“Smoking is bad for your health” is common knowledge today, and this common knowledge is printed on all cigarette packs. But this was only discovered decades ago. Before that time, people not only did not know that smoking was bad for their health, but they even thought it was good for their health.
Tobacco is native to the Americas. Before the arrival of European colonists, the Native Americans had been growing and using tobacco for thousands of years. They used tobacco as a sacred medicine and smoked as part of a solemn ritual during worship and negotiations. Native Americans also used tobacco as a medicine for many ailments and for pain relief and wound dressing. Hu Mu, Department of Thoracic Surgery, Xuanwu Hospital, Capital Medical University
When Columbus landed in the Bahamas in October 1492, the Native Americans probably thought of them as gods and offered them tribute of fruit and dried tobacco leaves. Columbus took these gifts back to his ship, ate the fruit, but didn’t know what the tobacco was for and threw them away. The two crew members he sent to Cuba in search of the “Emperor of China” saw for the first time how the locals smoked. One of them – Jerez – also learned to smoke and became addicted.
When Jerez returned to Spain in 1501, he also brought back tobacco and the smoking habit with him. He was not only the first European to smoke, but also the first to be punished for it: the smoke that came out of his nose and mouth when he smoked terrified his neighbors, who thought he must have been possessed by the devil. The Inquisition had him arrested and thrown into prison for seven years.
In 1518, the Spanish conquistador Cortez brought back tobacco from Mexico at the request of a monk who had sailed with Columbus. 1530, the Spanish crew brought back tobacco seeds, and tobacco was formally introduced to Europe, gradually spreading to all European countries, and then to the rest of the world by Spanish and Portuguese sailors. In 1560, Nicole, the French ambassador to Portugal, wrote an article about the medicinal value of tobacco, using it as a cure-all. In 1571, a Spanish physician wrote a book about the medicinal plants of the New World, which listed 36 diseases that tobacco could be used to treat. Building on this, doctors from other countries added new uses for tobacco from time to time.
A few years later (1575, the third year of the Wanli reign of the Ming Dynasty), tobacco was introduced from Luzon (Philippines) to Taiwan and Fujian, and in 1579, Ricci brought snuff to Guangdong, and smoking became popular in China. Chinese doctors also praised the benefits of tobacco, claiming that it could move gas and relieve pain, detoxify and kill insects, and even said that it was “the medicine of the nine orifices” and “all cold and blocked diseases, smoking this will pass”, which became a panacea for all diseases.
In the seventeenth and eighteenth centuries, tobacco has become an important cash crop, and in the American colonies even became a substitute for gold hard currency, known as “brown gold”. In the war of independence in the North American colonies, tobacco exports were the economic security of the revolutionary army. In 1776, Washington lost the battle with the British and asked his countrymen for help, asking them to finance his army: “If you can’t send money, send tobacco.” After American independence, the government paid off its debts during the war by taxing tobacco.
This scene was repeated in the American Civil War. Both Northern and Southern armies issued tobacco to soldiers as part of their rations, and many Northern soldiers were thus exposed to tobacco for the first time. After the war, the U.S. federal government relied on taxation of tobacco to help rebuild after the war. What was popular at this time was primarily chewing tobacco. Chewing tobacco became one of the representative images of western cowboys. After that smoking cigars and paper cigarettes gradually became popular. By the time the United States entered World War I in 1917, it was paper cigarettes that appeared in soldiers’ rations. A general at the time claimed that cigarettes were as important as bullets to win the war. Those who objected to giving cigarettes to soldiers were considered traitors to their country. During the Second World War, paper cigarettes were likewise part of the soldiers’ ration.
Resistance was also encountered in the promotion of tobacco. In many countries, smoking bans were issued, and even death sentences were imposed on violators, for example, in 1637, Emperor Chongzhen issued a ban on smoking, punishing those who grew and sold tobacco by beheading them. But these bans were motivated by religious, moral, economic, or security (for fire prevention) considerations, not by any real recognition of the health risks of tobacco. Something that is addictive and brings great economic benefits is difficult to eliminate by simple prohibition.
There were also some who suspected that tobacco could be harmful to human health. These initial suspicions had little scientific basis, and in 1602 an English physician anonymously published a work on the illnesses of chimney sweeps, arguing that the illnesses of these men were caused by soot and that tobacco caused similar illnesses. His theory was based on the tetralogy of fluids doctrine of traditional Western medicine. Some English doctors, upset that people could consume tobacco as a “medicine” without a doctor’s prescription, complained to King James I. In 1604, James I wrote an article attacking tobacco as harmful to the eyes, nose, brain, and lungs, and frightened his readers by saying that the lungs and brains of those smokers were covered with soot, apparently caused by smoking. Because his subjects did not heed his advice, James I imposed heavy taxes on tobacco imported into England, raising the tax on tobacco 40 times.
