Face masks revisited

Two weeks ago I was on vacation in New York. The city is bursting with beautiful places and impressive sights, but one thing immediately struck me: the number of people who were still wearing a face mask. In the metro, in museums, in theaters and even on the street or in the park. Young and old, mothers with prams. It seemed to affect everyone. In the Netherlands you can usually recognize a tourist by wearing a face mask, but in New York ordinary New Yorkers walked around with them. In one theater, even all the staff wore masks, as if it were mandatory.

It actually makes sense why face masks are still so popular in New York. The city votes predominantly Democratic, and during the corona period, face masks acquired a clear political connotation. By wearing a mask, you not only showed that you wanted to protect your fellow man, but also that you had confidence in science. Deviating ideas came mainly from Republicans. Anyone who wanted to “appear” as a Democrat faithfully wore a face mask. That willingness to wear a mask has been huge in New York during the pandemic.

But those who have been told for years that a face mask is necessary because "science" says so, often stick to it even after the pandemic. Because why would you check what the scientific basis actually was?

During conversations with Americans, I noticed that many people are still not well informed about the scientific facts surrounding face masks. This probably also applies to many Europeans outside the Netherlands. In the Netherlands, propaganda about face masks during the corona period was relatively limited compared to other countries. Because I had studied this subject extensively at the time, I thought it would be useful to refresh my knowledge and write it down.

So here we go: an overview of the scientific evidence surrounding the wearing of face masks by the public as protection against respiratory viruses.

1. What the evidence showed before COVID

Before 2020, decades of randomized controlled trials of influenza and other respiratory viruses consistently found that the use of face masks in community settings provided little to no measurable benefit. These were randomized controlled trials (RCTs), high-quality studies and the type of evidence considered the gold standard.

That's why health authorities worldwide (including Fauci in the US) advised against wearing face masks in public at the beginning of the pandemic. That recommendation was not arbitrary, but consistent with the best available evidence.

2. What changed during the pandemic

However, at the end of March 2020, public reporting changed drastically. Suddenly, the use of face masks was presented as the means to combat the pandemic, including the adage “my mask protects you, your mask protects me” to enforce compliance. However, the scientific basis had not changed at that time.

From then on, a wave of observational studies appeared, many of which were extensively reported in the media. Observational studies can be useful, but they are also very sensitive to confounding factors: ventilation, crowding, compliance and behavior all influence the results. Several high-profile examples, including the CDC study of two hairdressers¹The Face Masked Hairdressers (CDC): https://www.cdc.gov/mmwr/volumes/69/wr/mm6928e2.htm, were used to support wearing face masks, even though the data was far too weak to draw those conclusions. The CDC study itself actually made a strong argument for good ventilation, which is present in hair salons because of the chemicals they use, and is known to greatly reduce the risk of infection with respiratory diseases (which is why the risk of these types of infections while walking outside, even in very busy areas, is zero). Instead, they chose to focus on mask use, indicating how eager they were to find scientific support for their new direction.

When randomized trials were conducted during COVID, results were mixed or did not show a statistically significant benefit. The large Danish study by Bundgaard et al. ²Effectiveness of Adding a Mask Recommendation…: Bundgaard et al. is an example of that. Another major study in Bangladesh³The Impact of Community Masking on COVID‑19 https://www.science.org/doi/10.1126/science.abi9069 initially suggested a modest reduction, but was later reanalyzed and found to have methodological problems⁴Reanalysis Bangla Desh Study: https://trialsjournal.biomedcentral.com/articles/10.1186/s13063-022-06704-z. Adjusted, this study also found no statistically significant benefit.

3. The 2023 Cochrane Review

In 2023, the Cochrane Institute published an update to their paper “Physical interventions to interrupt or reduce the spread of respiratory viruses”⁵Physical interventions to interrupt or reduce the spread of respiratory viruses:https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/epdf/full. This review of physical interventions summarized all available high-quality evidence to date.

The Cochrane Collaboration is recognized worldwide as one of the most reliable sources for solid and well-researched evidence. What makes Cochrane so special is its strict methodology, transparency and commitment to avoiding bias as much as possible. Their systematic reviews are often used to guide everything from clinical guidelines to health policy and research choices. Because these reviews are updated regularly, the recommendations are always based on the most recent and reliable data. In this way, Cochrane helps doctors, researchers and policy makers to make decisions that are truly based on evidence and contributes to better healthcare worldwide.

Their conclusion in the article was that all the new scientific research into the use of face masks had not led to a different recommendation than previous updates: wearing face masks in society has not provided a clear or consistent benefit in reducing the spread of respiratory viruses.

That conclusion was not really a surprise, but since many health organizations and scientists had invested heavily in the new face mask policy, the criticism was as fierce as it was predictable. The political pressure was so great that the editor-in-chief of Cochrane, without consulting the authors of the review, felt the need to publicly state that the review did not mean that face masks do not work. This was condemned by the scientific community as it indicated a lack of scientific integrity. The lead authors themselves, Tom Jefferson and Carl Heneghan, explained in a public interview that their review well meant that the policy recommending the use of face masks by the public as a means of treating respiratory diseases was not scientifically based⁶Interview with Jefferson and Heneghan:https://www.youtube.com/watch?v=P_JTBftjQuA.

4. Why doctors and nurses wear face masks

There is also confusion about medical environments.

Surgical face masks are mainly used to:

• to prevent bacteria from the mouth/nose of a doctor or nurse from entering wounds
• protect doctors and nurses from splashes of bodily fluids

They are not used to prevent the transmission of viruses through the air.

