Even before COVID-19 forced much of the world to wear masks for protection, people have always had a variety of opinions regarding air pollution masks, especially as COVID-19 vaccines begin to roll out and call the necessity of masks into question.

But with many affordable masks widely available, numerous public health agencies strongly recommend that you continue to wear an anti-pollution mask to help protect yourself from both air pollution and airborne infections.

Substantial evidence suggests that masks are highly effective against air pollution and in environments with a high risk of exposure to harmful airborne infections, such as shared office spaces, classrooms, and public places like grocery stores.

The question of which is the best pollution mask to wear, however, is just as important a decision as choosing to wear a mask to begin with. And not all pollution masks are equal – some are nearly useless against the most dangerous and harmful particles like PM2.5 and COVID-19 aerosols.

Here’s a guide to differentiating between the good, the bad, and the ineffective when it comes to air pollution masks.

Key features guiding evaluation

Here are the features that we used to evaluate the efficacy of our recommended air pollution masks, also known as air quality masks or smog masks.

Pollution filtration

Many protective face masks are given a rating of N90, N95, or N99. This common notation stands for the percentage of fine particles (down to 0.3 microns) that the mask has been tested to block.

An N95 pollution mask, for example, blocks against 95% of fine particles, N90 blocks against 90%, and so on. Other common standards include KN95 and FFP2, both of which are equivalent to the N95 standard for particles down to 0.3 microns.

If your goal is protection against particle pollution or airborne infectious aerosols, a KN95, FFP2, or N95 pollution mask should be your standard.

Mask seal

The key to any mask’s effectiveness is the seal. A good seal suctions the air quality mask to your face during inhalation.

For flexible, disposable masks, this suction should be visible, causing the paper to bend inwards and create a concave surface. For masks with a firm plastic construction, you should be able to prevent the inflow of air by covering filters with the palm of your hand.

Ventilation

An air quality mask should be breathable, creating a breathing space by resting far away from the face to help reduce the tightness or difficulty breathing that snug-fitting masks can produce. This is particularly important for air quality masks used during outdoor exercise or during long periods of use outside of medical environments, as filtration is a much more pressing concern than breathability in critical medical contexts.

For air pollution masks, directed outflow through exhaust valves can also help stop some masks from becoming moist with condensation from your breath.

Recommended features of good masks

The best air pollution masks filter up to 95% of airborne particles down to 0.3 microns using internationally recognized standards, including:

• N95: NIOSH-42CFR84 (United States)
• KN95: GB2626-2006 (China)
• FFP2: EN 149-2001 (Europe)

These masks are generally tested for 95% efficacy against the following airborne particles:

• PM10
• PM2.5
• bacteria
• viruses (both large droplets and tiny aerosols)
• pollen
• mold spores
• household dust

Along with filtration efficacy, a mask’s seal is arguably the most important element of an effective air quality mask.

A good air pollution mask uses high-quality sealing techniques with fabric or silicone that allow the mask to comfortably fit the contour of your face. This helps keep particles from leaking in or out of your air quality mask, helping protect you from airborne particles while also protecting others from any infected aerosols that you may breathe out.

Lastly, a tight fit is also critical. Adjustable, comfortable straps help make the seal around your nose and chin airtight, providing another layer of protection against leakage while also helping prevent pain or discomfort from tightened straps.

Not recommended

Though a wide variety of protective scarves, fabric masks, and cotton face coverings are available in supermarkets and convenience stores, take note of the quality before making a purchase.

Many scarves and fabric masks are made of cotton, polyester, rayon, and other materials that are effective mostly against large infected droplets from coughs and sneezes along with other measures like social distancing, but do very little to protect you from:

• tiny infected aerosols from breathing, talking, shouting, and singing that can float in the air for hours
• fine and coarse pollution particles between 0.3-10 microns that can leak in through gaps in the mask

Cotton masks also tend to have large gaps that the pollution filter cannot reach. Even common N95 paper masks often lack a method to tighten straps, while others lack a sturdy clip to create a tight seal around the nose.

