 Existing substances include all 23,000 substances that were in use in Canada prior to the establishment of the New Substances Notification Program, and they are all listed on the "Domestic Substances List" (DSL).The "Act" required systematic screening of these substances, a process that was completed in September 2006, which led to the development of the Chemicals Management Plan.The 23,000 existing substances on the DSL included 67 microbial strains and 2 complex microbial cultures.