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1.
Sci Total Environ ; 609: 420-428, 2017 Dec 31.
Article in English | MEDLINE | ID: mdl-28755592

ABSTRACT

The freshwater and marine long-term ecotoxicity datasets used in the European REACH registration dossiers for molybdenum and molybdenum compounds resulted in the derivation of a HC5,50%,freshwater (38.2mgMo/L) and HC5,50%,marine (5.70mgMo/L) by means of the statistical extrapolation method. Both datasets, however, did not meet the US-EPA information requirements for deriving Final Chronic Values (FCV) that were based on chronic data. US-EPA compliance was achieved by generating chronic no-effect data for the freshwater benthic amphipod Hyalella azteca and the marine inland silverside fish Menidia beryllina, using sodium molybdate dihydrate as test substance. A 42d-EC10 of 44.6mgMo/L for reproduction was determined in a water-only exposure with H. azteca. For M. beryllina, a 37d-NOEC of 139mg mMo/L for standard length and blotted wet weight was found. Other endpoints (e.g., survival, hatching success) proved to be less sensitive. Data were added to the existing chronic toxicity datasets, together with new long-term no-effect values that were identified in open literature for brown trout Salmo trutta, the marine alga Isochrysis galbana, the marine snail Nassarius dorsatus and the marine barnacle Amphibalanus amphitrite. The updated data sets resulted in a freshwater and marine HC5,50% of 35.7 and 6.85mgMo/L, respectively. The same data sets were also used for the determination of US-EPA FCVs, where the FVCfreshwater was 36.1mg/L, and the FCVmarine was 3.85mgMo/L. As the Final Plant Values for both aquatic environments were higher than their respective FCVs, the Criterion Continuous Concentration (CCC) for molybdenum is equal to the FCV.


Subject(s)
Aquatic Organisms/drug effects , Environmental Exposure/adverse effects , Molybdenum/toxicity , Water Pollutants, Chemical/toxicity , Amphipoda/drug effects , Animals , Ecotoxicology , Europe , Fishes , Fresh Water , United States
2.
Sci Total Environ ; 435-436: 179-87, 2012 Oct 01.
Article in English | MEDLINE | ID: mdl-22854089

ABSTRACT

The REACH Molybdenum Consortium initiated an extensive research program in order to generate robust PNECs, based on the SSD approach, for both the freshwater and marine environments. This activity was part of the REACH dossier preparation and to form the basis for scientific dialogues with other national and international regulatory authorities. Chronic ecotoxicity data sets for the freshwater and marine environments served as starting point for the derivation of PNECs for both compartments, in accordance with the recommended derivation procedures established by the European Chemicals Agency (ECHA). The HC(5,50%)s that were derived from the generated Species Sensitivity Distributions were 38.2 mg Mo/L and 5.75 mg Mo/L for the freshwater and marine water compartment, respectively. Uncertainty analysis on both data sets and available data on bioaccumulation at high exposure levels justified an assessment factor of 3 on both HC(5,50%) leading to a PNEC(freshwater) of 12.7 mg Mo/L and a PNEC(marine) of 1.92 mg Mo/L. As there are currently insufficient ecotoxicological data available for the derivation of PNECs in the sediment compartment, the equilibrium partitioning method was applied; typical K(D)-values for both the freshwater and marine compartments were identified and combined with the respective PNEC, leading to a PNEC(sediment) of 22,600 mg/kg dry weight and 1980 mg/kg dry weight for freshwater and marine sediments, respectively. The chronic data sets were also used for the derivation of final chronic values using the procedures that are outlined by the US Environmental Protection Agency for deriving such water benchmarks. Comparing PNECs with FCVs showed that both methodologies result in comparable protective concentration levels for molybdenum in the environment.


Subject(s)
Aquatic Organisms , Molybdenum/toxicity , Toxicity Tests, Chronic/methods , Water Pollutants, Chemical/toxicity , Amphibians , Animals , Fishes , Geologic Sediments , Insecta , Mollusca , Molybdenum/analysis , No-Observed-Adverse-Effect Level , Water Pollutants, Chemical/analysis , Water Pollution, Chemical/adverse effects , Water Pollution, Chemical/legislation & jurisprudence
3.
Sci Total Environ ; 430: 260-9, 2012 Jul 15.
Article in English | MEDLINE | ID: mdl-22663766

