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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Endpoint:
bioaccumulation in aquatic species: algae / cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Read across from a study performed with zirconium dichloride oxide. The read across justification document is attached to IUCLID Section 13.
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Reason / purpose:
read-across source
Key result
Type:
BCF
Value:
0.052 - 0.64 L/kg
Basis:
whole body d.w.
Remarks:
for Zr (element)
Remarks on result:
other: Based on the read across data from Garnham et al. (1993) it was concluded that there is no potential for aquatic bioaccumulation of zirconium from tungsten zirconium oxide.
Endpoint:
bioaccumulation in aquatic species: algae / cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: No analytical measurement performed. No GLP compliance. No international guideline mentioned.
Qualifier:
no guideline followed
Principles of method if other than guideline:
Sorption/uptake - desorption study with various microalgae and cyanobacteria.
GLP compliance:
not specified
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material:
Zirconium dichloride oxide was used as test substance. Nevertheless, when put in water, zirconium dichloride oxide hydrolyses rapidly and precipitates as zirconium dioxide. Therefore, zirconium dioxide is actually the substance being tested in this study.
Radiolabelling:
no
Test organisms (species):
Chlorella emersonii
Details on test organisms:
For the bioaccumulation test, algae in the exponential phase of growth were centrifuged. The supernatant was removed and the cells washed once with 10 mM sodium acetate buffer, pH 5.0. Cells were centrifuged and resuspended in 10 mM sodium acetate buffer, pH 5.0 to cell densities of 5 x 10 6 mL-1.
Route of exposure:
aqueous
Test type:
not specified
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
4 h
Total depuration duration:
24 h
Hardness:
No information available
Test temperature:
23°C
pH:
5
Dissolved oxygen:
No information available
TOC:
No information available
Salinity:
No information available
Details on test conditions:
TEST SYSTEM
- Material, size, headspace, fill volume: 25 mL acid-washed plastic vials
- Biomass loading rate: 5E10+6 cells/mL
- Replicates: 3

TEST MEDIUM / WATER PARAMETERS
- Growth medium: BG11 medium which comprised: 1.5 g NaNO3, 0.04 g K2HPO4, 0.075 g MgSO4.7 H2O, 0.036 g CaCl2.2 H2O, 0.006 g citric acid, 0.006 g ferric ammonium citrate, 0.001 g disodium ethylenediaminetetraacetate (Na2EDTA), 0.02 g NaHCO3, 1 mL trace metal mix A5 (2.86 g H3BO3, 1.81 g MnCl2.4 H2O, 0.222 g ZnSO4.7 H2O, 0.039 g Na2MoO2.2 H2O, 0.079 g CuSO4.5 H2O, 0.0494 g Co(NO3)2.6 H2O in 1 L distilled water.

OTHER TEST CONDITIONS
- Adjustment of pH: 10 mM sodium acetate buffer, pH 5.0
- Light intensity: 300 µE m-2 s-1

RANGE-FINDING / PRELIMINARY STUDY
- Test concentrations: Aliquots from 10 mM and 100 mM zirconium dichloride oxide aqueous solution were added to give a final concentration in the range of 0.5-50 mM
Nominal and measured concentrations:
Nominal concentrations: 0.5 to 50 mM of Zr
Actual concentration: 3.7 g/L
Details on estimation of bioconcentration:
UPTAKE:
The amount of Zr taken up by cells was calculated from the reduction of Zr in the buffer, after taking into account any binding to the plastic vial (determined in control experiments without cells).

DESORPTION :
Cell suspensions were prepared in 10 mM sodium acetate buffer, pH 5.0, with 100 µM zirconium dichloride oxide. Cell suspensions were then incubated for at least 24 h in the light. Three replicate samples (1 mL) were taken from the cell suspensions and centrifuged after which the supernatant was removed and the Zr concentration measured by polarography.



