In the long run, humans aren't failsafe.

[rcjordan]

There is currently a radioactive capsule lost somewhere on the 1400km stretch of highway between Newman and Malaga in Western Australia. It is a 8mm x 6mm cylinder used in mining equipment. Being in close proximity to it is the equivalent having 10 X-rays per hour. It fell out of a truck.

In 1970 a capsule like this was lost and killed 4 people (leukemia)

Kramatorsk radiological accident
https://en.wikipedia.org/wiki/Kramatorsk_radiological_accident