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Plexiglass shields are everywhere, but it’s not clear how much they help

Plexiglass shields have become ubiquitous at offices, grocery stores and restaurants across the country in the coronavirus age. They were even installed on the vice presidential debate stage last week.



a group of people standing in a kitchen: Businesses and workplaces say plexiglass dividers are one way they are keeping people safe against the spread of the coronavirus.


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Businesses and workplaces say plexiglass dividers are one way they are keeping people safe against the spread of the coronavirus.

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.

The Centers for Disease Control and Prevention (CDC) has offered guidance to workplaces to “install physical barriers, such as clear plastic sneeze guards, where feasible” as a way to “reduce exposure to hazards,” and the Labor Department’s Occupational Safety and Health Administration (OSHA) has issued similar guidance.

That’s because the plexiglass shields can in theory protect workers against large respiratory droplets that spread if someone sneezes or coughs next to them, say epidemiologists, environmental engineers and aerosol scientists. Coronavirus is thought to spread from person to person “mainly through respiratory droplets produced when an infected person coughs, sneezes or talks,” according to the CDC.

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.

Moreover, the bigger problem is that even if they do, that’s not the only way that the coronavirus spreads. Last week, the CDC released new guidelines saying that the coronavirus can spread through aerosols — tiny particles containing the virus that float in the air and can travel beyond six feet — that are released when people breathe, talk or sneeze.

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.

The dividers “do not address all possible modes of transmission, such as aerosol transmission, or fully protect anyone from Covid-19,” the University of Washington’s Environmental Health and Safety Department said in a July review of the benefits and limitations of plexiglass barriers at campus facilities.

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

SC sends $43M in Plexiglass, masks to school; promises more

COLUMBIA, S.C. (AP) — South Carolina’s education superintendent said she has sent $43 million of protective equipment to more than 1,300 schools in the state — fulfilling every item in their requests to help them open for in-person classes during the COVID-19 pandemic.

And Superintendent Molly Spearman promised Tuesday there is enough money left in the billions of dollars the federal government sent to South Carolina for pandemic help to pay for whatever else schools ask for as she urges every school district to get children back in classrooms at least part of the time.

“You may hear some of them saying we need more things. We are telling them, let us know what you need. We have the funding to get it for you,” Spearman said.


The latest purchases include 300,000 sheets of Plexiglass, which Spearman cited health experts who have told her when combined with masks cut the distance needed to prevent the spread of COVID-19 in half to 3 feet (1 meter). The sheets are going up as barriers between students at desks and tables.

The Education Department has also bought 3.3 million masks, 87,000 face shields, 600,000 cases of disinfectant wipes, 108,000 boxes of disposable gloves and more than 41,000 gallons (155,000 liters) of hand sanitizer, Spearman said.

All that equipment combined with mask wearing, hand washing and deep cleaning of schools make them some of the safest indoor spaces in South Carolina, the superintendent said.

“Sending your child back to school is safer than them going with you grocery shopping,” Spearman said.

As the rate of new COVID-19 cases continues to alarmingly rise in the Midwest, the spread of the virus has stabilized in South Carolina. But experts said that is not a positive development, because the state is still averaging 843 new cases a day over the past week.

That’s still in the top half of the nation and similar to where South Carolina was in late August, with occasional spikes and dips. The rate of positive results from coronavirus tests still hovers above 10% most days. Experts said 5% or lower is needed to feel confident the virus is not spreading.

South Carolina has had more than 152,000 people infected with the coronavirus that causes the disease since the pandemic started seven months ago. More than 3,350 people have died, according to the South Carolina Department of Health and Environmental Control.

And COVID-19 is still affecting schools. Presbyterian College announced Monday it is returning to only online classes for two weeks after reporting 49 people on campus diagnosed with COVID-19 The college in Clinton has about 1,100 students.

The school held a graduation ceremony delayed from last spring on Saturday with more than 200 graduates returning to campus.

Public elementary, middle and high school across the state are also keeping up with COVID-19 infections. As of last Thursday, more than 800 students and 330 teachers had the virus, health officials reported.

Spearman said it is impossible to prevent any infection and she said

Plexiglass Barriers Won’t Stop the Virus at the Debate, Experts Warn

A box fan, an air filter — and duct tape to attach them.

With four such cobbled together devices, at perhaps a total of $150, the vice-presidential debate on Wednesday night could be made much safer, according to experts in airborne viruses.

Vice President Mike Pence and Senator Kamala Harris will be seated more than 12 feet apart on the podium, with plexiglass barriers between them. Mr. Pence and his aides had objected to the barriers, but relented on Tuesday night.

The barriers might make more sense if Mr. Pence and Ms. Harris were seated more closely together on the podium, scientists said. But the risk in this setting is airborne transmission of the coronavirus, and the barriers will do nothing to protect Ms. Harris and the moderator, Susan Page, Washington bureau chief of USA Today, if Mr. Pence were infected.

On Monday, the Centers for Disease Control and Prevention released new guidelines confirming that the virus can be carried aloft by aerosols — tiny droplets — farther than six feet indoors. In one recent study, scientists isolated infectious virus some 16 feet from an infected patient in a hospital.

Linsey Marr, an expert on airborne viruses at Virginia Tech in Blacksburg, Va., laughed outright when she saw a picture of the debate setup. “It’s absurd,” she said.

When she first heard there would be plexiglass barriers, Dr. Marr said, she had imagined an enclosure with an open back or top: “But these are even smaller and less adequate than I imagined.”

Other experts said the barriers might have made some sense if the debaters were to be seated close together.