ABSTRACT

A scientific research program was initiated by the International Molybdenum Association (IMOA) which addressed identified gaps in the environmental toxicity data for the molybdate ion (MoO(4)(2-)). These gaps were previously identified during the preparation of EU-REACH-dossiers for different molybdenum compounds (European Union regulation on Registration, Evaluation, Authorization and Restriction of Chemical substances; EC, 2006). Evaluation of the open literature identified few reliable marine ecotoxicological data that could be used for deriving a Predicted No-Effect Concentration (PNEC) for the marine environment. Rather than calculating a PNEC(marine) using the assessment factor methodology on a combined freshwater/marine dataset, IMOA decided to generate sufficient reliable marine chronic data to permit derivation of a PNEC by means of the more scientifically robust species sensitivity distribution (SSD) approach (also called the statistical extrapolation approach). Nine test species were chronically exposed to molybdate (added as sodium molybdate dihydrate, Na(2)MoO(4)·2H(2)O) according to published standard testing guidelines that are acceptable for a broad range of regulatory purposes. The selected test organisms were representative for typical marine trophic levels: micro-algae/diatom (Phaeodactylum tricornutum, Dunaliella tertiolecta), macro-alga (Ceramium tenuicorne), mysids (Americamysis bahia), copepod (Acartia tonsa), fish (Cyprinodon variegatus), echinoderms (Dendraster exentricus, Strongylocentrotus purpuratus) and molluscs (Mytilus edulis, Crassostrea gigas). Available NOEC/EC(10) levels ranged between 4.4 mg Mo/L (blue mussel M. edulis) and 1174 mg Mo/L (oyster C. gigas). Using all available reliable marine chronic effects data that are currently available, a HC(5,50%) (median hazardous concentration affecting 5% of the species) of 5.74(mg Mo)/L was derived with the statistical extrapolation approach, a value that can be used for national and international regulatory purposes.


Subject(s)
Environmental Exposure , Molybdenum/toxicity , Toxicity Tests, Chronic/standards , Water Pollutants, Chemical/toxicity , Animals , Aquatic Organisms/drug effects , Dose-Response Relationship, Drug , Eukaryota/drug effects , Invertebrates/drug effects , Killifishes/metabolism , Lethal Dose 50 , Molybdenum/standards , No-Observed-Adverse-Effect Level , Reference Values , Water Pollutants, Chemical/standards
4.
Ecotoxicology ; 14(6): 661-70, 2005 Aug.
Article in English | MEDLINE | ID: mdl-16215700

ABSTRACT

Most standard toxicity test results, used in present environmental risk assessment and water quality criteria (WQC) setting procedures are obtained with standard test media that are not representative for natural surface waters when metal toxicity modifying factors like pH, water hardness and dissolved organic carbon (DOC) are considered. The aim of this study was, using the green alga Pseudokirchneriella subcapitata, (1) to investigate the individual effects of Ca, Mg (the hardness cations) and pH on the toxicity of copper in reconstituted artificial test waters and (2) to study the copper toxicity in 13 spiked surface waters originating from different European eco-regions. Surface waters were selected such that a broad range of DOC (1.55-20.4 mg/l), pH (5.52-8.30) and water hardness (7-238 mg CaCO(3)/l) was covered. Tests in reconstituted artificial waters demonstrated that the 72 h-E(b)C50 (expressed as dissolved Cu) increased by about a factor of 3 when the Ca and Mg concentrations increased from 0.25 to 2.5 mM. When pH was increased from 5.8 to 8.0, dissolved 72 h-E(b)C50 decreased by a factor of 3. It is suggested that competition between Cu2+, Ca2+, Mg2+ and H+ ions at the cell surface are the most likely explanation for these observations. Dissolved 72 h-E(b)C50s in the natural surface waters varied between 32.0 and 245 mug Cu/l and were up to a factor 15 higher than the 72 h-E(b)C50 in standard artificial medium (16.5+/-4.8 mug Cu/l). Consequently, Water Effect Ratio's (WER, the ratio between the EC50 in natural water to the EC50 in standard test water) ranged from 1.9 to 14.8. Linear regression analysis revealed that higher E(b)C50 were significantly related to higher DOC-concentration of the natural waters (R2 = 0.69), but that water hardness and pH did not show a significant relation with copper toxicity in these surface waters. In European surface waters, a positive correlation is observed between water hardness and pH. As a result, hardness and pH effects on copper toxicity are counteractive in European surface waters, resulting in the highly significant relation between the 72 h-E(b)C50 and DOC-concentration. Normalisation of the obtained effect concentrations using a Biotic Ligand based predictive Cu-toxicity model revealed that variation in DOC and pH are mainly responsible for the observed differences of Cu-toxicity in natural waters.


