UPDATE: This article is old, from 2009; I have an updated article here from 2013 with a review of the best research as well as a review of three independent comparison tests of masks.
I get a lot of questions from expats, especially bikers and people walking to work, who wonder whether any type of mask is helpful. I also bike to work so I was curious as well. We’ve talked a lot about N95 masks for the flu, but how well do they work for pollution?
I previously discussed a fascinating small study done here in Beijing, with subjects walking along second ring road wearing masks. They had researched common masks and decided on the 3M company’s 8812 mask as the best for the study, which is N95 rated and also has an exhalation valve to help breathing and prevent fogging of eyeglasses. They compared this to other masks and decided that the 8812 was the best option for this test due to effectiveness, price and comfort. Here again is the graph:
The “N95” literally means that 95% of fine particles are blocked by this mask. Note that the 8812’s effectiveness in blocking particles over PM0.5 was over 96%; note also that this was far better than all 4 tested cycling masks, as well as the simple cloth masks we now see all over Beijing. Unfortunately, they did not specify which brand of cycling mask was tested. Also of note is that the simple cloth masks that are popular now in the winter (kouzhao 口罩) are minimally effective against fine particulates, only blocking 28%.
The 3M company is highly regarded as making professional-grade safety products, and they have a big line of dust respirators geared mostly for construction teams. I couldn’t find this 8812 locally, so I used Taobao and had a few boxes delivered from southern China.
I bike to work and back, so in the mornings and evenings I will check the website iphone.bjair.info to see the hourly-updated air quality at the US Embassy, only a couple hundred meters from me and therefore highly relevant. If the AQI is high (anything over 200) I will definitely use the mask on the way to and from work. Since it is at least 95% effective, that means that the most air-toxic days with AQI of 500 would bring my exposure down to 0.05% of that, or 25, which is considered safe by the WHO. So, indeed, these masks can work very well against fine particulates, the most serious pollutant. Yes, I get some looks but that’s a small price to pay for breathing better. At least in the winter it is less noticeable as most everyone is wearing some type of face mask (kouzhao) as a warmer. Today, I just bought a simple black kouzhao for 3RMB on the street and will try to wear it over the N95.
The Bottom Line
I’m very comfortable with the 8812’s effectiveness against air pollution. As for comfort, the yellow straps are fairly comfortable and the foam-lined mask is very comfortable. Plus, my eyeglasses do not fog up, a big problem with the regular N95 masks I previously used. And as for aesthetics, I do wish it were a bit snazzy and may get self-conscious in the spring and summer, but again, the health benefits far outweigh any loss of coolness.
What about other pollutants? Yes, it’s true, there are vapors, ozone, nitric oxides and others which may not be blocked by this mask. But fine particulates have the most evidence regarding long-term and short-term health risks, and are considered the most serious risk by the WHO.
What does everyone think?
I’d be very interested in having people write comments below as to what, if anything, they use, and when they decide to use it.
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