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Effectiveness of Face Masks in Preventing Airborne Transmission of SARS-CoV-2 – American Society for Microbiology

Airborne simulation experiments showed that cotton masks, surgical masks, and N95 masks provide some protection from the transmission of infective SARS-CoV-2 droplets/aerosols; however, medical masks (surgical masks and even N95 masks) could not completely block the transmission of virus droplets/aerosols even when sealed.

https://msphere.asm.org/content/5/5/e00637-20

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Fask Facts -The Association of American Physicians and Surgeons

A curated list of mask facts and medical publications.

COVID-19 is as politically-charged as it is infectious. Early in the COVID-19 pandemic, the WHO, the CDC and NIH’s Dr. Anthony Fauci discouraged wearing masks as not useful for non-health care workers. Now they recommend wearing cloth face coverings in public settings where other social distancing measures are hard to do (e.g., grocery stores and pharmacies). The recommendation was published without a single scientific paper or other information provided to support that cloth masks actually provide any respiratory protection. Let’s look at the data.

  • Surgical masks are loose fitting. They are designed to protect the patient from the doctors’ respiratory droplets.  There wearer is not protected from others’ airborne particles.
  • People do not wear masks properly. Many people have the mask under the nose. The wearer does not have glasses on and the eyes are a portal of entry.  If the virus lands on the conjunctiva, tears will wash it into the nasopharynx.
  • Most studies cannot separate out hand hygiene.
  • The designer masks and scarves offer minimal protection. They give a false sense of security to both the wearer and those around the wearer.
    **Not to mention they add a perverse lightheartedness to the situation.
  • If you are walking alone, no need for a mask. Avoid other folks; use common sense.
  • Remember: children under 2 years should not wear masks because of accidental suffocation and difficulty breathing in some.
  • Even if a universal mask mandate were imposed, several studies noted that folks do not use the mask properly and over-report their wearing.  Additionally, how would the mandate be enforced??
  • The positive studies are models that assume universality and full compliance.
  • If wearing a mask makes people go out and get Vitamin D – go for it. In the 1918 flu pandemic people who went outside did better.  Early reports are showing people with COVID-19 with low Vitamin D do worse than those with normal levels. Perhaps that is why shut-ins do so poorly.

https://aapsonline.org/mask-facts/

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Low-cost measurement of face mask efficacy for filtering expelled droplets during speech – Science Magazine

We noticed that speaking through some masks (particularly the neck gaiter) seemed to disperse the largest droplets into a multitude of smaller droplets (see fig. S5), which explains the apparent increase in droplet count relative to no mask in that case. Considering that smaller particles are airborne longer than large droplets (larger droplets sink faster), the use of such a mask might be counterproductive. Furthermore, the performance of the valved N95 mask is likely affected by the exhalation valve, which opens for strong outwards airflow. While the valve does not compromise the protection of the wearer, it can decrease the protection of persons surrounding the wearer. In comparison, the performance of the fitted, non-valved N95 mask was far superior.

https://web.archive.org/web/20200902201232/https://advances.sciencemag.org/content/6/36/eabd3083

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Particle sizes of infectious aerosols: implications for infection control – The Lancet

Note: Coughing and large droplets are note the issue beause breathing exhales more virus in fine aerosols than coughing. Finer aerosols bypass masks and nose to the lungs. Since masks nebulise particles, the solution is ventilation, not face masks.

The global pandemic of COVID-19, caused by severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2]) has been associated with infections and deaths among health-care workers. There have been conflicting recommendations from health authorities on the use of masks or respirators to protect health-care workers. When I first reviewed personal respiratory protection against tuberculosis for health-care workers more than 20 years ago, there was very little information on infectious aerosols. Since then, colleagues in various disciplines have provided a wealth of data. The purpose of this Viewpoint is to review the scientific literature on the aerosols generated by individuals with respiratory infections, and to discuss how these data inform the optimal use of masks, respirators, and other infection-control measures to protect health-care workers from those aerosols. This is not a review of the literature on the use of surgical masks or respirators, as several have been done already.

https://www.thelancet.com/journals/lanres/article/PIIS2213-2600(20)30323-4/fulltext