How do you protect yourself from slander?

I wear prescription safety gles at work. The main ingredient in the cleaning solution that the company provides is alcohol based.I have worked at this company for four months and the person that I believe is spreading these lies has spoken to me maybe twice. I do drink but not before work. (I work second shift.) The plant manager had spoken to me and seems to believe me, but what she said with out naming names leads me to further believe that the person I suspect is saying these things about me. What can I do to further protect myself and my reputation from further harm?