Key result
Type:
BCF
Value:
0.64 L/kg
Basis:
whole body d.w.
Time of plateau:
4 h
Calculation basis:
steady state
Remarks on result:
other: expressed in Zr
Remarks:
conc. in environment / dose: 3.7 g/L
Elimination:
yes
Parameter:
other: 28 to 87% of the Zr accumulated
Depuration time (DT):
5 min
Details on results:
Zr accumulation (µmol g dry wt-1) after 4 h: 25.6 +/- 0.7
Zr accumulation (µmol g dry wt-1) after 5 min: 25.0 +/- 1.0
Validity criteria fulfilled:
yes
Conclusions:
In conclusion, the BCF value is very low for Chlorella emersonii. Zr accumulation in µmol g dry wt-1 was in the same order of magnitude after 5 minutes and 4 hours of exposure. Similarly, rapid desorption (within 5 min) has been observed.
Endpoint:
bioaccumulation in aquatic species: algae / cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: No analytical measurement performed. No GLP compliance. No international guideline mentioned.
Qualifier:
no guideline followed
Principles of method if other than guideline:
Sorption/uptake - desorption study with various microalgae and cyanobacteria.
GLP compliance:
not specified
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material:
Zirconium dichloride oxide was used as test substance. Nevertheless, when put in water, zirconium dichloride oxide hydrolyses rapidly and precipitates as zirconium dioxide. Therefore, the actual test substance was zirconium dioxide.
Radiolabelling:
no
Test organisms (species):
other: Synechococcus PCC 6301
Details on test organisms:
For the bioaccumulation test, algae in the exponential phase of growth were centrifuged. The supernatant was removed and the cells washed once with 10 mM sodium acetate buffer, pH 5.0. Cells were centrifuged and resuspended in 10 mM sodium acetate buffer, pH 5.0 to cell densities of 5 x 10 8 mL-1.
Route of exposure:
aqueous
Test type:
not specified
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
4 h
Total depuration duration:
24 h
Hardness:
No information available
Test temperature:
23°C
pH:
5
Dissolved oxygen:
No information available
TOC:
No information available
Salinity:
No information available
Details on test conditions:
TEST SYSTEM
- Material, size, headspace, fill volume: 25 mL acid-washed plastic vials
- Biomass loading rate: 5E10+6 cells/mL
- Replicates: 3

TEST MEDIUM / WATER PARAMETERS
- Growth medium: BG11 medium which comprised: 1.5 g NaNO3, 0.04 g K2HPO4, 0.075 g MgSO4.7H2O, 0.036 g CaCl2.2H2O, 0.006 g citric acid, 0.006 g ferric ammonium citrate, 0.001 g disodium ethylenediaminetetraacetate (Na2EDTA), 0.02 g NaHCO3, 1 mL trace metal mix A5 (2.86 g H3BO3, 1.81 g MnCl2.4H2O, 0.222 g ZnSO4.7H2O, 0.039 g Na2MoO2.2H2O, 0.079 g CuSO4.5H2O, 0.0494 g Co(NO3)2.6H2O in 1 L distilled water.

OTHER TEST CONDITIONS
- Adjustment of pH: 10 mM sodium acetate buffer, pH 5.0
- Light intensity: 300 µE m-2 s-1

RANGE-FINDING / PRELIMINARY STUDY
- Test concentrations: Aliquots from 10 mM and 100 mM zirconium dichloride oxide aqueous solution were added to give a final concentration in the range of 0.5-50 mM
Nominal and measured concentrations:
Nominal concentrations: 0.5 to 50 mM of Zr
Actual concentration: 3.7 g/L
Details on estimation of bioconcentration:
UPTAKE:
The amount of Zr taken up by cells was calculated from the reduction of Zr in the buffer, after taking into account any binding to the plastic vial (determined in control experiments without cells).

DESORPTION :
Cell suspensions were prepared in 10 mM sodium acetate buffer, pH 5.0, with 100 µM zirconium dichloride oxide. Cell suspensions were then incubated for at least 24 h in the light. Three replicate samples (1 mL) were taken from the cell suspensions and centrifuged after which the supernatant was removed and the Zr concentration measured by polarography.



