Causes and risk factors for Lung Cancer

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Smoking is the main cause of lung cancer. Over 4,000 harmful substances have been identified in cigarette smoke, of which 60 are probably carcinogenic. Among the most harmful are tar, benzene and polycyclic aromatic hydrocarbons.

In Spain, 23% of men and 16% of women are regular smokers, with a progressive increase in smoking among women since the 1970s. This has an impact on the incidence and mortality of related tumours.

Risk factors


Smoking. 80–90% of lung cancers occur in people who smoke; the risk of a smoker developing lung cancer is 10 to 20 times greater than a non-smoker.

Second-hand smoker receiving smoke from a smoker

Passive smoking. Passive smoking also has an increased risk of developing lung cancer. Thus, the importance of banning smoking in public places.

Factory with a smoky, polluting chimney

Occupation. Workers in industries such as mining, insulation and textiles; these include exposure to asbestos, nickel and radon. 

Toxics signal

Radon. Radon is an invisible, odourless, tasteless gas that seeps through the ground and diffuses into the air by the normal breakdown of chemical elements in rocks and soil. This source represents a lower risk for lung cancer as most radon-related cases occur in smokers. However, about 10% of radon-related cancers occur in non-smokers.

10% non-smokers

Non-smokers. Lung cancer can also be diagnosed in non-smokers although, at 10% of cases, the incidence is lower.

DNA molecule or helix

Non-hereditary. Lung cancer is not a hereditary disease, although the risk may be higher if a number of family members have had this disease.

Two lungs, one of them affected

Other risk groups. Patients with chronic obstructive pulmonary disease (COPD), immunosuppressive states and pulmonary fibrosis.

What is Cancer?

General information about Cancer

Read more

Substantiated information by:

David Sánchez Lorente
Laureano Molins López-Rodó
Mari Carmen Rodríguez Mues
Noemí Reguart Aransay
Nuria Viñolas Segarra
Ramón Marrades Sicart

Published: 20 February 2018
Updated: 26 September 2023

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