[How Much Do You Know About Cancer] When you smoke, you may not realize that cancer is approaching you quietly.

1. How “close” are you to lung cancer if you smoke?

The lung is the main component of the human respiratory system. It is an important organ for inhaling oxygen, expelling carbon dioxide, and maintaining normal human metabolism. The lung is located on both sides of the heart in the chest cavity and is divided into the left lung and the right lung. The left lung is divided into two lobes, the upper and lower lobes, and the right lung is divided into three lobes, the upper, middle and lower lobes. The lung has a soft, spongy structure, and can contract and relax with breathing. Each lobe is connected to the trachea by a tube called a bronchus. With continuous differentiation, the bronchi gradually become thinner. We call them bronchi, bronchioles, terminal bronchioles, respiratory bronchioles and alveolar ducts, etc. The branches at the end of the bronchi are sac-shaped and called alveoli. There are nearly 300 million alveoli in our lungs. The alveolar ducts and alveoli are surrounded by capillaries. The alveoli are the place where the human body exchanges oxygen and carbon dioxide with the outside world. Oxygen is absorbed by the blood through the alveolar wall and transported to various parts of the body. Carbon dioxide and other waste gases produced by the human body enter the alveoli through the alveolar wall from the blood and eventually are expelled from the body with breathing. The total area of ​​the alveoli of an adult is 80-100 square meters. Normally, some alveoli are closed, but during strenuous activity, all alveoli are involved in gas exchange.

Normal people's lungs are ruddy in color, but smokers have a lot of tar and smoke poison in their bodies, so their lungs appear in different colors, which we call "colorful lungs". As the smoking time increases, the color of the lungs gradually deepens, and even if you stop smoking, the color of the lungs will not return to normal.

Lung cancer refers to cancer that originates from the bronchial epithelium or alveolar epithelium, and is medically known as primary bronchogenic lung cancer. Lung cancer is the most common malignant tumor in the lungs. Under the action of various carcinogenic factors, bronchial epithelial cells or alveolar epithelial cells in the lung tissues become cancer cells. The cancer cells grow and multiply uncontrollably, and their volume gradually increases to form solid tumors. According to the location of occurrence, lung cancer is divided into central lung cancer and peripheral lung cancer. The former mostly occurs in the trachea, left and right common bronchi, lobar bronchi and segmental bronchial cavities, and grows to the surrounding lung tissues; peripheral lung cancer occurs in alveolar tissues and spreads to other parts along the walls of bronchioles and lung tissues. In addition to continuously infiltrating and growing in the lungs, cancer cells can also enter the lymphatic vessels and metastasize to the lymph nodes; enter the capillaries and transfer to various parts of the body with the blood circulation, such as the liver, bones, and brain.

Lung cancer is now the fastest-growing malignant tumor in my country. The mortality rate of lung cancer is also far ahead of other malignant tumors. One in every four male malignant tumor patients is a lung cancer patient, and one in every five female malignant tumor patients is a lung cancer patient. In the past 30 years, the mortality rate of lung cancer in my country has increased nearly fivefold. The increasing number of smokers in my country is considered to be the main reason for the high incidence and mortality of lung cancer. Statistics show that the smoking rate of adult males in Beijing is 58.6%, and that of females is 5.7%. If the current smoking situation in China remains unchanged, then by 2050, nearly 100 million men under the age of 29 will die from smoking in middle age or old age; the number of female deaths will also reach millions. In recent years, there has been an increasing trend of smoking among teenagers. As long as tobacco production and sales are legal, there will be people smoking, and non-toxic cigarettes do not exist.

