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Hello, my name is Tyson Gabriel, I am an Environmental, Health, and Safety (EHS) professional and Industrial
Hygienist with nearly 20 years of experience.
EHS professionals design, implement, and guide companies through exposure mitigation efforts via customized
safety and health programs that were applicable to their industry, exposures, and work environments. These
factors must always be considered to ensure that personnel are properly protected and that the measures taken
will not fail in their specific work environment.
A one-size fits all approach cannot succeed due to the complexity of behaviors, various exposures, living/work
environments, climate, indoor air quality, etc. In addition, when designing a safety and health program, it is
critical to not suffer tunnel vision to a single exposure ( a.k.a. RISK). In doing so, exposure prevention measures
can cause more exposures and risks. An example of tunnel vision in exposure prevention was identified by the
CDC in the summer of 2020, when the organization informed the public that 25% of children committing self harm
or considering it due to the shutdown (isolation/quarantine) protocols in schools.
In our profession, we have learned that 95% of why safety and health programs fail is due to human behavior.
Therefore, having a principled safety and health program centered in being proactive, providing clarity, and
obtaining buy-in is critical. In addition, we utilize a system called the Hierarchy of Controls, which enables clarity
to which exposure prevention controls should be prioritized due to their effectiveness.
The Hierarchy of Controls is a system used to implement effective controls within an organization, workplace, or
community to identify the most effective ways to mitigate hazards. Within the inverted pyramid below the more
effective controls are on the large, top side of the pyramid, whereas the least effective controls are on the
bottom.
PPE is the least effective control due to the extreme dependency on the human element. The PPE failing is
always a concern, but human error occurs often with its use. In my career I have experienced personnel failing to
use their PPE due to a lack of comfort, poor training, or myths they carried with them from a previous employer.
Masks really do not fit in the Hierarchy of Controls. Masks do not seal to your face and thus cannot protect you.
It can reduce exposure to blood splatter for medical professionals at best, but it is not deemed a true protective
piece. Therefore, a mask can in no way scientifically be considered a primary solution to an exposure issue as
many doctors, politicians, and the CDC have falsely claimed. A competent response would be focused on
dilution, filtration, and destruction of the pathogen that are found with Engineering Controls.
The CDC’s publication on “Types of Masks and Respirators” conveys that a parent can put an N95 respirator on
children. This has been known for decades as an unsafe practice and is a form of misuse of PPE, and thus
would be a behavioral issue in preventing a successful safety and health program.
In most N95 manufacturer's instructions will instruct the user that the respirator is unsafe. It is important to know
that a surgical/cloth mask is different than an N95 respirator. They are not both masks, this is medical slang that
has gone mainstream, but it is an incorrect term and has led to the public being misinformed.
The “N” on the N95 designation means that the respirator can only be worn in non-oil environments. The “95”
means the filter has 95% efficiency. The non-oil use environment respirators are made of fragile material and as
the user sweats and breathes, the respirator becomes exposed to heat and moisture which will degrade the
respirator material. These respirators degrade in 2-4 hours in a medical environment and much quicker in other
settings. A medical setting has state of the art HVAC systems and enables a strong balance of indoor air quality.
Office, construction, manufacturing, or outdoor settings cause a quicker degradation of the N95 because the
user exposes it to more heat and moisture. At minimum a reusable respirator with P100 filters should be used in
such settings.
Before a respirator can be worn in a work setting, 29 CFR § 1910.134, requires that the employer assess the risk
of the exposure before implementing a respiratory protection program to understand the pathogen/contaminant.
Then those chosen to wear a respirator are required to be medically clear, fit tested, and trained. The training will
focus on how to properly wear the respirator, how to conduct a fit check (not a fit test), cleaning and maintenance
of the respirator, its limitations, and how to don and doff the respirator properly.
According to 29 CFR § 1910.132, Any form of PPE deployment requires that the employer conduct a risk
assessment and ensure proper training has been performed for those required to utilize it. Have you taken such
measures?
The CDC has failed to properly inform the public on exposure prevention methods and requirements. We
needed two responses to the pandemic which consisted of a medical response and an exposure mitigation
response. The medical response consisted of learning about the contaminate, how it affects the body, how it
enters the body, and what treatments work after exposure to the contaminate has occurred. The exposure
mitigation first takes the medical science, to specifically know how the contaminate travels, enters the body, and
what its composition is like to better understand its weaknesses.
