Triclosan. I hate the stuff.
It's used like a pesticide. It kills all kinds of bugs. If you give it enough time it will kill human too. So I call it The HumanKiller. The chemical is persistant.
I once used a soap with this stuff. People commented that it smelled like bug spray. I think they used to much in the soap to give it away. They love using this stuff in antibac soaps like softsoap. I'm phasing that out. They are only using 0.115% but every bit kills.