[Health] terrible! Is there really a legendary "seven-year contract" between smog and lung cancer?

Some time ago, "a haze and lung cancer have a "seven-year contract," that is, after years of severe haze, there will be a high incidence of lung cancer seven years apart." The blog came out and immediately caught the attention of the Internet. The "seven-year contract" on smog and lung cancer has become the focus of attention, and is even more concerned about the effects of air pollution on human health.

Is there really a legendary "seven-year contract" between smog and lung cancer? What is the scientific basis for this type of argument?

With regard to the main factors inducing lung cancer, a large number of studies have shown that smoking is the "culprit", including secondhand smoke. However, according to statistics from the health department, there has been no significant change in the level of smoking among Chinese people in the past 40 years, but the incidence of lung cancer has shown a clear upward trend. Many netizens questioned why the incidence of lung cancer continues to increase with no significant change in smoking levels.

Zhong Nanshan, academician of the Chinese Academy of Engineering, said in an interview with CCTV “News 1+1” that “ash is not only a sucking system, but also has an impact on cardiovascular, cerebrovascular, and nervous systems, but it is still the first to be sucked. Beijing has lung cancer for 10 years. With an increase of 60%, it should be said that air pollution is a very important reason." Since 2004, Pan Xiaochuan, a professor at Peking University's medical department, began monitoring the daily average concentration of PM2.5 in the air. He discovered that the number of emergency patients such as the nearby hospital sucking system would change significantly each time the value increases. Previous studies have shown that the growth of PM2.5 is positively correlated with the number of patients with emergency-related diseases in hospitals. For patients with circulatory diseases and sucking system diseases, the number of emergency patients is approximately 10 for every microgram of cubic meter of PM2.5. Increased by 0.5% to 1%.

Like dust storms, it belongs to PM10-level particles that can be excreted by the body through sneezing, runny nose, and coughing. But PM2.5 particles, the body's throat has been unable to stop, it can go all the way until the alveoli. In particular, PM2.5 is a carrier that contains harmful substances such as nitrogen oxides, sulfates, viruses, etc. These toxic particles that stay in the alveoli will eventually affect our epithelial tissues, inactivate tumor suppressor genes, and induce lung cancer.

Regarding whether PM2.5 is a cancer-causing problem, the International Agency for Research on Cancer (IARC) has already given an answer.

On October 17, 2013, at the meeting of the International Agency for Research on Cancer (IARC) in Lyon, the air pollutant PM2.5 was identified as a class 1 carcinogen (a definition of Class I: a carcinogen for humans). At this point, in addition to affecting cardiovascular disease and sucking system diseases, PM2.5 also increases the risk of lung cancer and bladder cancer.

Although it has been confirmed that PM2.5 will increase the risk of lung cancer, there are no studies to confirm that there will be a high incidence of lung cancer in seven years.

The “seven-year contract between smog and lung cancer” was first reported in a media report on the increase in the incidence of lung cancer in Guangzhou. The report cited the chief meteorologist of the Guangdong Meteorological Bureau Wu Zheng’s 2009 attack on lung cancer in Guangzhou City. Rising rate of research: After considering a seven-year lag period, the correlation between the mortality rate of lung cancer in Guangzhou and the particle concentration of plutonium is as high as 0.97, which means that the “toxic” air sucked in today may not produce until 7 years later.” Fatal harm." After seven or eight years, the mortality rate of lung cancer increased, and the time lag between the two coincided.

However, in this report, the expert added a sentence that was added by the netizens: “But the real cause of the pathogenesis of lung cancer and its exact increase in mortality rate, we still hope to come from sucking disease and epidemiologists. Complete the study together."

Many experts have stated that the “ seven-year contract of ash and lung cancer ” is somewhat exaggerated and inaccurate. As of now, epidemiological surveys have not had a lot of in-depth and direct research. ”

What effect PM2.5 will have on the human body depends mainly on which PM2.5 adsorbs toxic particles in the atmosphere. If it is carcinogenic, it is carcinogenic. If heavy metal is adsorbed, it may cause heavy metal poisoning. Different ingredients have different hazards. The economic development of each city is different, and the exposed chemical reactions are also different. Different cities have different hazards.

The occurrence of lung cancer is a long-term slow process. Even if the relationship between smog and lung cancer can be determined, it is the result of years of long-term living in a hazy environment. Lung cancer is a chronic lifestyle disease. The relationship between haze and lung cancer is similar to the relationship between tobacco and lung cancer. It is a cumulative process. Living in a place where the harmful substances are excessive for a short period of time will not have much impact on the induction of lung cancer. If the long-term stay in PM2.5 severely exceeded the place, the incidence of lung cancer is certainly to be increased. This is closely related to the concentration of local hazardous substances and the length of stay.

The relevant person in charge of the Beijing Cancer Prevention Office said: “A large number of studies have shown that smoking is the primary risk factor for lung cancer. The incubation period from the beginning of smoking to lung cancer takes about 15 to 50 years, and the number of smokers, age of smoking, etc The risk of the disease is related, but we are also exploring whether there are other incentives to increase the incidence of lung cancer."

The Beijing Cancer Prevention and Control Office once investigated 1,346 lung cancer patients who were specifically targeted at the Beijing municipality in 2010. The results showed that 56.8% of the respondents had smoking habits. Among them, the smoking rate was 79.4% for men and 19.4% for women. The average age for smoking was 25 years old. The average daily smoking rate was 20, the average duration of smoking was 40 years, and the cumulative smoking rate was 40 pack-years. All of them were truly “old smokers”. Among these smoking cases, those who have quit smoking accounted for 26.7%, the average age for starting smoking cessation was 62 years, and the average smoking cessation time was 7.5 years.

According to several monitoring data, it can be seen that the main factor inducing lung cancer is smoking. The current increase in the incidence of lung cancer is mainly an increase in the incidence of linear cell carcinoma. The biggest cause of lung cancer rise is smoking, including secondhand smoke, followed by air pollution and mental stress.