The Center for Biological Diversity’s challenge to the Environmental Protection Agency’s approval of radioactive road material in Polk County, Florida, proved unsuccessful before a federal appellate court.

The case involved Mosaic Fertilizer’s use of phosphogypsum, a radioactive byproduct of fertilizer production, in experimental road construction on the company’s private land. Wednesday, a three-judge panel of the U.S. Court of Appeals for the 11th Circuit took the EPA’s side.

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Phosphogypsum emits radon and is not permitted to be deposited anywhere but open-air stacks. The EPA, however, can permit its use on a case-by-case basis.

“The Center’s final argument is that vacatur or remand is necessary because the Road Project generally will serve as an ‘intermediate step between laboratory testing and full-scale’ approval of phosphogypsum in road construction, and these potential future regulatory amendments will be tainted by the EPA’s arbitrary and capricious assessment of the Project. This sweeping argument fails,” Judge Stanley Marcus wrote.

Marcus was appointed by President Bill Clinton. Judges Barbara Lagoa and Robin Rosenbaum sat on the panel, appointed by Donald Trump and Barack Obama, respectively.

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The judges, in denying the challenge, did not buy the argument that the EPA’s decision would foreshadow future approvals.

“Because the approval of Mosaic’s Road Project does not directly bear on potential future projects, which will be subject to separate Agency action and independent analysis, we can discern no basis to vacate or remand the Agency’s decision,” Marcus wrote.

The University of Florida and Mosaic are partnering to research use of phosphogypsum as a base for roads, underneath asphalt and above subgrade. The research is meant to monitor soil, air, and water around the experimental roads.

In December 2024, the EPA approved Mosaic’s application for the roads and they were laid in November 2025, starting an 18-month experiment.

The two sides had oral arguments in Miami in April.

Policy-making

The center argued the EPA precedents categorically prohibit phosphogypsum in road projects. In 1989, the agency barred its use for anything. In 1992, the agency concluded that using phosphogypsum in roads “presents an unacceptable level of risk to public health.”

The 1992 rule, however, permitted requests for individual approval for its use.

In 2020, the EPA approved a conditional use of phosphogypsum in road projects, for the first time in history. In 2021, however, the EPA withdrew that conditional approval because the applicant had not met legal requirements, according to court records.

In this case, Mosaic in 2022 applied for conditional use for a “small-scale road lot project on private land.” The application asked for four 500-foot sections.

Alleged injuries

Michael Lexner, who lives five miles from the facility and is a member of the center, claimed “harm to their recreational interests and the use and enjoyment of their property because of substantial concerns about radioactive contamination coming from the facility.” Lexner’s family stopped growing vegetables for fear of contaminated groundwater.

“Lexner has attested in no unclear terms — and has cited to supporting scientific literature — that his injuries are plausibly made worse by the Road Project, because the Road will create an additional source of radioactive air pollutants, beyond the contaminants emanating from the phosphogypsum stacks at the Facility,” Marcus noted.

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The potential damage extends beyond the roads themselves, Marcus added. In 2016, a sinkhole on the site polluted the aquifer in the area.

“If the Facility were ever redeveloped for residential use, the site as a whole — irrespective of the Road — would require the developer to undertake substantial remediation to address the radiological risks associated with the already existing radioactive residuals,” Marcus wrote.

In announcing the project, Mosaic called phosphogypsum a “worthwhile resource.”

“Federal regulations require the EPA to perform a rigorous scientific risk analysis when evaluating a request to reuse phosphogypsum beneficially,” the fertilizer company said on its website.

“The impacts to human health and the environment are the primary focus of that analysis. At the end of the day, we welcome robust testing. We want people to know this is a safe and worthwhile resource, not byproduct discarded as waste, and we are decades behind others who long ago realized just that.”