • The bag filter uses cylindrical fabric bags to trap and remove dust and other pollutants in the air.
  • Particulates aggregate on the filter’s surface as the polluted air travels through a baghouse.
  • This particle buildup improves the filter’s efficiency by reducing the surface area of openings.
  • This allows even smaller particles to be collected.
  • Fabric filters usually offer collection efficiencies exceeding 99.9%.
  • These filters find wide applications in industrial processes, such as power plants, metal processing centres, and foundries.

Periodic cleaning is crucial due to continuous dust accumulation and the associated pressure differential. Baghouses use a variety of methods to remove the accumulation from the filter bags, including:

  • Shaking the filter bags.
  • Increasing the air pressure on the bag such that the bag collapses or deforms and dislodges the accumulated dust. 

Particulates fall from the filter cloth to the bottom of the baghouse enclosure into a collection hopper for processing and disposal.

Bag Filter
Bag Filter

HEPA Filters

  • Also known as high-efficiency particulate air filters.
  • These filters use fibreglass filter mats to physically remove airborne particulates like pollen, smoke, dust, and bio-contaminants from the workspace.
  • Fibres in fibreglass filter mats typically range in size from 0.5 to 2 metres.
  • According to the US Department of Energy (DOE), a filtering system maintaining a 99.97% efficiency for collecting particulates more than or equal to 0.3 m in diameter can be designated as a HEPA filter.
  • Widely used in pharmaceuticals, computer and electronics manufacturing, aerospace applications and nuclear power plants.
HEPA Air filters
HEPA Air filters

Cyclones – Air pollution control measures

  • Cyclones, also known as cyclone dust collectors, are air pollution control equipment that collects and remove particulates using centrifugal force.
  • When gas streams enter a cyclone, they spiral around the cylindrical chamber.
  • The centrifugal force experienced by the spinning gas stream is considerably higher than gravity.
  • Hence the centrifugal force throws the larger particles against the chamber wall, slowing their inertia and forcing them to fall into the collection hopper below.
  • The treated gas streams proceed upward and out of the cyclone.

The separation factor of a cyclone is defined as the ratio of centrifugal force to gravitational force. The higher the separation factor, the better is the cyclone performance. 

Electrostatic Precipitators

  • Electrostatic precipitators (ESPs), like air filters and cyclones, collect and remove particulate matter, such as dust, from industrial emissions and exhaust.
  • ESPs establish a large static electrical potential difference between charging electrodes and collecting plates, using transformers.
  • At very high DC voltages of the order of 50 kV a corona discharge adjacent to the negative electrode.
  • This creates an electric field between the positively charged collecting surface and the emitter.
  • Consequently, the electric field ionises the dust particles as the particle-laden gas flows upwards.
  • The electrostatic force directs ionised particles towards the grounded plates.
  • Particulate Matter deposit is periodically removed from the collecting plates and dumped in a collection hopper below.
  • Wet ESPs uses water to rinse off the dust particles.
  • ESPs’ efficiency reaches 99% since they have several collection plates.
  • The Deutsch equation gives the collection efficiency of an ESP.
Electrostatic Precipitator (ESP)
Electrostatic Precipitator (ESP)

Mist Collectors

  • Also known as mist or moisture eliminator filters.
  • These air pollution control devices remove moisture and vapour from gas streams, such as smoke, oil, mist, etc.
  • Fine mesh-like filters separate liquid droplets from gas and collect them in a separate chamber.
  • Finds wide applications in food and chemical processing, desalination plants, paper and pulp mills etc.
  • For submicron liquid particles, mist collectors have exceptional filtering efficiencies, with some collectors offering 99.9% efficiency for particles 0.3 μm in diameter.

Shall we wrap up?

Conclusion – Air pollution control Measures

In this blog, we saw some air pollution control measures and For the effective control of air pollution, the National Green Tribunal and the pollution control boards should strictly monitor and ensure the usage of these devices in the industries. We are still in need of green technologies like solar cells for power generation instead of coal-fired power stations, clean coal technologies, electric vehicles etc. Together, it is possible to reduce and control air pollution for a green future.

What are air pollutants? | Types,sources and effects of air pollution

Most of the times you can’t see it or smell it, but air pollutants kill. As the level of air pollutants in our atmosphere are rising at an alarming rate we must be aware of them. In the previous blogs, we had described the causes and effects of air pollution. Today let’s dive deep into various air pollutants.

Let’s get started.

What are Air Pollutants ?

Air pollutants are substances that can contaminate the air and are hazardous to human and other living species’ health. They can be either primary pollutants like dust, smoke, ammonia etc that are emitted directly from their sources or secondary pollutants.

Secondary Pollutants are formed in the atmosphere by chemical reactions between primary pollutants and the other atmospheric constituents. The common examples include ozone, sulphur trioxide, Peroxy Acetyl Nitrate (PAN), ketones etc.

Air Pollutants Types

The Environmental Protection Agency regulates three types of pollutants:

  • Criteria air pollutants
  • Air Toxics
  • Greenhouse Gases

Criteria air pollutants

Criteria Air pollutants include Particulate matter (PM), photochemical oxidants (e.g., ozone), carbon monoxide, sulphur oxide, nitrogen oxide, and lead. They can have a significant impact on public health and wellbeing, the atmosphere and environment, and neighbouring structures.

