This would be a good promotional find for our hobby. I find everything from jagged metal can pieces to broken glass in the ground around play areas at parks. I usually take pictures of my finds (good and garbage) just for reference purposes, but I always remove anything hazardous and dispose of it.
Maybe we as metal detectorists, should document and photograph each instance when we find and remove a dangerous object like this in or near a children's play area. It would really help out our hobby whenever a park or city decides to ban metal detecting. We could use evidence like this to reinforce metal detecting and how it not only cleans up the ground but helps remove objects like needles around children's play areas. In this case, you may have saved the city thousands of dollars in damages if a kid has been stuck with that needle. You may have even indirectly saved a life, if that needle contains a bad infectious disease or bacteria.