Leslie, Vireo’s Admin, has been sewing cloth masks for her friends and loved ones. She asked during our quarantini gathering yesterday, how do I tell people my mask won’t protect them from coronavirus? It’s a great question. The short answer is, Cloth face coverings are not, “intended to protect the wearer, but rather prevent the wearer from unknowingly spreading the disease when in public.” Here is my view on this, as an Environmental Health Scientist and expert in nanoparticle safety (Yes, viruses are nanoparticles!). This is not medical advice, but as an expert in risk analysis, I wanted to share my perspective, because there is so much information out there, and it creates confusion. I tend to follow the advice of trusted public health resources like the US CDC or WHO.

WHEN?

It is confusing, because the US Center for Disease Control (CDC) now recommends people wear masks in public, in case they have no symptoms, but are carrying and unknowingly spreading infection, while the World Health Organization (WHO) says you only need to wear a mask if you are taking care of a person with suspected coronavirus infection.

While wearing a cloth mask can reduce your exposure to large particles by trapping them, cloth masks are worn mainly to protect people around you, in case you 1) are in public, 2) may have the virus, but 3) do not have symptoms. Some people need to take more careful precautions, such as people with lung diseases, immunocompromised, or with underlying illnesses. Researchers think up to half of the people with the virus have no symptoms. That’s where covering your mouth and nose really helps. You could be one of those people who is carrying the virus but not showing any symptoms.

The coronavirus may be transmitted by breathing in droplets from other people. So, if you cough or sneeze, the little droplets you spray in the air can be inhaled by other people. That’s why being at least 6 feet apart is important. Most of the droplets will fall to the ground before 6 feet. But, it might just be that when you talk you are releasing little bits of droplets. So, if you are in public, and in a grocery store, or at work, wearing a mask reduces the chances that you will give off aerosols to the people around you. If you don’t believe me, try tying a scarf over your mouth and talking. It will get wet pretty fast.

When you are physical distancing AND staying six feet apart, you don’t really need a mask, if you are outdoors. Except, if you are 1) coughing, or 2) running. In these cases, you can be spreading particles into the air much more than 6 feet away.

When you go to places where you interact with other people, first, those are places you should be avoiding right now, but you can’t always. You may have to go to work, or need groceries, a trip to the bank or a pharmacy, or you are taking a walk in a crowded area. That’s when the CDC wants you to wear cloth over your nose and mouth. Children under the age of 2 and people experiencing trouble breathing would be excluded from the mask guidelines, because masks can hinder proper breathing.

The basic tenet from the field of toxicology is, “the dose makes the poison.” That is true of COVID-19 too. Wearing even cloth over your mouth reduces your dose and your risk of infection, by reducing your exposure, and exposure to the people around you. For most of us, that’s all we need. Being home, and able to physically distance means even if we are exposed, it is to a very low dose. People on the front lines in health care are the ones with the highest exposures – from patients coughing or sneezing, from performing medical procedures, from direct contact with infected people, in ambulances, emergency rooms, hospitals. These people need more protection, because of the close contact with people with the virus, all day, every day. So while cloth masks are not as efficient as higher-grade protective equipment like N95 masks, CDC and other experts are asking us to reserve their use for hospitals and health care workers, who have faced severe shortages in personal protective equipment as the coronavirus pandemic has accelerated through the United States. Also, medical professionals are trained in wearing N95 masks. They won’t protect you if you don’t wear them correctly.

In between are people who deal with the public (bus drivers, grocery store workers, package deliverers). Cloth masks may help reduce their exposure, again, if worn properly, consistently, and the masks are clean and not touched. Most likely, casual exposure like being in a grocery store for 30 minutes does not require an N95 mask.

HOW?

The whole point of wearing a mask is to stop big particles from leaving (or entering) your nose and mouth. Only covering your mouth makes no sense. Be careful to only touch the edges or ties of the mask, not the part in contact with your face, or the front part. Masks need to be cleaned in between wearing them (or discarded). Wash your hands before putting a mask on, and avoid touching your face when wearing a mask. Soap and water, or a washing machine are sufficient to clean cloth masks.

Having more than one layer of fabric increases the ability to capture particles, some people put filter paper, like a layer or two of a vacuum bag, or a coffee filter, in between. But, make sure you can breathe, or you’ll just take it off!

Here are some recommendations from the World Health Organization:

Keep your mask clean. Wash your hands before wearing it. If you touch your mask, WASH YOUR HANDS before you touch anything else. After you wear it, make sure to wash it with warm water and soap, and dry it before you use it again. Learn how to properly put on, wear, and take off a face mask. There are many good resources out there for how to make masks, so I am not sharing any.