Subject(s)
Chlorophyta/drug effects , Copper/toxicity , Fresh Water/chemistry , Calcium , Chemical Phenomena , Chemistry, Physical , Computer Simulation , Europe , Hydrogen-Ion Concentration , Magnesium , Models, Biological , Water Pollutants/analysis
5.
Ecotoxicology ; 13(7): 697-705, 2004 Oct.
Article in English | MEDLINE | ID: mdl-15673218

ABSTRACT

During the time-course of ecotoxicity tests with algae and chronic (reproductive) toxicity tests with daphnids, in which algae are present as a food source, pH can dramatically increase due to photosynthetic activity. As pH changes can significantly affect metal speciation and thus its bioavailability, it may be necessary to buffer the pH of the exposure medium. One class of buffers (Good's N-subtituted aminosulfonic acids) are increasingly being used in biological and chemical applications, including ecotoxicity testing. However, the potential effect of these buffers on metal toxicity has, so far, scarcely been examined. In this study we investigated if MOPS (3-N morpholino propane sulfonic acid) affected the toxicity of copper and zinc to two standard test organisms: the cladoceran Daphnia magna and the green alga Pseudokirchneriella subcapitata. First, we demonstrate that up to a concentration of 750 mg l(-1) (which proved to be sufficient for pH buffering) MOPS did not affect 21-day net reproduction of D. magna or the 72-h population growth of P. subcapitata. Second, we conducted bioassays in copper and zinc spiked standard media for the pH range 6-8. For D. magna the possible effect of 750 mg l(-1) MOPS on acute copper and zinc toxicity was investigated by performing parallel 48-h toxicity tests in NaHCO3 and MOPS buffered test media. Seventy-two hour growth inhibition assays with P. subcapitata were performed in parallel in MOPS and NaHCO3 buffered test media and in test media with daily manual pH adjustment with HCl. For daphnids no significant differences in copper and zinc toxicity were observed between MOPS or NaHCO3 buffered test media. For algae no significant differences in metal toxicity were observed between MOPS and HCl buffered media, but in test media buffered with NaHCO3 an increased copper and zinc toxicity was observed as a consequence of pH increases during the test. Clearly, the results of this study demonstrate the importance of pH buffering in metal toxicity testing and the suitability of the MOPS buffer for that purpose.


Subject(s)
Biological Assay/methods , Copper/toxicity , Water Pollutants, Chemical/toxicity , Zinc/toxicity , Animals , Buffers , Chlorophyta/drug effects , Daphnia/drug effects , Hydrogen-Ion Concentration
6.
Environ Int ; 28(8): 793-800, 2003 Mar.
Article in English | MEDLINE | ID: mdl-12605929

ABSTRACT

In this paper, some of the main processes and parameters which affect metal bioavailability and toxicity in the aquatic environment and its implications for metal risk assessment procedures will be discussed. It has become clear that, besides chemical processes (speciation, complexation), attention should also be given to physiological aspects for predicting metal toxicity. The development of biotic ligand models (BLMs), which combine speciation models with more biologically oriented models (e.g. GSIM), has offered an answer to this need. The various BLMs which have been developed and/or refined for a number of metals (e.g. Cu, Ag, Zn) and species (algae, crustaceans, fish) are discussed here. Finally, the potential of the BLM approach is illustrated through a theoretical exercise in which chronic zinc toxicity to Daphnia magna is predicted in three regions, taking the physico-chemical characteristics of these areas into account.


Subject(s)
Metals, Heavy/adverse effects , Metals, Heavy/chemistry , Models, Theoretical , Water Pollutants/adverse effects , Animals , Biological Availability , Crustacea , Daphnia , Eukaryota , Fishes , Forecasting , Ligands , Metals, Heavy/pharmacokinetics , Risk Assessment , Water Pollutants/pharmacokinetics
7.
Arch Environ Contam Toxicol ; 44(2): 210-7, 2003 Feb.
Article in English | MEDLINE | ID: mdl-12520393

ABSTRACT

The effect of changes in pH, hardness, and dissolved organic carbon (DOC) and the possible interactions among these parameters on the chronic toxicity of zinc to D. magna were investigated. Based on a Central Composite Design, models were developed that can explain the observed variation in EC(10) and EC(50) as a function of these toxicity modifying factors. All three parameters significantly altered the observed effect concentrations based on net reproductive rate. The largest differences in 21-day EC(10)s and EC(50)s caused by these factors were 10.1 and 4.9, respectively. An increase in pH and/or DOC decreased zinc toxicity. The significant interaction between pH and DOC on observed chronic Zn toxicity is in accordance with earlier reported increased sorption efficiency of Zn to humic substances at higher pH levels. Lowest Zn toxicity was observed in tests performed with moderately hard test media (between 200 and 300 mg/L as CaCO(3)). Lower or higher hardness of the test medium resulted in lower effect concentrations. Based on physico-chemical characteristics of the test media, developed models can be used to explain the variation between reported NOECs for Zn and may improve current environmental risk assessment procedures of metals.