Type:
BCF
Value:
0.455 L/kg
Basis:
whole body d.w.
Time of plateau:
4 h
Calculation basis:
steady state
Remarks on result:
other: expressed in Zr
Remarks:
conc. in environment / dose: 3.7 g/L
Elimination:
yes
Parameter:
other: 28 to 87% of the Zr accumulated
Depuration time (DT):
5 min
Details on results:
Zr accumulation (µmol g dry wt-1) after 4 h: 18.2 +/- 0.8
Zr accumulation (µmol g dry wt-1) after 5 min: 19.9 +/- 0.1
Validity criteria fulfilled:
yes
Conclusions:
In conclusion, the BCF value is very low for Synechococcus sp. Zr accumulation in µmol g dry wt-1 was in the same order of magnitude after 5 minutes and 4 hours of exposure. As well, rapid desorption (within 5 min) has been observed.
Endpoint:
bioaccumulation in aquatic species: algae / cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: No analytical measurement performed. No GLP compliance. No international guideline mentioned.
Qualifier:
no guideline followed
Principles of method if other than guideline:
Sorption/uptake - desorption study with various microalgae and cyanobacteria.
GLP compliance:
not specified
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material:
Zirconium dichloride oxide was used as test substance. Nevertheless, when put in water, zirconium dichloride oxide hydrolyses rapidly and precipitates as zirconium dioxide. Therefore, the actual test substance was zirconium dioxide.
Radiolabelling:
no
Test organisms (species):
other: Synechococcus PCC 6803
Details on test organisms:
For the bioaccumulation test, algae in the exponential phase of growth were centrifuged. The supernatant was removed and the cells washed once with 10 mM sodium acetate buffer, pH 5.0. Cells were centrifuged and resuspended in 10 mM sodium acetate buffer, pH 5.0 to cell densities of 5 x 10 8 mL-1.
Route of exposure:
aqueous
Test type:
not specified
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
4 h
Total depuration duration:
24 h
Hardness:
No information available
Test temperature:
23°C
pH:
5
Dissolved oxygen:
No information available
TOC:
No information available
Salinity:
No information available
Details on test conditions:
TEST SYSTEM
- Material, size, headspace, fill volume: 25 mL acid-washed plastic vials
- Biomass loading rate: 5E10+8 cells/mL
- Replicates: 3

TEST MEDIUM / WATER PARAMETERS
- Growth medium: BG11 medium which comprised: 1.5 g NaNO3, 0.04 g K2HPO4, 0.075 g MgSO4.7H2O, 0.036 g CaCl2.2H2O, 0.006 g citric acid, 0.006 g ferric ammonium citrate, 0.001 g disodium ethylenediaminetetraacetate (Na2EDTA), 0.02 g NaHCO3, 1 mL trace metal mix A5 (2.86 g H3BO3, 1.81 g MnCl2.4H2O, 0.222 g ZnSO4.7H2O, 0.039 g Na2MoO2.2H2O, 0.079 g CuSO4.5H2O, 0.0494 g Co(NO3)2.6 H2O in 1 L distilled water.

OTHER TEST CONDITIONS
- Adjustment of pH: 10 mM sodium acetate buffer, pH 5.0
- Light intensity: 300 µE m-2 s-1

RANGE-FINDING / PRELIMINARY STUDY
- Test concentrations: Aliquots from 10 mM and 100 mM zirconium dichloride oxide aqueous solution were added to give a final concentration in the range of 0.5-50 mM
Nominal and measured concentrations:
Nominal concentrations: 0.5 to 50 mM of Zr
Actual concentration: 3.7 g/L
Details on estimation of bioconcentration:
UPTAKE:
The amount of Zr taken up by cells was calculated from the reduction of Zr in the buffer, after taking into account any binding to the plastic vial (determined in control experiments without cells).

DESORPTION :
Cell suspensions were prepared in 10 mM sodium acetate buffer, pH 5.0, with 100 µM zirconium dichloride oxide. Cell suspensions were then incubated for at least 24 h in the light. Three replicate samples (1 mL) were taken from the cell suspensions and centrifuged after which the supernatant was removed and the Zr concentration measured by polarography.



