With limited ICU beds and no confirmed therapeutics against COVID-19, masks might be our most effective countermeasure.
But are all masks created equal? A new study published in the Annals of Internal Medicine offers valuable insight. In it, the authors argue that cotton masks offer the best protection against SARS-CoV-2 virions.
Coronavirus particles evidence an average diameter of 0.1 micrometers. In aerosols, these particles remain active for roughly three hours. Disposable medical masks have been studied to block between 96% and 99% of viral debris. Impressive numbers but multilayered cloth material remain unmatched.
“Most virus transmission occurs via larger particles in secretions, whether aerosol or droplets, which are generated directly by speaking, eating, coughing, and sneezing; aerosols are also created when water evaporates from smaller droplets, which become aerosol-sized droplet nuclei,” the researchers write in the new report.” The point is not that some particles can penetrate but that some particles are stopped, particularly in the outward direction. Every virus-laden particle retained in a mask is not available to hang in the air as an aerosol or fall to a surface to be later picked up by touch.”
The researchers took several previously conducted studies into account before building their data set.
Their findings revealed that a four-layer cotton muslin mask can reduce the contamination of all particles by 99%.
Single layers of scarfs, sweatshirts, T-shirts, and towels were associated with a filtration efficiency of 10% to 40% in experiments testing, so it’s important to layer up if you’re using a makeshift mask out of any of these materials.
A single layer of fabric like cotton-flannel can stop over 90% of active viral particles. The data changes with some frequency but the protective utility of cloth in regards to viral infection has been consistent across studies using both human and animal models alike.
“We recognize the potential for unintended consequences, such as the use of formal personal protective equipment by the general public, incorrect use of cloth masks, or reduced hand hygiene because of a false sense of security; these can be mitigated by controlling the distribution of personal protective equipment, clear messaging, public education, and social pressure,” the authors continued.
Systems in Mainland China were essentially able to curb shutdown durations by employing contact tracing and adhering to The Center for Disease Control and Prevention mask guidelines.
The CDC and Wake Forest University experts recommend two layers of tightly woven 100% cotton fabric, a double layer of cotton with a thread count of at least 180, or a double layer of normal cotton with a layer of flannel in between. SARS-Cov-2 remains active on cotton for about 24 hours.
“Public-health decisions about public mask-wearing have been difficult to make, and why they differ around the world,” Catherine Clase of McMaster University said in a statement. Our review suggests that cloth can block particles, even aerosol-sized particles, and this supports Canadian public health policy on the issue.” “In terms of making masks, it is important to realize that more layers will give more protection, both inward and outward, but will make it harder to breathe.”
While traveling, you want to apply enough layers of durable material to filtrate active droplets from orifices without diminishing breathability, especially if you have a history of respiratory illness.
CW Headley is a reporter for the Ladders and can be reached at firstname.lastname@example.org