HomeMy WebLinkAboutItem 2 - Attachment A
COVID-19 and the Use of Cloth Face Masks
Summary of Findings
Issues:
Should cloth masks be worn during this COVID-19 pandemic in either the community setting or in
places of business where food is sold?
Conclusions:
1. There is no incontrovertible, compelling or even a preponderance of evidence to support an Order to
wear a cloth mask in the community setting at this time.
2. I am supportive of cashiers and customers wearing cloth masks inside a grocery store or any essential
business if social distancing is difficult to maintain. Supporting evidence is not strong enough to issue
an Order to mandate the use of cloth masks at this time; consumer preference is already
accomplishing this in most parts of the County.
Introduction
A number of counties in California have adopted recommendations regarding the use of cloth masks in the
community setting. The evidence is not conclusive regarding whether this practice is helpful or harmful in
reducing the spread of COVID-19. There are convincing arguments both for and against the use of cloth masks
in public places (see table: The Pros and Cons of Wearing a Cloth Mask). In creating a guideline for San Luis
Obispo County, we have considered the prevalence of COVID-19 in our community as well as our success in
flattening the curve by implementing known infection control strategies such as strict social distancing.
Note that local, state, and national guidelines, when they support the use of masks, uniformly support the use
of cloth masks only and recommend against the use of medical masks (whether called surgical or procedure
masks or N95 respirators). There is insufficient supply chain confidence of personal protective equipment
(PPE) for healthcare workers and without adequate supplies of masks, gloves and gowns, our medical
professionals are not only putting themselves at risk, they may be putting their patients at risk.
Observations of patrons at retailers in various parts of San Luis Obispo County reveals that about half of
people choosing to wear face masks in public are wearing medical-grade masks. We urge those of you who
have a supply of unused medical-grade masks to donate these for use by local health care providers by going
to ReadySLO.org and using the “donate” tab.
Commented [PEB1]: Exist?
The Pros and Cons of Wearing a Cloth Mask
The following is information about the effectiveness of cloth masks and medical (surgical, procedure) masks in
preventing infection that may prove useful in deciding whether to wear a cloth mask in the community
setting. The public should not use medical masks but rather save those for health care professionals.
Medical masks are discussed below because cloth and medical masks are often compared in medical studies
and also to show that they are by no means a perfect option for use in the community setting.
Arguments in Favor of Wearing a Mask Arguments Against Wearing a Mask
Conclusion: Wearing facemasks can be very
slightly protective against primary infection
from casual community contact, and modestly
protective against household infections when
both infected and uninfected members wear
facemasks. The risk of acquiring a viral
infection is reduced by 6%. When both ill and
well wear a medical mask in a household, the
risk is reduced by 19%.
https://www.medrxiv.org/content/10.1101/20
20.04.01.20049528v1 (not peer reviewed)
With near universal use of cloth and medical
masks worn in public in Wuhan, China during
the 2019-2020 flu season leading up to the
COVID-19 outbreak, the outbreak spread
virtually unchecked.
CDC Recommendation Regarding the Use of
Cloth Face Coverings, Especially in Areas of
Significant Community-Based Transmission
where other social distancing measures are
difficult to maintain (e.g., grocery stores and
pharmacies) due to the possible asymptomatic
spread of COVID 19 from individuals who are
not aware they have the virus.
https://www.cdc.gov/coronavirus/2019-
ncov/prevent-getting-sick/cloth-face-
cover.html
With no masking order in place, San Luis
Obispo County residents have successfully
“flattened the curve” by using social distancing.
Cloth masks should be considered the last
resort to prevent droplet transmission from
infected individuals but would be better than
no protection at all when in close proximity to
others. Both cloth and medical masks
significantly reduced the number of
microorganisms expelled but medical masks
were 3 times more effective. The testing was
In a study involving 1607 health care workers
across 14 hospitals, the rate of infection
outcomes were 13 times higher in the cloth
mask group compared with the medical mask
group. Penetration of cloth masks by particles
was almost 97% and medical masks 44%.
Arguments in Favor of Wearing a Mask Arguments Against Wearing a Mask
performed immediately after putting on the
mask.
“Any mask (cloth or medical), no matter how
efficient at filtration or how good the seal, will
have minimal effect if is not used in
conjunction with other preventative measures
such as… good respiratory etiquette and
regular hand hygiene.”
https://www.ncbi.nlm.nih.gov/pmc/articles/P
MC7108646/pdf/S1935789313000438a.pdf
Conclusions: “This study is the first RCT of cloth
masks, and the results caution against the use
of cloth masks. This is an important finding to
inform occupational health and safety.
Moisture retention, reuse of cloth masks and
poor filtration may result in increased risk of
infection.”
https://bmjopen.bmj.com/content/5/4/e0065
77
The California Department of Public Health
recommends people wear cloth masks if they
feel comfortable doing so however it should
not be a replacement for other evidence-based
practices such as physical distancing, frequent
hand washing, and remaining at home.
