Why does tobacco cause lung cancer?

Tobacco contains several harmful substances, including tar and nicotine, which are primarily responsible for causing lung cancer. Here are several ways in which tobacco contributes to the development of lung cancer:

1. Tar: Tobacco tar contains a mixture of over 7,000 chemicals, many of which are known carcinogens. These chemicals damage the DNA in lung cells, leading to mutations that can cause cells to become cancerous. Tar is released when tobacco is burned and inhaled into the lungs.

2. Nicotine: While not directly carcinogenic, nicotine plays a significant role in promoting lung cancer development. It is highly addictive and reinforces smoking behavior, making it difficult for individuals to quit. Nicotine also weakens the body's immune response, making it less effective in combating cancer cells.

3. Carbon Monoxide: Tobacco smoke contains carbon monoxide, a poisonous gas that competes with oxygen for binding sites on hemoglobin in red blood cells. This reduces the oxygen supply to the lungs and other organs, leading to tissue damage and impaired lung function.

4. Free Radicals: Tobacco smoke releases free radicals, which are unstable molecules that can damage cells and DNA. These free radicals contribute to the oxidative stress that can initiate and promote the growth of cancer cells.

5. Chronic Inflammation: Smoking tobacco causes chronic inflammation in the airways and lung tissue. This persistent inflammation can damage cells and promote the development of pre-cancerous lesions, which can eventually progress into lung cancer.

6. Weakened Immune System: Smoking tobacco weakens the immune system, impairing its ability to recognize and destroy abnormal or cancerous cells. This makes the body more vulnerable to developing lung cancer.

7. Altered Gene Expression: Tobacco smoke can disrupt the normal regulation of genes, leading to changes in cell behavior and growth patterns. These alterations can contribute to the development of lung cancer.

It's important to note that while smoking tobacco significantly increases the risk of developing lung cancer, it is not the sole cause. Other factors such as exposure to secondhand smoke, radon gas, asbestos, and air pollution can also contribute to lung cancer development.