Many have falsely assumed that the medical industry should handle both angles in this response but this is
incorrect. The medical industry is unschooled in exposure science and is in fact a customer to the exposure
science industry.
History has shown this before but the public and media did not catch these past mistakes. An example of the
inept training of control measures in the medical field occurred during the Ebola outbreak in 2014. A hospital in
Dallas, Texas took in Ebola patients in and found themselves completely unprepared. The medical professionals
got on the internet and threw some PPE together and when nurses were exposed, they became infected. They
were using improper PPE, likely not fit tested for respirator use, and had no training on their control plan.
Thankfully, the nurses survived but the following link will show what was unveiled in court to the bungled
measures taken (https://www.nbcnews.com/storyline/ebola-virus-outbreak/nurse-who-caught-ebola-settles-suitagainst-
dallas-hospital-n672081).
Even the famous Chinese doctor (Dr. Li Wenliang) who warned the world of this virus wore his PPE incorrectly.
Here is a picture of him wearing a surgical mask with a disposable N95 respirator on top of it. This is improper
use because the face mask was preventing the respirator from capturing a seal to his face.
A few months after the pandemic started, we began to monitor the OSHA citation data and found that 90% of the
OSHA citations were happening in medical facilities. We saw consistent law violations in regard to
29 CFR §1910.132 and 1910.134.
If the medical profession were the experts on respiratory protection and PPE use, why are they the largest
violators of the law?
I have trained medical professionals in these exposure prevention measures. The public might be surprised to
know that medical professionals do not learn a lot about masks and respirators in medical school. These aspects
are not a medical science matter, they are an exposure science issue.
Sure, doctors use masks and other PPE as tools in their workplace and in medical school, they learn enough to
know about using a mask, like which mask to wear for certain procedures or the special donning and doffing
maneuvers. That is, how to put them on and take them off without getting contaminated. Those procedures were
designed by people in my profession. A critical point to understanding why healthcare workers in hospital
environments have to follow specifically precise procedures for handling their PPE is because it has already
been scientifically established that PPE can gather and collect contamination from everything it touches and
from the air near it.
There are mechanics and sciences happening all around doctors, keeping them safe, that they are not aware of.
The same is true in the other direction. I'm not going to have opinions about how to perform open heart surgery.
The CDC has failed to properly inform the public on this matter. They have not used a single substantial study to
justify this recommendation and have given organizations like yours, poor guidance through this pandemic. This
opens the gates for other leadership and societal circles to do the same.
This Cambridge mask study ( 1 ) that's making the rounds in public media and academia, for example, took a
handful of volunteers and tested out numerous masks and testing a few different improvement hacks. Their idea
was to find reasonably simple things that people could improvise on their own to improve their mask to nearly the
same level of particle performance as N95's.
A major problem here is that the professionally manufactured N95s are precision manufactured for a specific
tightness and fit. And they are governed by specific laws. Such as anyone required to wear an N95 in the
workplace has to have a medical examination. [29 CFR § 1910.134(c)(1)(ii)]
Why is that do you supposed? Well its because 50 years of vigorously tested mask science has already
established that tightly fitting masks are potentially dangerous to anyone, which is why medical clearance is
required before the use of any tightly fitted mask.
So now you've got a study telling you to build your own mask out of whatever random material, and you can
wrap stuff around your head, to whatever tightness you think works. Hey, very little bit helps right?.
That's not science and you are potentially creating more collateral risks by these recommendations.
Then there's this gem found in that study...
“One participant was unable to fit the KN95 mask with ear bands tied. Another participant was unable to fit one
brand of pantyhose over his head without the pantyhose tearing. In these two cases, the problematic hack was
not tested. “
So now you just discarded 25% of your testing base. Are we to believe that in that whole college campus you
could not go find another person, who did not have an ear sore, to fill in.?
The real problem though is the CDC that allows this low-level science to be used for the same role that before
the Covid years was only reserved for high level, thorough, methodological science.
In July of last year I published an extensive mask science documentary which showed omissions, errors and
flaws, and in some cases provable fraud in studies.
Do you want to know why the CDC has gotten away with this sloppy science? It is leaders like you all at the local
level let them get away with it. City leaders, school boards, and district health departments are all responsible!
