CHICAGO, Oct 11 (Reuters) - Mosaic Co ( MOS ) said on

Friday that water supporting the chemical company's storage of a

waste byproduct from fertilizer manufacturing in Florida

probably made its way into Tampa Bay following a downpour from

Hurricane Milton.

The discharge of possibly more than 17,500 gallons from

Mosaic's facility in Riverview, a fast-growing Tampa suburb,

raised potential environmental concerns.

The industrial byproduct, phosphogypsum, is known to

emit radon, a cancer-causing radioactive gas.

Mosaic said a storage system for water around a pile of

phosphogypsum became overwhelmed in Riverview. The site received

nearly 15 inches of rain during Hurricane Milton less than two

weeks after Hurricane Helene, the company said in a statement.

Water quality impacts in Tampa Bay are expected to be

"modest," if any, Mosaic said.

The company addressed the overflow issue on Thursday and

it was not continuing on Friday, it said in the statement.

"We've been in constant communication with regulators who are

onsite today."

The affected phosphogypsum pile is closed, meaning the

company is not adding new material to it, Mosaic said.

Phosphogypsum contains radium, which decays to form

radon gas, the U.S. Environmental Protection Agency said, noting

that radium and radon are radioactive and can cause cancer.

The EPA requires that phosphogypsum be managed in

engineered piles or stacks to limit public exposure from radon

emissions.

The EPA told Reuters the Florida Department of

Environmental Protection regulates the design, construction,

operation and maintenance of phosphogypsum stack systems and

they must continue to comply with all regulatory requirements.

The Florida Department of Environmental Protection had

no immediate comment.

Mosaic, which mines phosphate rock in Florida and

produces about three-quarters of North America's phosphate

fertilizers, said it

idled Florida operations

in anticipation of Milton.