Can existing state and local laws that provide substantially similar emergency planning supersede the specific provisions of the federal law?

Title III (Section 321) generally provides that nothing in Title III shall preempt or affect any state or local law.  However, material safety data sheets, if required under a state or local law passed after August 1, 1985, must be identical in content and form to that required under Section 311.  Accordingly, while Title III does not supersede state or local laws, EPA has no authority to waive the requirements imposed under Title III.  These requirements, including the threshold planning quantities, are intended to be minimum standards.

EPA is working with states that have developed reporting forms and planning structures to determine the most efficient approaches to avoid duplication of effort with existing state or local structures, forms, and requirements.