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Face masks for the public during the covid-19 crisis

BMJ 2020; 369 doi: (Published 09 April 2020) Cite this as: BMJ 2020;369:m1435

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Face masks, where and when? Taking the precautionary principle too far

Dear Editor

We totally agree with the authors when they appeal to the precautionary principle to recommend the use of face masks “outside the home in situations where meeting others is likely (for example, shopping, public transport)” (1). The story of a choir practice with 60 people, of whom 45 are known to have developed covid-19, as well as the coronavirus disease outbreak in a call center (2), are good examples of the high risk of transmission in closed spaces with many people singing or speaking loudly for a long time.

In Spain, the wearing of hygiene masks by the general healthy population was made compulsory on public transport as from 4 May. Later on, the leader of Spain’s main opposition party issued a nationwide demand for “the compulsory wearing of masks in public places and mass testing”. Finally, on 20 May the use of some kind of mask, preferably hygiene or surgical, was made compulsory in Spain for all persons over the age of six, whether in the street, outdoors or in closed spaces used by or open to the public. Generalised use of masks by the general public to reduce community transmission of COVID-19 was justified on the principle of precaution. The argument put forward by those who initially and most energetically defended this measure is extremely attractive and tempting, i.e., mass testing and the compulsory wearing of masks would serve to avoid future lockdowns. If it were in fact true that the use of masks everywhere at every time could prevent a future lockdown, then we ourselves would be the first not to leave home without wearing one. However, this is not the case.

The wide use of masks by healthy people in the community setting is not supported by current evidence, as the authors themselves recognize, and carries uncertainties and risks (3). The potential risks (self-contamination that can occur by touching and reusing contaminated masks and a false sense of security, leading to potentially less adherence to other preventive measures, such as physical distancing and hand hygiene, among others) are much more likely to happen when people are forced to carry face masks all the time, particularly in open spaces where high temperatures make their use very uncomfortable, as is the case in Spain. In this context, for which there is no clear benefit-risk relationship, the application of the precautionary principle becomes more questionable.

Additionally, the substantial financial resources required to maintain the continued use of masks by the general public could be better allocated to other public health measures of tried and tested efficacy, such as the promotion of the appropriate respiratory etiquette and hand hygiene. What is more, if it were to be shown that the benefit of compulsory use of masks in open spaces in Spain was outweighed by the potential risks associated with their misuse (an apparently common phenomenon, judging by what can be seen daily on any city street), we would be confronted with a prejudicial health intervention which failed to comply with the maxim “primum non nocere” (first, do no harm), a precept that should govern all health actions.

With the degree of uncertainty currently surrounding the balance of potential benefits and risks of using face masks by the general population, especially in open spaces, it would seem more prudent to issue flexible recommendations than a set of compulsory measures aimed at restricting individual freedoms. While the precautionary principle may be appealed to to support advice to wear masks in certain circumstances, such as on public transport and in crowded closed spaces, any such recommendation should be combined with suitable information about how to use them and the potential risks of misuse.

Mandatory use of masks in open spaces by the general healthy population in Spain is an intrusive measure that restricts individual freedoms, and would not appear to be justified on the basis of available scientific evidence regarding the potential benefits and risks associated with this practice. Moreover, the compulsoriness of wearing a mask should be accompanied by measures designed to ensure that the entire population, and the lower-income strata in particular, enjoy unrestricted access to these, while simultaneously preventing the possible risk of a shortage—present or future—of surgical masks and respirators. Taking the precautionary principle too far might produce just the opposite consequences of what is intended.

1. Greenhalgh T, Schmid MB, Czypionka T, et al. Face masks for the public during the covid-19 crisis. Bmj 2020;369:m1435. doi: 10.1136/bmj.m1435.
2. Shin YP, Young-Man K, Seonju Y, Sangeun L, Baeg-Ju N, Chang BK, et al. Coronavirus Disease Outbreak in Call Center, South Korea. Emerg Infect Dis. 2020;26. doi: 10.3201/eid2608.201274. Online ahead of print.
3. World Health Organization. Advice on the use of masks in the context of COVID-19: interim guidance, 6 April 2020. (accessed 24 May 2020).

Competing interests: No competing interests

04 June 2020
Miguel Á Royo-Bordonada
Public Health Physician
Fernando García-López, Fátima Cortes, Gustavo A Zaragoza.
Public Health Association of Madrid
Santa Isabel, 51, 28012 Madrid