Everything you need to know about air pollution

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Air is the invisible gaseous substance surrounding the Earth. With the passage of time these gases have become impure due to several factors. The impurity is caused by Pollutants which pollute the air and make it hazardous.
Polluted Air causes hazardous effects on the humans and the nature’s ecosystem. Pollutants are generally classified into two categories primary and secondary. Primary air pollutants are produced through a process, for e.g the vehicular emission from motor vehicles, ashes due to fire. Secondary pollutants are indirect and not emitted directly. Ground level ozone is a prominent example of a secondary pollutant.

Some of the primary pollutants produce the following gases :

In the air the particulates are normally referred as particulate matter (PM). Particulate matter includes dust particles, smoke, soot, pollen etc.. These particulate matters affects the air pollution heavily. They can be emitted from the gases by vehicles too. During a windstorm dust particles may blow away into the air from land and as they are too small they do not settle on the ground. Pollen from plants and trees are also included in the list of particulate matter. Basically these particulate matter are divided into 3 categories.

PM10 : Particles are less than 10 micrometers in diameter are known as PM10. It includes ash and soot coming from the campfire. Carpenting also creates a large amount of air pollution by PM10. PM 10 are generally large in size. So our human nose blocks most of the particles from entering our body. But if there is a very large amount of PM 10 it can create breathing problems. Itching in throat can also be caused by Particulate matter which are less than 10 micrometers in size.

PM2.5 :In general,particles which are less than 2.5 micrometers in size are considered as PM2.5 .The gas emitted by the tailpipes of vehicles has the most amount of PM2.5. These are more hazardous to health as compared to PM10. The reason to this is that PM 2.5 are very small in size. So our nose is not able to stop these very small particles from entering our body . They enter our body while breathing and reach to the lungs causing lung cancer and asthma attacks. These particles can also enter our bloodstream and reach to our heart.causing heart problems and even heart attack.

DID YOU KNOW The amount of air pollution caused by PM 2.5 is the highest in cities.

PM1 :These are extremely fine particulate matter (PM) particles of diameter less than 1 micron significantly smaller than PM 2.5 (of diameter 2.5 microns). PM 10, PM 2.5 and PM 1 particles make up the total suspended particulate matter. These particles are byproducts of emissions from factories, vehicular pollution, construction activities and road dust; they are not dispersed, and stay suspended in the air that we breathe. 1 micron is about a thousandth of a millimetre. The finer the particles, the more difficult they are to disperse — and the deeper they can penetrate into the blood stream, causing more harm. They have been associated with risks like bronchitis, asthma, and upper respiratory tract infections. Studies in the west have shown that PM 1 can lead to premature births and affect foetal development.

They are expelled from high temperature combustion, and are also produced during thunderstorms by electric discharge. They can be seen as a brown haze dome above or a plume downwind of cities.

This is a colorless, odorless yet very harmful gas. It is a result of combustion of coal, wood, natural gas etc. Vehicular emission is one of the major sources of Carbon monoxide.

VOC gases are usually in the outdoor air. They are further classified into methane and Non methane. Methane contributes to enhanced global warming. Other hydrocarbon VOCs are also significant greenhouse gases because of their role in creating ozone and prolonging the life of methane in the atmosphere. This effect varies depending on local air quality. The aromatic NMVOCs benzene, toluene and xylene are suspected carcinogens and may lead to leukemia with prolonged exposure.

Normally our planet is covered by the ozone layer. But it is 10 to 15 kms higher as respect to the sea level. In our atmosphere where we live ozone is not directly produced. Ozone is indirectly produced by reactions of oxygen and the oxides of sulfur and nitrogen in presence of sunlight. Ground level ozone is colorless. As it is not produced directly it is called secondary pollutant.
Ozone is very dangerous gas if it comes in direct contact with humans. It affects lungs causing lung cancer or asthma attack. If children gets exposed to ozone for a longer time period it may cause negative effect on the lungs.

