- moon dust has very fine particles. It is very irritating for skin, and there was a very good chance it could damage lungs like azbestos.
- Electronics and dust do not mix well
- electrostatic properties were not known, it could stick to every surface and coat it, perhaps prevent vacuum seals etc... Look at images from inside capsule, before and after landing! And that was just dust, brought on suits, not full samples!
- it had horrible smell