Chemicals called carcinogens in cigarettes affect cellular DNA and can lead to the development of cancer. Quitting smoking can lower the risk of lung cancer, even if a person has already smoked for years.
Smoking is one of the leading risk factors for cancer in the United States. As of 2016,
Lung cancer has the strongest association with smoking. Cigarette smoking
Many people know that smoking can lead to lung cancer but may not understand how. In this article, experts explain the science behind how smoking causes lung cancer and other health concerns and how quitting can lower a person’s risk.
“There are a number of chemicals in tobacco cigarette smoke that cause damage to healthy lung tissue,” explained Dr. Susan Scott, a thoracic medical oncologist at Johns Hopkins Medicine. “Exposure to these chemicals, called carcinogens, causes changes to cellular DNA that can lead to the emergence of cancer cells that grow uncontrolled, with the potential to form tumors and spread through the body.”
When carcinogens enter the cells in the lungs, they can alter a person’s DNA. Some of these changes affect the way cells grow. If the cells in the lungs lose control over these processes, it can lead to lung cancer.
“The 2020 Surgeon General’s report identified 70 carcinogens in tobacco smoke,” said Dr. James Davis, director of the smoking cessation program at the Duke Cancer Institute in North Carolina.
He noted that some of the most harmful of these include:
- tobacco-specific nitrosamines
- polycyclic aromatic hydrocarbons
- aromatic amines
- aldehydes, such as formaldehyde
- ethyl oxide
“Some carcinogens, like cadmium and lead, come from the soil where tobacco is grown. Most carcinogens, however, come from burning tobacco,” Dr. Davis explained.
Similar chemicals are also found in other tobacco products, including cigars and smokeless tobacco.
What about e-cigarettes?
“At this early point, the scientific community cannot say with any certainty whether vaping causes lung cancer,” said Dr. Davis. Lung cancer takes a while to develop, and because vaping products are relatively new, it can be hard to assess the level of lung cancer risk they may cause.
“In another 10–20 years, we may start to see people with lung cancer who vaped but never smoked. At that point, we will know if e-cigarettes cause lung cancer,” he said.
However, many carcinogens in cigarette smoke are also in vaping liquid at lower levels. Dr. Davis suggested that people who use vaping products may still be more likely to develop lung cancer than people who do not. However, the risk may not be as high as the risk associated with cigarette smoking.
Dr. Scott noted that while levels of some known carcinogens are lower in vaping products, there are other chemicals in them that researchers have not yet studied well. The potential health effects of these chemicals, including their effects on cancer risk, are still unknown.
“If we smoke, the carcinogens we inhale cause mutations in our DNA. This is fact, and it occurs in everyone who smokes,” emphasized Dr. Davis.
According to a 2016 study, a person who smokes a pack of cigarettes a day on average has approximately
“With each mutation, there is a chance of getting lung cancer,” he explained. “Many mutations don’t lead to any problems at all. If, however, [a person] gets the wrong mutation, they can develop lung cancer.”
“Smoking is like rolling dice over and over and hoping not to get snake eyes,” he said.
“The magnitude of risk increases with the duration and intensity of exposure to smoking, but it’s not a guarantee,” added Dr. Scott. “Sometimes there are additional exposures or risk factors, and some of it is chance.”
- workplace exposure to other carcinogens, such as asbestos, diesel exhaust fumes, or some forms of silica
- a family history of lung cancer
- prior radiation therapy
- radon exposure
- some dietary choices, such as eating a lot of red meat or drinking alcohol
“When a person inhales smoke, carcinogens enter the lungs and then enter the bloodstream, where they reach every organ in the body,” explained Dr. Davis. “The lungs get the highest dose of carcinogens, but every organ in the body is exposed.”
Aside from lung cancer, smoking is linked to an increased risk for up to 14 other types of cancers, including:
- cancers of the mouth, nose, throat, and esophagus
- stomach cancer
- kidney and liver cancers
- pancreatic cancer
- colon cancer
- ovarian cancer
- bladder cancer
- cervical cancer
Damage to the cells in the lungs can also cause other forms of lung disease, including chronic obstructive pulmonary disease (COPD), also known as emphysema, and asthma. Additionally, chemicals in tobacco smoke can damage the blood vessels throughout the body, increasing the likelihood of a heart attack or stroke.
“Something many people do not know is that smoking is a major cause of type 2 diabetes,” added Dr. Davis. “In fact, people are
Many people worry that if they have smoked for many years, there is nothing they can do to prevent lung cancer. However, Dr. Davis explains that stopping can decrease their risk.
“The risk of lung cancer increases with the duration and intensity of exposure to cigarette smoking, so quitting can decrease that exposure for the time that a person is no longer smoking,” said Dr. Scott.
According to the
- larynx, or voice box
However, people with a history of smoking may still develop lung cancer even after quitting, so screening is important.
“The reason lung cancer is so deadly is that at early stages, it causes no symptoms,” explained Dr. Davis. He noted that in many cases, people might not have any symptoms or realize they have cancer until it has already spread beyond the lungs.
This is known as metastatic disease. Doctors diagnose
“Screening enables us to diagnose lung cancer at earlier stages before a patient experiences any symptoms and when the cancer can still be potentially cured,” added Dr. Scott.
Annual lung cancer screening starting at age 50 is recommended for some adults with a history of smoking, even if they have quit within the last 15 years. Although screening cannot prevent lung cancer, it can help detect it earlier when there is an improved likelihood of survival.
“If you have ever smoked, be sure to talk with your primary care doctor about annual lung cancer screening to see if it is appropriate for you,” Dr. Scott recommended.
People interested in quitting smoking can talk with their primary care physician about resources to help, including counseling and medications, or call 1-800-QUIT-NOW (1-800-784-8669) for more support.
Carcinogens in cigarette smoke can change the DNA in the cells of the lungs and other organs, increasing the likelihood of developing cancer. Smoking is the number one risk factor for lung cancer, and quitting can substantially decrease the likelihood of smoking-related health complications.
“Quitting smoking can be very challenging, and many people will need help,” said Dr. Scott. “There are many tools and resources to consider, including education, counseling, nicotine replacement, medications, and more.”