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Smog and Its Harmful Effects on Our Health

Dr. Javed Hayat Khan

5 min read

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Smog refers to community-wide pollution. Coined in the early twentieth century, the word is an amalgamation of “smoke” and “fog”, and is used to describe a thick haze that has soot, smoke, and other pollutants in it. Smog can lead to a number of problems, making the air difficult to breathe.

Some of the world’s most affected cities by smog are London, Los Angeles, Delhi, Lahore, and Beijing. Smog is visibly unpleasant, it makes the sky brown or gray and can also cause difficulties in seeing properly.

Types of Smog

Smog is a vivid projection of air pollution. It is composed of nitrogen oxides, ozone, sulfur oxide, smoke, dust, and other such pollutants. The formation of smog relies on both primary and secondary pollutants, where the former are emitted directly from the source.

The latter are often formed when the primary pollutants undergo chemical changes in the atmosphere. Smog is frequently categorized as being either summer smog or winter smog.

Summer smog is most commonly associated with the photochemical formation of ozone, while on the other hand, winter smog is paired with atmospheric inversions, such as an increase in the use of coal as fuel. There are two types of smog:

1. Sulfurous Smog

Also known as “London smog”, sulfurous smog is a result of a high concentration of sulfur oxides in the air. It is caused by the use of sulfur-bearing fossil fuels such as coal.

Coupled with dampness and a thick suspension of pollutants such as soot, carbon, and nitrogen oxides in the air, sulfurous smog can be quite toxic. Since it forms mainly from November to January, and in some cases, November to March, sulfurous smog is also known as winter smog.

2. Photochemical Smog

Synonymous with summer smog, photochemical smog is a chemical reaction among sunlight, nitrogen oxides, and volatile organic compounds in the atmosphere. This leads to ground-level ozone and airborne particles. It is formed typically in the summer months in subtropical zones.

Photochemical smog is also referred to as “Los Angeles smog” and is usually a problematic phenomenon in urban areas that have a large number of motor vehicles. But since it travels with the wind, it can affect sparsely populated areas as well. Photochemical smog causes a light brownish coloration of the atmosphere and leads to a number of hazards not just to human beings, but to plants as well.


The formation of smog is credited mostly to air pollution that takes place for a number of reasons. Although human beings contribute majorly to it, natural causes of smog are also responsible. One of them is volcanoes. An erupting volcano can emit high levels of sulfur dioxide, which is one of the main components in the creation of smog.

However, researchers usually refer to smog created by volcanoes as “vog”.  The second natural cause of smog is planted. They’re a natural source of hydrocarbons, which means that they undergo reactions in the atmosphere to produce smog.

Moreover, these reactions can also lead to an increase in ozone formation. But the cold, hard fact stands still: most of the air pollution is man-made. Here are some of the common causes of smog:

1. Burning Coal

Coal burning is the leading cause of air pollution, which means that it is also the top contributor to the formation of smog. Research reveals that a single coal power plant produces more than 7,000 tonnes of sulfur dioxide per year, despite modern pollution control strategies.

Coal burning is useful for many things: from powering industries and power plants to heating individual buildings and cooking food. Unfortunately, it generates significant smoke and produces particulate and gas emissions that contain a number of harmful chemicals such as benzene and carbon monoxide.

2. Industries

Urban centers and metropolitans have more smog compared to rural areas. This is because they house factories and booming industries that contribute daily to air pollution. Although with newer research and technology, there have been a number of creative ways to minimize pollution, none of them are still impactful enough for us to get rid of smog and other effects completely.

Each day, industries emit more toxic gases and pollutants more and more, creating what is known as “industrial smog”. The machines are reliant on fuel, which they create by mostly burning fossils like coal. As a result, factories are one of the leading sources of chemicals that cause smog.

3. Heavy Traffic

Another contributor to smog is transportation. Our cars, trucks, and buses are some of the most prominent causes of air pollution. They release pollutants such as nitrogen oxides, volatile organic compounds, and particulate matter that collectively lower the quality of the air we breathe.