It is because you have not done your job from day one. You are supposed to be another level of scientific rigor.
You are supposed to be the feedback.
Instead, you have become enablers of garbage science. An echo chamber of dangerous ignorance.
You chose to deflect and just do what you were told. You never questioned anything. You just assumed
everything they were telling you was done correctly and was proper science. You never actually looked at the
science personally or sought someone with professional training to advise you.
Take a few of these newest mask studies the CDC put up, for example. Ok well, they are not new studies; they
were done last year and the CDC has just been sitting on them and conveniently decided to put them up
recently.
Fikenzer S, Uhe T, Lavall D, et al.
“Ventilation, cardiopulmonary exercise capacity and comfort are reduced by surgical masks and highly impaired
by FFP2/N95 face masks in healthy individuals. These data are important for recommendations on wearing face
masks at work or during physical exercise. ” (3)
Lassing J, Falz R, Pokel C, et al
“In the healthy young men in this study, the use of surgical face masks was associated with a significant
increase in airway resistance, reduced oxygen uptake, and increased heart rate during continuous exercise.” (4)
Driver S, Reynolds M, Brown K, et al.
“Our data suggest that wearing a cloth face covering negatively impacts exercise performance in healthy adults
during a maximal treadmill test. As both physiological and perceptual factors were negatively impacted, coaches,
trainers and athletes should be aware of the effect of cloth face coverings “ (5)
Did any of you communicate the proper advisories to athletic directors? Or made any of the other nuanced
adjustments advised by the “science? Of course not. It was easier to absolve yourself from accountability by
being able to say “...hey we're just following the CDC guidelines”
Even if masks worked, why are you putting them on children? The “science” has clearly shown that children are
not being significantly harmed by the COVID-19 virus and even Tony Fauci had to admit that during the Delta
spike kids were not in hospitals because of the virus. In addition, children are not spreading the disease. So,
explain why the kids need a mask when the data clearly shows that they do not?
This letter may serve as notification that you have been informed that your policies, which are based on
erroneous or incomplete information, may be causing harm to your employees and students. Especially those
who have been denied exemptions.
Parents, you may have heard about the group of parents in Florida who had their child's masks tested for
contamination at the University of Florida. ( 6 )
“ Half of the masks were contaminated with one or more strains of pneumonia-causing bacteria. One-third were
contaminated with one or more strains of meningitis-causing bacteria. One-third were contaminated with
dangerous, antibiotic-resistant bacterial pathogens. In addition, less dangerous pathogens were identified,
including pathogens that can cause fever, ulcers, acne, yeast infections, strep throat, periodontal disease, Rocky
Mountain Spotted Fever, and more. “
This shows foundational information that warrants further investigation. Engage in scientific process!
Parents, if you are interested in testing your child's masks, you can email me at
tyscienceguy@protonmail.com and we will give you guidance on these processes
To our community leaders, in the future you can no longer claim that you were not made aware of the facts and
concerns in this issue, that excuse is gone. If you need assistance, please contact a local firm that has industrial
hygienists and safety and health professionals. My firm, as from the beginning, is always willing to assist as well.
It’s time that we protect the children, and we stop putting them through these unscientific and unnecessary
measures. These measures have caused worse exposure and risk for children than the actual virus.
We are two years into this dog and pony show and it’s time to shut it down.
Sincerely,
Tyson Gabriel, BS, IH
References:
( 1 )
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0262830
( 2 )
O’Kelly E, Pirog S, Ward J, Clarkson PJ. Ability of fabric face mask materials to filter ultrafine particles at coughing
velocity. BMJ Open. 2020;10(9):e039424.
( 3 )
Fikenzer S, Uhe T, Lavall D, et al. Effects of surgical and FFP2/N95 face masks on cardiopulmonary
exercise capacity. Clin Res Cardiol. 2020;109(12):1522–1530.
( 4)
Lassing J, Falz R, Pokel C, et al. Effects of surgical face masks on cardiopulmonary parameters during
steady state exercise. Sci Rep. 2020;10(1):22363.
( 5 )
Driver S, Reynolds M, Brown K, et al. Effects of wearing a cloth face mask on performance,
physiological and perceptual responses during a graded treadmill running exercise test. Br J Sports
Med. 2021; bjsports-2020-103758.
