Can the mask resist the smog?

Is the protective mask really effective? Considering that China’s former Minister of Health Chen Hao and the researcher of the Environmental Planning Institute of the Ministry of Environmental Protection, Wang Jinnan and others published in the review article of the December 13 issue of The Lancet, the number of people who died early in China due to air pollution reached 350,000-500,000. The meaning of the mask is especially prominent. In the winter of 2013, serious pollution first began to invade from Harbin and has recently spread to Shanghai and eastern China. During that time, I happened to take a train from Shanghai to Beijing. I felt very confused when we galloped between the city and the country and watched them disappear in the mist.

PM2.5 N95 masks Such incidents as the masks, as well as the “end of the air” in Beijing on January 2013, have significantly increased public awareness of air pollution in China, and the discussion has proliferated. A large number of anti-pollution products in online stores are emerging; in the chat topic of the Internet and cafes, comments on the use of masks are full. Now, even in convenience stores like the 7-11, you can see a large counter with a protective mask with N95, 99% or similar eye-catching labels.

Let's take a step back from this marketing hype – is there any evidence that these masks are really effective? This issue is of paramount importance to me and my family, to hundreds of patients, and to readers who have asked me this question for years.

I usually tell everyone this way: Yes, there is evidence to prove its effectiveness - to some extent.

It has been medically confirmed that small particles (called PM2.5) of less than 2.5 microns can cause severe inflammatory reactions leading to heart disease, lung disease and cancer. Many studies have also shown encouraging results – reducing air pollution in one area can help improve the health of community members, reduce the number of emergency visits, and reduce the total number of deaths. Reducing contact with polluted air can improve health: yes, this seems to be obvious, but scientific research is often filled with hypotheses that prove to be wrong afterwards, so we need to further reflect on previous research.

Let's go back to the mask. Construction sites around the world are filled with dust, heavy metals and dangerous gases. For decades, construction workers have relied on masks made by companies like 3M, and independent lab tests have shown that these masks have a filtration efficiency of at least 95% for inhaled air. This is exactly what we mean by the term N95: the N95 mask, if it passes the official certification of the National Institute for Occupational Safety and Health (NIOSH), it has already passed through the face. test. In this test, a person wears a mask for about 15 minutes. The person wearing the mask should move in many positions. The mask is attached to a special machine to record the particle concentration inside and outside the mask. If the amount of particles in the air inside the mask exceeds 95%, the mask passes the N95 test. Many masks have received this certificate, and given this, I can be sure that these masks can greatly reduce our exposure to the most dangerous PM0.3-PM2.5 particles in air pollution.

The main problem is that we are too sloppy when we move to the next level of assumptions: by wearing these masks, you can improve your health. Yes, this sounds logical again, but so far, no research has been done on tracking these mask users – tracking them for months and years, testing their breathing and determining what improvements are being made. In the absence of sufficient data, the best data we can get from two short-term studies of the same research team, the subjects of which are pedestrians walking on the streets of Beijing. In August 2008, these researchers from Cambridge and Beijing recruited 15 young volunteers from Beijing Fuwai Hospital. These volunteers did not smoke, took any medication, and had no previous medical history. The experimental team randomly divided them into two groups and let them walk for 2 hours on the secondary road of the Second Ring Road. As we all know, the Second Ring Road is one of the many heavily congested roads in Beijing, so it is filled with various pollutants such as automobile exhaust. When wearing the 3M 8812 mask, their blood pressure improved greatly. The systolic blood pressure of the mask group was 7 mm Hg lower than that of the control group, and the increase in systolic blood pressure caused by exercise was positively correlated with the disease. The study was published in the 6th issue of Particle and Fibre Toxicology, 2009.

But as a family doctor, the team's follow-up study published in the Environmental Health Perspectives in 2012 is more informative. This time they tested people who already had heart disease. They were stable but were taking medication. This test was conducted by nearly 100 people who used the same 3M mask for more than 24 hours of a test period and did not use a mask for another test period of more than 24 hours. When wearing a mask, their heart rate variability, blood pressure, and ischemic stress markers were improved, such as an average reduction in systolic blood pressure of 3 mm Hg when wearing a mask. All of these are considered to be factors in cardiovascular disease such as myocardial infarction and stroke, so any improvement in this objective data will have a large positive impact.

Why is this so important? Because air pollution does not only cause lung problems, it also causes myocardial infarction, chest pain and stroke. I am most worried about children, as well as older people with heart disease, and the study proves that using masks in extreme pollution can prevent the onset of myocardial infarction, so it can really save lives.

This research is also flawed. They admitted that the control group did not wear a "comfort" mask, and some of the reported effects may be caused by psychological effects, because the subject may be more relaxed when wearing a mask. But these are the best studies about masks we can find right now, and of course, I won't wait for better research. I am very convinced that the underlying principles are quite powerful and proven: reducing exposure to polluted air can improve health. And we have learned from decades of construction work that N95-rated masks are specifically designed to reduce the inhalation of PM2.5, and such atmospheric particles are considered to be the most harmful of many harmful chemicals in the air. of.

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