Date: May 18th, 2020

I was asked to participate in a debate regarding the issue of Masks4All in Canada by the people involved in the COVID Information for Canadian Physicians Facebook group. This is a private group ~22,000 physicians, residents, students and nurse practitioners from around the world.

Dr. Joe Vipond

I was reluctant to participate but was convinced after having a good conversation with the organizers and Dr. Vipond. They assured me it would be respectful, focus on the evidence and be an educational experience for the audience. These are stressful times and we all want the best recommendation for patients, based on the best evidence to ensure community well-being.

Arguing for the affirmative position was Dr. Joe Vipond. He is an emergency physician at the Rockyview General Hospital and a clinical assistant professor at the University of Calgary. He has generously made available his notes from the debate that include links to more information.

I argued against the resolution. This does not mean I am against wearing a cloth mask in public. Those who know my not so secret identity (BatDoc) know that I am often seen in public wearing a mask. This is not the type of mask Dr. Vipond and I were debating.

We were not talking about wearing medical masks, surgical masks, N95 masks or respirators by healthcare providers on the front lines of COVID19. The debate also did not include symptomatic people or those caring for high-risk people. We were only debating the issue of universal cloth Masks4All in public.

To be very clear, I am not anti-mask wearing in public. My position is “it all depends” as taught by my evidence-based medicine (EBM) mentor Dr. Andrew Worster from BEEM.  I am just not in favour of a mandatory universal Masks4All in public in Canada.

You can watch the Mask4All debate on YouTube.

ResolutionBe it resolved that a mandatory universal mask for all to prevent transmission of COVID19 be recommended for Canadians.

Dr. Kashif Pirzada

We were each given four minutes for an opening statement, three minutes for a rebuttal, four more minutes for a second affirmative statement and finished with three minutes for another rebuttal and closing statement.

We had two moderators for this debate. Dr. Kashif Pirzada is an emergency physician in Toronto with an interest in startups and innovation.  He is also a co-founder of Conquer-Covid19, a charity that sources personal protection equipment for frontline health workers.

Dr. Jennifer Kwan

Dr. Jennifer Kwan is a family physician in Burlington, Ontario. She is known for COVID19 data visualizations on Twitter (@jkwan_md) along with the HowsMyFlattening team, and is an advocate for #Masks4Canada and personal protection equipment donations with Halton Regional Chinese Canadian Association.

I am not against wearing a cloth mask in public. My position is that I am not convinced that a mandatory Masks4All in public by people that are practicing physical distancing will prevent transmission of clinical disease (COVID19). This is an important distinction.

Dr. Samir Grover

Questions on the Facebook feed were moderated by Dr. Samir Grover. He is an associate professor and program director for gastroenterology at the University of Toronto. Kashif and Samir have a podcast about COVID-19 called “The Medicine Club” which can be accessed on Twitter @TheMedClubTO

It is important in any discussion to be clear on the terms being used.

  • Mandatory: Required by a law or rule OBLIGATORY.
  • Universal: Including or covering all or a whole collectively or distributivity without limit or exception.
  • Public: All public places (not to private places)
  • Clinical Disease: There is a difference between a DOO (Disease Oriented Outcome- detection of COVID19 RNA) and a POO (Patient-Oriented Outcome – clinical disease). As a clinician, I am more interested in POOs and less interested in  DOOs.
  • Epistemology: The study or a theory of the nature and grounds of knowledge especially with reference to its limits and validity

I want to accept positions for good reasons not because it is someone’s opinion.  Just because someone is a gifted clinician and an excellent advocate for the environment does not mean they are an expert in clinical epidemiology, biostatistics and critical appraisal. This brings up the possibility of a Dunning-Kruger Effect.

Here is a link to a great video made by Dr. Rohin Francis (@MedLifeCrisis). It is a satirical ad for Dunning-Kruger Alcohol and uses humour as a COVID19 coping strategy.

“The Dunning-Kruger effect is a cognitive bias in which people wrongly overestimate their knowledge or ability in a specific area. This tends to occur because a lack of self-awareness prevents them from accurately assessing their skills.”

My credentials included 37 years of medical research, Senior Editor of Academic Emergency Medicine (AEM), advance training in clinical epidemiology, biostatistics and critical appraisal.  I teach these skills and cognitive bias and logical fallacies to MSc and PhD students in the Department of Epidemiology. I have published dozens of critical appraisals which are considered a higher level of evidence than a randomized control trial on the EBM pyramid of evidence.  Basically, I am an uber nerd.