Hydrogen sulfide is a very dangerous air pollutant. It is found in petroleum and natural gas. Its quantity is very high near industrial facilities. People living near industrial areas have the most danger of getting exposed to hydrogen sulfide.

Agricultural processes are the major source of ammonia emission. Ammonia reacts with oxides of nitrogen and sulfur to form secondary particles in the atmosphere.

Smog is a mixture of pollutants but contains a high level of ground level ozone. Smog usually is produced through a complex set of photochemical reactions involving volatile organic compounds (VOC's) and nitrogen oxides in the presence of sunlight that result in the production of ozone. Smog-forming pollutants come from many sources, such as automobile exhausts, power plants, factories, and many consumer products, including paints, hair spray, charcoal starter fluid, solvents, and even plastic popcorn packaging. In typical urban areas, at least half of the smog precursors come from cars, buses, trucks, and boats. It has been estimated that about 90 million Americans live in areas with ozone levels above the established standards for health safety. These individuals can be severely influenced by pollutants on a daily basis. Smog causes health problems such as difficulty in breathing, asthma, reduced resistance to lung infections and colds, and eye irritation. Ground-level ozone is responsible for the choking, coughing, and stinging eyes associated with smog.

Toxic metal compounds like lead and mercury compounds can also be counted in the list of primary air pollutants. Chlorofluorocarbons (CFCs) is harmful to the ozone layer in stratosphere.When CFC is released into the air it rises up to 10 to 15 km high in stratosphere and it comes in contact with other gases and damage the ozone layer allowing harmful ultraviolet rays to reach the earth's surface.It causes skin cancer and disease to human eye.

Radioactive pollutants are produced by nuclear explosions, nuclear events, war explosives. These are harmful to human skin and can cause major health problems.

Now as you know about the air pollutants, we are going to talk about different types of air pollution.
Basically there are 2 types of air pollution

Indoor and Outdoor air pollution:

What is indoor air pollution ?

Indoor air is the air inside a building like classroom, office, shopping center, hospital or gym. The word ‘Indoor Air Pollution’ is used when indoor air is contaminated by smoke, chemicals, smells or particles. Indoor air pollution refers to the air pollution inside a particular building or structure.Indoor air pollution is measured in indoor air quality (IAQ). IAQ is a term which refers to the air quality within and around buildings and structures and it relates to the health and comfort of building occupants.

DID YOU KNOW The amount of air pollution caused by PM 2.5 is the highest in cities.

What are the sources of indoor air pollution ?

  • Tobacco smoke
  • Gases created by cooking, heating etc.
  • Synthetic building materials
  • Paints and Strippers
  • Upholstered furniture and pressed-wood products (hardwood plywood, wall paneling, particleboard, fiberboard).
  • Smells from household care and furnishing chemicals

This sources pollute the air, the air is trapped indoors as less free air gets indoors, the concentration of pollutants trapped inside the building increases.

The burning of biomass like wood, charcoal, dung, or crop residue etc. for heating and cooking is a major source of indoor air pollution in developing countries.

DID YOU KNOW : The most hazardous pollutants are released from the air and less from the water and land together.

Now as we have seen the sources of the air pollution we will see what kind of pollutants are created by these sources

Tobacco smoke

It is a smoke created by burning cigarettes or exhaled by people smoking.

Biological Pollutants

Allergens like pollen from plants, hair from pets, fungi and some bacteria are included in the list of biological pollutants.

Pollen and nocturnal plants

pollen from the plants planted indoors can create a major issue. To avoid that try keeping the plants near a balcony or a window to reduce the amount of pollen in your home.


It is a gas which is emitted naturally from the ground.It can be trapped in the basements of building and homes. It is mostly known to cause cancer after exposure over longer period.

Carbon Monoxide

It has no color or smell. it is produced when fuels such as gas, oil, coal or wood do not burn fully it is generally produced when the biogas or LPG gases are not burned properly. It is very harmful if the windows and balconies are not open in the house.


