It's a lot more widespread than most people think. A quick look at Wiki yielded this: https://en.wikipedia.org/wiki/Unexploded_ordnance
France and Belgium-
"In the forests of Verdun French government "démineurs" working for the Département du Déminage still hunt for poisonous, volatile, and/or explosive munitions and recover about 900 tons every year. The most feared are corroded artillery shells containing chemical warfare agents such as mustard gas." (That's mostly WWI ordinance)
"Some 288 million cluster munitions and about 75 million unexploded bombs were left across Laos after the war ended. From 1996–2009, more than 1 million items of UXO were destroyed, freeing up 23,000 hectares of land. Between 1999 and 2008, there were 2,184 casualties (including 834 ...