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Fertilizer-Derived Uranium and its Threat to Human Health Ewald Schnug†,* and Bernd G. Lottermoser‡ †
Fakultät für Lebenswissenschaften der Technischen Universität Braunschweig, Pockelsstraße 14, D-38106 Braunschweig, Germany Environment and Sustainability Institute, University of Exeter, Cornwall Campus, Penryn, Cornwall, TR10 9EZ, U.K. Moreover, unconfined aquifers below agricultural land, groundwater has 3 to 17 times higher uranium concentrations than that below forested regions. Generally, there is a concurrent and strong correlation of dissolved uranium concentrations in groundwater with those of other highly mobile and fertilizerderived elements such as boron, magnesium, and potassium as well as nitrate.1 The likely reason for the strong uranium-nitrate correlation in groundwater could be due to (a) increased fertilization of agricultural land using NP and NPK fertilizers; (b) significant mobility of fertilizer-derived uranium as uranylcarbonate complex and transfer into the underlying aquifer; and (c) pronounced solubility of uranium as uranyl−nitrate complex into groundwater. In northern Germany, unmineralized groundwater used as drinking water supply contains variable uranium contents, with one-quarter to two-thirds likely impacted by fertilizer-derived uranium.1 Thus, agricultural soils and nearby land and water resources are becoming increasingly contaminated by uranium due to fertilizer use. Fertilizer-derived uranium has entered German drinking water supplies. Principal route of exposure of humans to uranium occurs via hosphate fertilization remains the main source of uranium ingestion, skin contact, and inhalation. In particular, naturally contamination of agricultural land, primarily due to mineralized groundwaters and bottled mineral waters can impurities in the phosphate rock used for fertilizer manufacture. contribute significantly to uranium uptake. In Germany, more In particular, long-term application of uranium-bearing than 2 million people currently receive drinking water that fertilizers can significantly elevate the uranium concentration contains >10 μg/L uranium. Here, a carnivore with a skewed in fertilized soils. The magnitude of uranium enrichment of taste for offal, shellfish, and bottled mineral water can achieve cultivated soils varies, depending on phosphate fertilizer the highest uranium uptake.1 application rate, uranium content of applied fertilizer, soil A considerable body of evidence suggests that overexposure type and prevailing climate. In Germany, the use of phosphate to uranium in drinking water may cause significant health fertilizer from 1951 to 2011 has resulted in a cumulative effects in both humans and animals. Reported health effects of application of approximately 14 000 t of uranium on uranium derive from experimental animal studies and human agricultural land, corresponding to an average cumulative epidemiology. Uranium may damage biological systems loading of 1 kg of uranium per hectare.1 through its chemical toxicity as well as its radioactivity, with Fertilizer-derived uranium in soils is prone to leaching the chemical toxicity perceived as the primary health hazard and because uranium is mobile in surface soils as uranyl complex the effects from uranium’s ionizing radiation being of secondary depending on prevailing pH and Eh conditions. Alternatively, concern. The main health concerns with respect to uranium are uranium can be immobilized in subsurface materials by sorption renal, developmental, reproductive, diminished bone growth, as well as DNA and brain damage.2 In humans uranium is or coprecipitation mechanisms. The fate of uranium in soil and particularly known for its nephrotoxic nature, with short-term subsurface environment is therefore influenced by a delicate and long-term exposure to uranium through drinking water balance of U6+ association between immobile and mobile leading to renal effects. The information available on the phases. Yet, uranium is highly soluble as uranyl (U6+) complex chronic health effects caused by the exposure to uranium in under oxidizing conditions. Consequently, mobility of fertilizerdrinking water points to the fact that regions with elevated derived uranium from agricultural soils into ground and surface groundwater uranium concentrations and more groundwater waters has been recognized in agricultural catchments and, use have an increased incidence of certain diseases. For numerous studies have established the transfer of fertilizerexample, increasing incidence in chronic kidney disease in Sri derived uranium from soils into ground, surface and marine Lankan nationals has been related to the low-level fertilizercoastal waters. For example in Germany, rivers and streams of agricultural catchments have 10 times higher uranium concentrations (0.08 versus 0.8 μg/L U) than those dominated Received: January 16, 2013 by forestry.1 Significantly enriched uranium concentrations (>2 Accepted: January 29, 2013 Published: February 27, 2013 μg/L U) were detected in heavily cultivated catchments. ‡
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© 2013 American Chemical Society
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Environmental Science & Technology
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derived uranium contamination of groundwater that is used as drinking water supply.3 Also, greater consumption of groundwater with higher uranium concentrations leads to a greater risk in humans in South Carolina to develop a range of cancer types.4 Furthermore, uranium is an endocrine-disrupting chemical, leading to an increased risk of fertility problems and reproductive cancers in animals when exposed to drinking water that contains uranium below the WHO and U.S. EPA water standard (30 μg/L).5 Clearly, further research is needed on the long-term exposure of humans to low-level uranium concentrations at or below water quality guidelines. Populations exposed to drinking water supplies contaminated with fertilizerderived uranium should be followed for their increased risks of developmental defects and health effects. Present research efforts must focus on understanding the source-pathway-receptor chains of fertilizer-derived uranium. Concurrently, the exposure of humans to this pollutant should be limited. Such reduced exposure can be achieved through uranium extraction during phosphoric acid manufacturing. This in turn would lead to an important supply of uranium fuel for nuclear power plants as well as reduced contaminant loadings of agricultural soils and limited transfers of a pollutant into the human food chain.
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AUTHOR INFORMATION
Corresponding Author
*Phone: +49 173 2367829; e-mail: e.schnug@tu-braunschweig. de. Notes
The authors declare no competing financial interest.
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REFERENCES
(1) Schnug, E. Uran in Phosphor-Düngemitteln und dessen Verbleib in der Umwelt. Strahlentelex 2012, 612−613, 3−10 (in German). (2) Brugge, D.; Buchner, V. Health effects of uranium: New research findings. Rev. Environ. Health 2011, 26, 231−249. (3) Chandrajith, R.; Seneviratna, S.; Wickramaarachchi, K.; Attanayake, T.; Aturaliya, T. N. C.; Dissanayake, C. B. Natural radionuclides and trace elements in rice field soils in relation to fertilizer application: Study of a chronic kidney disease area in Sri Lanka. Environ. Earth Sci. 2010, 60, 193−201. (4) Wagner, S. E.; Burch, J. B.; Bottai, M.; Puett, R.; Porter, D.; Bolick-Aldrich, S.; Temples, T.; Wilkerson, R. C.; Vena, J. E.; Hebert, J. R. Groundwater uranium and cancer incidence in South Carolina. Cancer, Causes Control 2011, 22, 41−50. (5) Raymond-Wish, S.; Mayer, L. P.; O’Neal, T.; Martinez, A.; Sellers, M. A.; Christian, P. J.; Marion, S. L.; Begay, C.; Propper, C. R.; Hoyer, P. B.; Dyer, C. A. Drinking water with uranium below the U.S. EPA water standard causes oestrogen receptor-dependent responses in female mice. Environ. Health Perspect. 2007, 115, 1711−1716.
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