Type:
BCF
Value:
0.052 L/kg
Basis:
whole body d.w.
Time of plateau:
4 h
Calculation basis:
steady state
Remarks on result:
other: expressed in Zr
Remarks:
conc. in environment / dose: 3.7 g/L
Elimination:
yes
Parameter:
other: 28 to 87% of the Zr accumulated
Depuration time (DT):
5 min
Details on results:
Zr accumulation (µmol g dry wt-1) after 4 h: 2.1 +/- 0.5
Zr accumulation (µmol g dry wt-1) after 5 min: 1.85 +/- 0.2
Validity criteria fulfilled:
yes
Conclusions:
In conclusion, the BCF value is very low for Synechococcus sp. Zr accumulation in µmol g dry wt-1 was at the same order of magnitude after 5 minutes and 4 hours of exposure. As well, rapid desorption (within 5 min) has been observed.
Endpoint:
bioaccumulation in aquatic species: algae / cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: No analytical measurement performed. No GLP compliance. No international guideline mentioned.
Qualifier:
no guideline followed
Principles of method if other than guideline:
Sorption/uptake - desorption study with various microalgae and cyanobacteria.
GLP compliance:
not specified
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material:
Zirconium dichloride oxide was used as test substance. Nevertheless, when put in water, zirconium dichloride oxide hydrolyses rapidly and precipitates as zirconium dioxide. Therefore, the actual test substance was zirconium dioxide.
Radiolabelling:
no
Test organisms (species):
other: Plectonema boryanum
Details on test organisms:
For the bioaccumulation test, algae in the exponential phase of growth were centrifuged. The supernatant was removed and the cells washed once with 10 mM sodium acetate buffer, pH 5.0. Cells were centrifuged and resuspended in 10 mM sodium acetate buffer, pH 5.0 to cell densities of OD680 of approx. 6.
Route of exposure:
aqueous
Test type:
not specified
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
4 h
Total depuration duration:
24 h
Hardness:
No information available
Test temperature:
23°C
pH:
5
Dissolved oxygen:
No information available
TOC:
No information available
Salinity:
No information available
Details on test conditions:
TEST SYSTEM
- Material, size, headspace, fill volume: 25 mL acid-washed plastic vials
- Biomass loading rate: OD680 of approx. 6
- Replicates: 3

TEST MEDIUM / WATER PARAMETERS
- Growth medium: BG11 medium which comprised: 1.5 g NaNO3, 0.04 g K2HPO4, 0.075 g MgSO4.7H2O, 0.036 g CaCl2.2H2O, 0.006 g citric acid, 0.006 g ferric ammonium citrate, 0.001 g disodium ethylenediaminetetraacetate (Na2EDTA), 0.02 g NaHCO3, 1 mL trace metal mix A5 (2.86 g H3BO3, 1.81 g MnCl2.4H2O, 0.222 g ZnSO4.7H2O, 0.039 g Na2MoO2.2H2O, 0.079 g CuSO4.5H2O, 0.0494 g Co(NO3)2.6 H2O in 1 L distilled water).

OTHER TEST CONDITIONS
- Adjustment of pH: 10 mM sodium acetate buffer, pH 5.0
- Light intensity: 300 µE m-2 s-1

RANGE-FINDING / PRELIMINARY STUDY
- Test concentrations: Aliquots from 10 mM and 100 mM zirconium dichloride oxide aqueous solution were added to give a final concentration in the range of 0.5-50 mM
Nominal and measured concentrations:
Nominal concentrations : 0.5 to 50 mM of Zr
Actual concentration : 3.7 g/L
Details on estimation of bioconcentration:
UPTAKE:
The amount of Zr taken up by cells was calculated from the reduction of Zr in the buffer, after taking into account any binding to the plastic vial (determined in control experiments without cells).

DESORPTION :
Cells suspensions were prepared in 10 mM sodium acetate buffer, pH 5.0, with 100 µM zirconium dichloride oxide. Cell suspensions were then incubated for at least 24 h in the light. Three replicates samples (1 mL) were taken from the cell suspensions and centrifuged after which the supernatant was removed and the Zr concentration measured by polarography.



