As of February 13, 2024, ASTM E1527–21 is the required ASTM standard for All Appropriate Inquiries (AAI) in real estate transactions. Conducting AAI is required to establish the innocent landowner defense, as well as the bona fide prospective purchaser and contiguous property owner liability protections, under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). Importantly, diligence activities already conducted for currently pending acquisitions may need to be revised before the acquisition closes if they rely on the previous ASTM standard (ASTM E1527-13). EPA’s final rule amending the AAI to reference ASTM E1527-21 can be found here.