Sept. 8, 2020 -- When the World Health Organization declared COVID-19 a pandemic in mid-March, the management at Milt & Edie's Drycleaners in Burbank, CA, knew they needed to protect their workers and customers. They mandated masks and hung plastic shields at every workstation where customers drop off clothes. The shields allow customers and workers to see each other and talk easily, but not worry about getting sneezed on or coughed on.

"We installed those almost immediately," says Al Luevanos, a manager at the cleaners. And it's not unnoticed by workers. "It makes me feel safer, knowing I work for people who care not only about the health of the customers but also the workers," says Kayla Stark, an employee.

Plexiglass partitions are seemingly everywhere these days -- grocery stores, dry cleaners, restaurant pickup windows, discount stores, and pharmacies. They're recommended by the CDC and the Occupational Safety and Health Administration (OSHA), among others.

"Grocers were among the first retailers to adopt the plexiglass barrier," says Dave Heylen, a spokesperson for the California Grocers Association, Sacramento, an industry group that represents about 300 retail companies operating over 7,000 stores. Nearly all grocers did so, he says, without any formal recommendation from the association.

That’s also true nationwide, says Jim Dudlicek, a spokesperson for the National Grocers Association, in Arlington, VA, with more than 1,500 members from the retail and wholesale grocery industry. The association polled members when the pandemic hit and found that 84% of those who replied had put plastic shields in their stores. The association did not issue formal guidelines about barriers, but ''we advised our members to follow the CDC guidelines," he says.

Because of COVID-19, the plexiglass business is now booming. Sales of plexiglass, and the trademarked Plexiglas, increased two to three times over the $250 million in sales from March to May 2019, according to statistics supplied by the International Association of Plastics Distribution.

Despite the widespread recommendations for the plexiglass barriers and their widespread use, research on how well they work to slow the spread of COVID-19 is lacking, experts say.

"There are, to my knowledge, no peer-reviewed studies assessing the efficacy of these barriers," says Michael Fischman, MD, a consulting doctor in occupational and environmental medicine and toxicology in Walnut Creek, CA, and clinical professor of medicine at the University of California, San Francisco. Even so, he says, "intuitively, it makes sense that the barrier would capture large droplets and that might reduce the risk of transmission."

He co-wrote a fact sheet for the American College of Occupational and Environmental Medicine on using barriers for workplaces. ''Plexiglass is advantageous because it is readily available, easily worked, smooth, transparent and easily cleanable," he wrote. Plexiglass is more durable and less expensive than other forms of barriers, such as tempered glass or polycarbonate, he says.

Fischman says he sees the barriers as ''a reasonable engineering control" that is a supplement and not a substitute for masks and physical distancing.

"It's just another layer of protection, and usually we add that layer when the risks go up," says Denise Bender, an assistant director in the environmental health and safety department at the University of Washington, Seattle. The university has been adding plexiglass barriers to lobby areas, reception desks, and in the student pharmacy. The barriers don't mean people can skimp on wearing masks and keeping social distance, she agrees.

While barriers may help protect against large droplets spread by coughing or sneezing, the coronavirus can also be spread through smaller droplets that hang in the air.

One expert says the plexiglass shields work kind of the same way as face shields. "Face shields will block the large droplets," says William Ristenpart, PhD, a professor of chemical engineering at the University of California, Davis. Likewise, plexiglass partitions ''would be less effective against aerosol transmission" than droplet transmission. "

Plexiglass may also be headed to restaurant tables soon. A French company is producing Plex'Eat, protective plexiglass bubbles that hang from the ceiling and enclose the heads of individual diners.

Michael Fischman, MD, consulting doctor in occupational and environmental medicine and toxicology, Walnut Creek, CA; clinical professor of medicine, University of California, San Francisco.

Denise Bender, assistant director, occupational safety and health, environmental health and safety department, University of Washington, Seattle.

University of Washington: "University of Washington Guidance for Plexiglass Barriers in Support of Covid-19 Prevention Efforts."

American College of Occupational and Environmental Medicine: "COVID-19 Resource Center."

The New England Journal of Medicine: "Barrier Enclosure during Endotracheal Intubation."

Gastrointestinal Endoscopy: "Plexiglas barrier box to prove ERCP safety during the COVID-19 pandemic."

News release, Plex'Eat: "The Innovative Design Solution Launches Its Large-Scale Production."

Al Luevanos, manager, Milt & Edie's Drycleaners, Burbank, CA.

Kayla Stark, employee, Milt & Edie's Drycleaners, Burbank, CA.

Dave Heylen, spokesperson, California Grocers Association, Sacramento.

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