Given that they’re just about everywhere, you may wonder how effective they actually are.
Businesses and workplaces have pointed to plexiglass dividers as one tool they are using to keep people safe against the spread of the virus. But it’s important to know there’s little data to support their effectiveness, and even if there were, the barriers have their limits, according to epidemiologists and aerosol scientists, who study airborne transmission of the virus.
But those benefits haven’t been proven, according to Wafaa El-Sadr, professor of epidemiology and medicine at Columbia University. She says there have not been any studies that examined how effective plexiglass barriers are at blocking large droplets.
Most droplets people release when they talk or breathe are in a “size range that will flow past the barrier,” said Pratim Biswas, an aerosol scientist at Washington University in St. Louis.
There’s also another problem in some cases: the size of the barriers. Marissa Baker, an assistant professor at the University of Washington, has been conducting a separate study of coronavirus safety measures at nine grocery stores in Seattle and seven in Portland, Oregon, each month since May.
She has observed that plexiglass shields at cash registers and self-checkout stations are often too small to even prevent droplet transmission between customers and workers.
“Some are smaller and don’t even cover the nose of a tall individual,” she said. “The airborne particles are going to be able to get anywhere, regardless of the barriers.”
Restaurants and retail industry trade groups say they view the barriers as one potential way to combat the spread of Covid-19, in addition to other measures.
“We know so much more now, and we follow the scientific data to guide our decisions. Based on the recommendations by public health authorities, it would be important to look at layered controls in any environment,” a spokesperson for FMI, a trade group for the grocery industry, said in an email. Mask wearing and maintaining social distancing “are still two effective means to mitigate risk of contracting the virus.”
The National Restaurant Association said in a statement that plexiglass shields and barriers are a tool that “when combined with other best practices — like face coverings, appropriate social distancing, and handwashing — provide an additional level of safety.”