Plastic microspheres, a.k.a. microbeads, are used to great effect in many biomedical and biotechnology research and clinical applications. However, polystyrene(PS), polyethylene(PE) and polylactic acid (PLA) microbeads should not be rinsed down the drain into the waterway.  Disposal should be as solid waste. Polyhydroxyalkanoate (PHA), cellulose, gelatin and silicone based microbeads are considered more environmentally friendly.  Always follow hazardous, radioactive and biohazard waste regulations associated with their application/protocol.  

For more information on this, and biotechs producing PHA based microbeads you can  read our labconscious blog post: THE MICROBEAD BAN AND RESPONSIBLE USE OF MICROSPHERES IN THE LAB