The Mask’s the Thing

As I’ve been watching the images of the destruction by the earthquake and tsunami in Japan over the past several weeks, I’ve been struck by one common factor among the Japanese people as they struggle with the devastation and the damage to the nuclear power plant.  Many of the Japanese wear masks.  Exactly why, I can’t say for any individual person, but I suspect, generally, they’re afraid of breathing something, most likely radioactive dust or some other noxious particles, like bacteria or viruses that might cause a dread disease.  The real question behind the wearing of the masks is, do they really work?

The simple answer is, yes, they can.

But if you’re going to wear a mask, there are several factors you have to take into account before wearing it will really help you ward off disease or keep out harmful dust particles.  First, you have to wear the mask properly.  A mask that doesn’t fit well is as useless as no mask at all.  Second, and very important, all the air you breathe has to go through the fabric of the mask.  All of it.

One of the most common masks I’ve seen on the news images is the traditional rectangular mask, similar to the type worn by surgeons in an operating room.  It has two sets of straps that are tied, one behind the head and one behind the neck.   I’ll bet you’ve seen them too, they’re ubiquitous and they’ve been around for a long time.  Worn properly, they can work, but I’ve seen many people in news footage and in still photographs who simply strap one on and leave large gaps on each side.  In this situation, all the air they breathe is going in and out through those gaps, and the mask is useless.  Totally.  It’s not filtering out anything.  I know, because I’ve worn this type of mask, and unless it’s fitted to the face properly and tied tightly in both places at the back, it won’t work.  Remember, all the air–all of it–has to go through the matrix of the mask in order to be of any value whatsoever.

Another type of mask is roughly circular and usually has an elastic band that slips over your head to hold the mask in place.  Some have straps that slip over each ear.  Personally, I prefer this type.  It usually has a metal strip at the top of the mask that you pinch down tightly over the bridge of your nose to make it air tight.  These masks, in my experience, can work well.  If you want to wear a mask, wear this type, and make damn sure it’s air tight.  Remember, all the air…

Why would you want to wear a mask anyway?  Or, more to the point, why are the Japanese wearing them?  Are they getting any benefit from them?  I suspect they’re deluding themselves somewhat.  Masks have their limits.  A mask has to be made of some material that allows air to flow through easily enough to make breathing not only possible, but reasonably comfortable.  I’ve worn several different types of masks, and all of them, worn properly, restrict breathing to one degree or another.  I’ve never worn a mask for longer than a couple of hours at a time, and at the end of that time, I’ve always been glad to get the mask off.  Breathing though a mask requires more work than normal.  If there’s a person, Japanese or otherwise, who wears a mask all day, or at least as long as they are out of the house, and that can be eight or ten or more hours, then they’re probably not wearing the mask properly, and much of the air they breathe is probably not going through the mask itself.

It’s that restriction of breathing that is at the heart of the mask’s effectiveness.  The mask is a filter; it’s designed to remove certain things from the air, either when breathing in (inhalation) or out (exhalation).  Not usually both.  Surgeons wear a mask to prevent their germs from getting into the incision of the patient and contaminating the wound.  They’re not too concerned about inhalation.  But people, like the Japanese, who wear masks outdoors, are wearing them to prevent something from contaminating them.  They’re not worried about what they exhale.  I wore a mask when I visited AIDS patients, not to keep from getting AIDS, no, the other way around, to prevent my germs from infecting them.  But how effective are those masks?

A mask, regardless of type, has a limit on how small a particle it can filter out.  No mask can filter out everything.  For all masks, particles will exist that are too small to be removed.  Any mask that could remove all particles would be too tightly made to allow breathing at all.  There’s always a practical limit.  I’m not an expert on radioactive particles, but I suspect some particles could exist that are smaller than the ability of the mask to filter them.  I doubt that masks do much good there.  Even the best mask won’t stop a gaseous vapor of radioactive iodine or cesium or whatever.  For that you would need a very special mask, like a gas mask.

I do know a little about viruses and bacteria, though, and masks can be effective at removing these and preventing the transmission of disease.  Strictly speaking, viruses and bacteria are smaller than the filtering ability of most masks.  That may sound like the mask wouldn’t work, but that’s not all there is to the transmission of these agents.  Viruses, especially, have to be kept wet in order to stay alive and transmit disease, and a virus particle all by itself, even though it’s smaller than the mask can filter, is invariably dead and won’t cause disease.  When a virus gets dried out, it’s inactivated.  Viruses and bacteria are transmitted through the air in small droplets of fluid from the nose or mouth, droplets that are much bigger than the microbe they carry.  In fact, there can be thousands or even millions of viruses in one droplet.  (That’s no exaggeration.)  These droplets are what you have to worry about, and this is how some diseases (mainly respiratory diseases like colds and flu) are transmitted.  But masks are designed to filter these small droplets (many of which are too small to see, even though they can hold lots of virus particles), and worn properly, the mask can work.

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