I read something a few month back, can't recall the source,warning about tainted mussels.Said first, toss out any which open before cooking (steaming). Then, discard any which fail to open as they ought, ~ 5 minutes.I don't get this. Isn't steam antiseptic? Are there microscopic critters that would survive?
Chemists are not magicians
who know an answer to every question
not even about chemistry.
Imagine you let a piece of meat lay a week at room temperature.
You would then cook it in pressurised cookware for an hour.
All microorganisms are killed now.
Would you eat it then ? Probably not.
Being sterile is not the only quality criteria.
The similar with mussels.
Poutnik ( the Wanderer )