In cities where there is little to no public transportation, heavy traffic is a norm, which means that these cities are at a higher risk of smog because of all the accumulating pollution. One way to reduce air pollution can then be governments investing in proper public transport and encouraging people to walk if their destinations are close by.

Harmful Effects of Smog on Health

The reason why smog has become an increasingly pressing issue is because of the effects it has on our health. Each day, air pollution continues to grow, contributing to more and more smog, particularly in urban areas. Not only does smog create a thick haze which can reduce visibility, and cause irritation to our eyes, it can also make breathing difficult.

This alone leads to the development of a number of diseases. Additionally, the ground-level ozone present in the smog also stunts plant growth and causes huge damage to forests. It also inhibits crop production, making them subject to various infections.

Similarly, animals are also adversely affected. When they are unable to adapt to breathing and surviving in the suffocating, toxic environment, they die. Research on smog has uncovered a plethora of detrimental effects it can have on human health. They are listed below:

1. Allergies

Breathing polluted air each day can contribute to the development of a number of allergies and infections. Studies reveal that illnesses such as colds and pneumonia are strongly related to smog. Moreover, research conducted shows a substantial link between early-life pollution exposure and the development of asthma. If not treated with care, it can only continue to grow worse.

As a result, even minor exposure to smog can lead to greater threats of asthma attacks. This is why it is really important for people with asthma to avoid exposure to smog as much as they can.

2. Decreased Immunity

Since smog can result in allergies and breathing problems such as asthma, it can slowly deteriorate your immunity. Constantly being exposed to polluted air can put your health in a precarious state, where your body is always fighting one infection after the other.

Recovering from illnesses takes energy too, and if repeatedly getting sick becomes a norm, there will be a point where your body no longer has the capacity to fight back. It is a slow process, but the result is that your body’s immunity will continue to weaken, making you more susceptible to infections and illnesses.

3. Respiratory Failure

Perpetual exposure to smog means that you are persistently breathing toxins and air that is filled with pollutants. This can result in inflammation in the tissues of the lungs, leading to pain in the chest. Additionally, a number of respiratory problems can arise.

These include bronchial diseases like bronchitis, which is an inflammation of the breathing tubes. Research reveals that deaths because of bronchial diseases have been related to smog. In extreme cases, smog can also lead to lung cancer, which is one of the fastest-growing diseases.

If diagnosed late, it can result in complete respiratory failure, and eventually lead to death. Experts have also stated that there has been a strong correlation between exposure to air pollution and the rate of mortality in China, where most cases were associated with respiratory diseases.

4. Infant Health

Smog is also known to cause adverse effects on pregnant women and their fetuses. Research reveals that smog can be linked to babies born with birth defects. These were particularly neural tube defects, which are commonly associated with the underdevelopment or absence of one part, or all of the brain.

Similarly, pregnant women who are constantly exposed to air pollution and smog also have higher chances of delivering babies with low birth weights, which can put their infants’ health in a challenging state.

5. Increased Risk of Diseases

Smog has also been revealed to put us at risk of developing of diseases such as Alzheimer’s. It has also been known to cause various heart and neoplastic diseases. Heavy smog is known to lead to low production of vitamin D, which means that we’re at a higher risk of diseases like rickets.

Moreover, it isn’t only direct exposure to the smog that we have to worry about. Studies show that consuming animals or plants that live in areas affected by smog can also cause health problems for us!


Smog should not be taken lightly. You are advised to stay indoors and take necessary precautions to stay safe from smog when going out. In case you feel like your health has been compromised, you can book an in-person or online appointment with a pulmonologist near you through oladoc.

Disclaimer: The contents of this article are intended to raise awareness about common health issues and should not be viewed as sound medical advice for your specific condition. You should always consult with a licensed medical practitioner prior to following any suggestions outlined in this article or adopting any treatment protocol based on the contents of this article.

Dr. Javed Hayat Khan
Dr. Javed Hayat Khan - Author Dr. Javed Hayat Khan graduated from King Edward Medical College, Lahore, and trained in Medicine and Pulmonary Diseases at the Stobhill General Hospital, Glasgow, UK, and the world-renowned Royal Brompton Hospital, London, UK. He has worked in major tertiary care hospitals in the UK and Saudi Arabia.

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