Human, other vertebrates and insect. Secretions and shed tissues from humans, other vertebrates and insects. Fungal spores and natural surface bacteria, mostly harmless unless you're immune-compromised, both dead and alive. Other microorganisms, dead and alive. Mineral dust and microplastics, if you find either gross. Pathogens carried with the human secretions, hopefully all dead.

Unless you work in semiconductor manufacturing, there's no such thing as perfectly clean. Even if you do it's mostly theoretical. For most practical purposes the standard used is something like:

The contaminants are too small and too few to be visible. All pathogenic contaminants are dead.

And I think that's entirely reasonable. We don't really have a choice, right?