Page "Shuriken" Paragraph 19

There are reports of shuriken being coated with poison intended either for a throwing target or for whoever may pick them up when left in a conspicuous place.

Other reports indicate that shuriken may have been buried in dirt or animal feces and allowed to harbor the bacterium Clostridium tetani — if the point penetrated a victim deeply enough, the bacteria transferred into the wound could cause a then-incurable tetanus infection.