Most people know that smoking is a key risk factor for lung cancer. Smoking also has links to a higher risk for numerous other cancers, including cancers of the mouth, esophagus, pancreas, liver, colon, cervix, and rectum.

Smoking causes several changes throughout the body, not just in the lungs. As the body attempts to heal from smoking, it can trigger a chronic state of inflammation that elevates the long-term risk of cancer.

Cigarettes and the smoke they produce contain at least 7,000 chemicals, 70 of which are known carcinogens. A carcinogen is a substance that can cause cancer.

The number of years a person smokes, as well as how heavily they smoke, can influence their risk of cancer. This means that the best strategy is always quitting now.

The longer a person avoids smoking, the lower their cancer risk becomes. Among people who quit before the age of 40, the risk of smoking-related death drops by 90%.

Read on to learn more about how smoking can cause cancer.

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Various cancer types have an association with smoking:

Lung cancer

Smoking damages the lungs. As long as a person continues to smoke, the damage to the lungs will become more extensive. This also increases the risk of many lung diseases, including lung cancer.

Specifically, smoking increases the risk of getting or dying of lung cancer by 15–30 times.

The Centers for Disease Control and Prevention (CDC) also report that in nearly 9 out of 10 lung cancer cases, the cause is smoking.

Heavier smoking and longer-term smoking more significantly increase the risk of lung cancer.

Other types of smoking-linked cancer

Besides the lungs, smoking can be harmful to other parts of the body. Smoking increases the risk of various forms of DNA damage, including genetic mutations that increase cancer risk.

As a result, it can substantially increase the risk of cancers such as:

Researchers do not yet fully understand the precise mechanism linking smoking and cancer, nor why some smokers get cancer and others do not.

However, significant research points to the role of the following:

Carcinogen exposure

Carcinogens are substances that increase the risk of cancer. These chemicals cause various forms of DNA damage, including:

  • breaks in DNA
  • the formation of harmful strands of DNA — known as DNA adducts
  • oxidative stress that damages tissue

These changes can alter the DNA’s structure and function, leading to atypical cell growth.

The harmful effect of carcinogens on a person can be unpredictable, such that some people with exposure to carcinogens have no disease, and others develop cancer or even multiple cancers.

Genetic mutations

Genetic mutations can increase the risk of cancer. When mutations occur, they damage DNA and can have a widespread effect on the body. This can alter the normal functioning of various organs or impair the ability of these organs to repair themselves.

Carcinogens and smoke exposure may lead to substantial DNA changes.

One theory is that carcinogens bind to DNA and form DNA adducts. Covalent bonds — which are a type of chemical bond — are important to the binding of the two compounds.

DNA adducts can cause mutations, which undermine the typical process of cellular growth and death. Over time, this can cause tumors to develop, as well as make it more difficult for the body to detect and fight tumors.

Immune system damage

The toxic chemicals in cigarette smoke weaken the immune system. This may make it harder for the body to detect cancer cells or fight off the cancer.

Quitting smoking after a cancer diagnosis may help reverse some damage and prolong survival. In a 2021 study, researchers found that people who quit smoking after an early stage lung cancer diagnosis lived a median of 22 months longer than those who continued to smoke.

Oxidative stress

Smoking causes oxidative stress. This means that there is an imbalance of free radicals and antioxidants in the body, which can lead to:

  • immune system dysfunction
  • inflammation
  • other risk factors for cancer

This oxidative stress may also help explain why smoking causes other diseases, such as heart failure.

Learn how oxidative stress affects the body.

It is never too late to quit smoking. Quitting smoking is the best strategy for preventing smoking-related cancer.

According to a 2018 study, more than 90% of lung cancer cases occur in heavy smokers, who smoke frequently and for a long time.

Quitting smoking now reduces exposure to carcinogens and allows the body to begin healing. Even among heavy smokers, the risk of developing lung cancer drops significantly 5 years after quitting.

Also, quitting smoking can reduce the risk of at least 12 types of cancer. For example, within 10 years of quitting, a person’s risk of kidney, esophageal, and bladder cancer drops. Specifically, the risk of oral and esophageal cancer reduces by half.

Some other ways a person can prevent cancer include:

  • regular physicals to detect early signs of cancer
  • avoiding secondhand smoke
  • adopting a healthy lifestyle that includes exercise, stress management, and adequate rest to support the body in healing

Learn more about how to quit smoking.

Below are some common questions and answers about smoking and cancer.

What are some types of carcinogens found in tobacco smoke?

Thousands of chemicals are present in tobacco smoke, and researchers do not know the effects of all of these. At least 70 are known carcinogens with clear links to cancer.

Some examples of carcinogens in cigarette smoke include:

  • lead
  • benzene
  • arsenic
  • ammonia
  • carbon monoxide
  • hydrogen cyanide

Can secondhand smoking impact cancer risk?

Secondhand smoke exposes people to many of the same carcinogens as smoking, especially if the exposure is prolonged and long-term.

It can also increase the risk of other diseases, such as asthma and heart disease.

Besides smoking, what else can cause cancer?

Genetic mutations that allow tumors to grow and that prevent the body from fighting those tumors are the primary cause of cancer.

Many different risk factors, besides smoking, can increase the chances of having these genetic mutations. They include:

  • exposure to radiation from tanning beds, the sun, or radiation therapy
  • genetically inherited mutations or cancer-causing syndromes
  • exposure to carcinogens in the environment or in products a person uses, such as some cleaning products or lead in old paint
  • certain infections, especially chronic infections
  • a sedentary lifestyle

Smoking is a significant risk factor for cancer, as well as many other diseases. Quitting smoking at any age offers health benefits, though the earlier a person quits, the greater the health benefits are likely to be.

While a person may quit independently, medical assistance can increase the odds of successful quitting. A person should consider consulting a healthcare professional for assistance in quitting smoking.