Air Toxics

The term “air toxics” consists of a list of over 180 air pollutants such as organic chemicals, volatile organic compounds (VOCs), metals, metal compounds, solvents, mercury, arsenic, asbestos, and benzene etc. Even when existent in trace amounts and emitted by fewer sources than criteria pollutants, they have harmful health and environmental impacts.

Greenhouse Gases

Greenhouse gases (GHGs) are gases such as carbon dioxide, chlorofluorocarbons (CFCs), methane, and ozone. They can harm human health. In addition, they contribute to the acceleration of the greenhouse effect on Earth and the resulting impact on global climate.

Major Air Pollutants – Sources and Effects

The sources of air pollutants can be natural or anthropogenic. Check out our previous blog Air Pollution Causes – A Comprehensive Guide for detailed information on various sources of pollutants. Let me describe each of the air pollutants in detail.

Nitrogen Oxides

  • Nitrogen oxides, notably nitrogen dioxide, are ejected from high-temperature combustion and created by electric discharge during thunderstorms.
  • This reddish-brown poisonous gas has a distinctive sharp, biting stench.
  • They appear as a brown haze above cities or as a plume downwind.
  • High levels of NO2 can irritate and inflame the lining of your airways.
  • This results in asthma or COPD flare-up, as well as symptoms like coughing and difficulty in breathing.

Carbon Monoxide

  • CO is a poisonous gas that is colourless and odourless.
  • It causes a smog-like buildup in the air.
  • CO reacts with haemoglobin in the blood to generate carboxyhaemoglobin when inhaled.
  • CO has a 200-fold higher affinity for haemoglobin than oxygen.
  • The tissues are deprived of oxygen as a result of this situation.
  • When carboxyhaemoglobin saturation levels are about 20%, it affects the heart and destroys tissues by preventing oxygen from reaching them.
  • This has been related to a variety of pulmonary ailments as well as environmental problems.

Sulphur Oxides

  • Sulphur compounds are common in coal and petroleum, and their combustion produces sulphur dioxide.
  • Further oxidation of SO2, usually in the presence of a catalyst like NO2, produces H2SO4, which results in acid rain.
  • It also arises from chemical, paper, and fuel manufacturing plants.
  • People with asthma or emphysema may find it more difficult to breathe after being exposed to sulphur dioxide.
  • It can also irritate the eyes, noses, and throats of people exposed to it.
  • Sulphur dioxide can injure trees and crops, cause structural damage, and impair people’s ability to see over long distances.
sulphur dioxide Pollution- Petroleum refinery
sulphur dioxide Pollution- Petroleum refinery

Volatile Organic Compounds

  • Compounds with high vapour pressure and low water solubility are known as volatile organic compounds.
  • VOCs are man-made substances that are utilised and created in the production of paints, medicines, and refrigerants.
  • Industrial solvents, such as trichloroethylene; fuel oxygenates, such as methyl tert-butyl ether (MTBE); or chlorination by-products, such as chloroform, are examples of VOCs.
  • The aromatic non-methane VOCs such as benzene, toluene, and xylene are suspected carcinogens. They can cause leukaemia in those who are exposed to them for a long time. 

Carbon Dioxide

  • The major greenhouse gas emitted by human activity is carbon dioxide.
  • Fossil fuel combustion, industrial emissions, wildfire etc. are the main sources of CO2 emissions.
  • It traps the solar radiations reflecting from Earth and increases the average temperature of Earth.
  • Due to its contribution to the greenhouse effect and climate change, it is often called the worst climate pollutant
  • It reaches the Earth’s surface as acid rain.

Particulate Matter

Fine particles, also known as atmospheric particulate matter, are microscopic solid or liquid particles suspended in a gas. Volcanoes, dust storms, forest and grassland fires, and sea spray are all sources of particulate matter. Particulate pollution comprises the following:

PM10:  inhalable particles with a diameter of 10 micrometres or less.

Can you imagine how small is 2.5 micrometre? Consider a single hair on your head. The average human hair is 70 micrometres in diameter, which is 30 times the size of the smallest microscopic particle. I hope this makes it clear how they penetrate deep into our lungs.


Aerosols are produced by human activities such as the combustion of fossil fuels in automobiles, power plants, and numerous industrial processes. Anthropogenic aerosols, or those produced by human activity, currently make up around 10% of our atmosphere. Increased fine particle levels in the air have been related to health risks such as heart disease.


  • CFCs are gases emitted by air conditioners, freezers, aerosol sprays, and other similar devices.
  • CFCs reach the stratosphere after being released into the atmosphere.
  • They interact with other gases here, causing harm to the ozone layer.
  • This allows UV radiation to reach the earth’s surface, which are hazardous.
  • This can result in skin cancer, eye problems etc.
  • As a result, they are currently restricted from usage in products.
Air Conditioners - Source of Chlorofluorocarbons
Air Conditioners – Source of Chlorofluorocarbons


Ammonia is a gas that is emitted primarily by agricultural waste. As a precursor to foodstuffs and fertilisers, it contributes considerably to the nutritional demands of terrestrial species. It is both corrosive and toxic, despite its widespread use. Ammonia combines with nitrogen and sulphur oxides in the atmosphere to generate secondary pollutants.


