[HiTech RedNeck]

I had never till recently heard of flour being a problem. Maybe it became a problem due to sloppy kitchen habits, getting stuff in the flour bag or canister that shouldn’t be there. I never understood hooking all the spoons and measures together on a ring, as neat as it looks. I keep mine separate.

[Rockingham]

The problem is not flour but raw eggs, which have a risk of salmonella or e. coli.

[Yo-Yo]

I had never till recently heard of flour being a problem. Maybe it became a problem due to sloppy kitchen habits, getting stuff in the flour bag or canister that shouldn’t be there.

You've never heard of flour mites?

[Calvin Locke]

In addition to the things you mentioned, the fertilizing manure from farm animals is a source of e.coli, including the "bad" variants, so, it can, and does, emanate from the ground up.

Don't know about mill sterilization processing techniques.