When fog and haze come, do you need to wear masks in indoor or outdoor environments? The first thing to judge is the severity of smog. The outdoor haze can be seen as it is. The indoor haze is not easy to judge and can easily be overlooked. The determination of haze depends on the sense system such as the sense of smell. This is because the sensory system of the human body generally feels the size of the difference. It is a relative value, not an absolute value. The ancients said, 'Into the room of the Chilan, long-lost smell of incense, into the abalone's ignorance, long-lost smell of smell' is the reason. If you think that there is no smell in an environment, you think that there is no smog. That is to put yourself in danger.

The contradiction in the picture is self-evident, and the first agency's proposal is that the weather is so good today that you can fly vigorously. The second agency’s proposal was ill and told you to wear a mask. Such examples are common. These two pictures were collected by me at ordinary times. Although the conclusions given by different institutions are different, the PM2.5 readings are very close, indicating that there are no problems in the data. Why do the same numbers lead to very different conclusions?

The main reason is that the standards are different. Different countries and regions use different health standards. The WHO's standard continuous 24-hour exposure limit is 25 micrograms/cubic meter, while our country's standard is 75 micrograms/cubic meter. So a reading of 50-70, a standard-derived conclusion is unhealthy, and a standard-derived conclusion is excellent. If you don't like numbers and only like conclusions, then God knows if you should wear a mask today. Why is China's standard three times the World Health Organization? Why not double, double, or five times? The decision process did not understand, but it happened to triple the data relationship, indicating that the standard may not be derived from experimental data.

So does the triple mean three times the risk? Does it mean that the cost of human sacrifice is three times? the answer is negative. The health effects of smog concentrations are obvious. The author is not engaged in pathology, there are many reports on the mechanism of the impact of related fine particles on health. Unlike PM10, PM2.5 such as nature is actually very small in concentration, and most of PM2.5 is produced by a variety of artificial combustion. Therefore, the human body may not have evolved corresponding resistance mechanisms.

Everyone may also have seen from media reports that both the International Agency for Research on Cancer and the World Health Organization (WHO) listed PM2.5 as a type of carcinogen. However, the two agencies did not provide quantitative indicators of haze concentration and disease. Let us first look at several recent studies.

In recent years abroad, large-scale studies have been organized to try to quantify the relationship between PM2.5 concentrations and the incidence of lung cancer. One of them is a study made by the EU in 2013. 17 teams from 9 countries in the European Union investigated 310,000 individual samples. According to a database of 4 million person-years and a total of 2,095 lung cancer samples, it was concluded that the concentration of PM2.5 increased by 10 μg/m3. The incidence of lung cancer increased by 36% [1].

According to this study, we have to calculate how the PM2.5 concentration changes from 25 micrograms/cubic meter to 75 micrograms/cubic meter.

The answer is 18 times.

If you are exposed to an environment where the concentration of PM2.5 is 75 μg/m3, the incidence of lung cancer is one, which means that it is 18 times higher than the environment exposed to 25 μg/m3. That is, the incidence of your lung cancer has increased by 18 times when you think that you have good and healthy weather. Of course, the EU study may not involve such a high concentration of 75, may be only 10-20 micrograms / cubic meter concentration difference study, so the 18-fold conclusion remains to be explored. However, no matter what the concentration of 75 micrograms/cubic meter is not good. This is just lung cancer. We do not consider other respiratory and cardiovascular diseases for the time being. And this is the case when the PM2.5 concentration reaches our country's health standard. In fact, recently, the concentration of PM2.5 in some cities in our country is often an ultra-high concentration of 200-500, and the indoor haze concentration is approximately 0.5-0.9 outside. The long-term exposure to such environment does not affect health. How much do you know?

In a recent similar study, the other one is the conclusion in 2014 that 18 research teams from the world and comprehensive research from various countries concluded that the concentration of PM2.5 increased by 10 micrograms/cubic meter and the incidence of lung cancer increased by 9%[ 2]. This study is weaker than the EU's findings above, but it is at an order of magnitude. Overall, the concentration of PM2.5 increases by 10 μg/m3 and the incidence of lung cancer increases by 9-30%.

These findings tell us that the concentration of PM2.5 is significantly sensitive to health effects, with an order of magnitude between 5-10 μg/m3. Our recent measured concentrations are often on the order of 100 μg/m3. With an increase of one order of magnitude, the impact on health will only be bigger and not smaller.

If you think our people have evolved different physiques, then look at the studies of our neighbors Thailand and Mongolia. In 2008, Thailand concluded that for every 10 micrograms/cubic meter of PM2.5 concentration, cardiovascular mortality increased by 1.9% and the risk of other diseases increased by 1%. After a series of measures such as the use of natural gas vehicles in Bangkok, when the PM2.5 was reduced from 65 to 52 μg/m3, the incidence of these diseases was significantly improved. In 2014, Mongolia concluded that respiratory disease has increased by 45% over the past five years.

The recent haze is frequent, and the public's attitude towards haze also turns from anger to ridicule and cynicism. When faced with difficulties and problems, people usually respond with anger and complaints, complaining about the Ministry of Environmental Protection, complaining about coal-fired power generation, complaining about farmers burning straw, complaining about loose coal, complaining about SUVs, complaining about unreasonable urban planning, and not complaining about themselves. Although these complaints are reasonable, they cannot understand the urgency. In fact, smog does not have to complain, do not have to wait, only need to hold their own serious attitude, make efforts to improve the home office environment, you can remove 90% of the harm of haze on your health.

To sum up, in the hazy weather, if you do not take any purification protection measures inside the room, it is extremely dangerous thing. Wear a mask, do not wear a mask, it is best to believe in numbers, do not believe that others help you to make the conclusion. If you don't improve the indoor environment, you may need to wear a N95 mask in both hazy and hot weather, both indoor and outdoor.

Friends living in the north, haze in this 'to visit', I hope everyone is ready!

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