Police departments have used tear gas and pepper spray on protesters in recent weeks, raising concern that the chemical agents could increase the spread of the coronavirus.

Medical experts say those rushing to help people sprayed by tear gas could come into close contact with someone already infected with the virus who is coughing infectious particles.

There’s no research on tear gas and COVID-19 specifically, because the virus is too new.

Last week, more than 1,000 medical professionals and students signed a letter urging public health officials to oppose any use of “tear gas, smoke, or other respiratory irritants, which could increase risk for COVID-19 by making the respiratory tract more susceptible to infection, exacerbating existing inflammation, and inducing coughing.”

And officials in Pittsburgh, New Orleans and Washington, D.C., have proposed bans or limits on tear gas use.