I've got a story for ya. One of my coworkers was cutting aluminum once. He was wearing safety goggles, so he had no risk of getting shit in his eyes. Or did he? As luck would have it, an aluminum shaving managed to pass through one of the ventilation holes on the side of the goggles, and lodged itself in his sclera (the white part of the eye). He flushed it out with water and thought he had gotten rid of it. The next day he experienced growing discomfort in his eye, but he thought it was just that the eye was sore. The day after that it got so bad that he had to go see a doctor.
Upon examination, the doctor discovered that he not only still had the shard lodged in his eye, but it had started to rust. They had to pry his eye open with forceps à la Clockwork Orange, and give him an injection in the eye before they could dislodge the rusty shard of metal.