New carpets are the major reason for the creation of volatile organic compounds.To avoid VOC, one should ask for low-VOC, formaldehyde-free adhesives. Before installing the new carpets try keeping it out in the air for first few days. After installing keeping windows open and running a fan for the next two or three days in the room helps reduce the VOC


New well furnished furniture may produce formaldehyde. It can also cause eye, nose, and throat irritation, wheezing and coughing, skin rashes and severe allergic reactions.

Indoor air pollution is a major health issue while the outdoor air pollution is a major Environmental issue which can create many great tragedies like the Great smog of London and also global warming.

What is outdoor air pollution ?

Outdoor air is the air which we breathe when we are out in the atmosphere. The air is polluted by natural or human activities it creates outdoor air pollution.
The main reasons behind the increase in the outdoor air pollution is Rapid industrialization, Fast urbanization, Rapid growth in population, Growth of vehicles on the roads and Activities of human beings. Due to these activities the natural balance is disturbed and outdoor air pollution increases.

What are the different sources of outdoor air pollution ?

Major types of outdoor air pollution sources are:

  1. Mobile sources like cars, buses, planes, trains etc.
  2. Stationary sources like power plants, oil refineries, industrial facilities, and factories etc
  3. Area sources like cities, agricultural areas, and wood burning fireplaces etc
  4. Natural sources like wildfires, and volcanoes etc

Mobile sources are the major reason of increase in air pollution. They account for more than half of all the air pollution in USA. Increase in the number of vehicles is the major reason of increase in the pollution due to mobile sources. In china 70% of the air pollution in cities is caused by tailpipes of the mobile vehicles. In automobiles the combustion of gasoline and other hydrocarbon fuels produces several primary pollutants like nitrogen oxides, gaseous hydrocarbons, and carbon monoxide along with large quantity of particulates mostly lead. In the presence of sunlight, nitrogen oxides produced from the automobile combine with hydrocarbons to form a secondary class of pollutants which includes the photochemical oxidants like ozone and peroxyacetyl nitrate (PAN).PAN is the major reason for the eye-stinging. Nitrogen oxides react with oxygen in the air to form nitrogen dioxide. Nitrogen dioxide is a foul-smelling brown gas.In urban areas where automobiles are the main cause of air pollution, nitrogen dioxide tints the air and blends with other contaminants and the atmospheric water vapor which in the end produces a brown smog. Using catalytic converters the smog-producing compounds can be reduced in motor vehicle exhaust emissions.

So The pollutants that are created by mobile sources are :

  1. Nitrogen oxides
  2. Sulfur oxides
  3. Ozone
  4. Carbon monoxide
  5. PeroxyAcetyl Nitrate (PAN)
  6. Gaseous hydrocarbons
  7. Large quantity of particulates like lead, dust particles etc. ( PM2.5)

Stationary sources are also known as point sources of pollution as they emit large amounts of pollutants from a single location like power plants and oil refineries. The amount of pollutants released from these sources is very high and it mainly contains pollutants which includes sulfur od lead or mercury. So it is very dangerous to human health. Ever industry emits its own pattern of pollutants.For example Petroleum refineries are responsible for extensive hydrocarbon and other kind of particulate pollution. Industries like Iron and steel mills, metal smelters, pulp and paper mills, chemical plants, cement and asphalt plant etc.all discharge vast amounts of various particulates.

To sum up stationary sources include pollutants like :

  1. Hydrogen sulfide
  2. Carbon Monoxide
  3. Large amount of particulate matter
  4. Extensive hydrocarbon compounds
  5. Smog
  6. Nuclear waste

Area sources are made up of lots of smaller pollution sources like wood burning fireplace, agricultural area etc. they do not cause a huge amount of air pollution solely but when they are considered as a group can be regarded as a major source of air pollution. In big cities,the air may be severely polluted not only by automobiles but also by the burning of fossil fuels like oil and coal in generating stations, factories, office buildings, and homes.This type of pollution may not be that harmful as compared to the harmful gases created by automobiles but if we add the pollution coming from the entire city, this type of pollution creates a significant impact. Area sources also includes Air pollution caused by Crop dusting, fumigating homes, household cleaning products and fertilizer dust which emit harmful chemicals into the air.

