In the 60's my fathers business developed film for the military...I mean 42" wide rolls by hundreds of feet long. The main by product of film developing is silver, back then no one cared about recovering the silver (or had the technology) so they created leaching fields behind the shop. The acre behind the shop became so black with the silver that it would no longer drain. 40 years later he was contacted by the "super fund" clean up company and said if there were any houses within 2 miles of the back that they would all be dead. It was totally legal back then, I can only think of the thousands of $$ in silver that were dumped.