Lung Cancer: Causes and Risk Factors
Learn about the main causes and risk factors of lung cancer, including smoking, genetics, and environmental triggers, to understand your risk better.
Written by Dr. M L Ezhilarasan
Reviewed by Dr. Rohinipriyanka Pondugula MBBS
Last updated on 14th Sep, 2025
Introduction
Lung cancer remains one of the most common and serious types of cancer worldwide. While a diagnosis can be daunting, understanding what contributes to it is the first powerful step toward prevention and early detection. Risk factors are anything that increases your chance of getting a disease like cancer. However, it's crucial to remember that having one or even several risk factors doesn’t mean you will get lung cancer, and some people who get it may have had few or no known risk factors. This article will demystify the leading causes, from the well-known dangers of smoking to lesser-known environmental threats. We’ll equip you with knowledge about your personal risk and provide actionable advice on how to protect your lung health for the long term.
The Primary Culprit: Smoking and Tobacco Use
It is no exaggeration to say that smoking is the single greatest risk factor for lung cancer. The American Cancer Society states that smoking is responsible for about 80% to 90% of lung cancer deaths. Cigarette smoke is a toxic cocktail of over 7,000 chemicals, hundreds of which are harmful and at least 70 are known to cause cancer (carcinogens). These substances damage the DNA in the lung cells immediately. While the body can repair this damage initially, repeated exposure overwhelms its ability to do so, leading to uncontrolled cell growth and, eventually, cancer.
Cigarette Smoking: The #1 Risk Factor
The risk isn't just binary (smoker vs. non-smoker). It's measured in "pack-years" (number of packs smoked per day multiplied by the number of years smoked). The higher the pack-year history, the greater the risk. This is why long-term smokers face the highest risk, but it's never too late to quit.
Cigars, Pipes, and Other Tobacco Products
While often perceived as safer, cigars and pipes carry a significant lung cancer risk. Their smoke contains similar carcinogens, and users still inhale them, albeit differently. Smokeless tobacco products, while primarily linked to oral cancers, are not a safe alternative and still expose the user to harmful chemicals.
The Power of Quitting: How Your Risk Decreases
The most encouraging fact is that quitting works. The risk of lung cancer drops significantly within the first decade of quitting. After 10-15 years, the risk of dying from lung cancer is about half that of a person who is still smoking. The body's remarkable healing process begins almost immediately, making quitting the most effective prevention strategy by far.
Consult an Oncologist for the best advice
Environmental and Occupational Hazards
You don't have to be a smoker to be at risk. Environmental and workplace exposures are major contributors, especially as causes of lung cancer in non-smokers.
Secondhand Smoke: A Real and Present Danger
Secondhand smoke is a proven cause of lung cancer in non-smoking adults. Inhaling the smoke from someone else's cigarette, cigar, or pipe exposes you to the same carcinogens. Living with a smoker can increase a non-smoker's risk of developing lung cancer by 20-30%. This makes avoiding secondhand smoke a critical public health issue.
Radon Gas: The Invisible Threat in Your Home
Radon is the second leading cause of lung cancer in the United States and the primary cause in non-smokers. This radioactive gas is formed naturally from the decay of uranium in soil and rock. It can seep into homes through cracks in the foundation, becoming trapped and building up to dangerous levels. It is odorless, tasteless, and invisible, making testing the only way to know if your home is safe. The EPA recommends all homes be tested for radon.
Workplace Carcinogens: Asbestos, Arsenic, and More
Certain occupations carry a higher risk due to exposure to carcinogens. Asbestos is a well-known example, famously linked to mesothelioma, a type of cancer that affects the lining of the lungs. Other substances include:
Arsenic (used in pesticides and some manufacturing)
Diesel exhaust
Some forms of silica and chromium
Nickel and beryllium
Key Industries and Associated Risks
Workers in construction, shipbuilding, mining, and manufacturing may be at higher risk. Modern regulations require safety protocols like proper ventilation and personal protective equipment (PPE), but historical exposure still affects many today.
Air Pollution: The Urban Risk Factor
Long-term exposure to highly polluted air, particularly fine particulate matter (PM2.5), is linked to a slightly increased risk of lung cancer. This risk is significantly lower than that from smoking but is a concern for those living in densely populated urban areas with high traffic or industrial activity.
