TALLAHASSEE — The U.S. Environmental Protection Agency has approved a controversial proposal that would lead to using phosphogypsum, a radioactive byproduct of the phosphate industry, in a road project.

The EPA on Friday issued a notice of approval for Mosaic Fertilizer, a subsidiary of The Mosaic Company, to move forward with the pilot road project on company property in Polk County. The possibility of using phosphogypsum in road projects has long drawn opposition from environmental groups, which have argued it could pose risks to people working on roads and to water quality.

Phosphogypsum is typically stored in huge stacks, but Mosaic proposed building four sections of test road that would include different mixtures of phosphogypsum in road base material, according to the EPA notice. The project would be at the company’s New Wales facility.

In the notice, which is expected to be published Monday in the Federal Register, the EPA said the “approval applies only to the proposed pilot project and not any broader use.” The notice acknowledged a large number of comments submitted in opposition to the proposal but said the EPA concluded the project would be safe.

“Results from multiple modeling efforts indicate that risks due to the proposed pilot project are low,” the notice said. “EPA believes that for this existing site, it is most appropriate to consider the potential risk to site workers and the nearest residents to the site when determining whether the pilot project is as protective as leaving the phosphogypsum in the stack. No comments raised topics which EPA did not consider in its technical evaluation or lead to a concern for human health or environmental impacts not previously considered.”

But Ragan Whitlock, a Florida-based attorney with the Center for Biological Diversity, which opposes the proposal, called the EPA decision “mind-boggling.” In a statement Friday, Whitlock cited risks to road crews and water quality and raised the possibility that the decision could be a step toward using phosphogypsum more broadly in road projects.

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“The well-documented harm to public health and the environment from this kind of waste leaking out of radioactive phosphogypsum storage stacks should be leading to better oversight of Florida’s biggest polluters,” Whitlock said. “Instead the EPA has bowed to political pressure from the phosphate industry and paved the way for this dangerous waste to be used in roads all over the country. We’ll do everything in our power to protect Florida’s people and precious environment from this reckless plan.”

As the EPA considered the Mosaic proposal, Florida lawmakers and Gov. Ron DeSantis in 2023 approved a bill that authorized the state Department of Transportation to conduct a study of using phosphogypsum in road projects.

“Upon a determination of suitability by the department, phosphogypsum from phosphate production may be used as a construction aggregate material in accordance with the conditions of the United States Environmental Protection Agency approval for the use,” the bill said.