In many countries, that ordnance is still found and disposed of more or less regularly. The decaying involves lots of nasty chemicals. It's happening at sea as well, by the way (because they dumped their leftovers after the wars there). Here's a short info piece by the German environment ministry about the issue: https://www.bundesumweltministerium.de/en/topics/marine-cons... and here's a European map: https://ec.europa.eu/maritimeaffairs/atlas/maritime_atlas/#l...