This does NOT make my position of the evidence on cloth Masks4All correct or an argument from authority. The information is presented as evidence of my expertise and to support my claim that this is my lane.

In the scientific method we start with the null hypothesis. The null would be that there is no statistical difference between universal/mandatory cloth masks4all and not wearing a cloth mask in public. The burden of proof is on those making the claim that cloth masks4all in public is superior in preventing transmission of clinical disease (POO) in those physically distancing. Without sufficient evidence we should not accept the claim. Therefore, we should accept the null hypothesis of no superiority.

Everyone will have a different level of evidence required to accept a claim. I want patients to get the best recommendation, based on the best evidence. Without evidence people are providing an opinion. Christopher Hitchens famously said “that which can be asserted without evidence, can be dismissed without evidence.” (Hitchens’ Razor)

Peltzman Effect: Risk Compensation and Risk Homeostasis

Prof Sam Peltzman

Sam Peltzman was a professor who wrote a paper in 1975 about seatbelt regulations (The Effects of Automobile Safety Regulation, J Political Economy 1975).

Professor Peltzman argued that the benefits of seatbelt would be offset by more pedestrian deaths and more nonfatal accidents because of “driving intensity”. This was driving faster and more recklessly with the security of the safety belt. His hypothesis was proven to be wrong and seatbelts were a net benefit but it did open a field of risk compensation.

Bill Booth

There are examples where an intervention did have a positive outcome (seat belts in cars and helmets when cycling) but there are other examples where the theoretical benefits did not materialize in the real world. This includes parachute equipment advancements to prevent morbidity and mortality from jumping out of a plane. Bill Booth was a person who designed safety equipment for parachutes. They should have decreased morbidity and mortality of jumping out of plane. The data showed it did not. There was risk compensation and it did not have the impact he hoped (Booth’s Second Law).

“The safer skydiving gear becomes, the more chances skydivers will take, in order to keep the fatality rate constant.” 


Another example is condoms to prevent HIV virus transmission during that pandemic. The no glove, no love was thought to be a “no brainer”. It was widely felt that condoms could help prevent the spread of the HIV epidemic. However, the impact of condoms alone was mitigated during a global pandemic due to risk compensation/homeostasis. There are a significant portion of people who dislike using condoms, use is often irregular, and condoms seem to give a sense of security. This can lead to disinhibition, in which people may engage in risky sex with condoms (Shelton JD. Ten myths and one truth about generalized HIV epidemics, Lancet 2006).

Risk compensation/homeostasis (Peltzman Effect) can also be seen in the unintended behavioral responses by patients and physicians to health care interventions. This may explain why certain health care interventions that seem logical and foolproof fail to demonstrate real-world benefits (Prasad and Jena Healthc Amst 2014).

EHR and Burnout

Electronic Health Records (EHRs) is just one newer example of the risk compensation hypothesis. One of the claimed benefits of introducing EHRs was to decrease medication errors. While they did demonstrate fewer of these errors they increased other errors. It is also unclear if the type of medication errors that were reduced had an important POO.

EHRs also have been shown to negatively impact emergency department efficiency. They have been blamed for contributing to physician burnout. Burnout is associated with worse patient care.

  1. Gray A et al. The impact of computerized provider order entry on emergency department flow. CJEM 2016.
  2. Shanafelt et al Changes in Burnout and Satisfaction With Work-Life Balance in Physicians and the General US Working Population Between 2011 and 2014. Mayo Clin Proc. 2015;90(12):1600-1613
  3. West CP, Huschka MM, Novotny PJ, et al. Association of perceived medical errors with resident distress and empathy: a prospective longitudinal study. JAMA. 2006; 296(9):1071-1078.
  4. Shanafelt TD, Balch CM, Bechamps G, et al. Burnout and medical errors among American surgeons. Ann Surg. 2010;251(6): 995-1000.
  5. Firth-Cozens J, Greenhalgh J. Doctors’ perceptions of the links between stress and lowered clinical care. Soc Sci Med. 1997; 44(7):1017-1022.
  6. Grol R, Mokkink H, Smits A, et al. Work satisfaction of general practitioners and the quality of patient care. Fam Pract. 1985; 2(3):128-135.

A cognitive bias is to over-estimate potential benefit and under-estimate potential harms. It has been shown that harms are systematically under-reported in the medical literature. If you don’t look for harms, you won’t find them (Saini et al. BMJ 2014).

