There was the incident at Lambert International a years ago where a little girl was killed during passenger boarding by running into the opposite side propeller on a commercial turboprop twin. She dropped a toy and the wind blew it under the fuselage; just enough room for her to duck under but the adults couldn't fit fast enough. I believe after that there was an embargo on engines (at least turboprops) running when passengers were on the apron. I can't imagine it's different for jet engines, though if the engine is far off the ground? That's the incident I would start with to see if it applies.
Google is no help on this - I think it was before the Internet was generally available.