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FIPR Report 2003-2004

Featured Research Topic
Fishing
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About this photo:
Central Florida anglers find fishing in lakes on phosphate mined lands some of the more productive in the area.


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"This study went a long way to helping us counter the recent misinterpretation of an EPA (U.S. Environmental Protection Agency) draft report that said there are elevated levels of radiation and metals in the water at Tenoroc (Fish Management Area). Elevated means above background - not unhealthy, but EPA did not clarify the draft data. While FIPR's work was unrelated to the EPA research that focused on drinking water, it allowed us to get out some information about radioactivity. It showed that when it comes to the pond water, radioactivity and metals may be there, but there is no build up (bioaccumulation) in the fish flesh and it is safe to consume."

Tim King
Florida Fish and Wildlife Conservation Commission


Fishing in phosphate mining pit lakes is popular in Florida's phosphate mining region, though central Florida contains many natural lakes as well. There are those, however, who have wondered if the fish in these phosphate lakes are safe to eat because local citizens are concerned about radiation associated with phosphate mining. Following a series of local citizen inquiries during the late 1990s, it was determined that, while much work has been performed on local lake water and sediments, studies targeting the specific issue of consumption of local freshwater finfish were very limited. FIPR funded this study to assess the risk from the radionuclide (Ra-226, Pb-210) and heavy metals (cadmium, mercury and lead) in freshwater finfish caught in these lakes.

Previous FIPR studies have noted mercury to be frequently associated with lake sediments. In earlier studies, lead and cadmium have been observed to a much lesser extent.

As for the fish, this study found there was no statistical difference in radionuclides or metals between the fish flesh from impacted or non-impacted lakes except for mercury. Mercury was found to be higher in the natural non-impacted lakes, primarily attributable to one lake. The mercury contamination is not associated with the phosphate industry and is likely the result of atmospheric deposition from non-local and even global sources.

The study analyzed the edible portion of six fish species from a mix of ten natural and phosphate industry-impacted lakes to determine if bioaccumulation of radium-226, lead-210, mercury, cadmium and lead was occurring to the extent of posing an elevated risk to those eating the fish. The following is a synopsis of this study's results and conclusions.

Results - (All results below are for the edible fish flesh, not lake water or sediments).

  • Cadmium was observed sporadically and at low levels, and appears to be an insignificant contaminant for this area.

  • Mean lead levels were generally an order of magnitude below the U. S. Fish and Wildlife 1984-1985 study observation of 0.110 µg/g. Only 20% of all samples exhibited measurable levels, and almost half of those were confined to two lakes, with no difference being observed between natural or impacted lakes.

  • Mercury was found to be widely distributed above 0.005 µg/g. At 84% positive results, all lakes were affected by mercury to some degree. Natural lakes exhibited a higher trend for mercury than impacted lakes.

  • Radionuclide data did not exhibit a significant difference between natural and impacted lakes.

Discussion and Conclusions

  • None of the results from this study would lead us to conclude there exists a potential human health risk for exposure to cadmium, lead, mercury, radium-226 or lead-210 from consuming normal dietary levels of popular freshwater finfish from the study lakes, either natural or phosphate mining-impacted.

  • Cadmium was not found to be a significant contaminant within the study area. Of the metals studied, it had the lowest frequency and distribution. Only 2% of the samples contained any measurable cadmium. These samples were well distributed among the test species (three of the five).

  • Lead was found to be well distributed by species and by lake. At the lower estimated detection limit it was observed in 20% of all samples. Lead's broad distribution is speculated to be from atmospheric distribution of fossil fuel combustion by-products.

  • Only one species (bass) from one study lake, Walk-in-Water, exhibited mean mercury levels near or above published regulatory guidance.

  • We recommend more extensive sampling and analysis of bass mercury levels from this lake in order to confirm this finding.

FIPR has a long history of studying radionuclide contaminants in the local environment. The Institute has been extensively studying the risk of consuming produce from crops and meat from animals raised on previously mined and reclaimed land. FIPR has published a large database of information on local land based foods. Three examples include: Radioactivity in Foods Grown on Florida Phosphate Lands, Radioactivity in Foods Grown on Mined Phosphate Lands and Production of High-Value Cash Crops on Mixtures of Sand Tailings and Waste Phosphatic Clays.

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Florida Institute of Phosphate Research
Affiliated with the University of South Florida

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