6793
The protocol grew out of the increasing public outcry against chemical warfare following the use of mustard gas and similar agents in World War I , and fears that chemical and biological warfare could lead to horrific consequences in any future war .
 event: World War I
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 event: World War I