> While they can reduce the risks of viral transmission in certain limited circumstances there's no scientific consensus on masks as a widespread public health

> While they can reduce the risks of viral transmission in certain limited circumstances there's no scientific consensus on masks as a widespread public health measure. It is hard to get good data to support a scientific consensus on how policy changes affect a large group of people. Running a controlled experiment is nearly impossible and looking at correlations is problematic because there are many confounding variables. Masks could be very effective at controlling pandemic group (reducing R by 20% could change growth into decay); whereas masks not being effective would result in people being less comfortable and excess waste of masks. There are additional psychological effects of masks that are more majorly negative: encouraging people to social distance less, mask wearing as a political statement, etc, but if those were not an issue, the safe default would be to wear masks when infection a preventable possibility (interacting with people outside the home).