Although WWI ended over a century ago the chemical munitions it left behind just keep on turning up when you least expect them. When they contain something persistent like Mustard then the effects are just the same today as they were in 1918.
The short article in the link below highlights the dangers when they do (although to be honest ‘fishing’ for vintage ordnance with a magnet does seem to be a life limiting activity!).
Our thanks to Belgian EOD and 1st Line Defence for highlighting the problem