Plastic shields, barriers for COVID-19 precaution not likely to help

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SC mother pushes back against proposed mask requirements in schools

Ashley Regan says she wants to make medical choices for her two children, arguing long-term effects of wearing masks for hours a day are not yet known.

Plastic shields propped up in classrooms to reduce COVID-19 spread likely don’t offer much benefit, interrupting airflow and increasing risk of exposure, according to a news report and emerging evidence.

While the barriers might block larger particles from coughs and sneezes, growing evidence suggests smaller aerosol particles waft around the barrier and risk exposing others.

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Linsey Marr, professor of civil and environmental engineering at Virginia Tech, likened the phenomenon to cigarette smoke, telling the New York Times in part: "One way to think about plastic barriers is that they are good for blocking things like spitballs but ineffective for things like cigarette smoke...The smoke simply drifts around them…"

Research published in the journal Science by Johns Hopkins indicated that desk shields increased the risk of COVID-19-related outcomes. 

"If you have a forest of barriers in a classroom, it’s going to interfere with proper ventilation of that room," Marr told the newspaper. "Everybody’s aerosols are going to be trapped and stuck there and building up, and they will end up spreading beyond your own desk."

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Experts said desk shields were unlikely to offer protection and may instead disrupt ventilation in rooms. In some conditions, the shields can result in build-up of viral particles, creating so-called "dead zones" with high concentrations of particles, the report noted. Scientists instead advised prioritizing the focus on vaccinations among eligible students and staff, boosting ventilation, requiring masks and including HEPA air filters where necessary.

Plastic barriers shouldn’t stir alarm, but people shouldn’t assume they offer full protection, Richard Corsi, incoming dean of engineering at the University of California, Davis told the paper. Corsi recommended face masks in addition to plastic barriers to lower risk of infection.