  • Carbon monoxide (CO), methane (CH4), or other volatile organic compounds (VOCs) are oxidised in the presence of nitrogen oxides (NOx) and sunlight to form ozone.
  • As a result, ozone is most abundant in the summer.
  • Ground-level ozone is a primary component of photochemical smog.
  • It is a significant health hazard connected to breathing issues, asthma, deterioration of lung function, and respiratory disorders.
  • People with asthma may experience more frequent asthma attacks as a result of ozone exposure, as well as sore throats, coughing, and breathing difficulties.
  • It could potentially result in premature death. Plants and crops can be harmed by ozone.


Lead is a neurotoxin. It was earlier used in petrol as an antiknocking agent. The fine particles emitted through automobile exhausts reaches the lungs and settles down there. At higher levels in the blood, it interferes with haemoglobin production. This results in oxygen starvation and anaemia. Higher levels lead to behavioural disorders.


Cigarette smoking is the main contributor to cadmium in the atmosphere. It can cause hypertension, cardiovascular diseases, kidney and liver damage.

 Cigarette Smoke - Source of Cadmium
Cigarette Smoke – Source of Cadmium


Finely divided nickel can react with carbon monoxide and forms Nickel Carbonyl. It is also formed in cigarette smoke. When it reaches our lungs it breaks down and deposits finely divided nickel inside our lungs. This is the main cause of lung cancer.


Mercury enters the aquatic systems and soil from the atmosphere through acid rain. The adverse effects of mercury poisoning include chromosomal aberrations, neurological damage and even death. It can damage the cerebellum and cortex of brain by penetrating the membranes separating bloodstream from the brain.

So, we had taken a quick trip understanding all the major air pollutants. In case of any doubts, feel free to ask in the comments.

Happy Learning!

Air Quality Index in Delhi – AQI categories and Causes

The air quality index (AQI) is a daily reporting index for air quality. According to the recently released IQAir AirVisual 2020 World Air Quality Report, India is home to 15 of the world’s 20 most polluted cities. Would you believe it if I say that a public emergency was declared after the air quality index in Delhi plunged to ‘severe plus’ levels of about 530? Read on to find more about the Delhi Air Quality Index and what were the causes of this extreme level of pollution. To understand the severity of air pollution in Delhi, we should first know about Air Quality Index and its categories. So let’s look into the details of AQI and its categories.

Air Quality Index

The air quality index (AQI) is a daily reporting index for air quality. It’s an indicator of how air pollution impacts one’s health over a short period. The AQI’s objective is to inform individuals about how local air quality affects their health. 

AQI disseminates the air quality information in real-time. It is necessary to be aware of daily levels of air pollution, especially for people who suffer from ailments related to exposure to air pollution.

The AQI is calculated by the Environmental Protection Agency (EPA) for five primary air pollutants for which national air quality guidelines have been set to protect public health. They are listed below:

  • Ground-level ozone
  • Particulate matter (PM2.5/PM10)
  • Carbon Monoxide
  • Sulphur dioxide
  • Nitrogen dioxide
Air pollution in delhi
Air pollution in delhi

The higher the Air Quality Index value, the more polluted the air is and the higher the health risks. For the past three decades, many developed countries has widely applied the principle of AQI.

Also Read : Air pollution Effects and Causes – A complete overview

How Air quality index (AQI) is calculated?

To report air quality, different countries use different point scales. For instance, the United States employs a 500-point scale, with a score of 0 to 50 deemed satisfactory. A rating of 301 to 500 is considered dangerous. India, too, uses the 500-point scale. 

Everyday air pollution monitors record the major contaminants’ concentrations. EPA-developed standard equations are used to translate these raw values into a separate AQI value for each pollutant (ground-level ozone, particle pollution, carbon monoxide, and sulphur dioxide and nitrogen dioxide). The highest of these AQI values gives the the AQI value for that day

Air pollution in delhi
Air pollution in delhi

Categories of Air Quality Index

Depending on the level of pollutants in the air and the health effects it can cause, AQI has the following categories.

  • Good (0 to 50) – Minimal Impact
  • Satisfactory (51 to 100) – In sensitive people, this may cause slight breathing difficulties.
  • Moderately Polluted (101 to 200) – May cause breathing difficulties in individuals with lung disorders such as asthma, as well as discomfort in persons with heart disease, children, and the elderly.
  • Poor (201 to 300) – May cause breathing issues in persons exposed for an extended period, as well as discomfort in persons who have heart ailments.
  • Very Poor (301–400) – May cause respiratory sickness in individuals exposed for an extended period. People with lung and heart issues may experience a stronger effect.
  • Severe (401-500) – May cause breathing problems in healthy persons, as well as major health problems in persons who have lung or heart diseases. Difficulties can arise even when engaging in light physical activity.
  • Severe Plus or Emergency ( Above 500 ) – Extremely high levels of air pollutants.

Goals of  Air Quality Index

Let’s have a look at the objectives of calculating the Air Quality Index.

