The concern isn't contamination of the medium -- you pasteurize the medium and use enough spawn so that your preferred mushroom mycelium outcompetes other fungi and bacteria. This intentionally happens fairly rapidly (because if it doesn't, you're very likely to get some form of bacterial or fungal contamination, which usually means tossing that chunk of medium). Once the mycelium have colonized the medium, it's fairly resistant to contamination in the same way that a healthy sourdough starter is resistant to contamination.

The main health concern is over spore production and inhalation of spores. If you're growing in a household environment you'll want to use a growing chamber with filtered air exchange.

Depends on the type of mushroom and cultivation method. You need to be careful with a sterilised environment. You need air filtering.

https://pubmed.ncbi.nlm.nih.gov/820538/ is an issue, for example. So is general contamination. This seems like a terrible idea.

Not to say that growing mushrooms at home is risk-free, but that paper is about industrial production.

Emphases mine: [0]

"Several persons concerned with the cultivation and industrial production of this mushroom fell ill, after close contact with it over a period of some months, with exhaustion, headache, chills and fever, and cough."

[0] (no snark intended - just pointing out potential differences from home cultivation)

yeah, but no one is tracking home growers. the issue is spore germination in lungs or allergic hypersensitivity which will be due to exposure.

I used to grow mushrooms at home, and worse, oyster mushrooms, and developed a persistent cough even for my relative low volume. it cleared up when I got rid of them, but you know, the area was just covered, covered in spores.

usually unsafe, as they drop a lot of spores

Would a good Air purifier help?