Lung Cancer: Potential Reasons, signs, and symptoms

Cigarette on aster

Lung cancer is a type of cancer that starts in the lungs. And the most common cancer diagnosed worldwide.

Cancer is a group of cells involving abnormal cell growth with the potential to invade or spread to other parts of the body.

In 2020, it occur in 2.2 million people and resulted in 1.8 million deaths (1).

It is the most common cause of cancer-related death in both men and women (2).

Lung cancer is 2nd most common cancer worldwide and 4th most common in “India“, and it is a major healthcare problem in India.

It originates from the tissue of the lung, usually from cells lining the air passages, which is also known as “lung carcinoma(3).

Most cancers that start in the lung, are known as primary lung cancers. And there are two main types: 

  • Small-cell lung (SCLC) 
  • Non-small cell lung (NSCLC)

As we know that people who smoke are at greater risk of lung cancer, however, it also occurs in people who have never smoked.

Non-smoking cases are often caused by genetic factors and exposure to radon gas, second-hand smoke, or air pollution (4).

The most common age at diagnosis is 70 years, In most countries, the 5-year survival rate is around 10 to 20%.

Whereas Japan has 33%, Israel 27%, Republic of Korea is 25%.

Potential Reasons for lung cancer

Cigarette on aster
Smoking is the leading cause of lung cancer globally

There are potential reasons for lung cancer which include:


It is a major reason for lung cancer estimated at around 90%, whereas cigarettes contain carcinogens, such as asbestos, etc.

Smoking is also associated with poorer quality of life.

It is suggested that repeated exposure to carcinogens, such as cigarette smoke leads to dysplasia of lung epithelium.

A 2021 report showed that patients ages 50 to 80 years are at high risk of lung cancer due to their smoking history.

Smoking does not only cause cancer but smoking-related illness is estimated to cause 5 million deaths per annum around the globe (5).

Vaping may also be a risk factor for LC, but less than that cigarettes.

Research has shown that 15-20% of men and around 50% of women with lung cancer are non-smokers (7).

Studies indicate that second-hand smoking around 85% is more prone or dangerous than direct mainstream smoke.

A 2014 study revealed that cannabis smoking doubles the risk of lung cancer, however, some other studies showed no clear effect (8) (9).

Radioactive gas

It is an invisible, odorless, tasteless gas that seeps up through the ground and diffuses into the air (10).

The main sources of indoor radon are – the soil around the foundation, building materials, fuels, and domestic water.

Radon or radioactive gas can significantly increase the levels of lung illness and is the second-leading cause of lung cancer.

It is estimated that more than 10% of radon-related cancer deaths occur among nonsmokers (11).

5 meta and pooled analyses of case-control studies revealed that residential radon exposure may be allied with an increased risk of lung cancer (12) (13).

Air pollution

Outdoor air pollution especially released from vehicle exhaust and burning fossil fuels increases the risk of LC.

But how air pollution causes lung cancer? overtime breathing small particles can get trapped in the lungs which damages the cells of the lungs.

This leads to inflammation over a period of time and can cause changes in how these cells replicate, which may cause cancer.

Air pollution whether it is indoor or (outdoor causes a 1–2% of LC) risk and affects about 2.4 billion people worldwide (14).

It is believed to result in 1.5% of lung cancer deaths (15).

Here are a few simple steps by which you can protect yourself from pollution (16) include:

  • Wear masks, especially outside to avoid second-hand smoke, Diwali, etc
  • Avoid burning wood and coal to heat
  • check the radioactive level of the home, if it is high, then install a radon-reduction system.


A gene mutation or change can increase the risk of lung cancer.

The study suggests that about 8% of lung cancers are inherited or occur as a result of a genetic predisposition (17).

Studies identified that polymorphisms on chromosomes are associated with an increased risk of lung cancer.

Animal studies have also confirmed that exposure to diesel exhaust promotes lung tumorigenesis (18).

Smoking is the most common reason for genetic changes in lung cells, but it isn’t the only one, contact with radon, and pollution are also the reason.

Other reasons for lung cancer

Apart from these reasons, there are many other reasons for lung cancer which include:

  • The metal compound which goes into your lungs
  • combustion whether it is coal, coal-tar pitch, soot, diesel exhaust, etc
  • x-ray, gamma, ionizing radiation, chemotherapy, etc
  • crystalline silica dust, underground hematite mining

Signs and symptoms

Nearby 40% of those people newly diagnosed with lung cancer already have metastasis to other parts of the body – liver, bone, brain, etc.

There are every sign and symptom that may suggest lung cancer which include:

  • Dropping eye fluid
  • hoarseness
  • chest pain
  • difficulty in swallowing
  • feel weak or weakness
  • clubbing of the fingernails
  • fever
  • blood clots

Early signs that may be an indication of lung cancer include:

  • Yellow skin and eye (which also may be a sign of jaundice)
  • headache
  • swelling in the armpits, neck, and around the collarbone (19)
  • abdominal pain on the right side
  • Cough with blood, that won’t quit and wheezing
  • loss of appetite
  • breathing difficulties, which increase the risk of pneumonia
  • unexplained weight loss
  • body pain whether it is bone, muscle pain

About 10% of people with LC do not have symptoms at diagnosis, these cancers are found on routine chest radiography (20).

However, this reason might be a sign of other illnesses, so don’t take it to sign lightly, consult the doctor.


Most cases of lung cancer are due to long-term tobacco use and 10–15% of cases occur in people who have never smoked.

There are many treatments, but it will be good to know the early signs of lung cancer and consult the doctor.

Cancer treatment may lead to severe side effects anemia, other healthy cell death, risk of other illnesses, constipation, etc.


Hello, I'm Sahil bisht, I am a Mechanical engineer, As well as, aspiring blogger with an obsession for health. This blog delicate to people who want to learn in health.

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