INVERNESS – Soil beneath Inverness Middle School has higher than normal levels of a radioactive element called radium, which caused the high levels of the cancer-causing gas found in the school last summer, recent tests show.
The tests of soil taken from just under the school’s floor revealedlevels of radium as high as three times the national average.
Federal soil scientist Paul Pilny said the tests confirmed that high levels of radon gas inside the school were caused by the soil beneath the school. Because the soil beneath the school is different than natural soil in the area, Pilny thinks it was trucked in from another location.
“It’s telling me that the soil is responsible for the elevated levels in those rooms,” Pilny said. When he inspected the soils beneath the school, Pilny said, he found “little bands of what appeared to be byproducts from a phosphate mining process.”
Natural soils around the school do not contain phosphate, Pilny said.
It’s the uranium in phosphate soils that produces radon gas. The uranium breaks down naturally to form radium 226, the element measured in the recent tests. In the next stage, radium breaks down to form radon gas, which can cause cancer if breathed over a long period of time.
The average level of radium in soil nationwide is 1 picocurie per gram of soil, Pilny said.
Recent tests of three soil samples from beneath the school showed radium levels of 1.04, 2.13, and 3.1 picocuries per gram of soil, according to Charlie Bradley, head of the county environmental health office.
“That’s significant,” Pilny said. A University of Florida study completed last year said that radium levels between 1 and 5 are considered “moderately high,” he said.
“These aren’t tremendously high samples,” said Harlan Keaton, head of the state Environmental Radiation Control Office in Orlando.
“Phosphate itself can go up to around 40.”
A high level of radium in the soil doesn’t necessarily lead to radon problems in a building built on that soil. The amount of radon gas that enters a building depends on how the building is constructed and whether open windows allow the gas to dissipate.
Radon is harmless when it dissipates in the air. It becomes a health hazard when it concentrates in buildings.
In Inverness Middle School, officials found cracks and holes in the floor that apparently allowed the gas to enter the building, Pilny said. And the high radium levels were found in soil that lies just below the floor of the school.
“This is right on top. It doesn’t have to work its way up to the surface,” Pilny said. “So if you have a crack, you’ve made the gas come in so easily; it’s like a hot knife through butter.”
Last summer, tests of three classrooms at Inverness Middle School found elevated radon levels. In one classroom, the radon level was more than twice the level the federal government considers acceptable.
Since then, school workers have plugged cracks in the three classrooms and other classrooms. That helped reduce the levels to below the federal standard.
But Pilny has suggested that further tests be taken throughout the school since other classrooms also could have high radon levels. School Superintendent Carl Austin said last week the district plans to test more than 25 other classrooms for radon.
The district also plans to monitor radon levels in the school throughout the year.
Meanwhile, Citrus County is considering an ordinance that would require borrow pit operators to have their fill material certified as radon-free. The ordinance is being developed by county officials and a task force appointed by the Citrus County Commission.
It is expected to be referred to the county Planning Commission for a recommendation within a few months. The ordinance would then go to the County Commission for final approval.