Recommended for limited use

One-strap paper or ordinary surgical masks can help reduce transmission of large infected droplets as long as they’re used along with other protective measures, such as social distancing.

However, this type of mask is not an effective face mask for air pollution since it does not protect against coarse and fine pollution particles ranging from 0.3-10 microns in size.

In addition to poor air pollution filtration, these masks almost always have ineffective or non-existent seals, as air can flow freely in and out of the sides of the mask. As a result, these masks are not recommended for use against air pollution or infectious aerosols in the absence of other protective measures.

Furthermore, while N95 pollution masks and KN95 masks with exhaust valves can help with breathability and moisture reduction, these valves will emit exhaled respiratory aerosols when you breathe out.

This can also release infected respiratory aerosols into the air. Even if you’re asymptomatic or vaccinated against COVID-19, you can still spread infected particles this way. This can put those around you at greater risk for airborne infections.

Why wear a mask?

There’s no question about the incredibly detrimental health effects caused by fine particle pollution as well as airborne infections like the flu and the SARS-CoV-2 coronavirus responsible for COVID-19. Wearing an air pollution mask can help reduce these health effects significantly.

The World Health Organization (WHO) estimates that nearly 1 in 8 deaths worldwide can be attributed to air pollution (1). A report by Greenpeace Southeast Asia using IQAir data further estimated the human cost of air pollution at over 160,000 people in the world’s five biggest cities in 2020 alone (2).

Data from the COVID-19 pandemic has also illustrated how air pollution can make COVID-19 cases worse. A 2020 Harvard study found that the risk for severe or fatal COVID-19 symptoms went up by 8% for every rise in PM2.5 of 1 microgram per cubic meter (𝜇g/m3) (3).

Wearing a highly effective air pollution mask has been shown to help reduce the risk of exposure to PM2.5 and other airborne particulates, decreasing the chance of illness and death related to air pollution. A 2018 study in Beijing, China suggests that smog masks with filtration equivalent to N95, KN95, or FFP2 were most effective for filtering PM2.5 and diesel soot (4).

Wearing air quality maskshas also been proven effective for reducing transmission of airborne COVID-19. A 2020 study in Health Affairs found that statewide mask mandates in the United States prevented 200,000 cases of COVID-19 between March 31 and May 22 alone (5).

Another 2020 study in One Earth suggests that air quality masks equivalent to N95, KN95, and FFP2 help provide protection from both PM2.5 and COVID-19 aerosols(6).

What if I’m vaccinated?

Wear a mask even if you’ve received one or more doses of a COVID-19 vaccine, especially if you’re around others who have not been vaccinated (7). Consult your local or national public health guidelines for the latest recommendations on mask-wearing following vaccination.

A 2021 study in Nature Medicine suggests that antibodies resulting from COVID-19 illness or vaccination for specific SARS-CoV-2 variants may not be as effective against transmission of newer or untested variants, such as those that have emerged from the United Kingdom, South Africa, and Brazil (8) (9) (10).

Get vaccinated and continue wearing an air quality mask to help protect yourself as research uncovers the long-term efficacy of vaccination against SARS-CoV-2 variants. Until herd immunity to SARS-CoV-2 is achieved from global vaccination efforts, widespread COVID-19 illness and mortality is still possible across the world(11).

The takeaway

The best air pollution masks are rated N95, KN95, or FFP2 since they are the most effective against particle pollution and airborne infections, especially if the mask has a tight seal and adjustable straps.

Basic cotton or fabric face coverings are largely ineffective against both air pollution and airborne infections, but can still provide some protection against large infected droplets from coughs and sneezes when used with other measures like social distancing.

Paper and surgical masks are only recommended for protection against large droplets as well, not aerosols or particle pollution.

And even if you’re vaccinated against COVID-19, continue to wear an air quality mask, especially in public or around those who are unvaccinated.