Masks also protect you from flu
By UNIVERSITY OF EAST ANGLIA
The peer-reviewed study found that face shields did not
give high levels of protection against external droplets.
According
to a recent study from the University of East Anglia, if you used a face
shield during the epidemic, it probably didn’t provide you with a high degree
of protection against Covid. A study released today evaluated 13 different
types of face shields in controlled laboratory environments.
While all of the face shields offered some protection, none provided high levels of protection from external droplets. In addition to doing laboratory studies on face shields, the research team polled individuals, including health workers, in middle-income nations (Brazil and Nigeria), regarding their attitudes about face shields as PPE.
Professor
Paul Hunter, from UEA’s Norwich Medical School, said: “Face shields have been
popular because they don’t hinder breathing, they allow more natural
communication than face masks and they provide splash protection. They were
widely used throughout the Covid pandemic. But until now there hasn’t been a
great deal of evidence about how protective they really are – particularly
taking into account how people use them in the real world, and especially in
poorer parts of the world. We wanted to find out more about how protective
different styles of face shields might be, both in the lab and in real-world
settings.”
UEA
researchers collaborated with staff at the Health and Safety Executive (HSE),
Britain’s regulator for workplace health and safety, who tested 13 face shield
designs in a controlled laboratory setting, using a ‘coughing machine’ that
ejected fluorescent drops onto manikin heads.
How
much the manikin face was contaminated by the simulated cough droplets was
graded from most to least.
Dr.
Julii Brainard, from UEA’s Norwich Medical School, said: “The lab tests showed
that all of the face shields provided some protection, but none gave high
levels of protection against external droplet contamination. The level of
protection provided was influenced by design features, as well as which way the
manikin had its head turned when it was ‘coughed’ at. We found that large gaps
around the sides, and sometimes the bottom or top, allow respiratory droplets
from other people to get to the face and this means exposure to possible
viruses. The shields that offered most protection were closed across the
forehead and extended well around the sides of the face and below the chin.
It’s important to know that the lab experiments are in the scenario of someone
actively coughing at the shield wearer from close proximity. But the chances of
droplets getting around the shield onto the face from just speaking are much
lower.”
To
learn more about how face shields are used in a real-world setting, the team
surveyed more than 600 people across Nigeria and Brazil, including health care
staff.
Dr.
Brainard said: “We wanted to know about how users cleaned them, and the things
that mattered most when choosing facial PPE during the pandemic. Not
surprisingly, we found that people want proven protective products that are
comfortable, stable on their heads, easy to clean and don’t look strange. This
study is important because the acceptability of facial PPE during the pandemic
has been mostly studied in richer countries like the UK or USA. The
participants in our study were in Nigeria and Brazil and we shouldn’t assume
that people in all countries view facial PPE in the same way. It is also
important to understand what design features in face shields could be more or
less protective so that people are able to choose the most effective designs.
“Finally,
we wanted to know how people cleaned reusable face shields – methylated or
surgical spirits were popular, for instance, but so was plain water and soap.
Some cleaning chemicals could be incompatible with shield coatings intended to
prevent fogging or facilitate quick-drying, for instance. Dust outside and
fogging inside shields were occasional problems, too,” she added.
The
study was recently published in the American Journal of Infection
Control. In a related project, the HSE team tested face shields
available for use in the UK. The results of this work, together with more
details of the cough simulator, are published in the journal Annals of Work
Exposures and Health.
Dr.
Brian Crook, a microbiologist on the HSE team, said: “It is important that
people using any type of PPE to protect themselves from infection know how
effective it is, but also its limitations. We are working with an international
standards committee to write guidance towards a better means of providing that
information.”
Reference:
“Evaluation of Face Shields, Goggles, and Safety Glasses as a Virus
Transmission Control Measure to Protect the Wearer Against Cough Droplets” by
Samantha Hall, Paul Johnson, Claire Bailey, Zoe Gould, Robert White and Brian
Crook, 20 July 2022, American Journal of Infection
Control.
DOI:
10.1093/annweh/wxac047