I am not claiming cloth mask wearing will increase harm. My position is I do not know if it will or will not. However, there is not sufficient evidence to accept the claim that wearing a cloth mask in public by asymptomatic people who are physically distancing will result in a benefit by reducing clinical disease. Without sufficient evidence we should accept the null hypothesis of no superiority.

Again, I am not anti-mask but rather pro-SmartMask (masks sometimes) and it all depends. We should use masks where the risk is high but not make it into a law. I would rather convince people to do something for the right reason rather than force them to do it for very weak reasons. It would erode our credibility as scientists and impact negatively on the therapeutic alliance as physicians.

Logical Fallacies

  • Strawman Arguments– Misrepresenting my argument to easily knock it down…I’m not anti-mask but rather pro-Smart Mask
  • False Analogies– Peeing on each other does not usually cause UTIs in others. Urine is not a respiratory illness.
  • Appeal to Emotion– Manipulate an emotional response in place of a valid or compelling argument (all these people could die…what if you are wrong)
  • Nirvana Fallacy– If the evidence is not perfect then it is not accepted. I am not asking for perfect evidence that cloth masks4all work…just sufficient evidence to accept the claim.
  • Tu Quoque– Avoid discussing the evidence by turning it back on the accuser and answer a criticism of their point with a criticism not directly related to the issue. (evidence for hand washing, evidence for shelter in place…not debating those topics)
  • Personal Incredulity– Just because it is difficult to understand does not make it untrue (Peltzman Effect or risk homeostasis/compensation)
  • Special Pleading– moving the goal posts
  • Shifting the Burden of Proof– The burden lies with those making the claim. Not for me to disprove. I am not required to disprove masks work. Also, I have not claimed masks are necessarily dangerous. I have asked that the hypothesis of risk compensation be considered (no considered true but recognized as a potential mitigating factor in any efficacy of the mask4all policy)
  • Bandwagon– Appeal to popularity. Just because all the other countries are doing it does not make it correct. If all your friends jumped off a cliff would you?
  • Black or White– Presenting only two alternative states. Dichotomizing when there are in fact more possibilities. It is not maks4all and no mask but rather masks sometimes.
  • Begging the Question –Circular argument in which the conclusion was included in the premise. Cloth masks have not been demonstrated to work in preventing clinical disease. You cannot pre-suppose they do work and just need to be implemented.
  • Texas Sharpshooter– Cherry pick the data cluster to suit your argument. Look at these countries rather than all the countries.
  • Correlation- This is not causation. There may be many unmeasured confounders for the results seen from observational trials comparing countries with and without mandatory mask regulations.

Again, we often have a cognitive bias to over-estimate potential benefits of an intervention and under-estimate the potential harms. It is important not to just do something but sometimes to just stand there. Not doing something is doing something and it may have a net benefit. There is an excellent article by Keijzers  et al called: Don’t Just Do Something…Stand There! The value and art of deliberate clinical inertia (Emerg Med Australas. 2018).

Precautionary Principle: The Precautionary Principle was argued by Dr. Vipond in considering the proposed mandatory universal masks for all resolution. This principle is described as:

“a broad epistemological, philosophical and legal approach to innovations with potential for causing harm when extensive scientific knowledge on the matter is lacking. It emphasizes caution, pausing and review before leaping into new innovations that may prove disastrous. Critics argue that it is vague, self cancelling, unscientific and an obstacle to progress.”

A main argument against the precautionary principle is the precautionary dilemma.


Sweden: This country’s approach to COVID19 has been controversial. They did not implement strict lock down and mandatory mask policy. However, a reason for flattening the curve was to spread out the morbidity and mortality to not overwhelm the healthcare system. Flatting the curve was not to decrease COVID19 morbidity and mortality.

Comparing Sweden to other countries this early into a pandemic that will play out over weeks, months or even years is premature. It is like stopping a hockey game after the first period and saying Norway wins because their statistics are better. The rest of the pandemic needs to play out to the end before we know the final results.

All Cause Morbidity and Mortality: We should not just count COVID morbidity and mortality. This is a disease specific outcome. We need to consider all-cause morbidity and mortality. If less people die from COVID but the over-all mortality rate is higher due to mandatory public health policies, it should not be considered a “win”.

It has been argued that the absence of evidence is not evidence of absence. However, the absence of evidence is not evidence of efficacy. Just because you don’t have evidence does not mean the intervention (cloth masks worn by all in public) does not work but it also does not mean that masks do work. Just because there is no evidence that I can dunk a basketball does not mean I can dunk a basketball.