Area Sources contains pollutants like :

  1. Ashes and soot
  2. Large amount of PM 10

Natural sources includes air pollution caused by natural disasters like wildfire or volcanoes. They can sometimes be significant but they do not cause as much problem as the upper three sources cause. The dust particles which are blown by wind is also a natural source of air pollution. It is also a major source which increases the amount of air pollution.

Natural sources mostly include pollutants like:

  1. Pollen from trees and plants.
  2. Volcano eruption which generate hydrogen sulphide
  3. Large amount of dust and smog

These were the major sources of pollution. More than 90% of total air pollution is caused from these sources.

But how do we know that which source of air pollution is polluting more? We need to assign a unit as a measuring parameter for air pollution.

Air pollution is very hazardous to our human health. Small amount of air pollution can produce itching throat and burning of eyes. If the air pollution is very high it can cause health problems like breathing problems, lung cancer or even heart attack.

DID YOU KNOW : The most hazardous pollutants are released from the air and less from the water and land together.

India’s capital New Delhi has the highest amount of PM 2.5 in the entire world.That much high amount reduces the life expectancy by almost 6.4 years. Which is roughly 2 hours per day. Delhi has almost 153 µg/m3 average PM 2.5 level Which is equivalent to smoking 8 cigarettes per day.

DID YOU KNOW : Outdoor air pollution ranks in the top ten killers on Earth.

High air pollution also increases the number of premature deaths. In India Uttar pradesh has the highest number of premature deaths due to exposure to the air pollution. Number of premature deaths in UP due to the exposure to air pollution is 86,000, followed by Maharashtra which is 56,000. These premature deaths has cost our nation almost $640 billion. This is 10 times more than what we are spending on our health care.

DID YOU KNOW : More people die due to Air pollution than HIV

Particulate matters which are less than 2.5 micrometer in diameter are the worst.

Our nose fails to stop these particles from entering our body. These particles enter our body through our nose and creates breathing problems, asthma and lung cancer.

These particles also enters our heart through bloodstream and cause heart diseases or even heart attack.

DID YOU KNOW : 65% of the deaths in Asia and 25% deaths in India are due to air pollution.

Children have lesser lung capacity and smaller physical size. So children are most affected by air pollution. Air pollution affects them fast causing them breathing problems or even asthma. This causes them to be absent in school because the air pollution can cause asthma attack or because their parents keep the child at home in order to avoid pollution exposure. This is the major reason of school absenteeism.

DID YOU KNOW : According to the Lancet journal, air pollution caused by waiting in traffic increases the chances of death caused due to heart attack.

During heavy traffic jam if the driver shuts all the car windows and turn on the A.C. then the outdoor air pollution comes inside through AC and as there is no way out for this pollution, it stays in the car. Thus the air pollution inside the car becomes almost 10 times more harmful than outdoor. This may cause heart attack to the driver.

DID YOU KNOW : 2 million cars in Manila, Philippines cause 80% of air pollution.

Also the traffic police gets most affected by the air pollution. So traffic police and people living near heavy traffic area have greater risk of getting exposed to the air pollution.

DID YOU KNOW : Air pollution from cars, buses and other vehicles causes almost 80% of lung diseases.

Air pollution has created many tragedies in the past. The great smog of London is one of them. In 1952, the smog covered the entire city of London for a week.That smog caused over 8000 lives. Most of them were children and elderly people.It lasted from Friday 5 December to Tuesday 9 December 1952, and then it dispersed quickly after a change of weather.

