Comment by analog31

In addition to knowing how much stuff is released by one particle, we have a decent handle on how much is needed in order to be dangerous, due to us being constantly bombarded by various cosmic rays. That's how we can say that it's not dangerous.

The article is behind a paywall, but it seems likely that the bigger safety concern is whatever produced the large quantity of particles needed to have a chance of trapping just one. And those kinds of experiments are conducted in regulated facilities for good reason.