( 6 )
https://rationalground.com/dangerous-pathogens-found-on-childrens-face-masks/
Hygienist with nearly 20 years of experience.
EHS professionals design, implement, and guide companies through exposure mitigation efforts via customized
safety and health programs that were applicable to their industry, exposures, and work environments. These
factors must always be considered to ensure that personnel are properly protected and that the measures taken
will not fail in their specific work environment.
A one-size fits all approach cannot succeed due to the complexity of behaviors, various exposures, living/work
environments, climate, indoor air quality, etc. In addition, when designing a safety and health program, it is
critical to not suffer tunnel vision to a single exposure ( a.k.a. RISK). In doing so, exposure prevention measures
can cause more exposures and risks. An example of tunnel vision in exposure prevention was identified by the
CDC in the summer of 2020, when the organization informed the public that 25% of children committing self harm
or considering it due to the shutdown (isolation/quarantine) protocols in schools.
In our profession, we have learned that 95% of why safety and health programs fail is due to human behavior.
Therefore, having a principled safety and health program centered in being proactive, providing clarity, and
obtaining buy-in is critical. In addition, we utilize a system called the Hierarchy of Controls, which enables clarity
to which exposure prevention controls should be prioritized due to their effectiveness.
The Hierarchy of Controls is a system used to implement effective controls within an organization, workplace, or
community to identify the most effective ways to mitigate hazards. Within the inverted pyramid below the more
effective controls are on the large, top side of the pyramid, whereas the least effective controls are on the
bottom.
PPE is the least effective control due to the extreme dependency on the human element. The PPE failing is
always a concern, but human error occurs often with its use. In my career I have experienced personnel failing to
use their PPE due to a lack of comfort, poor training, or myths they carried with them from a previous employer.
Masks really do not fit in the Hierarchy of Controls. Masks do not seal to your face and thus cannot protect you.
It can reduce exposure to blood splatter for medical professionals at best, but it is not deemed a true protective
piece. Therefore, a mask can in no way scientifically be considered a primary solution to an exposure issue as
many doctors, politicians, and the CDC have falsely claimed. A competent response would be focused on
dilution, filtration, and destruction of the pathogen that are found with Engineering Controls.
The CDC’s publication on “Types of Masks and Respirators” conveys that a parent can put an N95 respirator on
children. This has been known for decades as an unsafe practice and is a form of misuse of PPE, and thus
would be a behavioral issue in preventing a successful safety and health program.
In most N95 manufacturer's instructions will instruct the user that the respirator is unsafe. It is important to know
that a surgical/cloth mask is different than an N95 respirator. They are not both masks, this is medical slang that
has gone mainstream, but it is an incorrect term and has led to the public being misinformed.
The “N” on the N95 designation means that the respirator can only be worn in non-oil environments. The “95”
means the filter has 95% efficiency. The non-oil use environment respirators are made of fragile material and as
the user sweats and breathes, the respirator becomes exposed to heat and moisture which will degrade the
respirator material. These respirators degrade in 2-4 hours in a medical environment and much quicker in other
settings. A medical setting has state of the art HVAC systems and enables a strong balance of indoor air quality.
Office, construction, manufacturing, or outdoor settings cause a quicker degradation of the N95 because the
user exposes it to more heat and moisture. At minimum a reusable respirator with P100 filters should be used in
such settings.
Before a respirator can be worn in a work setting, 29 CFR § 1910.134, requires that the employer assess the risk
of the exposure before implementing a respiratory protection program to understand the pathogen/contaminant.
Then those chosen to wear a respirator are required to be medically clear, fit tested, and trained. The training will
focus on how to properly wear the respirator, how to conduct a fit check (not a fit test), cleaning and maintenance
of the respirator, its limitations, and how to don and doff the respirator properly.
According to 29 CFR § 1910.132, Any form of PPE deployment requires that the employer conduct a risk
assessment and ensure proper training has been performed for those required to utilize it. Have you taken such
measures?
The CDC has failed to properly inform the public on exposure prevention methods and requirements. We
needed two responses to the pandemic which consisted of a medical response and an exposure mitigation
response. The medical response consisted of learning about the contaminate, how it affects the body, how it
enters the body, and what treatments work after exposure to the contaminate has occurred. The exposure
mitigation first takes the medical science, to specifically know how the contaminate travels, enters the body, and
what its composition is like to better understand its weaknesses.
