To evaluate the influence of polymers with similar chemical structures to polystyrene synthesized through soap-free emulsion polymerization on the indicator microorganism Micrococcus luteus, styrene derivative monomers were polymerized using a cationic initiator, namely 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride. During bioassay, these polymers showed an inhibition zone against M luteus. Hence, the supernatant containing polymers with lower molecular weights, which were toxic to M luteus, obtained from soap-free emulsion polymerization should be treated carefully prior to discharge to the environment.