“Those plexiglass barriers are really only going to be effective if the vice president or Kamala Harris are spitting at each other,” said Ellie Murray, an epidemiologist at Boston University. “Those are really just splatter shields.”

The C.D.C. on Tuesday cleared Mr. Pence for the debate, saying he had not been in close contact with anyone known to be infected. The agency’s definition of close contact is being within six feet of an infected person for at least 15 minutes.

Yet Mr. Pence said at a rally on Tuesday evening that he had met with President Trump, who last week tested positive for the coronavirus, that morning in the Oval Office.

“What we’ve been seeing over the past week is that there are a lot of spaces in the White House that are pretty enclosed, pretty poorly ventilated, where people can come into close contact even if they are more than six feet away,” Dr. Murray said.

“I would be very surprised if he has not been close enough to some of these people to at least potentially have been infected.”

Mr. Pence has cited multiple negative tests as proof that he is not infected. But tests for the coronavirus may not yield positive results for up to 14 days after exposure to the virus.

Given the risk that Mr. Pence may be infected, experts said, the Commission for

Plexiglass barriers at Pence-Harris debate ‘are a joke,’ won’t stop coronavirus, medical experts say

The Commission on Presidential Debates is taking extra precautions at Wednesday night’s Vice Presidential debate given the coronavirus outbreak in the White House, but pictures of two curved plexiglass barriers they plan to use has some epidemiologists and airborne pathogen specialists scratching their heads.

Vice President Mike Pence and Sen. Kamala Harris will be seated more than 12 feet apart and separated by two plexiglass barriers. But those barriers are “entirely symbolic,” according to Dr. Bill Schaffner, an epidemiologist at Vanderbilt University.

The commission became worried after President Donald Trump and several White House staff contracted Covid-19 shortly after last Tuesday’s presidential debate. The Centers for Disease Control and Prevention said Pence was not in “close contact” with Trump, who announced that he was infected with the virus early Friday morning.

Nonetheless, a person familiar with the debate planning told NBC News that Harris’ campaign asked for the plexiglass to be used at the event at the University of Utah in Salt Lake City.

The plexiglass is “minimal protection,” Schaffner said in a phone interview, adding that the barriers are mostly “cosmetic.” 

However, he added that barriers are one part of a “layered approach” that includes testing and distancing of everyone on stage. Everyone in the debate hall is required to wear a mask and there will be no handshake or physical greeting between Pence and Harris, according to the commission. Altogether, he said, the steps have likely reduced the risk of spread occurring.

The plexiglass barriers are just one “part of the CPD’s overall approach to health and safety,” according to a fact sheet distributed by the commission.

The debate is due to take place indoors and, of course, plenty of talking is expected. That’s important because the CDC released new guidance on Monday that said the virus can spread through particles in the air between people who are further than six feet apart in certain environments. The CDC said the risk of that occurring increases indoors and when people are doing certain activities, including speaking.

Jeff Siegel, a professor of civil engineering at the University of Toronto and a specialist in indoor air quality, ventilation and filtration, said the risk of virus-carrying particles going airborne in an environment like a debate when people are talking loudly is “huge.”

“On the plus side, it’s a pretty big space, so there’s a big dilution effect,” he said over the phone, adding that Harris, Pence and the moderator, Susan Page, will be spaced out appropriately. The high ceiling and large room will also help to reduce risk, he said.

“But they’re not addressing things like ventilation,” Siegel said, adding that he hopes the debate hall has appropriately up-to-date air filtration and ventilation systems. “If I was Vice President Pence’s staff or Harris’ staff, I would certainly want to get a portable HEPA filter in there.”

HEPA filters are high-performing air filters that capture very small particles in the air. The commission did not return CNBC’s request for comment on the building’s

The plexiglass barriers being used at tonight’s debate are pretty useless, experts say.

A box fan, an air filter — and duct tape to attach them. With four such devices cobbled together for a grand total of about $150, the vice-presidential debate on Wednesday night can be made much safer than with the plexiglass barriers being used, according to experts in airborne viruses.

Vice President Mike Pence and Senator Kamala Harris will be seated more than 12 feet apart, with barriers between them. But the barriers will do nothing to protect Ms. Harris if Mr. Pence is infected and exhaling virus that can be carried through the air, experts said.

On Monday, the Centers for Disease Control and Prevention released new guidelines indicating that indoors, the virus can be carried aloft by aerosols — tiny droplets — farther than six feet. In one study in August, scientists found infectious virus at a distance of 16 feet from an infected patient.

Linsey Marr, an environmental engineering professor at Virginia Tech and an expert in airborne viruses, laughed outright when she saw a picture of the debate setup.

“It’s absurd,” she said. When she first heard there would be a plexiglass barrier, she said, she imagined an enclosure with an open back or top. “But these are even smaller and less adequate than I imagined.”

Other experts said the barriers would have made some sense if the debaters were seated close together.

“Those plexiglass barriers are really only going to be effective if the vice president or Kamala Harris are spitting at each other,” said Ellie Murray, an epidemiologist at Boston University.

“Those are really just splatter shields.”

“At 12 feet 3 inches apart, spray droplet transmission is not the issue,” said Donald Milton, an aerosol expert at the University of Maryland. “What is the ventilation like? What is the direction of the airflow?”

Dr. Milton and his colleagues contacted the debate commission and both campaigns to recommend purchasing plug-and-play air filters — excellent ones run to just about $300 each — or four box fans and air filters taped together. Each debater would have one device positioned to suck up and clean the air exhaled, and another to produce clean air.

In research conducted with singers over the past few months, they have found that this so-called “Corsi box” — named for Richard Corsi, the scientist who cobbled together the first one — can significantly decrease aerosols.

The safest solution, experts said, is to move the debate online.

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