From what I’ve seen, the 6 foot distance relates to things like sneezing or possibly ordinary speech. (There’s a lot of ambiguity, disagreement, and confusion about it - see e.g. here - and I get the sense that it’s one of these things like twice-a-year-dental-visits which have been widely accepted as a rule of thumb without a firm scientific basis. But that’s perhaps a digression.)
So what about ordinary breathing? Is there a “safe” distance correlating to the 6 foot rule which would apply in such cases? This comes up all the time when passing people on the street and the like. If they’re not talking at the time, is there a reason you need to give them a 6 foot berth, or can you cut it closer (unless you’re afraid they might sneeze or cough at that exact instant) and if so, how close can you cut it?
I’ve also been curious about this. My understanding is that virus transmission in the outdoors much lower than in enclosed spaces. Are there known instances of transmission from passing people on the sidewalk?
Short answer, you’re fine. Even infected people just don’t expel that many virus particles if they’re just breathing, and you aren’t in their proximity long enough if you’re passing them on the sidewalk. Sit next to the same person in a cafe for an hour, though, and the calculus changes.
ETA: I’d be more worried about the shopping scenario. Not specifically walking past infected people, but just being in an enclosed area where potentially infected people have expelled a large number of virions, including sneezes and coughs that you aren’t presently in the proximity of, without the advantage of a massive amount of air for dispersal. I’d stay away from indoor spaces where most people aren’t masked, and if that’s unavoidable, I’d minimize my time in them. Also, wear a mask yourself to protect others - you might be an asymptomatic carrier!