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Materials 2017, 10(7), 754; doi:10.3390/ma10070754

Toxicity of Nine (Doped) Rare Earth Metal Oxides and Respective Individual Metals to Aquatic Microorganisms Vibrio fischeri and Tetrahymena thermophila

1
Laboratory of Environmental Toxicology, National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn, Estonia
2
School of Science, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia
3
Ceramic Powder Technology AS, Kvenildmyra 6, 7093 Tiller, Norway
4
Estonian Academy of Sciences, Kohtu 6, 10130 Tallinn, Estonia
*
Author to whom correspondence should be addressed.
Received: 22 May 2017 / Revised: 13 June 2017 / Accepted: 30 June 2017 / Published: 5 July 2017
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Abstract

Despite the increasing use of rare earth elements (REEs) and oxides (REOs) in various technologies, the information on their ecotoxicological hazard is scarce. Here, the effects of La3+, Ce3+, Pr3+, Nd3+, Gd3+, CeO2, and eight doped REOs to marine bacteria Vibrio fischeri and freshwater protozoa Tetrahymena thermophila were studied in parallel with REO dopant metals (Co2+, Fe3+, Mn2+, Ni2+, Sr2+). The highest concentrations of REOs tested were 100 mg/L with protozoa in deionized water and 500 mg/L with bacteria in 2% NaCl. Although (i) most REOs produced reactive oxygen species; (ii) all studied soluble REEs were toxic to bacteria (half-effective concentration, EC50 3.5–21 mg metal/L; minimal bactericidal concentration, MBC 6.3–63 mg/L) and to protozoa (EC50 28–42 mg/L); and (iii) also some dopant metals (Ni2+, Fe3+) proved toxic (EC50 ≤ 3 mg/L), no toxicity of REOs to protozoa (EC50 > 100 mg/L) and bacteria (EC50 > 500 mg/L; MBC > 500 mg/L) was observed except for La2NiO4 (MBC 25 mg/L). According to kinetics of V. fischeri bioluminescence, the toxicity of REEs was triggered by disturbing cellular membrane integrity. Fortunately, as REEs and REOs are currently produced in moderate amounts and form in the environment insoluble salts and/or oxides, they apparently present no harm to aquatic bacteria and protozoa. View Full-Text
Keywords: lanthanides; nanoparticles; doped metal oxides; speciation; hazard evaluation; bioluminescence; cellular membrane integrity; viability; ciliates; Microtox™ lanthanides; nanoparticles; doped metal oxides; speciation; hazard evaluation; bioluminescence; cellular membrane integrity; viability; ciliates; Microtox™
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MDPI and ACS Style

Kurvet, I.; Juganson, K.; Vija, H.; Sihtmäe, M.; Blinova, I.; Syvertsen-Wiig, G.; Kahru, A. Toxicity of Nine (Doped) Rare Earth Metal Oxides and Respective Individual Metals to Aquatic Microorganisms Vibrio fischeri and Tetrahymena thermophila. Materials 2017, 10, 754.

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