6 foot study is actually based on a study done in the 30s. Frankly the distance should be more like 20-24 feet. There are animations now including one done by MIT showing how a cough can disperse over multiple isles in a supermarket. More over simple surgical masks are not up to keeping anyone completely safe.It may be impossible to stay six feet away from a person in a store....that is why a mask is recommended. The six foot distance is based on how far a a sneeze or cough can carry the virus. If you are in a store with narrow aisles, a mask will
provide protection that distancing cannot.
If you're going to use a sown cotton mask, you want to get some HEPA vacuum cleaner bags and cut them up to put inside the cotton masks.