As Florida braces for Hurricane Ian, our thoughts and prayers are with everyone in the storm’s way. The storm has already knocked out electricity to the entire island of Cuba, causing major flooding, damage to homes and countless toppled trees.

As the storm approaches Florida’s shores, we’re thinking about the 24 phosphogypsum stacks, also called called “gypstacks,” scattered throughout the state that hold polluted remnants of the state’s phosphate fertilizer mining industry.

These stacks resemble enormous ponds that are hundreds of acres wide and hundreds of feet tall—and they are at risk for leaks and other contamination when a storm the size of Ian makes landfall.

We’ve written about the issues at Piney Point, one former fertilizer manufacturing plant in Manatee County. It’s been a problem for years, but the 676-acre site made headlines when the uncontrolled release of toxic wastewater seeped out into Tampa Bay and caused massive fish kills.

“A major storm event like the one we are bracing for can inundate the facilities with more water than the open-air ponds can handle,” Ragan Whitlock, staff attorney for the Center for Biological Diversity environmental group, said in an email Tuesday to the Associated Press. “We are extremely concerned about the potential impacts Hurricane Ian may have on phosphate facilities around the state.”

The fertilizer industry creates more than 30 million tons of phosphogypsum in Florida each year, according to the Florida Industrial and Phosphate Research Institute.

Phosphogypsum is radioactive and can contain uranium, thorium and radium, which decay into carcinogenic radon. In addition to these radioactive carcinogens, phosphogypsum and process water can contain heavy toxic metals like antimony, arsenic, barium, cadmium, chromium, copper, fluoride, lead, mercury, nickel, silver, sulfur, thallium and zinc.

More than 1 billion tons of the radioactive and toxic waste have already been stored in these stacks, perched precariously atop the Floridan aquifer that supplies drinking water to about 10 million people.

Florida State Department of Environmental Protection records show that Piney Point has about 24 inches (60 centimeters) of rainfall capacity.

A big spill or leak could seriously damage rivers and other wetlands near any of the stacks.

“Phosphate companies have had over 50 years to figure out a way to dispose of the radioactive gypsum wastes in an acceptable manner, they have yet to do so,” according to the environmental nonprofit ManaSota-88. “The EPA should not permit phosphate wastes to be used in Florida landfills, or in construction or agricultural applications.”

The hurricane is expected to produce catastrophic storm surge, destructive winds, and flooding rainfall, The Weather Channel reports.

Where to dump our toxic waste only gets more complicated as our climate continues to change and storms become more intense.