Probably the first clinical study of the dangers of tobacco was done by John Hill, a London physician. He noticed that several of his patients with nasal cancer were addicted to snuff and suspected a connection between the two. After some investigation, Hill published a paper in 1759 warning against excessive snuff use. Although he did not say that snuff was an absolute contributor to cancer, he was certain that it was at least one of the contributing factors.
The link between smoking and cancer was not noticed for another hundred years. Prior to the 20th century, lung cancer was extremely rare, with fewer than 80 medically documented cases. However, in 1911, New York physician Adler published a monograph on lung cancer that showed nearly 400 cases at once and was the first to point out that the development of lung cancer was related to smoking.
But at this time there was no medical consensus on the dangers of smoking. On the one hand, there were researchers who continued to publish papers arguing for a relationship between smoking and cancer, and on the other hand, there were researchers who denied the relationship and even argued for the health benefits of smoking. The first edition of the authoritative Merck Manual of Diagnosis, released in 1899, went so far as to recommend smoking as a treatment for bronchitis and asthma. Although the American Medical Association claimed to oppose the health benefits of smoking, it published tobacco company advertisements for cigarettes in its publications for 20 years, beginning in November 1933. It was not until 1953 that the AMA banned cigarette advertisements from its publications because by then there was strong evidence that smoking caused lung cancer.
Before the 20th century, lung cancer was an extremely rare disease, with fewer than 80 medically documented cases. However, after the 20th century, lung cancer cases increased dramatically and increased each year, quickly becoming one of the leading causes of death. For example, between 1922 and 1947, the annual number of deaths from lung cancer in England and Wales increased from 612 to 9,287, an approximate 14-fold increase. Similar phenomena existed in other European countries as well as in North American and Asian countries.
This phenomenon was already a cause of much concern in the 1940s. Was the incidence of lung cancer really greatly increased, or was there actually not much of an increase in lung cancer incidence, but simply an illusion that more cases of lung cancer were being detected because of greatly improved diagnostic techniques for lung cancer? Some researchers believe it is the latter. Advances in diagnostic techniques are undoubtedly a factor, but they are unlikely to be the only one. The dramatic increase in the incidence of lung cancer has been found in both rural areas, where diagnostic techniques are relatively backward, and in urban areas, where diagnostic techniques are relatively advanced, and has increased year by year, and obviously cannot be explained entirely by advances in diagnostic techniques. The dramatic increase in the incidence of lung cancer appears to be real. So what factors are causing it?
There were two main views at that time. One view was that the increase in lung cancer was due to environmental pollution caused by automobile exhaust, tarmac dust, industrial waste gases, etc. The other view was that smoking was the main culprit. Although humans have used tobacco for a long time, it was mainly with snuff, chewing tobacco, pipes and cigars until the 20th century, after which smoking paper cigarettes became extremely popular and produced numerous heavy smokers. There have been some previous clinical observations linking smoking to lung cancer. For example, in 1939, the Germans found that of 86 men with lung cancer, only 3 were nonsmokers and 56 were heavy smokers. However, the samples of these clinical observations were small and insufficient to make a statement.
In 1950, American and British researchers published findings from large samples that more conclusively demonstrated a strong correlation between smoking and lung cancer. 1948, while watching the autopsy of a deceased lung cancer patient, Wendell, a first-year medical student at Washington University School of Medicine in St. Louis, noticed that the deceased’s lungs were black. This piqued his interest. Asking the deceased’s wife, he learned that the deceased had smoked two packs of cigarettes a day for 30 years during his lifetime. Was smoking the cause of lung cancer? Winder made this a research topic and over the next two years worked with Graham to find more lung cancer cases to prove the relationship between lung cancer and smoking, and published their findings in the Journal of the American Medical Association in 1950. They found that only 1.3% of 605 men with lung cancer were “non-smokers” (less than 1 cigarette a day for the past 20 years), while heavy smokers (more than 20 cigarettes a day for the past 20 years) accounted for 51.2%. As a control, they surveyed 882 patients with other diseases, from which they estimated that 14.6% of the same age group of patients with general diseases were nonsmokers and only 19.1% were heavy smokers. in September 1950, Doyle and Hill also published their findings in the British Medical Journal. Their study, which began in 1947, surveyed patients in 20 London hospitals. Their findings were similar to those of the Americans, with only 0.3% of the 649 men with lung cancer not smoking and 26% smoking 25 or more cigarettes a day, compared to 4.2% of the non-smoking men and 13.% of the heavy smokers in the control group of non-cancer patients.