Asymptomatic Transmission: Much of the data on asymptomatic transmission of COVID19 comes from close contact and family members sheltering together. This includes people sharing a bed, bathroom, toothbrushes, kitchens, etc. COVID19 had been found in semen and feces. There is evidence COVID19 can linger for hours if toilets are not flushed with the lids down. What is the external validity of asymptomatic household transmission data compared to that of public transmission of asymptomatic people wearing cloth masks in public who are practicing social distancing?

Selection Bias: There are 195 countries in the world with most of them reporting cases of COVID19. If only a few countries are used as an example of how mandatory masks for all is associated with better outcomes, this can suffer from selection bias. Bias is  something that systematically moves us away from the “truth” or the most accurate point estimate of effect size. If only certain countries are selected it is cherry picking the data and can be considered a Texas Sharp shooter fallacy.

A more rigorous way to quantify the association between countries with and without a mandatory public mask policy would be to conduct a systematic review (SR). IF only some countries are selected this can lead to selection bias. There are the MOOSE guidelines that provides methodology for a SR of observational studies. This includes a checklist for assessing the quality of this type of SR.

Top Countries: Without selecting all countries, another way to assess the association between masks and outcomes would be to look at the countries that are doing the “best” and the strengths of various associations. This article describes the top eight countries in the world in dealing with the COVID19 global pandemic at the time of its publication (Wittenberg-Cox, Forbes April 13th, 2020).

Three out of the eight countries (37.5%) have a mandatory mask policy. However, seven out of the eight (87.5%) have a woman as their head of state. This is a 50% absolute greater association compared to masks. Should we not be advocating for a woman Prime Minister to address this global COVID19 pandemic? Women leaders have been hailed as voices of reason amid the coronavirus chaos (Hassan and O’Grady, Washington Post April 20th, 2020).

Culture and Religion: Nunavut is the largest part of Canada by geographic area. The vast majority of its population are Inuit people. There have been zero cases of COVID19 at the time of the debate. Does that mean all of the Inuit people representing the largest part of Canada will be forced to wear a mask in public? This was to illustrate how complicated such a mandatory mask for all policy can be. As a white male of European dissent from the south, I would be very cautious about making a law without consulting the Inuit people.


It gets even more complicated with religion. A year ago, the Quebec government enacted Bill 21 that banned wearing religious symbols. The bill forces everyone to uncover their face to give or receive specific public services. This disproportionately targets Muslim women as opponents of Bill 21 have pointed out because it bars niqab-wearing women from fully participating in society..

Last month, Dr. Theresa Tam (Chief Public Health Officer) recommended that people wear non-medical face masks in public to help prevent the transmission of COVID-19, especially by people who show no symptoms and may be transmitting the virus unknowingly.

What message are we giving this religious minority if we have conflicting laws. One that says they must uncover their face and this other law saying they must cover their face? This seems hypocritical.

Masks4All but Not for Young Children: The American Academy of Pediatrics (AAP), Canadian Paediatric Society (CPS) and the Centre for Disease Control (CDC) recommend not using cloth face covering that covers their nose and mouth when they are out in the community. Cloth face coverings should NOT be put on babies or children younger than 2 because of the danger of suffocation. Children younger than 2 years of age are listed as an exception as well as anyone who has trouble breathing or is unconscious, incapacitated, or otherwise unable to remove the face covering without assistance.

Private vs. Public: Most of the data on asymptomatic transmission is from family members and close contact. It was previously mentioned that COVID19 is found in semen. Does that mean we need to enter the private lives and homes of people to prevent transmission? Do we need a law for condom use or abstinence? It was former Prime Minister Pierre Elliot Trudeau who said in 1967 “there’s no place for the state in the bedrooms of the nation.” 

Change of Behaviour (Possible Peltzman Effect): Michigan has a stay an home order and cell phone data showed that more than 50% were abiding by that order in the prior six weeks. Since not everyone who has a cellphone agreed to share their data, and some people don’t have cellphones, the figures could actually be much higher.

A mandatory mask order in public came out at the end of April in Michigan. Cell phone data from the first week of May showed the number of people abiding by the stay at home order had decreased by 11%. This means that the mandatory mask order was associated with an increase of about one million people violating the stay at home order. This is only an association but it does provide evidence that making a mandatory mask order could give people a false sense of security and encourage them to violate the stay at home order (risk compensation).

