Will Florida’s “radioactive roads” glow in the dark?

It might be considered a cost-saver: Last month, Florida passed a law to force the state’s highway department to conduct “demonstration projects” using phosphogypsum as a roadway material. Critics decry the idea of creating what they call “radioactive roads” with a fertilizer industry byproduct that at least one federal agency says emits radon gas. While the headline is tongue-in-check (phosphogypsum is not phosphorescent), there’s still plenty of controversy about the suggestion.

Why does Florida want “radioactive roads”

So just what is phosphogypsum, and how is it that Florida lawmakers want it on roadways? A key ingredient in plant fertilizer is phosphorus from phosphoric acid. That’s made by dissolving phosphate rock in sulfuric acid. The byproduct of the process is phosphogypsum, that there’s a lot of it. For every ton of phosphoric acid produced, industry says 5.2 tons of phosphogypsum is made.

While gypsum is widely used in the construction industry, phosphogypsum is considered the ugly stepsister. That’s because the latter contains naturally occurring radioactive elements including uranium and thorium, and their daughter isotopes radium, radon, and polonium. It costs too much to remove the radioactivity from phosphogypsum, and so most of it is dumped in enormous piles called stacks, where it sits, waiting for a potential safe use, sometime in the distant future.

So why do the so-called “radioactive roadways” have such an attraction to Florida lawmakers? Florida is blessed with being the largest producer of phosphogypsum in the country. Estimates say Florida is home to some one billion tons of the stuff, put up in “gypstacks,” some covering hundreds of acres and as tall as a five story building. They don’t have a particularly good reputation.

Two years ago, at Piney Point, Florida, a leaky containment liner at a gypstack caused a crisis, threatening to create a collapse. To prevent that, 215 million gallons of waste water from the gypstack were pumped into Tampa Bay. Happily, the water was not radioactive, but was loaded with nitrogen and phosphorous. There were concerns the load could create a toxic algae bloom and fish kills in the waterway.

Creative thinking

With some billion tons of phosphogypsum hanging around in Florida, creative thinkers went to work. Why not use the stuff as an aggregate in roads, much like gravel, sand, or crushed rock? Much cheaper, and a great place to “off” the fertilizer makers’ unwanted byproduct. The Tampa Bay Times suggests that might have been part of the reason that a major fertilizer manufacturer, Mosaic, hosted a political fundraiser for the legislative bill’s sponsor.

The bill, signed off by the state’s governor, says that the Florida Transportation Department must conduct “demonstration projects using phosphogypsum in road construction aggregate material to determine its feasibility as a paving material.” That must be done by April of next year. But any future radioactive roadways currently face a roadblock of their own. According to comments made to news network NPR by the U.S. Environmental Protection Agency (EPA), “Any request for a specific use of phosphogypsum in roads will need to be submitted to EPA, as EPA’s approval is legally required before the material can be used in road construction.”

Two sides to the “radioactive roads” issue

Concerns about using phosphogypsum in “live” roadways include fears about the potential release of radon gas. A statement on the EPA website notes this about radon gas: “Breathing radon over time increases your risk of lung cancer. Radon is the second leading cause of lung cancer in the United States. Nationally, the EPA estimates that about 21,000 people die each year from radon-related lung cancer. Only smoking causes more lung cancer deaths.”

A fertilizer-trade support group, the Fertilizer Institute, begs to differ. While radon gas is associated with an increase in lung cancer, it’s often associated with trapped air. Think residential basements. The institute contends that an analysis which it paid for shows using phosphogypsum in roadways “can be done safely and results in doses that are a small fraction of those arising from natural background radiation.” The Institute says radon doses where phosphogypsum is used as a roadway aggregate wouldn’t produce radiation above EPA levels of acceptability.

Don’t look for “glow in the dark” roadways in Florida anytime soon. Keep your headlights on. Watch while interest groups duke it out to see if there really is radioactive roadway in Florida’s future.

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