Domande riguardo a frasi esempio con, spiegazione d'utilizzo di "Unsanitary"s

A: it's unsanitary to not wash your hands.
it's unsanitary to eat off the floor.
The boy was very unsanitary when he played in the mud

A: × Unsanitary water is one major cause for the spread of infectious disease.
✓ Unsanitary water is one of the major causes for the spread of infectious diseases.

The sentence you have written isn't wrong.
This would just be a better way of saying it.