April 28, 2021

expert reaction to whether masks need to be worn outdoors

An expert debate on whether masks should be worn outdoors has been published in the BMJ.

Dr Simon Clarke, Associate Professor in Cellular Microbiology at the University of Reading, said:

“The evidence for mandating mask wearing indoors remains weak and circumstantial and it should be remembered that in the UK, it is intended to support other measure like social distancing, rather than act as an alternative.  Their effectiveness outdoors remains even more questionable, and will remain so without evidence.  It’s highly unsatisfactory, not to mention profoundly unscientific, to point the finger at outside events that have had substantial indoor elements and claim that they’re evidence of spread outdoors.  Similarly, localities with stricter mask mandates are also likely to be stricter with other measures. 

“In order to get buy-in from the public and retain their trust as the pandemic grinds on, any new or continued restrictions on people’s lives need to be based on sound science rather than supposition.”

Prof Paul Hunter, Professor in Medicine, The Norwich School of Medicine, University of East Anglia, said:

“Face masks do not need to be worn out of doors for the reasons clearly stated by Dr Cevik. Indoor transmission is about 19 times more effective than outdoor transmission.  In the UK there has been no obvious impact of crowded beaches or demonstrations on subsequent transmission. Events such as Cheltenham last year that did seemed to be followed by increased transmission seem to also have packed pubs and public transport.

“There are also good reasons for not wearing masks outdoors. If the masks get wet through rain or through condensation in cold weather they do not filter properly, so could be less effective when you do go indoors.”

Prof Jonathan Ball, Professor of Molecular Virology, University of Nottingham, said:

“We know that masks, when worn correctly and in certain settings, can reduce the risk of virus transmission. However, it is less clear if this benefit extends to when masks are worn more generally, even less so when outdoors. It is too easy to draw on anecdotal evidence to support or refute the impact of mask wearing on reducing virus transmission, and until we have robust controlled trial data we will never know for sure.”

‘Should masks be worn outdoors?’ by various authors was published in The BMJ at 23.30 UK TIME on Wednesday 28 April 2021.

DOI: 10.1136/bmj.n1036

Declared interests

Prof Jonathan Ball: “No COIs.”

None others received.