SARAH MCCAMMON, HOST:
In nationwide demonstrations against the police killing of George Floyd and other black Americans, protesters are frequently pepper-sprayed or enveloped in clouds of tear gas. These crowd control weapons are generally not lethal. But in the middle of the coronavirus pandemic, there are growing calls for police to stop using them. Will Stone explains how these chemical irritants damage the body in ways that can make COVID-19 worse.
WILL STONE, BYLINE: Clouds of smoke, people coughing, clutching their faces. Professor Sven-Eric Jordt has seen this unfold nightly in cities across the country, and he knows exactly what the tear gas and pepper spray are doing because he studies them in his lab at Duke University. Actually, he has a different term for them.
SVEN-ERIC JORDT: I call these gases, in fact, more like pain gas.
STONE: That's because these chemicals activate pain-sensing nerves on the skin and the mucous membranes around the eyes, mouth and nose.
JORDT: You have this excruciating pain, sneezing, coughing, the production of a lot of mucus that obstructs breathing.
STONE: When it comes to chemical irritants, police generally use two different kinds. First, pepper spray - the active agent is capsaicin, which is derived from chilies. Police spray it from cans or sometimes lob it into crowds. The other is CS gas, a chlorinated organic chemical. Cartridges are fired into crowds, producing plumes of whitish smoke. It hurts. And Jordt says it's a corrosive chemical.
JORDT: So it can cause burn injuries on the skin, in the eyes and the airways.
STONE: Jordt says tear gas is being used more frequently around the world and in greater amounts. But the research hasn't kept up. Police tend to rely on outdated safety studies from the 1950s and '60s. But Jordt says there is a newer, troubling study from 2014 involving U.S. Army recruits. The ones who are exposed to tear gas as part of a training exercise were more likely to get sick with a respiratory illness like the flu.
JORDT: Using it in the current situation with COVID-19 around is completely irresponsible. There are sufficient data proving that tear gas can increase the susceptibility to pathogens, to viruses.
STONE: Not only that - the Army study was on healthy, young recruits. Now apply that to a civilian population, like those protesting - people of all ages, some with underlying health conditions.
JORDT: This is a recipe for disaster.
STONE: Coronavirus is still a new pathogen. But Dr. John Balmes of the University of California, San Francisco, says we can look to studies from China and Italy. Those show that lung irritants like smoking or air pollution made COVID worse. And like those, tear gas injures the cells that line the nose and airway.
JOHN BALMES: So these exposures, the tear gas would increase the risk of progression from asymptomatic infection to symptomatic disease.
STONE: And Balmes says it's like when you skin your knee on the sidewalk.
BALMES: It causes injury and inflammation to the lining of the airways. And it gets red, literally. I actually think we could be promoting COVID-19 by tear-gassing protesters who are already congregating and putting themselves at risk for infection.
STONE: Specialists in infectious disease say it does help that protests are outside. But people are usually jammed together and often singing or chanting. Dr. Amesh Adalja at Johns Hopkins University says those activities tend to produce lots of droplets.
AMESH ADALJA: You couple that with the fact that they're being exposed to tear gas and pepper spray, which are noxious and make people cough. That also is something that could accelerate the transmission of this virus.
STONE: He believes there will be a spike in infections as a result of the protest. Dr. Jade Pagkas-Bather is an infectious disease expert at the University of Chicago. She says it will be hard to determine whether any spike in cases came from the protests because many states are already reopening businesses. She and more than a thousand other health professionals have actually signed a letter in support of the demonstrations.
JADE PAGKAS-BATHER: In everyday life, we weigh the risks and benefits of our actions. People who are going out to protest clearly are sort of a critical juncture where they're saying this state-sanctioned violence is unacceptable, and I'm willing to put myself and others potentially at risk.
STONE: But the letter also says that the protests can be made safer. Everyone should wear masks, and police should not be using tear gas or pepper spray.
For NPR News, I'm Will Stone in Seattle.
MCCAMMON: This story is part of NPR's partnership with Kaiser Health News.
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