The first plastic invented by humans was cellulose nitrate, the formulation of which was discovered by accident in a chemist's kitchen. The ivory market was one of the first to be displaced, celluloid being an easy replacement for everything from knife handles to billiard balls. Being highly combustible--and explosive with a forceful strike-- these early plastic billiard balls occasionally exploded upon being hit by a pool player's cue.
"Three ball in the corner pocket..." BANG!
I reckon this had the general effect of increasing the number of gun fights in the Old West.