Lead shot is being replaced with steel because it is supposed to be more environmentally friendly, so we are told. A lot of clay shoots only allow steel shot, but in time will this pollute the ground as it rusts away?

A friend of mine showed me some lead bullets, from what seemed to be from a Martini Henry, that had been that had been dug up by someone metal detecting in a park.
The Home Guard used to practice there during the war so that makes them around 70 years old. They looked as though they had only been shot recently. Still fairly clean, no corrosion and obviously not a problem to the environment.