How does cigarette smoke cause cancer?

Cigarette smoke contains over 7,000 chemicals, many of which are known carcinogens. These chemicals damage DNA, leading to mutations that can cause cancer.

Here are some of the key ways that cigarette smoke causes cancer:

* Direct DNA damage: Many of the chemicals in cigarette smoke are DNA damaging agents. This means that they can directly alter the structure of DNA, leading to mutations that can cause cancer.

* Oxidative stress: Cigarette smoke produces free radicals, which are highly reactive molecules that can damage cells and DNA. Oxidative stress has been linked to a number of chronic diseases, including cancer.

* Inflammation: Cigarette smoke triggers inflammation, which is a natural response to injury or infection. However, chronic inflammation can damage cells and DNA, and it is a risk factor for many types of cancer.

* Epigenetic changes: Cigarette smoke can cause epigenetic changes, which are changes in the way that genes are expressed. These changes can alter the function of genes and increase the risk of cancer.

In addition to these mechanisms, cigarette smoke also impairs the body's natural defenses against cancer. For example, smoke can damage the cilia that line the respiratory tract, which help to clear away mucus and bacteria. Smoke can also suppress the immune system, making it less effective at fighting off infections and cancer cells.

The risk of cancer increases with the number of cigarettes smoked per day, the number of years a person has smoked, and the age at which a person starts smoking. Quitting smoking at any age can reduce the risk of cancer and improve overall health.