Type:
BCF
Value:
0.4 L/kg
Basis:
whole body d.w.
Time of plateau:
4 h
Calculation basis:
steady state
Remarks on result:
other: expressed in Zr
Remarks:
conc. in environment / dose: 3.7 g/L
Elimination:
yes
Parameter:
other: 28 to 87% of the Zr accumulated
Depuration time (DT):
5 min
Details on results:
Zr accumulation (µmol g dry wt-1) after 4 h: 16.0 +/- 0.1
Zr accumulation (µmol g dry wt-1) after 5 min: 16.8 +/- 0.1
Validity criteria fulfilled:
yes
Conclusions:
In conclusion, the BCF value is very low for Plectonema boryanum. Zr accumulation in µmol g dry wt-1 was at the same order of magnitude after 5 minutes and 4 hours of exposure. As well, rapid desorption (within 5 min) has been observed.
Endpoint:
bioaccumulation in aquatic species: algae / cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: No analytical measurement performed. No GLP compliance. No international guideline mentioned.
Qualifier:
no guideline followed
Principles of method if other than guideline:
Sorption/uptake - desorption study with various microalgae and cyanobacteria.
GLP compliance:
not specified
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material:
Zirconium dichloride oxide was used as test substance. Nevertheless, when put in water, zirconium dichloride oxide hydrolyses rapidly and precipitates as zirconium dioxide. Therefore, the actual test substance was zirconium dioxide.
Radiolabelling:
no
Test organisms (species):
other: Scenedesmus obliquus
Details on test organisms:
For the bioaccumulation test, algae in the exponential phase of growth were centrifuged. The supernatant was removed and the cells washed once with 10 mM sodium acetate buffer, pH 5.0. Cells were centrifuged and resuspended in 10 mM sodium acetate buffer, pH 5.0 to cell densities of 5 x 10 7 mL-1.
Route of exposure:
aqueous
Test type:
not specified
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
4 h
Total depuration duration:
24 h
Hardness:
No information available
Test temperature:
23°C
pH:
5
Dissolved oxygen:
No information available
TOC:
No information available
Salinity:
No information available
Details on test conditions:
TEST SYSTEM
- Material, size, headspace, fill volume: 25 mL acid-washed plastic vials
- Biomass loading rate: 5E10+7 cells/mL
- Replicates: 3

TEST MEDIUM / WATER PARAMETERS
- Growth medium: BG11 medium which comprised: 1.5 g NaNO3, 0.04 g K2HPO4, 0.075 g MgSO4.7H2O, 0.036 g CaCl2.2H2O, 0.006 g citric acid, 0.006 g ferric ammonium citrate, 0.001 g disodium ethylenediaminetetraacetate (Na2EDTA), 0.02 g NaHCO3, 1 mL trace metal mix A5 (2.86 g H3BO3, 1.81 g MnCl2.4H2O, 0.222 g ZnSO4.7H2O, 0.039 g Na2MoO2.2H2O, 0.079 g CuSO4.5H2O, 0.0494 g Co(NO3)2.6 H2O in 1 L distilled water.

OTHER TEST CONDITIONS
- Adjustment of pH: 10 mM sodium acetate buffer, pH 5.0
- Light intensity: 300 µE m-2 s-1

RANGE-FINDING / PRELIMINARY STUDY
- Test concentrations: Aliquots from 10 mM and 100 mM zirconium dichloride oxide aqueous solution were added to give a final concentration in the range of 0.5-50 mM
Nominal and measured concentrations:
Nominal concentrations: 0.5 to 50 mM of Zr
Actual concentration: 3.7 g/L
Details on estimation of bioconcentration:
UPTAKE:
The amount of Zr taken up by cells was calculated from the reduction of Zr in the buffer, after taking into account any binding to the plastic vial (determined in control experiments without cells).

DESORPTION :
Cell suspensions were prepared in 10 mM sodium acetate buffer, pH 5.0, with 100 µM zirconium dichloride oxide. Cell suspensions were then incubated for at least 24 h in the light. Three replicate samples (1 mL) were taken from the cell suspensions and centrifuged after which the supernatant was removed and the Zr concentration measured by polarography.