Smoking has been recognized as the leading cause of lung cancer. And it has been proven that it has an additive relationship with the age at which smoking starts, the number of years of smoking, the number of cigarettes smoked per day, and the type of cigarettes. The probability of long-term heavy smokers suffering from lung cancer is 10-20 times that of non-smokers. The younger the age at which smoking starts, the higher the incidence of lung cancer. A person who smokes 15-20 cigarettes a day is 14 times more likely to suffer from lung cancer than a non-smoker. In my country, smoking is the main risk factor for male lung cancer, and the increase in cigarette consumption is an important factor in the rising trend of male lung cancer. The rapid increase in the incidence of lung cancer now may reflect the rapid increase in cigarette consumption in my country after the 1970s. According to statistics, my country's per capita cigarette consumption ranks first in the world, and it is one of the only six countries in the world where per capita cigarette consumption continues to rise. If this trend continues, the increase in the incidence of lung cancer will continue until after 2030, by which time my country may become the country with the highest incidence of lung cancer in the world.

In my country, the relationship between female lung cancer and smoking is not as close as that between male and female lung cancer, and smoking can only explain 24%-35% of the causes of lung cancer. It has been confirmed that the occurrence of small cell lung cancer in female lung squamous cell carcinoma is very closely related to smoking, but the relationship between female lung adenocarcinoma and smoking is weaker. In recent years, with the increase in the incidence of female lung cancer, especially lung adenocarcinoma, it may indicate that there have been new changes in the characteristics of environmental risk factors, such as outdoor air pollution and environmental pollution factors, or related to indoor air pollution and micro-environmental pollution such as low-tar cigarettes, "second-hand smoke", "third-hand smoke", kitchen fumes, and house decoration materials.

The susceptibility of smokers to lung cancer is related to the following factors:

1. Smoking age of more than 20 years.

2. Start smoking before the age of 20.

3. Smoking more than 20 cigarettes a day.

4. Quit smoking for less than 15 years.

5. A large amount of smoke is inhaled with each puff, and most of it is inhaled into the lungs [lung smokers].

6. Total smoking amount = [number of cigarettes smoked per day × number of years of smoking] \ 20, which takes into account the impact of daily smoking amount and smoking duration on lung cancer. The total smoking amount is more than 20 cigarettes per year.

7. Having chronic bronchitis and smoking for a long time.

8. Long-term exposure to indoor "second-hand smoke" environment.

At present, the harm of smoking to lung cancer among teenagers may only appear after several years. Studies have confirmed that the lung tissue of adolescents in their developmental period is more sensitive to carcinogens, and the harm of lung cancer in the future will be greater.

2. Are you a “passive smoker”?

Inhaling "second-hand smoke" should never be understood as taking over someone else's unfinished cigarette and then smoking it, like buying a used car. What we call "second-hand smoke" refers to non-smokers inhaling environmental cigarette smoke created by smokers when they smoke. Passive smoking is commonly known as "inhaling second-hand smoke." Passive smoking is also one of the risk factors for lung cancer. Foreign studies have shown that severe passive smoking is equivalent to the exposure of smoking a few cigarettes a day. The harm of "second-hand smoke" to passive smokers is no less than that to active smokers, especially to the health of children and adolescents. Surveys show that in China, the main victims of passive smoking are as high as 740 million, most of whom are women and children. Although they do not smoke themselves, they often suffer from "second-hand smoke" at home, in public places, and in the workplace. Although there is no direct smoking, inhaling a large amount of tobacco smoke in the body can still cause harm to the body, and even greater harm to the health of the smoker himself. Non-smokers living or working with smokers and smelling the smell of smoke for 15 minutes a day for more than 10 years are equivalent to smoking. Some middle-aged and elderly women who live with smokers are six times more likely to develop lung cancer than the average person.

While smoking harms the health of smokers themselves, "second-hand smoke" also affects non-smokers. In addition to irritating the eyes, nose and throat, "second-hand smoke" will also significantly increase the probability of non-smokers suffering from lung cancer, heart disease and respiratory diseases, seriously harming people's health.

