Test results released Thursday show some private wells near the Coronet Industries factory in Plant City may have slightly elevated levels of radioactive particles, including four wells that previously showed higher levels of boron.
Health officials said it's not clear whether the levels are beyond what occurs naturally and, if they are, whether Coronet's phosphate processing plant is to blame.
They also said there is not an immediate health threat.
"I would not be alarmed by these results," said Doug Holt, director of the Hillsborough County Health Department.
The testing for radionuclides, as the slightly radioactive and cancer-causing particles are known, is part of a multiagency effort to determine whether pollution from Coronet could be sickening nearby residents.
Of 42 wells tested in August within a quarter-mile of the plant, 29 showed no problems with radioactive particles. But five appeared to have levels beyond federal drinking water standards and eight had levels that were close. More tests will be done on those wells before any action is taken. Results are expected next month.
Four of the wells with the highest numbers also tested high for boron, a substance that can cause stomach ailments and is both a byproduct at the Coronet plant and an ingredient in strawberry fertilizer. All four wells are a few hundred yards from the plant.
"That doesn't seem to be random," Holt said.
But, as they have since the pollution probe began in June, authorities said it is too early to say if the plant is responsible.
The drinking water standard for radionuclides is 15 units per liter. The five highest wells showed levels ranging from 18 to 42 units.
Radionuclides occur naturally, but higher levels have been linked to areas near phosphate mining and production facilities. The land near Coronet was mined for phosphate for decades. The company now turns phosphate into an additive for animal feed.