Many have falsely assumed that the medical industry should handle both angles in this response but this is
incorrect. The medical industry is unschooled in exposure science and is in fact a customer to the exposure
science industry.
History has shown this before but the public and media did not catch these past mistakes. An example of the
inept training of control measures in the medical field occurred during the Ebola outbreak in 2014. A hospital in
Dallas, Texas took in Ebola patients in and found themselves completely unprepared. The medical professionals
got on the internet and threw some PPE together and when nurses were exposed, they became infected. They
were using improper PPE, likely not fit tested for respirator use, and had no training on their control plan.
Thankfully, the nurses survived but the following link will show what was unveiled in court to the bungled
measures taken (https://www.nbcnews.com/storyline/ebola-virus-outbreak/nurse-who-caught-ebola-settles-suitagainst-
dallas-hospital-n672081).
Even the famous Chinese doctor (Dr. Li Wenliang) who warned the world of this virus wore his PPE incorrectly.
Here is a picture of him wearing a surgical mask with a disposable N95 respirator on top of it. This is improper
use because the face mask was preventing the respirator from capturing a seal to his face.
A few months after the pandemic started, we began to monitor the OSHA citation data and found that 90% of the
OSHA citations were happening in medical facilities. We saw consistent law violations in regard to
29 CFR §1910.132 and 1910.134.
If the medical profession were the experts on respiratory protection and PPE use, why are they the largest
violators of the law?
I have trained medical professionals in these exposure prevention measures. The public might be surprised to
know that medical professionals do not learn a lot about masks and respirators in medical school. These aspects
are not a medical science matter, they are an exposure science issue.
Sure, doctors use masks and other PPE as tools in their workplace and in medical school, they learn enough to
know about using a mask, like which mask to wear for certain procedures or the special donning and doffing
maneuvers. That is, how to put them on and take them off without getting contaminated. Those procedures were
designed by people in my profession. A critical point to understanding why healthcare workers in hospital
environments have to follow specifically precise procedures for handling their PPE is because it has already
been scientifically established that PPE can gather and collect contamination from everything it touches and
from the air near it.
There are mechanics and sciences happening all around doctors, keeping them safe, that they are not aware of.
The same is true in the other direction. I'm not going to have opinions about how to perform open heart surgery.
The CDC has failed to properly inform the public on this matter. They have not used a single substantial study to
justify this recommendation and have given organizations like yours, poor guidance through this pandemic. This
opens the gates for other leadership and societal circles to do the same.
This Cambridge mask study ( 1 ) that's making the rounds in public media and academia, for example, took a
handful of volunteers and tested out numerous masks and testing a few different improvement hacks. Their idea
was to find reasonably simple things that people could improvise on their own to improve their mask to nearly the
same level of particle performance as N95's.
A major problem here is that the professionally manufactured N95s are precision manufactured for a specific
tightness and fit. And they are governed by specific laws. Such as anyone required to wear an N95 in the
workplace has to have a medical examination. [29 CFR § 1910.134(c)(1)(ii)]
Why is that do you supposed? Well its because 50 years of vigorously tested mask science has already
established that tightly fitting masks are potentially dangerous to anyone, which is why medical clearance is
required before the use of any tightly fitted mask.
So now you've got a study telling you to build your own mask out of whatever random material, and you can
wrap stuff around your head, to whatever tightness you think works. Hey, very little bit helps right?.
That's not science and you are potentially creating more collateral risks by these recommendations.
Then there's this gem found in that study...
“One participant was unable to fit the KN95 mask with ear bands tied. Another participant was unable to fit one
brand of pantyhose over his head without the pantyhose tearing. In these two cases, the problematic hack was
not tested. “
So now you just discarded 25% of your testing base. Are we to believe that in that whole college campus you
could not go find another person, who did not have an ear sore, to fill in.?
The real problem though is the CDC that allows this low-level science to be used for the same role that before
the Covid years was only reserved for high level, thorough, methodological science.
In July of last year I published an extensive mask science documentary which showed omissions, errors and
flaws, and in some cases provable fraud in studies.
Do you want to know why the CDC has gotten away with this sloppy science? It is leaders like you all at the local
level let them get away with it. City leaders, school boards, and district health departments are all responsible!
It is because you have not done your job from day one. You are supposed to be another level of scientific rigor.