Both of these studies were retrospective studies of hindsight, investigating causative factors after the disease had been identified. Doyle and Hill realized that it would be more convincing to do prospective studies that captured the smoking status of patients before the disease occurred. They decided to target British physicians because they were required to register, were easy to contact and track, enjoyed the best medical care, were easy to confirm their cause of death, and were generally more concerned about their habits and happy to cooperate with medical investigations. in October 1951, Doyle and Hill sent questionnaires to 59,600 physicians throughout the United Kingdom asking about smoking, and received 40564 more complete responses. Because smoking by women was extremely rare at the time, they focused on only 34,439 of these male physicians. By March 31, 1956, 1,714 of these physicians over the age of 35 had died, 84 of them of lung cancer. Only one of these lung cancer deaths was a nonsmoker, and 34 were heavy smokers. Accordingly Doyle and Hill published their first statistics in 1956, calculating the lung cancer mortality rate (per 1,000 per year) to be 0.07 among nonsmokers, 0.90 among smokers, and 1.66 among heavy smokers, after which Doyle and Hill (and Doyle and Bitto after 1971) continued to track these physicians at 10-year intervals. By the time the project ended in 2001, there had been 25,346 deaths among the male physicians who participated in the survey, 1052 of them from lung cancer. the lung cancer mortality rate (per 1,000 per year) was 0.17 for nonsmokers, 0.68 for ex-smokers (who had smoked and then quit), 2.49 for smokers, and 4.17 for heavy smokers. smokers lived on average 10 years less than nonsmokers.
In the 1950s, when the link between smoking and lung cancer became increasingly apparent, the tobacco industry formed the Tobacco Industry Research Committee (later renamed the more confusing Tobacco Research Committee) to try to counter the academic argument that there was no conclusive evidence that smoking caused lung cancer. evidence that smoking caused lung cancer and that the increase in lung cancer rates was caused by other factors, such as air pollution.
But as the research progressed and the evidence that smoking causes lung cancer grew, the tobacco industry’s pushback became increasingly weak. First, surveys in various countries have shown a clear and strong correlation between smoking and lung cancer. The lung cancer mortality rate for smokers is more than ten times that of nonsmokers, and 80 to 90% of lung cancer deaths are associated with smoking. Secondly, there is also a clear correlation between the amount of smoking and the level of lung cancer mortality; the more you smoke, the higher the lung cancer mortality rate. The lung cancer mortality rate (per 1,000 people per year) was 1.31 for smokers who smoked 1 to 14 cigarettes per day, 2.33 for those who smoked 15 to 24 cigarettes per day, and 4.17 for those who smoked 25 or more cigarettes per day. again, the risk of getting lung cancer decreases once you quit smoking. In a follow-up survey of British physicians, it was found that as more British physicians quit smoking, the lung cancer mortality rate among British physicians decreased. In the 1960s, about half of American men smoked. Now, less than one-third of U.S. men smoke. Accordingly, the incidence of lung cancer among U.S. men is no longer on the rise. In contrast, the number of women in the United States who smoke continues to rise, and the incidence of lung cancer among women in the United States has increased each year, surpassing breast cancer as the most deadly cancer among women in the United States in 1987.
In addition, comparisons of different populations can exclude the influence of other factors. If the study is done on similar populations, such as those living in cities, it is difficult to exclude the effects of other factors such as air pollution. For this reason, American researchers did a study to examine the incidence of lung cancer among male Mormons and non-Mormons living in urban and rural areas of the Jewish state. The incidence of lung cancer was higher among non-Mormons living in cities than among non-Mormons living in villages. It should be the former, because Mormons living in cities do not have a higher incidence of lung cancer than Mormons living in the countryside, and Mormons are non-smokers. In fact, all other religious denominations that prohibit smoking have very low lung cancer rates.
However, the tobacco industry is correct in one respect in its counterattack; correlation does not equal causation. While epidemiological surveys can demonstrate a clear and strong correlation between smoking and lung cancer, they cannot prove that smoking causes lung cancer. To prove that smoking is a causal factor in lung cancer, it is also necessary to discover the mechanism by which smoking causes lung cancer: what component of tobacco, in what way, causes lung cancer. This has to be done with the help of laboratory studies.
Since the 1950s, a growing number of studies have shown that the incidence of lung cancer is related to smoking, and that smokers are much more likely to develop lung cancer than nonsmokers. The tobacco industry first denied that smoking was associated with lung cancer, by sponsoring studies and publishing books that promoted the idea that “smoking is safe”. For example, a 1957 U.S. book entitled A Scientific Look at Smoking claimed that “all those who have tried to prove the evil consequences of tobacco have failed to establish a valid scientific basis. As the evidence linking smoking to lung cancer became more conclusive, the tobacco industry changed tack and concluded that even if smoking was associated with a high incidence of lung cancer, it could not be proven to cause lung cancer. In many cases where lung cancer patients or their relatives have sued tobacco companies, the tobacco companies have prevailed.
