Today we’re talking about whether haze can cause lung cancer or not.
Haze and lung cancer: why are scientists arguing?
The haze and cancer link is hotly debated, splitting into different camps within scientists, with some supporting the idea that haze causes cancer and others arguing for more caution.
Scientists are mainly debating whether there is scientific “direct evidence” that strictly proves that haze causes cancer. Contrary to popular belief, there are not many research papers on “haze causes cancer”, so why? Because research is hard to do and evidence is hard to come by.
(Image from Station Cool Helo)
First, this study couldn’t find a perfect control group.
You have to have a control group to study the effect of a new drug on patients, otherwise it’s meaningless. Similarly, to study the effect of haze on cancer, you have to have a control group. We should compare whether there is a difference in the probability of getting lung cancer in the same group of people, with or without haze.
Theoretically, the perfect experiment to get “direct evidence” that Chinese haze causes cancer would be this: In a parallel universe, there are 1.3 billion other Chinese people who are just as hard-working, kind, party-loving, and dedicated as we are, but just don’t pollute the air, so let’s compare them to the 1.3 billion Chinese in our universe. The Chinese people in this universe, the 1.3 billion people in this universe, are not polluting the air, so let’s see if there is a difference in the incidence of lung cancer.
Or let’s find a lot of twins on the planet, split them up, divide them into two groups, put them on respirators permanently, and the only difference is that one group is breathing the air from the G20 and the other group is breathing the air from Hebei now, and after a decade or so, let’s see if there’s a difference in incidence.
This is obviously science fiction, and a perfect experiment is impossible. So can we step back and compare two groups of people who are similar?
For example, can we compare the occurrence of lung cancer in China before pollution occurred (before 1950) and after severe pollution (after 2000)? Can’t the fact that we have tens of times more lung cancer now than before liberation suggest that environmental pollution is the main cause?
It really doesn’t.
First of all, before industrial pollution occurred in China, medical care was also very backward, and many lung cancer patients in rural areas died without knowing what the cause was, so the number of lung cancer patients before must have been grossly underestimated and cannot be directly compared. If we find a large increase in lung cancer patients, maybe it’s just because more are being diagnosed and registered.
Also, the average life expectancy in China has been increasing because of improved health care, and aging is the number one contributor to cancer, so it’s not at all surprising that the incidence of lung cancer has increased.
So even though lung cancer has increased dozens of times in China, it’s hard to study how much of it is environmental. The rigor of science requires that we not make judgments based on intuition.
(Image from Station Cool Helo)
Would it be possible to compare countries with different levels of pollution over the same period? How about comparing the US and China now, for example?
This is also problematic, because there are very many differences between countries, regions, besides just air pollution.
In the United States and China, for example, the ethnic composition is different, the average life expectancy is different, smoking control in public places is different, water pollution is different, diet is different, the obese population is different, and so on. All of these factors can affect the incidence of lung cancer, and it is scientifically very difficult to eliminate all of these factors and quantitatively compare the effects of air pollution on lung cancer.
Even if lung cancer rates are lower in the US than in China, it is possible that this is because fewer people smoke in public and has nothing to do with air pollution such as haze. (In fact, the US, Canada, Denmark, and several other developed countries with clean air have higher lung cancer rates than China)
Second, the “proof that the haze in China now causes cancer” is itself a false proposition.
The effect of haze or any environmental pollution on cancer must be chronic and long-term, and it is unlikely to have an immediate effect. For example, after the United States dropped the atomic bomb on Japan during World War II, a large number of surviving residents were exposed to severe nuclear radiation, which is a cancer-causing factor N times worse than haze. But even with such a strong cancer-causing factor, the concentrated outbreak of leukemia in victims came 5 years after exposure to radiation, and the outbreak of other cancer types came 10-15 years later!
To study the effect of haze on lung cancer in China now, we have to wait 10 to 20 years before we can draw conclusions.
So no matter what data are produced now, there is no scientific “direct proof” that the current haze causes cancer. If we think the increase in lung cancer in China in recent years is due to environmental factors, we should go back 10 to 20 years and see what other kinds of environmental pollution were happening in China at that time.
