Barring any unfortunate explosions involving the lighting equipment, this job doesn't register very high on the Danger-O-Meter. (Okay, you got us—we made that one up. Clearly, we don't have room for that many "-o-Meters" in our basement.)
Cinematographers should live to a ripe old age so long as they watch what they eat and don't smoke. The biggest physical danger comes from neck and shoulder injuries from lugging around heavy camera equipment all day.
More physical trauma comes from operating a Steadicam rig, which is famous for destroying more knees and backs than any other piece of equipment. Still, the DP will rarely will be the one operating these pieces of equipment. Most of the danger is handled by his crew. It's good to be the boss.