The United States of America: The CDC increased their guidance on cloth mask wearing to “recommended” (not mandated) on April 3, 2020. There were ~280,000 cases of COVID19 and ~9,000 deaths at that time. As of May 15th, there are ~ 1.5 million cases and 90,000 deaths. This represents a five fold increase in cases and ten fold increase in COVID19 deaths since stronger mask recommendations were announced. That means stronger masks recommendations are associated with more cases and more deaths. The USA is now number one in the world based on these metrics.  This is only an association and does not provide information on whether or not a national mandate for universal cloth masks in public would have a net positive or negative impact on COVID19 transmission.  

To state it again, I am not anti-mask in public but rather pro-SmartMask. I am saying we can be smarter than that and “it all depends”. One size does not fit all. What may work in Calgary, Alberta (population 1.3 million) may not work in Exeter, Ontario (population 4,600).

This could be another case of Urbansplaining. Urbansplaining is when an urban clinician comments on or explains something to a rural clinician in a condescending, overconfident and often inaccurate or oversimplified manner.

Professor Richard Feynman famously said…It’s ok to say “I don’t know”. We need to get comfortable with uncertainty. I am comfortable with saying I don’t know. The “what if you are wrong” is a logical fallacy (appeal to emotion) and cuts both ways…what if they are wrong?

The strength of recommendations/laws should be proportional to the evidence. Any intervention that has potential benefit also has potential harm.  Anyone who says they know what the net impact of these social policies like Masks4All in public is expressing some hubris.

We have been fooled many times in the past in medicine. We have over interpreted basic science (pathophysiology) only to be shown that the intervention did not work or even increased harm (ex: epinephrine for out of hospital cardiac arrest or supplemental oxygen in acutely ill patients). There is a literature database on medical reversal.

It was George Santayana who said “those who cannot remember the past are condemned to repeat it.” We are seeing this with pandemic science out of control. Jeanne Lenzer and Shannon Brownlee wrote that the “toxic legacy of poor-quality research, media hype, lax regulatory oversight, and vicious partisanship has come home to roost in the search for effective treatments for COVID-19.” Here is the first paragraph from their excellent article:

On September 14, 1918, in the midst of the worst pandemic in modern history, an article in the New York Times quoted Dr. Rupert Blue, then surgeon general of the US Public Health Service. Blue reported that doctors in many countries were treating their influenza patients with digitalis and the antimalaria drug quinine.There was no evidence that the two drugs were any more effective than folk remedies being used by patients, including cinnamon, goose grease poultices, and salt stuffed up the nose, but doctors were desperate and willing to try just about anything. They would eventually abandon quinine and digitalis as treatments for flu when studies showed they were not only ineffective but caused serious and sometimes deadly side effects.

The veil of ignorance was proposed by a Philosopher John Rawls. He suggested that we should imagine we sit behind a veil of ignorance that keeps us from knowing who we are and identifying with our personal circumstances. By being ignorant of our circumstances, we can more objectively consider how societies should operate.

So, according to Professor Rawls, approaching tough issues through a veil of ignorance and applying these principles can help us decide more fairly how the rules of society should be structured. And fairness, as Rawls and many others believe, is the essence of justice. Unless we operate under a veil of ignorance we risk being dictated by the tyranny of the majority.

I am just encouraging reason combined with kindness. Instead of Masks4All why not SmartMasks? We can educate when wearing one might be best (crowded situations, high prevalence and where physical distancing is impossible). But we should not force people to wear a mask by shaming, blaming, fining or jailing them for not wearing a mask if asymptomatic and properly adhering to physical distancing principles.

Here is a wonderful article by Ivry Zagury-Orly and Richard M. Schwartzstein in NEJM April 28th, 2020. It is entitled A Reminder to Reason. I encourage everyone to read the entire article but here is the last paragraph.

We are living through an unprecedented biopsychosocial crisis; physicians must be the voice of reason and lead by example. We must reason critically and reflect on the biases that may influence our thinking processes, critically appraise evidence in deciding how to treat patients, and use anecdotal observations only to generate hypotheses for trials that can be conducted with clinical equipoise. We must act swiftlybut carefully, with cautionand reason.

Summarize: We all want what is best for the well-being of society. Two caring and smart physicians can look at the same information and come to a different conclusion and interpretation. I am not anti-mask or claim that cloth Masks4All in public will increase harm. I am just not convinced that it will have a net benefit of preventing transmission of clinical disease.

  • The observational data does not support Masks4All is necessary for successfully addressing COVID19
  • I suggest a SmartMask initiative
  • Children under the age of two years should not have cloth face coverings
  • I advocate for more women leaders and in particular our first elected woman Canadian Prime Minister.
  • Any laws on public masking need to be thought through carefully to not infringe on aboriginal rights, religious beliefs and other serious concerns.