Are anti-pollution masks effective?

Question

In Toronto when the temperature goes above 30 degrees Celcius (90 degrees Farenheit), for a few days and without wind, there is smog.

I find the smog irritates and makes it difficult to breathe in through my nose. Worse, if I breathe in though my mouth instead of my nose then it hurts my bronchial tubes.

A related question is, Is pollution a problem in urban cycling? - which says that it is a problem, but doesn't ask whether a mask or other anti-pollution measure is effective.

Might a mask help me for this situation, i.e. breathing on the hottest days? Are they effective and are they usable? If so what type or brands or models should I look for?

Answer 1

I get this question once in a while (working in Danish Cyclist Federation). It seems to be based on the idea that commuting by bike will expose you to more pollution than commuting by car. I have seen no research that proves this. However, I have seen research indicating that the opposite might be true. Some was in danish, but here's some in english and french (links to pdf's at the end of this article): http://www.pollution-china.com/Blog/More-exposed-to-pollution-in-a-car.html

You should also consider the possible danger of wearing a mask while being physically active. There has been little research in this field that I'm aware of but there could be a risk of creating negative pressure by obstructing the airway which has been known in some cases to produce pulmonary edema. We (again Danish Cyclist Federation) sent some masks to some danish specialists who concluded that the risk was very small, but since pulmonary edema is a very serious thing, I still want to lead your attention to this. Maybe you can find some research (I would be interested to hear about it).

Also keep in mind that if the research on "in-car pollution" vs "on-bike pollution" cited above is true it is much more important for car drivers to consider wearing a mask than it is for bicycle commuters.

On top of this comes all the additional beneficial factors that bike commuting produces.

Happy cycling.

Answer 2

To answer this question (which is different from asking "Which mask?") you have to define what "pollution" means and then examine the available masks to see if they do anything to reduce it.

Just offhand, I believe that "pollution", in an urban traffic setting, consists of carbon dioxide, carbon monoxide, sulfur dioxide (and various other sulfur compounds), nitric/nitrous oxide (and various other nitrogen compounds), and soot (which contains a significant amount of unburned hydrocarbons). (Lead used to be a significant component of exhaust but is no longer, with unleaded gasoline.) Of these, only the soot is really "visible", while the sulfur and nitrogen compounds can contribute to "yellow haze".

A simple filter mask will remove only the soot (if that). You need a mask containing at least a reasonable layer of activated charcoal (ie, a canister) to remove much of the others. The masks I see advertised just have a thin layer of "activated charcoal cloth" or some such, not enough to make a noticeable difference.

I was unable to find any evidence of rigorous testing of these masks anywhere -- by the manufacturers or independent bodies. They do test for particulate filtering, but that's of minimal value, and, besides, you can buy (much) cheaper particulate filters if you skip the "pollution" moniker.

Answer 3

I know of at least one peer-reviewed article which shows that wearing a (proper) filtering facemask does have noticeable effects on one's vital signs compared to when not wearing a facemask.

However, some people still say that they make very little difference in terms of long-term health effects. Moreover, the actual quality of the "filtering" of masks varies wildly — Each has different tests done on it by different companies... and even on different parts of the mask: Some certify the filters themselves but don't have a certification for how much air goes through the filters as opposed to past the sides of the mask (and is therefore unfiltered).

Finally, although it is merely a personal anecdote, for about a year I commuted on a heavily-trafficked route and would have a runny nose and a scratchy throat when I arrived at my destination. I then ordered a mask from totobobo and saw that the filters were indeed getting visibly dirty over little time, so something must be happening. I also noticed less nose-running and throat stratchiness — but this could just as easily have been a placebo effect, a random change in average pollution levels or a number of other confounding variables.

So, I'd tentatively say that yes, a good facemask can be (somewhat) effective at reducing the amount of particulates and other pollution a cyclist inhales while travelling through heavily-polluted areas. Whether the amount it is reduced by is enough to make a significant health difference, I can't say. However, when riding on especially heavily-trafficked roads for a longer period of time (either on a pushbike or a motorbike), I do still get out the mask, 'cuz I'm paranoid like that.