DID YOU KNOW : By 2050, 6 million people will die per year due to air pollution.

These were some very harmful effects caused by the air pollution. These effects will increase day by day if we fail to control the air pollution.

Now we know about the hazardous effects caused by air pollution. We also know that there are 2 types of air pollution indoor and outdoor air pollution. Both of these air pollutants are measured in their own different ways.
Let's see how the air pollution is actually measured.

There are many ways to measure outdoor air pollution. Government agencies have built special stations to measure the air pollution very precisely.

To measure any type of air pollution first of all the sample of air is taken in a container. The air is kept in that container for the known period of time with the known period of volume. Then there are many calibrated equipments are used to give precise data.These equipments take samples of the outdoor air and then use methods like spectroscopy to find the exact amount of Carbon dioxide, Carbon monoxide, oxides of sulfur and nitrogen and the exact amount of ozone. The exact amount of PM 2.5 and PM 10 can also be found using these high resolution measurement equipments. The results are generally in µg/m3.

Another way to measure outdoor air pollution is to use mobile vehicles with high tech equipments.Air pollution can be measured continuously or during discrete time period by these mobile vehicles. In continuous monitoring the air is constantly measured by the mobile vehicle and the result is constantly updated.In non continuos monitoring the air quality in a particular area is measured in a week or in 5 to 6 days randomly and then the AQI is measured.

The third and last way to measure air pollution is to use electronic equipments. These equipments are placed on a place like street lamp and then they will give the reading continuously. Polludrone is one of the most compact measuring equipment. It is created by Oizom instruments it can be used to measure air pollution in a city area, industrial area, residential area, public places , wildlife or tourism places. The main advantage of this polludrone is that it is solar powered. It gives the precise value of the pollutants like PM10, PM2.5, oxides of sulfur and nitrogen, carbon monoxide and ozone.It also measures noise and temperature humidity. Now we will see some ways to measure the air pollution indoor.

Source control, filtration and the use of ventilation to dilute contaminants are the primary methods for improving indoor air quality in most buildings. Residential units can further improve indoor air quality by routine cleaning of carpets and area rugs. Air purifiers can also be used to measure the indoor air pollution.

There are many different monitoring equipments to measure the air pollution in a small area like a school classroom. One such device is Airowl. Airowl is an easy and simple Do It Yourself kit which helps in monitoring the air in a particular area. Even a small kid can make Airowl after reading and following the given instructions. The results of this Airowl is updated online so everyone can know about the air quality in that area.

So now we know about the types of air pollution and how they can affect our human health.We also learned about how to measure the air pollution in a particular area. So now we will see some steps to avoid the increase in the air pollution.

First and the most important thing is that the air pollution will always be there and it will always increase. If it is not increased by humans then natural disasters like volcanic eruption will increase the air pollution. Our aim is to try and avoid the rapid increase of air pollution.

Here are some thoughts about how to avoid further increase in the air pollution.

At personal level you can still try and do something to avoid air pollution.

Here are some ways to avoid air pollution on personal level.

The first and the most important step is to know about the air quality around you. If you know about the quality of air you breathe only after than you will be able to try and avoid the increase in air pollution.

DID YOU KNOW : By 2050, 6 million people will die per year due to air pollution.

Now after you know about the air quality first and the important thing is to maximize the use of public transport. As mentioned earlier a single bus will carry the passengers which are most likely to drive 40 cars. And we know that the cars produces the maximum number of air pollutants. So by using public transport the amount of air pollution can be controlled very easily.If you can’t completely give up your car you can try to minimize its use. For example, if you are going in the grocery store every day using your car try going every week or every month etc. You can even share your car with your neighbour if you are going at the same stop.

The best way to reduce air pollution is by walking and riding bicycle.It is even better then using public transport. It can keep you healthy and also helps the environment to be clean.

Looking after the trees in your neighbourhood is also a good way to reduce air pollution. The trees reduces noise and sucks the carbon dioxide from the air. So planting and then maintaining the trees also helps in controlling the air pollution.

