We may not realize it but we’re all surrounded by tiny particles suspended in the air. Pollen, sea salt, and dust are just some of the aerosols floating around us that are mostly invisible to the naked eye.
“Basically wherever the air is going, the aerosol is going and there is infectious potential in that,” said Alex Huffman, an aerosol scientist who teaches at the University of Denver.
Huffman said while heavier respiratory droplets produced by coughs or sneezes don’t usually travel very far.
“Particles that are below a certain size are not gonna just fall down,” he said. “There’s no physical way that’s possible.”
They tend to hang around and linger in the air much longer and that, he argued, is a huge problem during this pandemic.
“When the ‘choral case’ broke, many of us thought this must be aerosol transmission,” said Shelly Miller, another aerosol scientist who teaches at the University of Colorado.
Miller was referring to a coronavirus outbreak in Washington state in March. 53 of 61 members of a choral singing group contracted the disease after a two-and-a-half-hour practice. It was a super spreading event, she concluded, with a high release of infectious particles, due to three factors:
“Duration of rehearsal, low ventilation to no ventilation, and many people at the event,” Miller said.
January outbreaks in a restaurant in China and on a cruise ship are also believed to have stemmed from aerosol transmission of the virus.
“These are not really answerable unless the aerosol route is invoked,” Huffman said.
Miller said animal studies have confirmed this route of infection. Until recently, the public didn’t associate the word aerosol with virus transmission but rather with products like air fresheners.
“And if you’re old enough you associate it with hair spray in the 80s basically,” Huffman said laughing.
But experts, who admit the respiratory side of aerosols is a young science, argue it should be taken seriously. 239 of them, including Huffman and Miller, wrote to the World Health Organization in July, asking it to add indoor aerosol transmission to the likely ways the coronavirus is spread.
“I think it’s had a huge impact,” Miller said. “I’m hoping they will provide much stronger, clearer recommendations on how to reduce risk from airborne transmission.”
That means, she said, social distancing to get away from high-density aerosol clouds around people, well ventilated indoor spaces and masks. You won’t be surprised to hear these aerosol scientists aren’t fond of the mask debate.
“It’s stupid,” Miller said.
“Universal wearing of masks is possibly the single most potent tool we have as a community to fight this pandemic,” Huffman said.
And, they added, keep us from inhaling droplets perhaps a millionth of a meter in size that could do us great harm.