We can prove that smoking causes lung cancer through controlled trials. Similar to clinical trials to prove the efficacy of drugs, the subjects would be randomly divided into two groups, one smoking and one not smoking, and the results would be compared over a number of years to see if the smoking group had a higher incidence of lung cancer than the non-smoking group. But we can not take people to do this inhumane and very long test. The next best thing is to do animal experiments. As early as 1953, it was reported that applying cigarette tar to the backs of rats would cause them to develop tumors. Then there were experiments that showed that letting rats inhale concentrated cigarette smoke would give it lung cancer. However, the results of animal experiments cannot simply be extended to people.
Since epidemiological investigations have proven that there is a clear and strong correlation between smoking and lung cancer, it is possible to prove that smoking is a causative factor for lung cancer if we can discover the mechanism by which smoking causes lung cancer and figure out what components of cigarette smoke, in what way, cause lung cancer. It has been found through animal experiments that cigarette smoke has many kinds of carcinogens. How do these carcinogens cause cancer? The first thing that needs to be clarified is what cancer is all about.
Cancer is caused by cell division that is out of control. There are a series of genes that control the rate of cell division, just as people drive cars with alternating gas pedals and brakes, with some genes acting as accelerators and some genes acting as brakes. If a mutation occurs in these genes, it is equivalent to slamming on the gas pedal or letting the brakes fail, and the cell division loses control and grows wildly, turning into cancer cells.
One of the genes that controls cell division is called p53. If a mutation causes p53 to lose its role, there is one less barrier to inhibit cell division. In about 70 percent of all lung cancer patients, p53 is out of function. Mutations in the p53 gene in cancer cells of lung cancer patients are concentrated in one of three positions (codons 157, 248 and 273).
In 1996, it was found that benzo(a)pyrene was absorbed by epithelial cells and converted into dihydrodiol-epoxy benzo(a)pyrene, which binds directly to p53 and mutates it at the three codons 157, 248 and 273. This suggests that the genetic mutation that causes lung cancer is due to the carcinogens in cigarette smoke.
This experiment was seen by some as the “final proof” that smoking causes lung cancer, and since then even some tobacco companies have been embarrassed to deny the causal relationship between smoking and lung cancer. Benzo(a)pyrene is produced by the high-temperature decomposition of the tar in cigarettes. For this reason, some tobacco companies have introduced a non-combustion vaporizer technology to avoid the production of benzo(a)pyrene when smoking. But this product did not spread. And benzo(a)pyrene is only one of many carcinogens in cigarettes. For example, acrolein, which is found in cigarette smoke and causes the same cancer-causing genetic mutations as benzopyrene, is found in smoke at a thousand times the level of benzopyrene.
In addition to lung cancer, smoking can cause many types of cancer, especially in the kidneys, larynx, mouth, breast, bladder, esophagus, pancreas, and stomach. In addition to cancer, smoking can also cause damage to the body in a variety of other ways. Long-term inhalation of carbon monoxide and cyanide from cigarette smoke can cause alveoli to lose their elasticity. Smoking increases the risk of heart disease and sudden brain stroke, and the risk of heart attack is five times higher for smokers than for nonsmokers under the age of 40. Smoking lowers the body’s immune system and makes people more susceptible to infectious diseases; for example, smokers have a fourfold increased risk of getting a lung infection. Smoking also reduces the quality of sperm, affects men’s sexual function, leads to miscarriage, and affects the health of the fetus.
Even if you don’t smoke, passive inhalation of secondhand smoke can be harmful in many ways, including causing cancer, heart disease, respiratory infections, asthma and miscarriage. A 2004 study in China found that nearly as many women died from secondhand smoke as from smoking: 48,400 died from lung cancer and heart disease caused by secondhand smoke, compared to 47,000 who died from smoking.
Although smoking may also have some health benefits, such as a reduced risk of ulcerative colitis, this is insignificant compared to the enormous harm caused by smoking. According to several different estimates, the average life expectancy of smokers is reduced by 10 to 17.9 years. Another calculation states that for every cigarette smoked, life expectancy is reduced by 10.7 minutes, which is even longer than the time it takes to smoke a cigarette. Smoking kills 4.9 million people worldwide each year. According to the World Health Organization, smoking is the second leading cause of death and the largest preventable cause of death. Because secondhand smoke is equally harmful to health, not only should smoking cessation be promoted, but smoking should be banned.
The harmfulness of smoking, especially its relationship with lung cancer, is now uncontested, and even the tobacco industry can no longer deny it. The U.S. government had claims against tobacco companies for the health hazards caused by smoking, and in 1998 an agreement was reached in which tobacco companies agreed to pay annual reimbursements of $200 billion over 25 years, mainly to compensate the government for medical funding for smoking-related diseases. While the number of smokers in developed countries has declined, the number of smokers in developing countries has increased by 3.4 percent each year. Government connivance and economic incentives have made it difficult to enforce smoking bans in developing countries. This is no longer relevant to science.