You are supposed to be the feedback.
Instead, you have become enablers of garbage science. An echo chamber of dangerous ignorance.
You chose to deflect and just do what you were told. You never questioned anything. You just assumed
everything they were telling you was done correctly and was proper science. You never actually looked at the
science personally or sought someone with professional training to advise you.
Take a few of these newest mask studies the CDC put up, for example. Ok well, they are not new studies; they
were done last year and the CDC has just been sitting on them and conveniently decided to put them up
recently.
Fikenzer S, Uhe T, Lavall D, et al.
“Ventilation, cardiopulmonary exercise capacity and comfort are reduced by surgical masks and highly impaired
by FFP2/N95 face masks in healthy individuals. These data are important for recommendations on wearing face
masks at work or during physical exercise. ” (3)
Lassing J, Falz R, Pokel C, et al
“In the healthy young men in this study, the use of surgical face masks was associated with a significant
increase in airway resistance, reduced oxygen uptake, and increased heart rate during continuous exercise.” (4)
Driver S, Reynolds M, Brown K, et al.
“Our data suggest that wearing a cloth face covering negatively impacts exercise performance in healthy adults
during a maximal treadmill test. As both physiological and perceptual factors were negatively impacted, coaches,
trainers and athletes should be aware of the effect of cloth face coverings “ (5)
Did any of you communicate the proper advisories to athletic directors? Or made any of the other nuanced
adjustments advised by the “science? Of course not. It was easier to absolve yourself from accountability by
being able to say “...hey we're just following the CDC guidelines”
Even if masks worked, why are you putting them on children? The “science” has clearly shown that children are
not being significantly harmed by the COVID-19 virus and even Tony Fauci had to admit that during the Delta
spike kids were not in hospitals because of the virus. In addition, children are not spreading the disease. So,
explain why the kids need a mask when the data clearly shows that they do not?
This letter may serve as notification that you have been informed that your policies, which are based on
erroneous or incomplete information, may be causing harm to your employees and students. Especially those
who have been denied exemptions.
Parents, you may have heard about the group of parents in Florida who had their child's masks tested for
contamination at the University of Florida. ( 6 )
“ Half of the masks were contaminated with one or more strains of pneumonia-causing bacteria. One-third were
contaminated with one or more strains of meningitis-causing bacteria. One-third were contaminated with
dangerous, antibiotic-resistant bacterial pathogens. In addition, less dangerous pathogens were identified,
including pathogens that can cause fever, ulcers, acne, yeast infections, strep throat, periodontal disease, Rocky
Mountain Spotted Fever, and more. “
This shows foundational information that warrants further investigation. Engage in scientific process!
Parents, if you are interested in testing your child's masks, you can email me at
tyscienceguy@protonmail.com and we will give you guidance on these processes
To our community leaders, in the future you can no longer claim that you were not made aware of the facts and
concerns in this issue, that excuse is gone. If you need assistance, please contact a local firm that has industrial
hygienists and safety and health professionals. My firm, as from the beginning, is always willing to assist as well.
It’s time that we protect the children, and we stop putting them through these unscientific and unnecessary
measures. These measures have caused worse exposure and risk for children than the actual virus.
We are two years into this dog and pony show and it’s time to shut it down.
Sincerely,
Tyson Gabriel, BS, IH
References:
( 1 )
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0262830
( 2 )
O’Kelly E, Pirog S, Ward J, Clarkson PJ. Ability of fabric face mask materials to filter ultrafine particles at coughing
velocity. BMJ Open. 2020;10(9):e039424.
( 3 )
Fikenzer S, Uhe T, Lavall D, et al. Effects of surgical and FFP2/N95 face masks on cardiopulmonary
exercise capacity. Clin Res Cardiol. 2020;109(12):1522–1530.
( 4)
Lassing J, Falz R, Pokel C, et al. Effects of surgical face masks on cardiopulmonary parameters during
steady state exercise. Sci Rep. 2020;10(1):22363.
( 5 )
Driver S, Reynolds M, Brown K, et al. Effects of wearing a cloth face mask on performance,
physiological and perceptual responses during a graded treadmill running exercise test. Br J Sports
Med. 2021; bjsports-2020-103758.
( 6 )
https://rationalground.com/dangerous-pathogens-found-on-childrens-face-masks/
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