May 19, 2026

Proposal to Keep Phosphogypsum Unregulated Under RCRA

Phosphogypsum, a radioactive by-product from processing phosphate ore to make phosphoric acid, contains radium, which decays to form radon gas, the emissions of which are regulated under CAA regulations. [Part 61, Subpart R] However, under RCRA, phosphogypsum is excluded via one of the “Bevill” mineral processing provisions at §261.4(b)(7)(ii)(D). While uses for phosphogypsum exist, such as a soil conditioner, road base, or as an ingredient in Portland cement, the majority of this by-product is stored in “stacks,” which are gargantuan above-ground piles.

In 2021, the Center for Biological Diversity petitioned EPA to reverse the agency’s 1991 regulatory determination excluding phosphogypsum and process wastewaters from hazardous waste regulations. After consideration, EPA finds that the petition does not present any information that was not already known during a prior review of the RCRA mining waste exclusion and was not submitted in the 1990 Report to Congress on Special Wastes from Mineral Processing. Consequently, EPA proposed to deny the petitioner’s request to regulate phosphogypsum under RCRA on April 24, 2026. Comments on the proposal may be submitted through May 26, 2026 via Docket ID No. EPA-HQ-OLEM-2026-0232.

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