Thanks to Robert Wenzel's "Yet Another Medical Study on the Nasty Contamination by Respiratory Viruses on Outer Surfaces of Masks."
We've
all seen people tug, pull, grab and smear the outside of their facemasks,
including mask proponents Trump, Fauci,
Newsom, etc.
In a previous
post, Doctor David
Lang of Wisconsin says a face mask is "basically a giant Petri dish you
have strapped to your face"
Following is an
interesting 2019 medical study which points out the common contamination
problems associated with face masks.
Respiratory pathogens on the outer surface of the used medical masks may result in self- contamination. The risk is higher with longer duration of mask use... Respiratory pathogens may be present on used masks layers and lead to infection of the wearer... While using masks, or during long periods of time of re-using them, these pathogens may cause infection through hand or skin contamination, ingestion, or mucus membrane contact.
Following are more
excerpts. The most interesting parts I highlighted in bold text. You can read
the full study here.
Contamination by
respiratory viruses on the outer surface of medical masks used by hospital
healthcare workers Page
7 We also aimed to identify the area on the mask surface with maximum
respiratory virus concentration. A laboratory-based pilot study showed
maximum fluorescent contamination on upper sections of the masks, which is also
the likely area to be touched on removal. Of the three positive tests
in the hospital-based pilot study, two samples were positive from the outer sections of the mask, while one sample was positive from the middle section. In the main study, we
were able to check the location of contamination on a quarter of mask
samples. Of the 38 mask samples, one or more viruses were isolated from
four (10.5%) samples–two from the middle section of masks and two from the right
section of the masks. This presents a large area of potential
contamination which place HCW at risk when removing a mask. These data may
assist in developing policies on for doffing of masks after an encounter with
infective cases. As a general rule, HCWs should not reuse masks, should
restrict use to less than 6 h and avoid touching the outer surface of the mask
during doffing, and practice hand hygiene after removal.
Page
6 Theoretically, there may be a risk of infection [to the] wearer if
contaminated masks are used for a prolonged time. Currently, there are no data
around risk associated with reuse and extended use of masks and other PPE. One
study showed that the influenza virus may survive on mask surface and maintained
infectivity for at least 8 h [25]. Our study showed very low infection
among HCWs who used masks for ≤6 h. High virus positivity on masks samples worn
by HCWs who examined > 25 patients, may be due to more frequent clinical
contact with infective cases and transfer of more pathogens from patients to
mask surface.
Page
7 Conclusion: To maintain the functionality and capacity of the health care
workforce during outbreaks or pandemics of emerging infections, HCWs need to be
protected. This study provides new data, which will help developing policies
for a safe workplace environment. The study shows that the prolonged use
of medical masks (> 6 h) and frequent clinical contact in healthcare settings
increase the risk to health workers through contaminated PPE. Protocols on the duration of mask use should specify a maximum time of continuous use.
Page
1 Abstract
Background: Medical masks are commonly used in health care settings to protect healthcare workers (HCWs) from respiratory and other infections. Airborne respiratory pathogens may settle on the surface of used masks layers, resulting in contamination. The main aim of this study was to study the presence of viruses on the surface of medical masks.
Background: Medical masks are commonly used in health care settings to protect healthcare workers (HCWs) from respiratory and other infections. Airborne respiratory pathogens may settle on the surface of used masks layers, resulting in contamination. The main aim of this study was to study the presence of viruses on the surface of medical masks.
Methods:
Two pilot studies in laboratory and clinical settings were carried out to
determine the areas of masks likely to contain maximum viral particles. A
laboratory study using a mannequin and fluorescent spray showed maximum
particles concentrated on the upper right, middle, and left sections of the medical
masks. These findings were confirmed through a small clinical study. The main
study was then conducted in high-risk wards of three selected hospitals in
Beijing China. Participants (n = 148) were asked to wear medical masks for a
shift (6–8 h) or as long as they could tolerate. Used samples of medical masks
were tested for the presence of respiratory viruses in upper sections of the
medical masks, in line with the pilot studies.
Results: Overall
virus positivity rate was 10.1% (15/148). Commonly isolated viruses from masks
samples were adenovirus (n = 7), bocavirus (n = 2), respiratory syncytial virus
(n = 2) and influenza virus (n = 2). Virus positivity was significantly higher
in masks samples worn for > 6 h (14.1%, 14/99 versus 1.2%, 1/49, OR 7.9, 95%
CI 1.01–61.99) and in samples used by participants who examined > 25
patients per day (16.9%, 12/71 versus 3.9%, 3/77, OR 5.02, 95% CI
1.35–18.60).
Most of the participants (83.8%, 124/148) reported at least one problem associated with mask use. Commonly reported problems were pressure on the face (16.9%, 25/148), breathing difficulty (12.2%, 18/148), discomfort (9.5% 14/148), trouble communicating with the patient (7.4%, 11/148) and headache (6.1%, 9/148).
Conclusion: Respiratory
pathogens on the outer surface of the used medical masks may result in self-
contamination. The risk is higher with longer duration of mask use (> 6 h)
and with higher rates of clinical contact.
Protocols
on the duration of mask use should specify a maximum time of continuous use, and should consider guidance in high
contact settings. Viruses were isolated from the upper sections of
around 10% samples, but other sections of masks may also be contaminated. HCWs
should be aware of these risks in order to protect themselves and the people around
them.
Keywords:
Mask, Health care workers, Viruses, Infection control
Virus positivity was
significantly higher in masks samples worn for > 6 hours. Most of the participants (83.8%,
124/148) reported at least one problem associated with mask use. Commonly
reported problems were pressure on the face (16.9%, 25/148), breathing difficulty
(12.2%, 18/148), discomfort (9.5% 14/148), trouble communicating with the
patient (7.4%, 11/148), and headache (6.1%, 9/148).
Page
2 Reuse and extended use of masks are also common in many parts of the world,
particularly during outbreaks and pandemics [8, 9]. Respiratory pathogens
may be present on used masks layers and lead to infection of the wearer [10].
In hospital settings, these pathogens may be generated from breathing,
coughing or sneezing patients or during aerosol-generating medical procedures
[11]. Studies have shown that influenza virus can remain airborne for 3 h after
a patient has passed through an emergency department [12]. While using
masks, or during long periods of time of re-using them, these pathogens may
cause infection through hand or skin contamination, ingestion, or mucus
membrane contact [10]
Previous
studies show that influenza and respiratory syncytial virus (RSV) may survive
on the outer surface of PPE [11–14]. A study showed that influenza viruses may
survive on hard surfaces for 24–48 h, on cloth up to 8–12, hand on hands for up
to 5 min.
Page
2 If health departments do not provide clear guidance on the use of
masks in these situations, HCWs may continue using contaminated masks and may
get infection [15]. The risk of self-contamination of HCWs is influenced by the
mask itself, its shape and properties, and the virus concentration on its
surface. To our knowledge, only one study examined the presence of
contamination on masks and various bacteria were isolated from the outer surface of
medical masks [16].
The main aim of this study was to study the level of contamination on the surface
of medical masks.
Page
2 The aim of this pilot study was to identify areas of maximum virus
concentration on the surface of masks...In all three experiments, most
particles were concentrated on upper right, middle and left sections of the
masks (Figs. 1 and 2).
Currently, there is very limited data on the testing of mask surfaces for the presence of pathogens. In previous studies, influenza virus was detected on over 50% of the fomites tested in community
settings during the influenza season [17].
