It is well known that smoking is the number one cause of lung cancer, and smokers are more than 15 times more likely to get lung cancer than non-smokers. In China, lung cancer is the number one cancer, which is inextricably linked to the staggering 350 million smokers. There is no doubt that if you do not want to get lung cancer, you must first quit smoking. But comparing the United States and China, there is a very strange phenomenon: about 85% of female lung cancer patients in the United States are smokers (American women smoke very heavily), while in China, more than 80% of female lung cancer patients never smoke! Studies have found that women in East Asia, aged 40-70, are 2-3 times more likely to get cancer than American women, even though the percentage of women who smoke is much lower than in the United States! What’s going on? Obviously, smoking is not the leading cause of lung cancer in Chinese women, so what is the cause? There are two types of cancer risk factors: endogenous and exogenous. Endogenous factors are not controllable, mainly genetic factors and age, while exogenous factors are controllable, mainly lifestyle habits and environment. Are they endogenous factors? There is no doubt that genetic predisposition has a significant impact on a person’s risk of developing cancer. There are people like Angelina Jolie who directly inherited the cancer-causing gene mutation, resulting in more than 80% of cancer risk, and there are also people who are born beautiful and have been an old smoker all their life without cancer. The world is indeed unfair. So, is it some genetic factor in the Asian race that causes the high risk of lung cancer in the Chinese? There are some studies, but the conclusions are not yet clear. But whether there are endogenous factors or not, I think we should all focus on exogenous factors. For one thing, endogenous factors cannot be changed, and for another, endogenous factors often do not cause cancer directly, but make a person more susceptible to various external stimuli that produce abnormalities. Therefore, understanding and avoiding exogenous cancer-causing factors can greatly reduce the risk, even if the genetic predisposition is not strong. Besides smoking, what other exogenous factors can cause lung cancer? The one that comes to mind most easily is secondhand smoke. Secondhand smoke is a clear carcinogen. China has the worst secondhand smoke problem in the world, bar none! More than 700 million women and children in China are chronic victims of secondhand smoke in their homes and in public places. I myself fondly remember watching my grandfather play cards in a smoky teahouse every day when I was a child. Unfortunately, I didn’t know anything about it at the time. The World Health Organization estimates that secondhand smoke kills 100,000 people each year in China, the equivalent of one Wenchuan earthquake per year! Among these 100,000 people, there are many non-smoking women with lung cancer. Studies show that if the husband smokes, the wife’s probability of getting lung cancer is more than 200% of the general population. Again, please don’t smoke in your home or in public! Hidden Factors Secondhand smoke is obviously harmful, but I don’t think it is the biggest cause of lung cancer in Chinese women. The main evidence comes from genetic studies: lung cancer in non-smoking women and lung cancer in smokers, although they look similar on the surface, are very different from a genetic mutation point of view, so to speak, and are two completely different diseases! Non-smoking women get almost all lung adenocarcinoma, mostly with EGFR and ALK gene mutations, which are amenable to targeted drugs, whereas smokers have a wide variety of lung cancers but fewer EGFR and ALK gene mutations, usually without targeted drugs but responding better to recent immunotherapies. If women are primarily victims of secondhand smoke, then their cancers should be closer to those of smokers. It seems that there is another factor. What is it? Is it the haze? Haze is undoubtedly a serious health risk, but it should not be a major factor either. The evidence is mainly twofold: 1. Theoretically, it takes a long time for haze to cause cancer, if at all (the average for lung cancer from smoking is about 25 years). So the haze of the last few years may lead to a large increase in lung cancer in the future, but not the answer we are looking for today. 2. The high incidence of lung cancer in non-smoking women in China was evident in the 1970s and 1980s, when there was no haze problem at all. Looking for the reasons for the high incidence of lung cancer in women now, we should look forward to see what factors have been exposed to Chinese women for a long time in recent decades, while Americans are less exposed? The answer is indeed air pollution. But not haze, but indoor air pollution which is ignored by many people! There are two most important sources of indoor pollution: Criminal number one: indoor fuel. I believe that many people, especially northerners remember a thing called “honeycomb coal”. Honeycomb coal, usually boiling water for cooking, winter fire for heating. Similarly, there are a large number of wood burning stoves in rural areas. The common feature of these things is very choking, smoky, my mother was often smoked to tears. If the weather is cold, the windows and doors are usually closed, ventilation is extremely poor, and harmful gases and particulates are hoarded in large quantities, becoming a serious health hazard. A large number of studies in the 1980s and 1990s found that the proportion of women with lung cancer in northern China, especially in the northeast, was significantly higher than in the south. Pollution from indoor fuels like cellular coal, briquettes and firewood is considered one of the main causes. Of course, for many urbanites, these are a thing of the past, are we relieved of the danger? Not really, because there is another equally serious source of pollution. Criminal number two: frying fumes! The Chinese and Americans cooking a huge difference is that we fry especially like to use hot oil. We all love to hear the ingredients put into the hot oil pan that “prickly” sound, it sounds very fragrant. But many people do not notice, along with the pleasant “prickly”, the smoke rolled up. Oil smoke, is as bad as the haze of carcinogens! Do not believe? I recently asked a few friends to simply measure the PM2.5 when stir-frying, and the results were surprising. Fried eggs with tomatoes, PM2.5 over 1000! At night, eating barbecue is even worse, PM2.5 more than 7000! Studies have found that when fried or stir-fried in hot oil, PM2.5 can quickly rise by tens of times. Sichuan cuisine is the hardest hit area, my mother stir-fried vegetables, from the onion, ginger and garlic into the hot oil, PM2.5 spiked all the way up, and eventually easily exceeded 2000. Oil smoke PM2.5 is transient, short-term, and can not be directly compared with the long-term haze who is more serious. But numerous studies have shown that kitchen fumes are a potential carcinogenic factor and can also cause many various diseases, especially respiratory and cardiovascular diseases.