Thimerosal has been used in the process of making certain prescription or non-prescription products, including vaccines and other medicinals, for over 60 years. Containing about 50 percent mercury, thimerosal has been valued as an anti-bacterial agent or as a preservative in vaccine vials that hold a number of doses. Because of
the presence of mercury, unusable products containing thimerosal might be regulated as hazardous waste under state and federal waste management requirements. Therefore, South Dakota DENR is providing these guidelines to assist the regulated community within South Dakota to determine options for properly managing waste pharmaceuticals that contain thimerosal.