“There may be a benefit to reducing
asymptomatic transmission and reinforcing
physical distancing from the use of (cloth) face
coverings.”
https://www.cdph.ca.gov/Programs/CID/DCDC
/Pages/Face-Coverings-Guidance.aspx
“Available evidence shows that (cloth masks)…
may even increase the risk of infection due to
moisture, liquid diffusion and retention of the
virus. Penetration of particles through cloth is
reported to be high.” “Altogether, common
fabric cloth masks are not considered protective
against respiratory viruses and their use should
not be encouraged.”
https://www.cdc.gov/coronavirus/2019-
ncov/hcp/ppe-strategy/face-masks.html
CDC recommends wearing cloth masks in
public settings where other social distancing
measures are difficult to maintain (e.g., grocery
stores and pharmacies) especially in areas of
significant community-based transmission.
https://www.cdc.gov/coronavirus/2019-
ncov/prevent-getting-sick/cloth-face-
cover.html
“Moisture retention, reuse of cloth masks and
poor filtration may result in increased risk of
infection.”
The virus may survive on the surface of the
facemasks.”
“Self-contamination through repeated use and
improper doffing is possible.”
https://bmjopen.bmj.com/content/5/4/e0065
77
In close proximity (approximately 3 ft.),
medical masks can block up to 90% of large
droplets (not viral aerosols) expelled directly
onto the front surface of the mask. In this
study, only 7% of the droplets penetrated the
mask.
Textile materials (that can be used for cloth
masks) can contain harmful chemicals and dyes
(i.e. formaldehyde). There is no research
available regarding the safety of breathing
through such materials but formaldehyde is a
gas that can irritate a person’s eyes, nose,
throat and lungs, or trigger an asthma attack,
Arguments in Favor of Wearing a Mask Arguments Against Wearing a Mask
https://www.ncbi.nlm.nih.gov/pubmed/21197
329
even at low concentrations. Prolonged
exposure to formaldehyde can cause cancer.
https://ww2.arb.ca.gov/resources/fact-
sheets/formaldehyde
https://www.gao.gov/new.items/d10875.pdf
Medical masks can reduce but not eliminate
the emission of viral particles into the
environment in respiratory droplets (not viral
aerosols) emitted by someone who is wearing
the mask. (Studied in individuals with a fresh
mask for the first 30 minutes of use.)
https://www.nature.com/articles/s41591-020-
0843-2
According to the World Health Organization,
the use of a medical mask by healthy people to
protect themselves from COVID-19 in
community settings is not supported by current
evidence.
The following potential risks should be
carefully taken into account in deciding to wear
a medical mask in the community setting:
• self-contamination that can occur by
touching and reusing a contaminated mask
• depending on type of mask used, potential
breathing difficulties
• diversion of mask supplies and consequent
shortage of masks for health care workers
• diversion of resources from effective public
health measures, such as hand hygiene
https://www.who.int/publications-
detail/advice-on-the-use-of-masks-in-the-
community-during-home-care-and-in-
healthcare-settings-in-the-context-of-the-
novel-coronavirus-(2019-ncov)-outbreak
“Of the nine trials of facemasks identified in
community settings, in all but one, facemasks
were used for respiratory protection of well
people. They found that facemasks and
facemasks plus hand hygiene may prevent
infection in community settings, subject to
early use and compliance.”
https://www.bmj.com/content/350/bmj.h694.
full
Wearing cloth masks in public can create a
false sense of security and complacency in
which people may neglect other hygiene
practices.
https://www.who.int/publications-
detail/advice-on-the-use-of-masks-in-the-
community-during-home-care-and-in-
healthcare-settings-in-the-context-of-the-
novel-coronavirus-(2019-ncov)-outbreak
Arguments in Favor of Wearing a Mask Arguments Against Wearing a Mask
There is limited (some) evidence that wearing
a medical mask by healthy individuals in the
households or among contacts of a sick
patient, or among attendees of mass
gatherings may be beneficial as a preventive
measure.
https://www.who.int/publications-
detail/advice-on-the-use-of-masks-in-the-
community-during-home-care-and-in-
healthcare-settings-in-the-context-of-the-
novel-coronavirus-(2019-ncov)-outbreak
Frequent washing and drying of a cloth mask
can decrease the filtration capacity of the
mask.
https://www.ncbi.nlm.nih.gov/pmc/articles/P
MC6599448/
Failing to wash a cloth mask daily increases the
risk of self-contamination for the person
wearing the mask due to contaminants found
on the outer surface of the mask after use. The
risk increases with longer duration of use.
https://bmcinfectdis.biomedcentral.com/track
/pdf/10.1186/s12879-019-4109-x
Buying pre-manufactured masks such as N95
and medical masks can create shortages of PPE
for health care providers.
https://www.who.int/news-room/detail/03-
03-2020-shortage-of-personal-protective-
equipment-endangering-health-workers-
worldwide
Virus-contaminated aerosols can pass through
cloth and medical masks with coughing and
sneezing.