  • Compare air quality conditions in various locations or cities.
  • It also aids in the detection of incorrect standards and insufficient monitoring programmes.
  • The Air Quality Index (AQI) helps to monitor the changes in air quality (improvement or degradation).
  • The Air Quality Index (AQI) provides information to the public regarding environmental conditions. Therefore it’s particularly beneficial for persons who have ailments that are intensified or triggered by air pollution.

Who is most vulnerable to air pollution?

  • People who suffer from lung disorders such as asthma, chronic bronchitis, and emphysema.
  • Teenagers, as well as children
  • People of all ages who exercise or work outdoor often
  • Even individuals who are healthy can be sensitive to certain pollutants like ozone.

Now, we are done with the basic information about AQI. Keeping this in mind, lets analyze the AQI in Delhi.

Air Quality Index in Delhi

According to the AQI report, PM2.5 (particulate matter) is the most prevalent pollutant in Delhi and its outskirts, consistently exceeding the standard. It was the second most polluted city in India, barely behind the number one most polluted city, Ghaziabad, with an exceptionally high value of 110.2 g/m3 for PM2.5. In addition, Delhi came in the fifth rank out of every city in the world.

For the past few years, the concentration of NO2 in the air ranges from high to critical as per the AQI values. Also, the pollution level of particulate matter (PM10) crosses the critical level every year.

Surprised about such drastic levels of pollutants? Well, I have the answer for how this had happened. Read on to find the main causes of air pollution in Delhi.

Air Pollution in Delhi – Causes

Following are the main causes which made Delhi the second most polluted city.

Stubble Burning

To begin with, agricultural stubble burning by farmers produces nearly 15% of Delhi’s air pollution during the winter months. Farmers in the neighbouring regions burn the stubble to clear land after the September harvest, which contributes to the poor air quality. This is accompanied by changes in the weather, such as lower wind speeds and less rain in the winter season. Thus the smog remains in the atmosphere persistently. 

Stubble burn - Reason for air pollution
Stubble burn – Reason for air pollution

Topographical Factors

Due to its location as well as how the wind and its direction deposits pollutants in the air, Delhi is at a significant disadvantage in terms of topography. Winds blowing towards Delhi bring enormous volumes of smoke and particulates from neighbouring states as well.

When winter arrives, these winds typically die down, trapping the accumulated pollutants in Delhi’s atmosphere. This has a bigger impact on pollution levels than one might think. A 2019 estimate claims that dust brought in by the winds amounted to 21.5% of the entire pollution in Delhi.

Also read : Air Pollution Meteorology and Plume Types

Construction Activities and Vehicular Emissions

In addition, construction activities contribute significantly to the city’s pollution burden. According to the Delhi Pollution Control Committee, dust from construction sites is responsible for 30% of air pollution in the city. A large number of cars in the city, many of which have problematic engines, emit massive amounts of smoke and haze. Thus, coating the city in soot and black carbon (BC). It is a form of carbon that is exceptionally hazardous to all living organisms. 

Air pollution due to construction activities
Air pollution due to construction activities

Industrial Emissions

The industrial sector is responsible for an estimated 18.6% of total air pollution in Delhi. The industries alone release hundreds to thousands of tonnes of pollutants into the atmosphere each year. It should come as no surprise that PM2.5 levels have reached 829.2 g/m3. This was more than 80 times the WHO’s (World Health Organization) recommended yearly level.

Now it’s time for some good news.


The National Green Tribunal is entrusted with delivering adequate and sustainable remedies in situations involving the protection of the environment, forest and pollution prevention. The Tribunal has authority over all civil matters involving significant environmental issues, including the implementation of any environmental legal right. It is playing a key role in bringing down pollution levels in Delhi.

The National Green Tribunal (NGT) ruled in 2015 that all diesel vehicles older than ten years will be prohibited from operating in Delhi-NCR. In 2017, the NGT issued an interim ban in Delhi on plastic bags having a thickness lesser than 50 microns. This was because they were causing animal deaths, blocking sewers, and polluting the environment.

Let’s hope that the National Green Tribunal along with the Delhi Pollution Control Board is able to bring positive changes in curbing Delhi’s air pollution. That’s it about Air Quality Index in Delhi. Let us know your opinions in the comments.

Air Pollution Effects and Causes – A complete overview

Air pollution is one of our era’s biggest scourges, not only because of the impact it causes on climate change but also because it influences public and individual health due to chronic illness and death. The effects of air pollution range from environmental effects like global warming to even financial and health effects like coma and death.

Here’s the truth. According to WHO figures, air pollution-related diseases claimed the lives of 6.5 million people globally in 2012. That’s more than HIV/AIDS, TB, and road accidents combined, accounting for 11.6% of all world deaths. Shocking, right?

In this blog, I will show you the different effects of air pollution in detail. Let’s get started with the classification of the effects.

Also readCauses of Air Pollution

Classification of Air Pollution Effects

The adverse effects of air pollution can be divided into two classes.

Acute Effects

Acute effects of air pollution appear immediately upon short term exposure to the pollutants at relatively high concentrations.

Chronic Effects

Chronic effects don’t appear immediately, rather become evident only after long term exposure to low levels of air pollutants.