Try to switch off the light and fans or any electronic equipment when you are not using it. Because very high amount of air pollution is created while creating electricity.

You can also wear masks to protect yourself from PM 2.5 .Wearing a mask will create a large impact on your health in the longer run.

At public level :

The only thing you can do is to spread more and more awareness about air pollution. Spreading more and more awareness about the air pollution helps and if people know how polluted air they are breathing they may start using public transport.

Cigarette smoking is very dangerous to the person smoking it and it also affects people around it. So Cigarette smoking must be avoided in public places and indoor places. Quitting smoking is the best answer for overall health around you.

Now Government is doing their best they can to control the air pollution in the country. For instances, Delhi government passed the odd even rule to control the heavy air pollution in the national capital. Maharashtra government has also planned to plant over 2 crore trees in mumbai.

If the air pollution in a particular area becomes very high then the government may ask some industries to stop their productions.

Indian government has also passed the AIR Act in 1981 to prevent and control the air pollution in the country.

The centre has been asked by the top court to give traffic police masks so their health is not compromised. Luxury SUV’s and diesel cars above 2000cc has also been banned by supreme court in the national capital. There are many other actions taken by the government to reduce the air pollution in the national capital. But in the end it is upto us whether we want to avoid spreading the air pollution or not.

Air quality Index is used to measure air quality. It helps the government to spread awareness about the quality of air around them. If the AQI is very high that means that the air pollution in that area is very high. Different countries have their own AQI standards.

In India the Minister for Environment, Forests & Climate Change Shri Prakash Javadekar launched The National Air Quality Index (AQI) in New Delhi on 17 September 2014 under the Swachh Bharat Abhiyan. The AQI is divided in 6 categories which are Good, Satisfactory, Moderately polluted, Poor, Very Poor, and Severe. It consists of 8 pollutants as shown in the table

AQI Category (Range) PM10 (24hr) PM2.5 (24hr) NO2 (24hr) O3 (8hr) CO (8hr) SO2 (24hr) NH3 (24hr) Pb (24hr)
Good (0-50) 0-50 0-30 0-40 0-50 0-1.0 0-40 0-200 0-0.5
Satisfactory (51-100) 51-100 31-60 41-80 51-100 1.1-2.0 41-80 201-400 0.5-1.0
Moderately polluted (101-200) 101-250 61-90 81-180 101-168 2.1-10 81-380 401-800 1.1-2.0
Poor (201-300) 251-350 91-120 181-280 169-208 10-17 381-800 801-1200 2.1-3.0
Very poor (301-400) 351-430 121-250 281-400 209-748 17-34 801-1600 1200-1800 3.1-3.5
Severe (401-500) 430+ 250+ 400+ 748+ 34+ 1600+ 1800+ 3.5+

And here is the table showing how the different AQi levels affect human health.

Good (0-50) Minimal impact
Satisfactory (51-100) May cause minor breathing discomfort to sensitive people.
Moderately polluted (101–200) May cause breathing discomfort to people with lung disease such as asthma, and discomfort to people with heart disease, children and older adults.
Poor (201-300) May cause breathing discomfort to people on prolonged exposure, and discomfort to people with heart disease.
Very poor (301-400) May cause respiratory illness to the people on prolonged exposure. Effect may be more pronounced in people with lung and heart diseases.
Severe (401-500) May cause respiratory impact even on healthy people, and serious health impacts on people with lung/heart disease. The health impacts may be experienced even during light physical activity.

When the AQi levels are very high the government agencies may provoke some emergency plans like closing down of some industries.

The AQi can increase rapidly during traffic jams or when there is some fire in the city. At that time the low speed wind will make the air pollution remain in that local area. So by measuring the Air Quality Index the government warns people to wear masks or they can even take strict actions against industries which causes air pollution. But prior to that they have to measure the air quality of that area.



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