Everybody wanted them: Sales of clear plastic dividers soared in the U.S. after the pandemic hit — tripling year-over-year to roughly $750 million in the first quarter of last year, by industry estimates.
Offices, schools, restaurants and retail stores all sought plexiglass protection from the droplets that health authorities suspected were spreading the coronavirus.
There was just one hitch. Not a single study has shown that plastic barriers in places like schools and offices actually control the virus, said Joseph Allen of the Harvard T.H. Chan School of Public Health.
“We spent a lot of time and money focused on hygiene theater,” said Allen, an indoor-air researcher. “The danger is that we didn’t deploy the resources to address the real threat, which was airborne transmission — both real dollars, but also time and attention.”
“The tide has turned,” he said. “The problem is, it took a year.”
For the first months of Covid-19, top health authorities pointed to larger droplets as the key transmission culprits, despite a chorus of protests from researchers like Allen. Tinier floating droplets can also spread the virus, they warned, meaning plastic shields can’t stop them. Not until last month did the World Health Organization and U.S. Centers for Disease Control and Prevention fully affirm airborne transmission.
That meant plastic shielding had created “a false sense of security,” said building scientist Marwa Zaatari, a pandemic task force member of the American Society of Heating, Refrigerating and Air-Conditioning Engineers.
Recent CDC research found that desk or table barriers in Georgia elementary schools didn’t correlate with lower infection rates. Mask mandates and ventilation improvements did.
An April study published by the journal Science suggested that desk shields might even slightly raise the risk of Covid-like symptoms. And a prepublication paper from Japan late last month linked plastic shielding with infections in a poorly ventilated office.
Such studies raise the ironic possibility that when venues install too much plastic and impede ventilation, they could be raising the very risk they’re trying to reduce.