Air Pollution Effects on Environment

Not only does air pollution impair our health, but it also harms the environment in which we live. The following are the most significant environmental effects.

Air Pollution Effects
Global Warming

Global Warming 

One of the most alarming effects for scientists and environmentalists is likely global warming. The greenhouse effect, which is caused by the excessive emission of CO2 and methane into the atmosphere, causes global warming. 

Climate Change

Another effect of global warming is climate change. When the planet’s temperature rises, the typical climatic cycles are disrupted, accelerating the changes of these cycles noticeably.

Acid Rain

Sulphur dioxide (SO2) and nitrogen oxides (NOx) are two gases released into the atmosphere as a result of fossil fuel combustion. When those compounds build up in the atmosphere and react with water, they produce dilute nitric and sulphuric acid solutions. They mix with the rain and reaches the surface of Earth as acid rain.

Effects of Air Pollution - Smog
Effects of Air Pollution – Smog


  • The smog effect, sometimes known as the beret effect, occurs when a dense dark fog forms over cities and fields. This fog is made up of pollutants.
  • There are two varieties of smog: sulphurous smog and photochemical smog.
  • The smog of both forms is a result of industrial and urban activity.
  • When nitrogen oxides and volatile organic compounds (VOCs) combine with sunlight, photochemical smog is created, resulting in a brown cloud above cities.
  • Sulphurous smog, on the other hand, is mostly caused by the usage of coal in numerous industrial operations.

Deterioration of Crop Fields

  • The Earth’s surface is degraded by acid rain, climate change, and smog.
  • Polluted water and gases infiltrate into the ground, altering the soil’s makeup.
  • This has a direct impact on agriculture, as crop cycles change and the composition of the food we eat changes.
  • In India, it was reported in 2014 that air pollution from black carbon and ground-level ozone had cut crop yields in the most impacted areas by nearly half in 2011 compared to 1980 levels in the most afflicted districts.

Extinction of animals

  • Many animal species that rely on oceans and rivers for existence are threatened as the poles’ ice melts and sea levels rise.
  • Because currents, ocean temperatures, and migratory cycles fluctuate, many creatures are driven to seek food in unfamiliar environments.
  • Ecosystems and habitats are also disappearing as a result of deforestation and low soil quality. And, without a doubt, this leads to the extinction of many wild animals.

Deterioration of construction materials

Because air pollutants degrade and modify the composition of building materials, many structures and infrastructure are weakened, degraded, or destroyed at a faster rate over time. The air pollution has been turning the Taj Mahal yellow-brown.

Destroys Vegetation

The pollutants penetrate the inner leaf tissues through stomata and destroy the chlorophyll. This disrupts photosynthesis. The damages caused ranges from chlorosis, necrosis, epinasty to the death of the plant. Cement dust deposits along with mist or rain cause incrustations in the leaves. 

Air Pollution Effects on Materials

Pollutants in the air have the following effects on materials, resulting in economic losses.

  • Abrasion
  • Materials deposition
  • Chemical attack 
  • Corrosion 

Sulphuric Acid mist in the atmosphere leads to the deterioration of structural materials like marble and limestone. Leather readily absorbs sulphur dioxide and gets disintegrated. Ozone causes the weathering of fabrics like acetate, cotton, nylon and polyester. At atmospheric levels of 0.01 to 0.02 ppm, it can cause the cracking of synthetic rubber. Particulates erode the exposed surface of materials and accelerate their corrosion.

Air Pollution Effects on Human Health

Air pollution has a variety of negative health consequences. Even on days when air pollution is low, vulnerable and sensitive people’s health can be harmed. COPD (Chronic Obstructive Pulmonary Disorders), cough, shortness of breath, wheezing, asthma, and respiratory disease are all linked to short-term exposure to air pollution.

Let me describe the health effects caused by each of the major air pollutants.

Oxides of Sulphur

  • When people are exposed to an atmosphere with sulphur dioxide concentrations above permissible levels, they get respiratory ailments.
  • At higher temperatures, their visibility is also affected.
  • Even at low concentrations of 1.6 ppm, it can cause bronchoconstriction in healthy individuals.
  • At higher concentrations, it leads to throat and eye irritation and immediate coughing. 

Carbon Monoxide

  • Carbon monoxide is released as a result of incomplete combustion of fuels in petrol engines, industrial operations, and other sources.
  • When CO is inhaled it mixes with the haemoglobin in the blood and forms carboxyhaemoglobin.
  • The affinity of CO towards haemoglobin is 200 times that of oxygen.
  • This condition deprives the tissues of oxygen.
  • When carboxyhaemoglobin saturation levels are about 20%, it affects the heart and also damages tissues by restricting oxygen.
  • Since the blood supply to vital organs including the brain is obstructed it can lead to mental impairment, visual acuity and even fatal coma at higher COHb levels in the blood. 

Oxides of Nitrogen

When NO2 is inhaled it reaches the moist alveoli of the lungs. There it is converted to nitrous and nitric acids which are highly irritating. They can damage the lung tissues. Long term exposure leads to symptoms resembling emphysema and biochemical alterations in blood.