The harmful substances inhaled by passive smoking are often more severe than those inhaled by active smoking. This is because the smoke emitted by smoking can be divided into mainstream smoke and sidestream smoke. Mainstream smoke is the smoke inhaled by smokers, and sidestream smoke is the smoke emitted after the cigarette is ignited. The mixture composed of the smoke exhaled by smokers and the smoke emitted by the cigarette when it is ignited [sidestream smoke] is called "second-hand smoke", also known as passive smoking. The harmful substances contained in "second-hand smoke" are often more than mainstream smoke. Compared with mainstream smoke, "second-hand smoke" has 2 times nicotine, 3 times tar, 5 times carbon monoxide and about 50 times carcinogens. It is calculated that in a poorly ventilated place, the amount of smoke inhaled by non-smokers in 1 hour is equivalent to the dose inhaled by each person of a cigarette. In addition, smokers have their own fixed time period for smoking, while passive smokers smoke smoke exhaled by multiple smokers repeatedly, continuously and repeatedly. In a poorly ventilated room where someone smokes, the most common symptoms for non-smokers are eye irritation, headache and cough. Therefore, it is said that the harm of inhaling "second-hand smoke" is greater.

3. Do you know that “third-hand smoke” is unavoidable?

The health hazards of "third-hand smoke" cannot be ignored. For example, when taking a taxi, dining in a restaurant or staying in a hotel, the previous group of guests have smoked and the smell of smoke is very strong; or smokers smoke in the family living room or bedroom when the children are not at home. In these places, because smokers have smoked here, after the smokers leave for a while, the harmful substances or carcinogens in the tobacco will remain on the sofa, carpet, pillows, quilts and various decorations of the home, or the harmful substances in the tobacco will also remain on the smokers' hair and clothes after they finish smoking outdoors. These harmful substances in the tobacco combine with certain substances in the air to become carcinogenic nitrites.

In daily life, people have such a mentality that safety anxiety and risk indifference coexist. Ordinary people are highly alert to sudden and serious risks, but are not sufficiently prepared for hidden risks that do not directly harm life. Philosopher Feuerbach has a widely circulated saying: "Man is what he eats." Through the window of smoking, we can see more about the relationship between people and people, and between people and society. Compared with "second-hand smoke", "third-hand smoke" has stronger privacy. In other words, the family, as a relatively closed social space, is the main source of "third-hand smoke". In smoking families, how to protect the health of family members has become the most pressing question for people.

The biggest harm of "third-hand smoke": hidden and long-lasting! Unlike "second-hand smoke" inhaled in public places, "third-hand smoke" can cause hidden harm. If it is not cleaned thoroughly regularly, these toxic substances can adhere to the surfaces of various objects in the room and the car for a long time, and generate "third-hand smoke" toxins. The main victims of "third-hand smoke" are infants and children. According to a study by Harvard Medical School in the United States, children like to touch and lick various objects with their tongues, and put their fingers in their mouths. Therefore, the harm caused by "third-hand smoke" to children is more than 20 times greater than that of adults. Housewives, hotel and domestic service personnel have more opportunities to contact various objects, so they are also the main victims of "third-hand smoke".

We must pay attention to "third-hand smoke", because even a small problem cannot withstand the cumulative harm of time. We hope that smokers will take care of our infants and young children, who often play on the sofa and carpet and put food that falls on the ground into their mouths. Some young parents know that smoking is harmful to the health of their families and children. They do not smoke at home or in the living room, but go outside to smoke enough before going home. The harmful substances of tobacco are left on their hair, sweaters or coats. When they hold their children, these "third-hand smoke" will also harm young children. We hope that the whole society will work together to expand the scope of smoking bans in indoor workplaces and public places through legislation, and reduce the health hazards of "second-hand smoke" and "third-hand smoke" to non-smokers.

4. Can “low tar smoke” reduce the incidence of lung cancer?

To protect their commercial interests, tobacco companies continue to improve cigarette processing technology and design, thereby reducing the standard tar content. The low-tar promotion on cigarette packaging makes consumers mistakenly believe that choosing low-tar cigarettes can reduce harm, and some people have given up the idea of ​​quitting smoking. Studies have shown that whether they smoke low-tar cigarettes from the beginning or switch to low-tar cigarettes, the quit rate of these people is lower than that of ordinary cigarettes. The reduction in the quit rate has further exposed a large number of smokers to the harm of tobacco for a long time.

