Here's what we know about wearing masks -- and when you don't need one

The debate over masks has devolved into a binary and partisan choice, but a conservative editor explains why it doesn't have to be that way.

Jonathan Last, executive editor of The Bulwark, laid out the evidence for wearing protective masks in some situations, and shows why they're unnecessary in others.

"There is some debate over how effective masks are in curbing the spread of aerosolized particles and that level of efficaciousness will depend on a bunch of factors: what the mask is constructed of, how it’s worn, etc," Last wrote. "But there is no serious debate that there is some effectiveness."

It doesn't matter whether masks slow the spread of virus particles by 80 percent or 20 percent, he argued, because masks are a low-cost way to reduce the broadcast of aerosolized saliva droplets which carry virus particles.

"It’s basically a freebie," he argued. "In the grand scheme of economic expense and behavior modification, wearing a mask costs us next to nothing."

Research shows masks aren't necessary while taking a run outside or going for a walk, because they're low-risk events, and they're probably not necessary if proper social distancing is observed.

"What we’re thinking about is reducing large-spread events," Last wrote. "The big-ticket items are places where you spend significant amounts of time face-to-face with multiple people in closed spaces: Riding mass transit, in the work place, in a school setting, at social gatherings. You should not be in a movie theater, for instance, without a mask. Or a bar. Or sitting in a doctor’s office or any place that is indoors and has a waiting room."

Last dismissed arguments that masks are unhelpful, at best, or harmful at worst.

"This is BS on the order of magnitude of anti-vaccine and flat-earth theories," he argued. "There is not merit to both sides here."

Any risks involved in wearing a mask can be easily mitigated by washing them occasionally or disinfecting them between uses.

"These ought to be no-brainers for everyone while the outbreak is still operating at a large scale," he wrote. "Being smart about masks is one of the ways we can keep pushing on the virus."