Particulate Matter

  • Particulate matter of size less than 0.5 micrometres gets deposited in the alveoli and damage the respiratory tissues.
  • They can also act as carriers of toxic gases such as SO2 and produce synergistic effects.
  • Long-term exposure to PM2.5 raises the risk of non-accidental mortality by 6% for every 10 micrograms/m3 increase in concentration.
  • PM2.5 exposure was also linked to an elevated risk of lung cancer mortality ranging from 15% to 21% per 10 micrograms/m3 increase.

Shall we wrap up?


To sum up, air pollution affects not only humans but also our mother nature and other living beings. The effects of air pollution include environmental, economical and health effects. So it’s our responsibility to keep air pollution in check for a better tomorrow.

Air Pollution Meteorology and Plume Types

Air Pollution meteorology deals with the meteorological processes near to the earth’s surface which consist of the impacts of meteorology on air pollutants and the effects of pollutants on meteorology. In this blog, I will show you some important terms related to air pollution meteorology, environmental stability and types of plumes. 

If the air is still and pollutants are unable to disperse, the local concentration of pollutants will rise. Strong, turbulent winds, on the other hand, remove pollutants fast, resulting in reduced pollutant concentrations.

Thus, the destiny of air pollutants is influenced by air movements. As a result, any study of air pollution should also include a look at the weather patterns in the area that is meteorology.

The following are some of the benefits of analysing meteorological data:

  1. Identify the source of pollution.
  2. Predict the occurrence of inversions and days with high pollutant concentrations.
  3. Simulate and predict air quality with the help of computer models.

Also read Air Pollution Causes – A Comprehensive Guide

Meteorological Factors affecting Air Pollution

The following factors should be measured while examining air quality because they can help us better understand the chemical reactions that take place in the atmosphere.

Air Pollution Meteorology
Air Pollution Meteorology

Wind speed and direction

Wind data records can be used to estimate the general direction and range of emissions when high pollutant concentrations occur at a monitoring station. Identifying the sources allows for the creation of a plan to decrease the negative effects on air quality.


Temperature measurement aids in the assessment, modelling, and forecasting of air quality. The chemical processes that occur in the atmosphere to generate photochemical smog from other pollutants are influenced by temperature and sunlight (solar radiation). 


Water vapour plays a key role in a variety of thermal and photochemical reactions in the atmosphere. They can dramatically raise the amount of light scattered by particles suspended in the air if they are bound to particles . If corrosive gases, such as sulphur dioxide, bond to water molecules, the gas will dissolve in the water and generate an acid solution that can harm people and property.


When the rain washes particulate matter out of the atmosphere and dissolves gaseous contaminants, it has a scavenging effect. Visibility is improved by removing particulates. Also, when there is a lot of rain, the air quality is usually improved. Acid rain can arise when rain dissolves gaseous pollutants like sulphur dioxide, causing possible damage to objects and plant.

Solar Radiation

Solar radiation must be monitored for use in modelling photochemical smog occurrences because the intensity of sunlight has a significant impact on the rate of chemical reactions that form smog. The intensity of sunlight is affected by cloudiness in the sky, time of day, and geographic location.

Lapse Rate in Air Pollution Meteorology

  • The rate of change in the measured temperature as we move up through the Earth’s atmosphere is known as the lapse rate.
  • When the temperature drops with elevation, the lapse rate is positive.
  • It is zero when the temperature remains constant with elevation.
  • When the temperature rises with elevation the adiabatic lapse rate is negative. This is called temperature inversion.

Environmental Lapse Rate

The rate of decrease of temperature with altitude in the stationary atmosphere at a given time and location is known as the environmental lapse rate (ELR). The International Civil Aviation Organization (ICAO) has defined an international standard atmosphere (ISA) with a temperature lapse rate of 6.49 K/km (1.98 °C/1,000 ft) from sea level to 11 km.

                                   (dT/dz)env = -6.5 K / 1000 metres

Adiabatic Lapse Rate

The adiabatic lapse rate (ALR) refers to the rate with which the temperature of an air parcel changes in response to compression or expansion associated with elevation change. This process is assumed to be adiabatic, that is, no heat exchange happens in between given air parcel and its surrounding.

                                       (dT/dz)adia  = -g/Cp = -9.86 0C / 1000 metres


                g = acceleration due to gravity

  Cp = Specific heat at constant pressure

Atmospheric Stability

The degree of atmospheric stability plays a key role in the ability of atmosphere to disperse the pollutants emitted to it. It is determined by comparing ELR and ALR.

When ELR = ALR, the atmosphere is neutrally stable.

If ELR > ALR, the atmosphere is superadiabatic and unstable.

When ELR < ALR, the atmosphere is subadiabatic and stable.

Under an unstable atmospheric condition, the lapse rate is super adiabatic. The actual temperature gradient is more negative than the dry adiabatic temperature gradient. A rising parcel of air gets warmer and tends to travel upwards due to increasing buoyancy. Air from different altitudes mixes thoroughly. There is rapid dispersion of pollutants throughout the entire atmosphere. As a result, this is highly desirable in pollution prevention.

Under a stable atmospheric condition, the lapse rate is subadiabatic. In this condition, a rising parcel of air gets denser, cooler and tends to fall back. The vertical mixing is very less and the dispersion of pollutants is very slow.

