I don't read safety sheets often so I'm likely off base here, so please correct me if I'm wrong. My interpretation is that when used correctly it's safe.

Section 2 states it is non-hazardous.

Section 4 states it is not expected to present a significant ingestion/inhalation hazard under anticipated conditions of normal use.

Finally, Section 11 indicates that the Ammonium compounds present in RNALater may be harmful, but only when they are administered at LD50 concentrations.