30 September 2023

Misleading: Japanese study on mask hygiene does not support dropping mask mandate

The 2022 study by researchers at an Osaka-based university actually recommends the hygienic use of masks and cautions people, especially those with immune issues, against repeated use of the same masks to avoid pathogenic microbes potentially growing on the surface.

In a video posted on Twitter on Jan. 10, James Cintolo, a man who describes himself as a medical and nutritional health expert, claimed that the findings of a “brand-new” Japanese study demonstrate “masking breeds dangerous bacteria and fungi.”

The clip has been viewed over 71,000 times and shared more than 2,800 times at the time of writing.

However, what he says in the video takes the research paper, which was actually published in Nature last year in July, out of context.

In the study titled “Bacterial and Fungal Isolation from Face Masks Under the COVID-19 Pandemic,” researchers from Kindai University looked into hygiene issues from prolonged mask-wearing.

They concluded that mask-wearing remained “the most traditional and reasonable method to prevent” respiratory infections but cautioned that people with immune problems should avoid using the same masks repeatedly to prevent microbial infection.

Analyzing microbes cultured from non-woven masks and the washable ones made of polyurethane, gauze and cloth collected from 109 users between September and October in 2020, they found bacterial and fungal colonies did grow on both sides of the masks.

Cintolo admitted in the video that most bacteria and fungi found on the inside and outside of the sampled masks were not harmful, but he emphasized that there were certain “disease-causing” ones, claiming the findings provided enough reasons to end mandatory mask-wearing.

However, in the paper, the medical researchers did not say the public should stop wearing masks. In fact, they simply recommended the hygienic use of masks for all.

It specifically advised people who were immunocompromised against repeated use of masks (no more than a day) because they are more likely to be affected by potentially pathogenic microbes.

Efficacy also questioned

Cintolo also said face masks could not filter COVID-19 virus particles, a claim that has been debunked many times by health experts in the past.

This included those of the University of Vermont and Mayo Clinic, who said small viral particles travel through saliva and water droplets, which masks could help entrap.

Gill Allen, a pulmonologist and critical care physician from the University of Vermont Medical Center, said in an article published on the university’s website, “it is also not true that N95 masks do not filter particles smaller than 0.3 microns. They can and do.”

The same claim about N95 masks was also fact-checked by USA Today on June 11, 2020.

Meanwhile, the Twitter user also claimed that masks “didn’t meaningfully reduce the spread of COVID-19,” citing an unidentified “cluster randomized trial” conducted in Bangladesh.

A cluster randomized trial refers to randomly allocating or testing interventions among clusters or groups of people, instead of individuals.

Through a keyword search, Annie Lab identified a study titled “Impact of Community Masking on COVID-19: A Cluster-Randomized Trial in Bangladesh” which was published on Dec. 2, 2021.

According to the researchers who conducted the research, the trial was led by U.S. and Bangladeshi academics across 340,000 people in 600 villages, where they introduced various interventions or strategies such as mask distribution to encourage more people to wear masks.

As opposed to the Twitter user’s claim, the researchers concluded that “surgical masks are particularly effective in reducing symptomatic seroprevalence of SARS-CoV-2.”

Meanwhile, similar claims about the Japanese university study were also debunked by the Australian Associated Press on Aug. 4, 2022.