Types of Plume

A plume is a column of liquid, gas, or dust that moves through another fluid, gas, or dust. The term plume is commonly used to describe things like smoke rising from a chimney. Depending on the degree of atmospherical instability, exit velocity from a stack and the prevailing wind turbulence, the plume emitted from a stack behave in different ways. Let’s have a look at each one of them.

Plume behaviour in Air Pollution Meteorology
Plume behaviour

1. Coning Plume

  • Formed when horizontal wind velocity exceeds 32 km/h and cloud blocks solar radiation during the day and terrestrial radiation during the night.
  • There is little vertical mixing.
  • The environment is slightly stable under sub-adiabatic conditions (ELR<ALR).
  • The plume shape is vertically symmetrical about the plume line.

2. Fanning Plume

  • Formed at extreme inversion conditions owing to a negative lapse rate.
  • When the environment is under conditions of inversion, a stable environment occurs just above the stack, and the plume moves horizontally rather than upwards. 
  • Occurs more frequently when there is less turbulence.
  • For high stack, fanning is considered a favourable meteorological condition as it doesn’t cause ground pollution.

3. Looping Plume

  • The wavy looping plume arises in a super adiabatic environment (ELR>ALR), resulting in a very unstable atmosphere due to rapid mixing.
  • In an unstable atmosphere, rapid vertical air motions occur both upward and downward, resulting in a looping plume.
  • As a result, large pollution concentrations may arise near the ground.
  • It is preferable to create high stacks where the environment is normally hyper adiabatic to scatter these contaminants.

4. Neutral Plume

  • In neutral atmospheric circumstances (ELR=ALR), a neutral plume forms. 
  • A neutral plume rises vertically in an upward direction.
  • The plume will continue to rise until it reaches a height where the density and temperature of the surrounding air are equal.

5. Lofting Plume

  • Lofting plume is produced by a strong super adiabatic lapse rate immediately above the stack and a negative lapse rate (inversion) immediately below the stack opening.
  • The downward movement is stopped by inversion.
  • This results in a very rapid and turbulent upward mixing of the plume. But the downward mixing is less. 
  • As a result, the dispersion of pollutants becomes quick, and pollutants cannot come down to the ground.
  • Such a plume is good for dispersing air contaminants and providing significant protection to living beings.

6. Fumigating Plume

  • The fumigant plume is the exact opposite of the lofting plume.
  • Formed when there is a negative lapse rate (inversion) just above the stack and a strong super adiabatic lapse rate below the stack.
  • Pollutants cannot escape above the stack under these conditions, thus they settle towards the ground due to turbulence and mixing.
  • As a result, the dispersion of contaminants in a fumigant plume is exceedingly poor.

7. Trapping Plume

  • When an inversion layer exists above and below the stack, the plume does not rise or fall.
  • Rather, it is constrained or trapped between the two inversion levels, resulting in a trapping plume.
  • This plume isn’t optimal for pollution dispersion since it can’t go past a particular height.

That’s it about air pollution meteorology. Hope you found it insightful.

Air Pollution Causes and effects – A Comprehensive Guide

Air pollution killed approximately 1.7 million Indians in 2019, according to a report by the interdisciplinary journal Lancet Planetary Health. The causes of air pollution can be natural or man-made. Breathing fresh and pure air has become nearly impossible due to the increased quantity of contaminants in the air.

All of us are concerned about our health these days due to the rising level of air pollutants. Since the pollutants in the air are invisible to the human eye, we are unaware of the main sources of pollution. To understand the sources of air pollution, we must first identify the fundamental causes of air pollution.

In this blog, l will walk you through some common activities that knowingly or unknowingly are becoming the major causes of air pollution. Now, off we go.

Air pollution causes

Let me list down the 9 major causes of air pollution.

  • The Burning of Fossil Fuels
  • Agricultural Activities
  • Waste in Landfills
  • Industrial Emissions
  • Mining Operations
  • Natural Phenomena
  • Indoor Pollution
  • Construction and Demolition
  • Open Burning of Waste and stubble

Let’s have a look at each of them in detail.

Burning of Fossil Fuels – Chief cause of air pollution

  • Millions of diesel and gasoline-powered vehicles run on our roads daily.
  • Gasoline is composed mainly of hydrocarbons and trace amounts of nitrogen and sulphur bearing compounds.
  • The gasoline doesn’t undergo complete combustion always.
  • As a result, the exhaust gases coming out of gasoline-powered vehicles consists of harmful oxides of sulphur ( SO2, SO3), nitrogen (NOX), Particulate matter, carbon monoxide, etc.
  • PAHs, or polycyclic aromatic hydrocarbons, are also emitted from automobile exhaust.
  • When humans are exposed to large amounts of the same, it can harm their liver and lungs and even permanently destroy them.
  • It is not surprising that vehicular pollution contributes about 80% of nitrogen oxides and carbon monoxide in Delhi’s air.

Also read : Electric Vehicles- 5 Types & Advantages Full Guide

Agricultural Activities

  • Ammonia is the most common source of agricultural air pollution.
  • Heavily fertilised fields and livestock waste emit this gas in large amounts.
  • It combines with pollutants from combustion, primarily nitrogen oxides and sulphates from automobiles, power plants, and industrial operations, to form small solid particles known as aerosols.
  • They are little larger than 2.5 micrometres in diameter, or approximately 1/30 the width of a human hair.
  • These particles can get deep into the lungs and cause heart or lung diseases. 

