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Radioactivity in Foods Grown on Mined Phosphate Lands



Post, Buckley, Schuh & Jernigan, Inc. (PBS&J) was retained by the Florida Institute of Phosphate Research to study the radioactivity in foods grown on mined phosphate lands in the central Florida phosphate district. This study was a follow-up to a previous study of radioactivity in foods in which over one hundred food samples were collected from sixty two land parcels. While the initial study surveyed radioactivity in foods on a variety of land types including unmined lands and mined lands, this current study concentrated on lands which were reclaimed after phosphate mining. Since lands reclaimed from clay settling areas will constitute the majority of lands to be reclaimed, this current study concentrated mostly on foods grown on reclaimed clay lands.

Approximately seventy individual food samples were collected from five land parcels in the central Florida phosphate district and subjected to radioassay for radium-226, lead-210 and polonium-210. Corresponding soil samples were collected and analyzed for these radionuclides and also for a variety of soil chemistry parameters. The results of the radioactivity and soil chemistry analyses of these samples were integrated into the data base which had been created from the initial study and a variety of statistical analyses were conducted on this integrated data set. The results of these analyses indicated, as in the initial study, that concentrations of radium-226 and lead-210 observed in foods grown on mined phosphate lands were statistically higher than concentrations of these radionuclides exhibited in foods grown on unmined phosphate lands. Concentrations of polonium-210 observed in these foods were found to be extremely low; in fact, a substantial number of the measurements for polonium-210 were below the limit of detection of the analytical methodology.

Although the radioactivity concentrations measured in foods grown on mined phosphate lands were found to be statistically higher than in foods grown on other lands, the radiation dose to the consumers of these foods was found to be only a small fraction of the dose received by an average individual from other environmental sources of radioactivity. The study evaluated the dose to a hypothetical person who obtains all of the foods sampled in this study from reclaimed clay lands and the remainder of his diet from the general food pool. This person is estimated to receive 19.1 mrem per year in committed effective dose equivalent from the ingestion of the radionuclides reported in this study. This is only 2.7 mrem per year more than the estimated radiation dose to a similar individual who obtains all of his foods from lands unaffected by phosphate deposits or phosphate mining. Both of these dose levels are quite low and are not considered to be a health hazard.