adulterator adulterator /ˈædəltəˌreɪtər/

noun

1. A changer who lessens the purity or effectiveness of a substance  ( adulterator )
   a changer who lessens the purity or effectiveness of a substance
   
2. Any substance that lessens the purity or effectiveness of a substance  ( adulterant , adulterator )
   any substance that lessens the purity or effectiveness of a substance
    It is necessary to remove the adulterants before use
   it is necessary to remove the adulterants before use