For both of these reasons, it is not strictly scientifically proven that the haze that now hangs over China can cause lung cancer.
Does haze cause lung cancer: gut feeling and science say yes
As you can see, the reason the link between haze and lung cancer has not been nailed down is purely due to the limitations of the research tools. That doesn’t mean we can’t scientifically analyze whether haze can cause cancer.
Pineapple’s take: Haze is definitely a pathogen and a carcinogen!
Why do I think haze causes cancer? On the one hand, the World Health Organization has come to this conclusion, and on the other hand, my own years of research into the pathogenesis of cancer support this conclusion.
At the end of 2013, the World Health Organization (WHO) came to the conclusion that air pollution causes cancer after compiling more than 1,000 studies from around the world, and also clearly classified airborne particles (including PM2.5) as a class 1 carcinogen.
Carcinogens are classified into four levels of severity: Level 1 “definite carcinogen,” Level 2 “probable carcinogen,” Level 3 “indeterminate carcinogen,” and Level 4 “unlikely carcinogen. and Level 4 “unlikely to cause cancer”. The classification of haze (PM2.5) as a Class I carcinogen is tantamount to saying that the World Health Organization believes there is sufficient evidence of a direct causal relationship between air pollution and cancer (lung cancer).
The World Health Organization also noted that in 2010 there were about 3.2 million deaths worldwide from air pollution, mostly from cardiovascular disease, of which 220,000 were expected to be from lung cancer, with more than half of the lung cancer deaths occurring in China and other Asian countries.
(Image from Station Cool Helo)
Haze can cause disease and cancer, a conclusion that has been agreed upon by a large number of experts at the World Health Organization.
As I explained earlier, some would argue that much of the WHO evidence is indirect and there is too little direct evidence. But even without the WHO report, Pineapple is flagging in favor of the theory that haze causes cancer (lung cancer). There are two big reasons for this scientifically.
First, haze contains cancer-causing chemicals. The composition of haze, or PM2.5, is very complex, and it varies from place to place, but it includes hundreds of different kinds of physicochemicals. Some of these are clearly linked to cancer, such as sulfur dioxide and nitrogen oxides. Inhaling large amounts of these compounds over time can lead to genetic mutations and increase the chances of lung cancer.
Second, fine particles in haze can cause long-term chronic lung damage and increase the chances of cancer. The root cause of cancer is genetic mutations. Removing congenital genetic factors, the probability of genetic mutations occurring is directly related to the number of cell divisions. The higher the number of cell divisions, the higher the chance of getting cancer, which is why it is mainly older people who get cancer.
With heavy air pollution, the various physical particles and chemicals that are inhaled can cause cellular damage in the lungs, even if you don’t consider the direct carcinogens in them. In order to repair this damage, lung cells then need to divide and proliferate even more. Thus, long-term air pollution can cause a repeated “damage-repair-damage-repair” cycle in the lungs, leading to massive cell division, which increases the probability of lung cancer.
The more haze particles are inhaled, the more harmful they are to the body. Children are outside, unprotected, breathing deeper and more often, and therefore are certainly the biggest victims. The adults do not do protection in the haze for long-distance running, square dancing and other strenuous sports, also taking life in fitness, is strongly not recommended.
Things that are scarier than haze
Haze must be cured, but eliminating it is not enough if only in terms of avoiding cancer, because haze is far from being a major factor in causing cancer.
According to a recent large-scale study, outdoor air pollution doesn’t even rank in the top 5 of factors that cause cancer, more so than it does: smoking (a distant second), alcohol consumption, lack of fruits and vegetables, obesity, and lack of exercise.
(Image from Station Cool Helo)
Maybe there’s nothing anyone can do about the haze, but there’s already a lot everyone can do to keep themselves and their families safe from cancer: quit smoking, quit drinking, eat more fruits and vegetables, exercise more, eat less high-salt and pickled foods, etc.
Smoking (including secondhand smoke), in particular, is N times more likely to cause lung cancer than haze, and frankly, what good is a cure for haze when there are still large numbers of people smoking in public places?
If you’ve read this far, you’ve been looking at your phone for too long, so get up and move around and eat a fruit.