Is Autoclaved Waste Sterile?

Autoclaving is a cost-effective means of sterilization that works by generating high pressure and temperature steam over a set duration of time. The Texas Commission on Environmental Quality (TCEQ) and the United States Environmental Protection Agency (U.S. EPA) regulations mandate proper disposal of biohazard waste generated by hospitals. Such waste may be incinerated and the ashes disposed of in sanitary landfills, or sterilized by autoclave and disposed of as municipal solid waste. However, we wondered if every item that makes it out of the autoclave is sterile.  The aim of this project was to validate the effective use of autoclave for cost effective sterilization and disposal of biohazardous waste and to establish a verification system insuring autoclaved waste were properly sterilized according to protocol and in accordance with TCEQ regulations. We determined that there were four methods of verification of sterilization of biohazardous waste: autoclave tapes, autoclave print-outs, chemical integrators, and biological indicators. The first two methods were required by law; the fourth method was only required where there was incomplete documentation of any of the first two. However, after repeated test-running of the four methods we determined that use of autoclave tapes and print-outs were unreliable and that in addition, frequent use of biological indicators should be mandated, to ensure the validity of autoclave cycles. Autoclaved waste can be said to be sterile only if biological test spores are rendered non-viable.