Most smokers are misled! According to a survey conducted in 2008 on 1,403 people, more than two-thirds of the smokers surveyed were more willing to buy low-tar cigarettes at the same price, nearly 60% believed that smoking low-tar cigarettes would inhale less tar than smoking regular cigarettes, nearly half believed that low-tar cigarettes could reduce the risk of cancer, and half of the current low-tar smokers felt that it was softer than smoking regular cigarettes. The "World No Tobacco Day Smoking Survey" conducted by Family Doctor Online in 2013 showed that 51.61% of netizens still believed that low-tar cigarettes were less harmful than regular cigarettes.

Low tar cannot reduce the harm of smoking. The results of clinical epidemiological studies have confirmed that smokers who choose low-tar cigarettes do not have a lower risk of tobacco-related diseases. Cigarettes labeled "light" and "low tar" do not substantially reduce smokers' risk of disease. Studies have found that smokers who smoke very low tar (7 mg per cigarette), low tar (8-14 mg) and medium tar (15-21 mg) filter cigarettes have the same risk of dying from lung cancer. Other studies have found that smokers who switch to "low tar" cigarettes often desperately inhale cigarette smoke deep into the lungs to make up for the lack of nicotine intake, which increases the incidence of lung adenocarcinoma (cancer that occurs deep in the lungs).

At the same time, the tar content measured by the machine can no longer represent the actual tar intake of smokers. For example, when smoking with a machine, part of the outside air will be inhaled through one or more circles of air holes around the filter tip, thereby diluting the inhaled tobacco smoke and reducing the tar concentration measured by the test machine. However, smokers will intentionally or unintentionally pinch these small holes with their fingers or hold them with their lips when smoking, so in the actual smoking process, these air holes cannot really play a role in diluting tobacco smoke.

All tobacco products, including so-called "low-tar" cigarettes, are similar or similar in their harm. The only effective way for smokers to protect themselves from the harm of smoking is to quit smoking.

author

Zhi Xiuyi

Chief Physician, Professor

my country's famous thoracic surgery and lung cancer prevention and treatment expert

Director of Lung Cancer Diagnosis and Treatment Center, Capital Medical University

Chief expert of thoracic surgery at Xuanwu Hospital, Capital Medical University

Director of the Lung Cancer Center, Beijing Chang Gung Memorial Hospital, Tsinghua University

Chief expert in thoracic surgery at Beijing Chang Gung Memorial Hospital affiliated to Tsinghua University

President of the National Lung Cancer Alliance for the Elderly

Chairman of the Chinese Thoracic Surgery Lung Cancer Alliance

Vice President of China Tobacco Control Association

Founding Chairman of the Thoracic Surgery Branch of the Beijing Medical Association

Vice Chairman of the Thoracic Surgery Branch of the Chinese Medical Promotion Association

Standing Committee Member of the Chinese Medical Association Society of Thoracic and Cardiovascular Surgery

Chairman of the Lung Cancer Prevention and Control Branch of China Medical Promotion Association

Vice Chairman of the Accelerated Recovery Surgery Branch of the Chinese Medical Association

Chairman of Lung Cancer Medical Education Committee of China Medical Education Association

Leader of the National Health Commission's Expert Group on "Primary Lung Cancer Diagnosis and Treatment Guidelines"

Leader of the Thoracic Surgery Expert Group of the National Health Commission’s Clinical Pathway Review Expert Committee

This article is excerpted from the Chinese Anti-Cancer Association's popular science series "How Much Do You Know About Cancer - Lung Cancer", which selects the most frequently asked questions by outpatients and inpatients, and provides vivid, concise, accurate and authoritative answers, so that every patient can "have this book in hand and ask for nothing else".