Personal and Genetic Predispositions
Beyond external exposures, individual health history and genetics play a role.
Previous Radiation Therapy to the Chest
Individuals who have undergone radiation therapy to the chest for other cancers (e.g., Hodgkin lymphoma or breast cancer) have a higher-than-average risk of developing lung cancer later in life. The risk is highest for those who also smoke.
Family History and Genetic Mutations
Having a parent, sibling, or child who had lung cancer may slightly increase your risk, even after accounting for shared smoking habits. This suggests a potential inherited genetic susceptibility. Furthermore, certain acquired genetic mutations (like EGFR) are more common in non-smokers who develop lung cancer and are now key targets for treatment.
Pre-existing Lung Diseases: COPD and Fibrosis
Chronic inflammatory lung diseases can scar lung tissue, increasing risk. Chronic Obstructive Pulmonary Disease (COPD) and pulmonary fibrosis are strongly linked to a higher chance of developing lung cancer, independent of smoking history. The constant cycle of damage and repair in these conditions can sometimes lead to cellular errors.
Other Potential Contributing Factors
Aside from smoking, several other factors can also increase the risk of developing lung cancer.
Arsenic in Drinking Water
In some parts of the world, high levels of arsenic in drinking water have been linked to an increased risk of lung cancer. This is a more significant concern in areas with natural geological arsenic or contaminated wells.
The Role of Diet and Beta-Carotene Supplements
The data on diet is less clear. Some studies suggest a diet low in fruits and vegetables may increase risk, but the evidence isn't conclusive. More strikingly, several large studies found that beta-carotene supplements actually increased the risk of lung cancer in heavy smokers. This highlights that supplements are not a substitute for a healthy diet and quitting smoking.
Conclusion
Understanding lung cancer risk factors empowers you to take control of your health. While some factors, like genetics or family history, are beyond our control, the most significant ones are often modifiable. Quitting tobacco, testing your home for radon, avoiding secondhand smoke, and adhering to safety protocols at work are powerful, proactive steps you can take. It's also vital to listen to your body. If you have a persistent cough, chest pain, or shortness of breath, especially if you have known risk factors, it's essential to seek medical advice. Early detection saves lives. If you are a current or former long-term smoker over the age of 50, talk to a doctor on Apollo24|7 about whether low-dose CT screening is right for you. Your lungs are vital; taking steps to protect them is one of the most important investments you can make in your long-term well-being.
Consult an Oncologist for the best advice
Dr. Harsh J Shah
Surgical Oncologist
15 Years • MS, MCh (GI), DrNB (GI)
Ahmedabad
Apollo Hospitals Gandhinagar, Ahmedabad
Dr. Amit Choraria
Surgical Oncologist
18 Years • MBBS, MS (Surgery) Fellow, Surgical Oncology, Tata Medical Center (FSO) Fellow, European Board of Surgery (Surgical Oncology) (FEBS) Fellow, Minimal Access Surgery (FMAS) Fellow, Indian Association of Gastrointestinal Endosurgeons (FIAGES) UICC Fellow, Royal Marsden NHS, London, UK Visiting Scholar, Plastic Reconstructive Surgery, CGMH, Taiwan Fellow, Robotic Surgical Oncology, Vattikuti Foundation, USA
Kolkata
Apollo Multispeciality Hospitals , Kolkata, Kolkata
Dr. Vishal Choksi
Head and Neck Surgical Oncologist
20 Years • American Head & Neck Society (AHNS) certified from Memorial Sloan-Kettering Cancer Centre, American Board of Surgery (ABS) certified general surgeon, MBBS (India)
Ahmedabad
Apollo Hospitals Gandhinagar, Ahmedabad
Dr Sunita Samleti
Oncologist
18 Years • M.D. (Pathology)- TN Medical College, Mumbai University, Mumbai, Mar 2005 M.B.B.S. Grant Medical College, Mumbai University, Mumbai, Oct 1999
Chinagadila
Apollo Hospitals Health City Unit, Chinagadila
Dr. Praveen Kumar Garg
Surgical Oncologist
26 Years • MBBS, M.S.(Gen.Surg.), M.Ch.(OncoSurg.)
Delhi
Apollo Hospitals Indraprastha, Delhi
(50+ Patients)
