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Air Pollution, Environmental engineering

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

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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

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.

Chlorofluorocarbons

  • 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

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.

Ozone 

  • 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

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.

Cadmium

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

Nickel

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

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 Pollution, Environmental engineering

Air Pollution Causes and effects – A Comprehensive Guide

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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

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.

Conclusion

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.