Why does Smoking Cause Lung Cancer?

Tobacco smoke contains more than 71 carcinogenic substances that will eventually be deposited in the respiratory tract and in the lungs, making this organ highly susceptible to the development of cancer. Currently, there are mountains of evidence that confirm tobacco consumption gives rise to the appearance of various cancers, particularly, lung cancer. It is estimated that almost 90% of lung cancer is due to smoking. This alarming number was determined around the 50’s.

One of the main substances present in tobacco is nicotine. Nicotine is an alkaloid, responsible for the highly addictive nature of cigarettes. The effects of nicotine in the body occur at the central nervous system (CNS) level, interacting with the nicotinic receptors of the brain. When nicotine reaches these receptors, they release a chemical called neurotransmitters, some of which are acetylcholine, dopamine or noradrenaline.

The physiological effect that causes the release of these substances in the brain generates a sensation of calm and pleasure. Since nicotine only has an active life of 2 hours in the body, nicotine levels decrease after this time, reducing the neurotransmitters and causing withdrawal symptoms. This is precisely the reason why tobacco causes addiction. Nicotine is one of the main and most abundant carcinogenic chemicals in tobacco. Unfortunately, there are many other substances with harmful effects on the body.

Tobacco smoke contains thousands of toxins that are formed from the combustion of the 71 chemicals present in cigarettes. Some of these chemicals are: carbon monoxide, benzene and nitrosamines. In addition to cancer, these substances can also cause conditions such as heart and/or lung disease.

Lung cancer includes different types of carcinomas such as: squamous cell carcinoma, small cell carcinoma, adenocarcinoma and large cell carcinoma. All these subtypes of lung cancer involve the existence of cancer cells that multiply uncontrollably, generating malignant tumors in the respiratory tract and in the alveoli. When these masses grow, they generate respiratory symptoms by negatively affecting normal lung function.

This type of cancer has one of the lowest survival rates and the leading cause of cancer deaths. Its high mortality is due to the difficulty in diagnosing it early on. For this reason, it is especially important to carry out screening tests, especially in those patients who can be classified as high-risk candidates due to their smoking history. It is logical that the lung is one of the organs most affected by tobacco since it is the main organ in contact with carcinogenic substances. Nowadays, it is known that the substances found in cigarettes (and their filter) can cause cellular alterations with high mutagenic potential. This implies that the cells suffer from mutations in their DNA. These mutations often end up affecting certain genes involved in the development of cancer (proto-oncogenes).

In summary, carcinogenic substances inhaled with tobacco smoke can reach our cells and cause mutations in them. If any of these mutations end up altering the cell cycle and increase the rate of division to a point where growth is uncontrollable, it could lead to cancer.