For airborne viruses, healthcare workers rely on N95/FFP2/FFP3 respirators, which must be tested for fit (not leaking through the edges) and used under controlled conditions. If there is even the smallest leak, the filtering will not work as intended. These conditions do not apply to use outside controlled environments, making these masks no better than surgical masks when used by the public.

5. Disadvantages and risks

Every intervention has potential advantages and disadvantages, including face masks.

Effects on the wearer

Research shows that:

• Long-term use of respirators can affect breathing comfort and measurable physiological parameters⁷Effects of surgical and FFP2/N95 face masks… https://link.springer.com/article/10.1007/s00392-020-01704-y
• some disposable masks release micro- or nanoparticles, which have been linked to damage to lung tissue. Also by the RIVM⁸Nanomaterials in face masks: https://www.rivm.nl/nanotechnologie/consumentenproducten/Zijn-niet-medische-mondkapjes-met-nanomaterialen-veilig ⁹Face masks and chemical safety: https://www.rivm.nl/publicaties/chemische-veiligheid-mondkapjes
• prolonged use and reuse of masks is associated with higher bacterial contamination¹⁰Effects of surgical and FFP2/N95 face masks: https://link.springer.com/article/10.1007/s00392-020-01704-y

Effects on interactions

Masks can affect communication, especially:

• young children who rely on facial expressions. The use of masks by caregivers hinders the development of these children¹¹The effect of face mask wearing on language processing… https://pmc.ncbi.nlm.nih.gov/articles/PMC9637007/
• people with dementia who need facial reassurance. The use of masks by caregivers has led to frightening situations for people with dementia and problems with face-to-face therapies.

This was widely recognized even during the pandemic, although often downplayed.

Environmental consequences

This is an area where the evidence is very clear: disposable masks have caused significant environmental pollution, including microplastic pollution. Examples:

• Used disposable masks are a major source of microplastics in the environment¹²Chen et al.: Used disposable face masks are significant sources of microplastics to environment https://pubmed.ncbi.nlm.nih.gov/34087638/
• Disposable masks release microplastics into the aquatic environment, which is further enhanced by natural weathering¹³Mater: Disposable masks release microplastics… https://pubmed.ncbi.nlm.nih.gov/34015713/
• Environmental hazard of polypropylene microplastics from disposable medical face masks: acute toxicity to Daphnia magna and current knowledge about other polypropylene microplastics¹⁴Environmental hazard of polypropylene microplastics https://microplastics.springeropen.com/articles/10.1186/s43591-021-00020-0
• Effects of discarded face masks on marine microorganisms during the COVID-19 pandemic¹⁵Effects of Discarded Masks… https://www.mdpi.com/2305-6304/10/8/426

This led to this article in The Guardian, warning us about the chemical time bomb we have created:

“Disposable masks used during Covid left behind a chemical time bomb, study finds”

Kop in The Guardian¹⁶Disposable face masks used during Covid have left chemical timebomb, research suggests https://www.theguardian.com/environment/2025/sep/08/disposable-face-masks-covid-chemical-timebomb

Finally

I didn't write this to downplay intentions. Nearly everyone who embraced wearing masks did so because he or she wanted to protect themselves or others. But now that we've stepped back and have more extensive evidence, I think it's important that we look at the full scientific picture rather than the simplified version that dominated early reporting.

I hope this piece helps to clarify the scientific view on wearing face masks in society. These can be summarized as: Given the benefits of the use of face masks in society that can hardly be measured and the disadvantages that are clearly present, the use of face masks should never be encouraged for the general public.

References

• 1
  The Face Masked Hairdressers (CDC): https://www.cdc.gov/mmwr/volumes/69/wr/mm6928e2.htm
• 2
  Effectiveness of Adding a Mask Recommendation…: Bundgaard et al.
• 3
  The Impact of Community Masking on COVID‑19 https://www.science.org/doi/10.1126/science.abi9069
• 4
  Reanalysis Bangla Desh Study: https://trialsjournal.biomedcentral.com/articles/10.1186/s13063-022-06704-z
• 5
  Physical interventions to interrupt or reduce the spread of respiratory viruses:https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD006207.pub6/epdf/full
• 6
  Interview with Jefferson and Heneghan:https://www.youtube.com/watch?v=P_JTBftjQuA
• 7
  Effects of surgical and FFP2/N95 face masks… https://link.springer.com/article/10.1007/s00392-020-01704-y
• 8
  Nanomaterials in face masks: https://www.rivm.nl/nanotechnologie/consumentenproducten/Zijn-niet-medische-mondkapjes-met-nanomaterialen-veilig
• 9
  Face masks and chemical safety: https://www.rivm.nl/publicaties/chemische-veiligheid-mondkapjes
• 10
  Effects of surgical and FFP2/N95 face masks: https://link.springer.com/article/10.1007/s00392-020-01704-y
• 11
  The effect of face mask wearing on language processing… https://pmc.ncbi.nlm.nih.gov/articles/PMC9637007/
• 12
  Chen et al.: Used disposable face masks are significant sources of microplastics to environment https://pubmed.ncbi.nlm.nih.gov/34087638/
• 13
  Mater: Disposable masks release microplastics… https://pubmed.ncbi.nlm.nih.gov/34015713/
• 14
  Environmental hazard of polypropylene microplastics
• 15
  Effects of Discarded Masks… https://www.mdpi.com/2305-6304/10/8/426
• 16
  Disposable face masks used during Covid have left chemical timebomb, research suggests https://www.theguardian.com/environment/2025/sep/08/disposable-face-masks-covid-chemical-timebomb