I am testing air for Beijing.

As a foreigner, I feel that I have a certain degree of freedom to do something weird. One of my favourite weird activities is to go to the streets, suburbs and mountains of Beijing to measure the level of air pollution there. I came to Beijing the year before the 2008 Beijing Olympics, and since then, I have been interested in air pollution (or is it fascinated?). Sometimes, I also borrow a handheld particle monitor from an air purifier brand team. It should be noted that this handheld monitor measures the index of PM0.3 in the air. This kind of particle is more common than PM10. It is smaller than PM2.5, but it can also be used as reference data for air pollution.

On weekends, my wife and I would drive around Beijing. I used one hand to drive the car. I used the other hand to extend the tiny nozzle of the particle detector out of the window and let it smell the air like a dog. Sometimes, I will ride a bicycle through the streets of Beijing, stop from time to time, then take out this large device from the bag, monitor the level of particles in the air, and record it in the notebook. People passing by will be very polite to avoid contact with me. But this is not necessary, because I usually wear air-proof masks and bicycle helmets; as early as a few years ago, both of them were rare on the streets of Beijing (unfortunately, helmets are still rare).

During these adventures, I recorded many details about air pollution, and this data really surprised me. From 2009 to 2011, I conducted three, one-week tests every time in Beijing. I have found that air quality has remained almost constant. One of the most disappointing discoveries was the air condition in the beautiful mountains of the Jingxi Gunsan Temple. My expectation is of course that the air in the mountains is cleaner than the "yellow fog" in Beijing. Isn’t the mountain scenic spot a place away from troubles? Unfortunately, the air pollution values ​​there are no different from the values ​​in Beijing's urban area and are equally disappointingly high - according to news reports, one of the reasons may be the burning of fallen leaves. After the official website, zx.bjmemc.com.cn went online at the end of last year, I will also go to see the air quality map above. Based on my observations over the past few months, I noticed that the official data is the same as my current measurement: the PM2.5 level of the suburban air monitoring station is almost the same as that of the urban area, but in the windy or sunny weather, the suburban air Quality is usually better. Throughout the year, especially on hot summer days, people still like to go out and climb, but we don't expect the sky there to be bluer.

In addition, I also spent a lot of “geeks” to monitor PM2.5 data in various shopping malls and streets in Beijing. One surprising finding is that the PM2.5 level of a bustling street is not much different from a secluded alley. I often read in the paper that there is a peak of pollution in a section within 150 meters from a busy street. This situation has been confirmed in London studies, but in Beijing, from the loop to the tree-lined avenue on the bank of the canal, I Air quality has never been found to increase by more than 10%. I guess this is because my handheld monitor only measures PM0.3, a pollutant, and if you add carbon monoxide, nitrogen dioxide and other pollutant data that is more common in urban main roads, the result may not be the case. In addition, a study by the Swiss Tropical and Public Health Institute in Los Angeles County, California found that people living within 75 meters of busy streets have major diseases such as adult heart disease and childhood asthma. The incidence rate is much higher. So, I think this general rule still applies: avoid strenuous exercise, cycling or walking on busy streets.

And if you have to go to or along these main streets, be sure to consider wearing a regular N95 respirator. In Beijing, the University of Edinburgh and the Union Medical University conducted research. They recruited 15 healthy young people to participate in the trial in August 2008. The subjects were between 8 am and 10 am, along the second. The loop and other busy streets walk for two hours and monitor their breathing, heart rate and blood pressure. You can imagine their image: carrying a huge bag, various antennas stretched out, and wearing a mask! But the good news is that when they wear a mask (3M N95 respirator), their blood pressure and heart rate variability are reduced. This study can be said to provide the most powerful evidence at the moment that a suitable N95 mask will indeed protect you.

Another monitoring that I was very disappointed during the monitoring period was that in the case of very serious pollution (ie, when the air quality index exceeded 300), the indoor air was almost as dangerous as the outdoor air in most shops and restaurants. I found that indoor air pollution is usually 50%-80% of outdoor. In Xi'an, Xi'an Jiaotong University and other units in the three offices and outdoor sampling in 2008, the results show that indoor and outdoor particulate matter concentration has the same trend, the ratio of PM2.5 to outdoor in three rooms were 79.7%, 50.1%, 83.0%. But keep in mind that this is an environment where the air quality index is over 300, so indoor air is also very unhealthy. What surprised me the most was that one day I went to the most famous imported bookstore in Beijing and found that the indoor air there was even worse than the outdoors! It seems that literature can't escape reality. I think the reason for this may be indoor smoking, and some research reports support my guess about smoking indoor air. Fortunately, the bookstore completely banned indoor smoking shortly thereafter. In China, every move of a company is not a trivial matter. I very much hope that other companies can follow it as an example.

Also on that day (that was a terrible day, the air quality index exceeded 400, reaching a "very dangerous" level), I found that the PM2.5 level in a store and building in the "Green Zone" was safe. of. The Sanlitun Village shopping mall is particularly serious, and the air in each store is very bad. Those open doors and open-air corridors inflicted on my lungs and also violated the health of shop employees.

On this day, I think the best place is my own home, especially the bedroom. For most adults, a lot of time is spent indoors, and in our lives, one-third of the time is sleeping; therefore, installing air purifiers in the bedroom to protect the family is a matter of course. It is. Turn on the purifier, close the door, and go to sleep. Hey! In this case, in China, one-third of the time is free from pollution. My life is not based on imagination; when I purchased the air purifier, I personally compared the performance of multiple brand products. Close the bedroom door and open a purifier. After two hours, the indoor PM2.5 level is reduced by 95%-99% compared with the outdoor. This is still the result of the mute setting; for many other machines, this is not an easy task. I am now used to their buzz and see it as white noise that is relaxed and protected.

This is an adventure that a person is addicted to in Beijing. Although a lot of my data will be worrying, I still think that these solid data will give people some peace of mind. At least, I now know how bad the situation is, and I know how much I can improve.

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