https://annals.org/aim/fullarticle/2764367
“The evidence is not sufficiently strong to
support widespread use of facemasks as a
protective measure against COVID-19.”
https://www.medrxiv.org/content/10.1101/20
20.04.01.20049528v1
Arguments in Favor of Wearing a Mask Arguments Against Wearing a Mask
“Neither surgical nor cotton masks effectively
filtered SARS–CoV-2 during coughs by infected
patients… the size and concentrations of SARS–
CoV-2 in aerosols generated during coughing
are unknown. Oberg and Brousseau
demonstrated that surgical masks did not
exhibit adequate filter performance against
aerosols measuring 0.9, 2.0, and 3.1 μm in
diameter. Lee and colleagues showed that
particles 0.04 to 0.2 μm can penetrate surgical
masks. The size of the SARS–CoV particle from
the 2002–2004 outbreak was estimated as 0.08
to 0.14 μm; assuming that SARS-CoV-2 has a
similar size, surgical masks are unlikely to
effectively filter this virus.”
https://annals.org/aim/fullarticle/2764367
“The CDC does not mandate that face
coverings be worn statewide.”
https://www.cdph.ca.gov/Programs/CID/DCDC
/Pages/Face-Coverings-Guidance.aspx
There is no evidence that cloth masks or
medical masks worn in public plus practicing
social distancing is any better than social
distancing alone.
The outer surface of a mask in a patient with
COVID-19 is almost always positive for virus,
even more often than the inside surface.
Coughing and speaking have been
documented to disperse the virus out into the
air.
https://annals.org/aim/fullarticle/2764367
Given the breadth of published and observed findings, San Luis Obispo County Public Health will not mandate
that cloth face masks be worn in all public places in at this time. Were the prevalence in our community to
increase or with the advent of more convincing evidence in favor of this strategy, this guidance may change.
This review is not intended to lead to the conclusion that one should use medical masks over cloth masks;
medical masks should be preserved for health care providers. Thus, there are two valid choices for use of face
coverings - a cloth mask in a community setting or no mask at all.
The fact that there are more comments listed in the “Against” column is not a reflection of bias on behalf of
this reviewer but rather that there seem to be more researchers performing studies that produced those
results. More plentiful results do not mean more meaningful results.
The reason that this document is lengthy and does not point to a clear-cut conclusion is because there is no
conclusive evidence on either side of the issue. One might say that the obvious choice then is to choose the
more conservative masking side of the issue. This choice might be the clear approach were it not for concerns
raised about the safety of wearing cloth masks and their effectiveness.
Statements of endorsement and concern exist regarding the use of cloth masks by reputable organizations on
both sides of the issue. Absent an absolute conclusion, individuals are left to accept the complexity of the
issue and make their own decisions.
Recommendations for Homemade Cloth Face Masks
The following guidance outlines safety considerations associated with homemade cloth masks.
Material Considerations
When considering a fabric to make your mask, please keep in mind that some textile fabrics can contain dyes
and chemicals from the factory.
Try to avoid any fabrics that are labeled "wrinkle-free", "durable press" or "easy care finish" since these
fabrics may be treated with a product that includes formaldehyde.
CDC recommends using 100% cotton fabric for making a cloth face mask. Although “organic cotton” would be
the best choice, any clean woven cotton fabric should work.
Do not use fabrics that have been in contact with harmful household chemicals such as paint removers,
stain removers and cleaning products.
Once you have chosen a fabric to create your mask:
Please make sure to launder the fabric at least two times before first use in order to ensure any
harmful contaminants are removed. Be cautious of using scented detergent because the residual odor
may cause a respiratory reaction.
Other Considerations
Cloth face coverings should not be placed on:
Children under age 2
Anyone who may have difficulty breathing
Anyone who is unconscious
Anyone who is incapacitated or otherwise unable to remove the mask without assistance
For CDC guidance on how to make a cloth mask, please visit https://www.cdc.gov/coronavirus/2019-
ncov/prevent-getting-sick/diy-cloth-face-coverings.html
If you should decide to wear a cloth face mask, please remember to:
Wash your hands after putting the mask on and after taking the mask off
Do not touch your face or the mask while wearing it
Disinfect areas where the mask is stored while not in use
Wash your cloth mask daily
Do not fail to abide by social distancing standards
Plexiglass Shields
Plexiglass shields have been placed in many essential businesses as a barrier between the cashier and the
customer. If interfering with the passage of respiratory droplets is the intent of those who wish to wear a
mask, the same outcome might be achieved by the placement of plexiglass barriers at points of cashier-
customer interaction in the grocery store and in other essential businesses where 6 feet of distance can’t be
maintained. https://abc3340.com/news/coronavirus/grocery-stores-protecting-workers-and-customers-from-
covid-19
Penny Borenstein, MD, MPH
County Health Officer/Public Health Director
May 3, 2020
Adapted from Ventura County Public Health Department White Paper, with gratitude to Robert Levin, MD,
Ventura County Health Officer