Whoa—seriously? Eight to 12 people a year from WWI bombs? That’s incredible. Counting my blessings; no matter how much I poke around in the flower and tomato beds, I’ll never disturb a mustard gas bomb.
At the beginning of the war the various armies were literally caught with their pants down around their ankles.
With regard to the amount of ammunition needed, the ramping up of both production & the increase of the number of soldiers who had never even fired a weapon of any sort led to a roughly 60% failure rate of artillery shells .
When you are firing hundreds of thousands of shells in week long barrages that adds up in a hell of a hurry.