The designations are based on reporting by chemical manufacturers, importers, and processors, which concluded on October 5, 2018, under the agency's TSCA Inventory Notification (Active-Inactive) Rule. "Active" substances also include those that were reported during the 2012 and 2016 Chemical Data Reporting cycles. All substances not reported as “active” are identified as “inactive.”
While seemingly mundane, this is important stuff: chemicals that are classified as “inactive” will not be able to be manufactured or imported into the U.S. without going through EPA’s pre-manufacture notice (PMN) and review process. PMN is something to avoid, particularly after the 2016 amendments shifted the burden of proof to require that EPA now make an affirmative finding that the substance does not pose an unreasonable risk to health or the environment before allowing it on the market.