Subject(s)
Daphnia , Water Pollutants/toxicity , Zinc/toxicity , Animals , Calcium Carbonate , Carbon , Hydrogen-Ion Concentration , Risk Assessment , Water/chemistry
8.
Comp Biochem Physiol C Toxicol Pharmacol ; 133(1-2): 207-18, 2002 Sep.
Article in English | MEDLINE | ID: mdl-12356528

ABSTRACT

Biotic ligand models have been developed for various metals (e.g. Cu, Ag, Zn) and different aquatic species. These models incorporate the effect of physico-chemical water characteristics (major cations, pH, dissolved organic carbon) on the bioavailability and toxicity of the metal. In this study, the individual effects of calcium, magnesium, potassium, sodium and pH on zinc toxicity to the green alga Pseudokirchneriella subcapitata (formerly and better known as Selenastrum capricornutum and Raphidocelis subcapitata) were investigated. Stability constants for binding to algal cells (K(BL)) were derived for those cations affecting zinc toxicity, using the mathematical approach proposed by De Schamphelaere and Janssen [Environ. Sci. Technol. 63, (2002) 48-54]. Potassium proved to be the only cation tested that did not alter zinc toxicity to algae significantly. Log (K(BL)) values for Ca, Mg and Na, derived at pH 7.5, were 3.2, 3.9 and 2.8, respectively. Toxicity tests performed at different pH values (5.5-8.0) indicated that competition between H(+) and Zn(2+) reduces zinc toxicity. However, the observed relationship between (H(+)) and the 72h-EbC(50) [expressed as microM (Zn(2+))] is not linear and suggests that pH affects the physiology of the biotic ligand. Although, in general, our findings seem to suggest that zinc toxicity to algae can be modelled as a function of key water characteristics, the results also demonstrate that the part of the conventional BLM-hypothesis-i.e. that the binding characteristics of the biotic ligand are independent of the test medium characteristics-is not valid for algae. The observed pH-dependent change of stability constants should therefore be further investigated and incorporated in future BL-modelling efforts with algae.


Subject(s)
Chlorophyta/drug effects , Models, Biological , Zinc/toxicity , Chlorophyta/metabolism , Forecasting , Ligands , Zinc/metabolism
9.
Chemosphere ; 47(10): 1073-80, 2002 Jun.
Article in English | MEDLINE | ID: mdl-12137040

ABSTRACT

Corrosion and runoff from zinc-coated materials and outdoor structures is an important source for the dispersion of zinc in the environment. Being part of a large inter-disciplinary research project, this study presents the bioavailability of zinc in runoff water immediately after release from the surface of 15 different commercially available zinc-based materials exposed to the urban environment of Stockholm, Sweden. Runoff water was analysed chemically and evaluated for its possible environmental impact, using both a biosensor test with the bacteria Alcaligenes eutrophus (Biomet) and the conventional 72 h growth inhibition test with the green alga Raphidocelis subcapitata. Chemical speciation modelling revealed that most zinc (94.3-99.9%) was present as the free Zn ion, the most bioavailable speciation form. These findings were confirmed by the results of the biosensor test (Biomet) which indicated that all zinc was indeed bioavailable. Analysis of the ecotoxicity data also suggested that the observed toxic effects were due to the presence of Zn2+ ions. Finally, regression analysis showed that, for this type of runoff samples, the rapid screening biosensor was capable of predicting (a) the total amount of zinc present in the runoff samples (R2 of 0.93-0.98; p < 0.05) and (b) the observed 72 h-EbC50s (R2 of 0.69-0.97; p < 0.05).


Subject(s)
Manufactured Materials , Zinc/pharmacokinetics , Biological Assay , Biological Availability , Cities , Cupriavidus necator , Environmental Monitoring , Housing , Rain , Regression Analysis , Rhodophyta , Sweden , Zinc/analysis
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