Waste in Landfills

  • Garbage is buried or dumped into sites called Landfills.
  • Microbes act on these deposited or buried wastes and generate methane.
  • Methane is a significant greenhouse gas that is extremely combustible and dangerous.
  • It can form explosive mixtures along with air.

Industrial Emissions

Industrial activities release a variety of pollutants into the atmosphere, affecting air quality in ways we can’t even imagine. Industries that use coal and wood as their principal energy sources release PM 2.5 and 10, nitrogen dioxide, sulphur dioxide, and carbon monoxide.

Also read : Air Pollution Meteorology and Plume Types


Mining is one of the largest causes of air pollution. Excavations, blasting, and transportation of materials generate particulate matter. Also, Exhaust emissions from mobile sources such as trucks and heavy equipment raise these particulate levels.

Mining - A cause of Air Pollution
Mining – A cause of Air Pollution

Ever thought that there were natural causes of air pollution? Well, let me show you how this happens.

Natural Phenomena

  • Climate change is causing not only an increase in wildfires but also an increase in air pollution.
  • 0 -90% of wildfire smoke, by mass, lies within the particle size range of 2.5 micrometres in diameter or smaller.
  • PM 2.5 in the air combine with other dangerous chemicals, gases and pollen.
  • As a result, it causes smog.
  • Smog makes the air cloudy, making it difficult for people to breathe.
  • On warmer days, trees like Black gum, poplar, oak and willow emit substantial volumes of volatile organic compounds (VOCs) into the environment.
  • In addition, these VOCs combine with pollutants like NOx, SO2, and anthropogenic organic carbon compounds to form a seasonal haze of secondary pollutants.
  • Volcanic activity also produces pollutants like sulfur, chlorine, and ash particulates.

For a detailed insight on the major air pollutants, make sure that you go through our blog, What are air pollutants? | Types, sources and effects of air pollution.

Indoor Pollution – A hidden cause of air pollution

Have you ever observed that when you paint your house’s walls, it emits a noxious odour that makes it nearly impossible to breathe? This is due to the VOCs released by paints, perfumes, home decor, cleaning products etc. VOCs including acetone, formaldehyde, xylene, etc are chief causes of air pollution indoors.

Indoor Burning
Indoor Burning

Around 3 billion people still cook over open flames using solid fuels such as wood, crop wastes, charcoal, coal, and dung. These inefficient methods of cooking can release CO, CO2 and soot particles which can penetrate deep into the lungs. Above all, indoor smoke levels can be 100 times higher than permitted values in poorly ventilated houses. Shocking, right?

Here’s the truth. According to WHO, every year, around seven million people die prematurely as a result of the combined impacts of ambient (outdoor) and residential air pollution.

Also read : Waste water treatment – Stages and process

Construction and Demolition

Several construction sites and raw materials such as bricks and concrete produce haze and filthy air. This is endangering people, particularly children and the elderly. For instance, the Central Pollution Control Board (CPCB) recorded the highest number of air pollution complaints in the Delhi NCR due to building and demolition activity.

Open Burning of Waste and Stubble.

  • Garbage burning in the open is far more hazardous to your health and the environment than you might believe.
  • It is one of the major air pollution causes in Delhi along with the stubble burning by farmers.
  • Delhi produces 9500 tonnes of garbage each day, making it India’s second-largest waste dumping city.
  • Exposure to open rubbish burning poses a major health risk, including cancer, liver problems, immune system impairment, and reproductive dysfunction.

Causes of Air Pollution in Delhi

  • Firstly, the crop stubble burning by farmers of Punjab and Haryana contributes as much as 40% of Delhi’s air pollution in the winter months.
  • Secondly, construction activities add a great deal to the city’s pollution load. Dust from construction sites is responsible for 30% of air pollution in Delhi, according to authorities from the Delhi Pollution Control Committee (DPCC).
  • Automobile emissions and industrial pollution are also major contributors to poor air quality in Delhi.
  • A major source of airborne particulates in Delhi is a fire in the Bhalswa landfill.
  • Some other causes include cow dung cake combustion, fires on agricultural land, diesel generator exhaust, waste burning, and illicit industrial activity.

If you wish to dig deep into the pollution levels in Delhi, check out our blog, Air Quality Index in Delhi – AQI categories and Causes.


To sum up, air pollution has a variety of causes, each with its own set of problems. Residential energy for cooking and heating, vehicle emissions, electricity generation, agriculture/waste incineration, and industry are all major sources of air pollution. Integrated policies supporting sustainable land use, energy-efficient housing, power generation, and better municipal waste management can effectively reduce significant sources of ambient air pollution.

The National Green Tribunal has played a key role in delivering effective and timely resolution in cases involving environmental preservation, forest conservation, and air quality management. Let’s all be a part of reducing air pollution and do our bit to protect the air quality.

To know more about air pollution control measures, have a look at our blog, Air Pollution Control measures – Top 9 Air pollution control devices.