How Smoking Increases Risk for Lung Cancer Explained

With about 1.76 million deaths per year worldwide, lung cancer is considered the leading cause of cancer death according to WHO (World Health Organization). In the United States, 80% to 90% of lung cancer deaths are associated with cigarette smoking, making it the number one risk factor for lung cancer.


Compared with nonsmokers, people who smoke have an increased risk of developing lung cancer. They are about 15 to 30 times more likely to get lung cancer. Regardless of the number of cigarettes a person smokes per day or even if a person is an occasional smoker, they might still be at risk. If a person quits smoking, the risk is lower than if they continued to smoke but is higher than for those who have never smoked.

It is also essential to note that smoking does not automatically cause lung cancer. Some nonsmokers also develop the disease due to other risk factors like exposure to radon, asbestos, and air pollution, as well as a family history of lung cancer. About 20,000 to 40,000 or 10% to 20% of lung cancer cases every year occur in people who never smoked or smoked less than 100 cigarettes in their lifetime.


What’s in tobacco smoke?

A cigarette is beyond its chopped-up tobacco leaves ingredient which is wrapped in paper. When these leaves burn, thousands of dangerous chemicals are released. Three of the most common include:

  • Tar

This sticky brown substance accumulates in the lungs and causes the formation of yellow stains on the teeth and fingers.

Aside from increasing smokers’ risk for lung cancer, it also increases their risk for other lung diseases like chronic obstructive pulmonary disease and emphysema.

  • Nicotine

Compared to other chemicals found in tobacco, nicotine is harmless except for its addictive effect. Smokers often associate smoking with stress or anxiety relief so they continue smoking. In reality, it is the continuous smoking that reduces the undesirable symptoms of nicotine withdrawal.

  • Carbon monoxide

This poisonous gas interrupts blood’s ability to carry oxygen throughout the body. As a result, smokers can have an increased risk fofheart disease and stroke.

Other tobacco products like pipe tobacco, cigars, snuff, and chewing tobacco also contain the same—a mix of more than 5,000 toxic chemicals, where 70 are known to be cancer-causing or carcinogens. Many of these carcinogenic chemicals have other surprising applications. Examples of these are:

  • Cadmium – used in batteries
  • Chromium – used in the manufacture of dyes and paints
  • Formaldehyde – used as a preservative of bodies in mortuaries and science laboratories
  • Benzene – refined from crude oil and used as an industrial solvent
  • Polycyclic aromatic hydrocarbons (PAHs) – known to be DNA-damaging chemicals

Some of the strongest carcinogens like N-nitrosamines, aromatic amines, and PAHs are present in minimal amounts. Weaker carcinogens like isoprene and acetaldehyde occur in the highest amounts.


Mechanism of action of tobacco chemicals in the body

Thousands of chemicals get into the lungs as a person breathes in tobacco smoke. They then enter the bloodstream and are carried to all parts of the body. Many of these chemicals can potentially damage the DNA in the lung cells. DNA is the instruction manual of the cell responsible for controlling a cell’s normal growth and function.

While the body has the ability to repair the damages done by these chemicals, the damage may become irreparable over time. Once this happens, the cells mutate and grow abnormally. These are the ones that turn into cancer. However, not all cell mutations are cancerous.

The normal cell repair process involves a series of cell divisions until any damage is repaired. Healthy cells know when to stop dividing, but cells that have mutated into cancerous ones do not have that ability so they keep dividing and growing, producing a cancer tumor. Additionally, poisons in tobacco smoke weaken the body’s immune system which makes it harder for the body to kill cancer cells.


Can secondhand smoke also increase one’s risk for lung cancer?

Non-smokers who are exposed to secondhand smoke are also at a greater risk for lung cancer. As a person breathes in smoke that drifts from a burning cigarette or from what other people blow out after a puff, he or she takes in the same toxic chemicals but just in smaller amounts. However, no certain amount is safe even with secondhand smoke. The amount from just one cigarette is enough to do harm.

The 2021 report by the U.S. Department of Health and Human Services indicates that secondhand smokers are 20-30% likely to develop the said disease, and about 7,300 deaths result from this every year. As a consequence, there have been increased measures to ban indoor smoking in the country over the past 25 years.


Can smoking also increase the risk of other types of cancer?

Although carcinogens from tobacco smoke primarily affect lung cells, they also lead to other types of cancer since they enter the bloodstream and travel to different parts of the body. Studies found that 22% of cancer deaths are related to tobacco use.

Parts of the body that may also develop cancer due to smoking cigarettes include the throat, esophagus, colon, liver, stomach, bladder, cervix, kidney, and blood.


How can quitting smoking improve overall health?

The risk of lung cancer and many other health problems due to smoking can be reduced by quitting smoking at any age. Quitting at a younger age can improve one’s health even more.

People who quit smoking for 10 years may cut their risk of lung cancer by 30 to 50%, compared to those who have kept smoking. Furthermore, the risk of cancer of the esophagus or the mouth may also be cut in half just within 5 years after quitting.

Particularly for people who have had cancer already, quitting smoking is highly encouraged because cancer recurrence, development of new cancer, and experiencing long-term side effects of cancer treatment are likely to occur.

Click here for our blog Disclaimer.