Arboriculture happens to be among the most dangerous legal jobs in America. Certain types of mining and timber harvesting are probably still more dangerous. Prostitution and drug dealing are also likely more dangerous, but not legal. The danger in arboriculture can not be understated. It can, however, be italicized. Danger.
You must always keep your head about you, or before you know it, you may not have your head about you. Climbers can fall long distances, groundsmen can have heavy branches - or whole trees - land on them, and utility arborists risk electrocution. Also, if any of those trees come alive and start throwing apples, look out.