Type:
BCF
Value:
0.55 L/kg
Basis:
whole body d.w.
Time of plateau:
4 h
Calculation basis:
steady state
Remarks on result:
other: expressed in Zr
Remarks:
conc. in environment / dose: 3.7 g/L
Elimination:
yes
Parameter:
other: 28 to 87% of the Zr accumulated
Depuration time (DT):
5 min
Details on results:
Zr accumulation (µmol g dry wt-1) after 4 h: 22.0 +/- 0.6
Zr accumulation (µmol g dry wt-1) after 4 h: 21.3 +/- 0.5
Validity criteria fulfilled:
yes
Conclusions:
In conclusion, the BCF value is very low for Scenedesmus obliquus. Zr accumulation in µmol g dry wt-1 was at the same order of magnitude after 5 minutes and 4 hours of exposure. As well, rapid desorption (within 5 min) has been observed.
Endpoint:
bioaccumulation in aquatic species: algae / cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: No analytical measurement performed. No GLP compliance. No international guideline mentioned.
Qualifier:
no guideline followed
Principles of method if other than guideline:
Sorption/uptake - desorption study with various microalgae and cyanobacteria.
GLP compliance:
not specified
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material:
Zirconium dichloride oxide was used as test substance. Nevertheless, when put in water, zirconium dichloride oxide hydrolises rapidly and precipitates as zirconium dioxide. Therefore, the actual test substance was zirconium dioxide.
Radiolabelling:
no
Test organisms (species):
other: Chlamydomonas reinhardtii
Details on test organisms:
For the bioaccumulation test, algae in the exponential phase of growth were centrifuged. The supernatant was removed and the cells washed once with 10 mM sodium acetate buffer, pH 5.0. Cells were centrifuged and resuspended in 10 mM sodium acetate buffer, pH 5.0 to cell densities of 1 x 10 7 mL-1.
Route of exposure:
aqueous
Test type:
not specified
Water / sediment media type:
natural water: freshwater
Total exposure / uptake duration:
4 h
Total depuration duration:
24 h
Hardness:
No information available
Test temperature:
23°C
pH:
5
Dissolved oxygen:
No information available
TOC:
No information available
Salinity:
No information available
Details on test conditions:
TEST SYSTEM
- Material, size, headspace, fill volume: 25 mL acid-washed plastic vials
- Biomass loading rate: 1E10+7 cells/mL
- Replicates: 3

TEST MEDIUM / WATER PARAMETERS
- Growth medium: BG11 medium which comprised: 1.5 g NaNO3, 0.04 g K2HPO4, 0.075 g MgSO4.7H2O, 0.036 g CaCl2.2H2O, 0.006 g citric acid, 0.006 g ferric ammonium citrate, 0.001 g disodium ethylenediaminetetraacetate (Na2EDTA), 0.02 g NaHCO3, 1 mL trace metal mix A5 (2.86 g H3BO3, 1.81 g MnCl2.4H2O, 0.222 g ZnSO4.7H2O, 0.039 g Na2MoO2.2H2O, 0.079 g CuSO4.5H2O, 0.0494 g Co(NO3)2.6H2O in 1 L distilled water.

OTHER TEST CONDITIONS
- Adjustment of pH: 10 mM sodium acetate buffer, pH 5.0
- Light intensity: 300 µE m-2 s-1

RANGE-FINDING / PRELIMINARY STUDY
- Test concentrations: Aliquots from 10 mM and 100 mM zirconium dichloride oxide aqueous solution were added to give a final concentration in the range of 0.5-50 mM
Nominal and measured concentrations:
Nominal concentrations: 0.5 to 50 mM of Zr
Actual concentration: 3.7 g/L
Details on estimation of bioconcentration:
UPTAKE:
The amount of Zr taken up by cells was calculated from the reduction of Zr in the buffer, after taking into account any binding to the plastic vial (determined in control experiments without cells).

DESORPTION :
Cell suspensions were prepared in 10 mM sodium acetate buffer, pH 5.0, with 100 µM zirconium dichloride oxide. Cell suspensions were then incubated for at least 24 h in the light. Three replicate samples (1 mL) were taken from the cell suspensions and centrifuged after which the supernatant was removed and the Zr concentration measured by polarography.



Type:
BCF
Value:
0.188 L/kg
Basis:
whole body d.w.
Time of plateau:
4 h
Calculation basis:
steady state
Remarks on result:
other: expressed in Zr
Remarks:
conc. in environment / dose: 3.7 g/L
Elimination:
yes
Parameter:
other: 28 to 87% of the Zr accumulated
Depuration time (DT):
5 min
Details on results:
Zr accumulation (µmol g dry wt-1) after 4 h: 7.5 +/- 0.5
Zr accumulation (µmol g dry wt-1) after 5 min: 11.2 +/- 0.6
Validity criteria fulfilled:
yes
Conclusions:
In conclusion, the BCF value is very low for Chlamydomonas reinhardtii. Zr accumulation in µmol g dry wt-1 was at the same order of magnitude after 5 minutes and 4 hours of exposure. As well, rapid desorption (within 5 min) has been observed.

Description of key information

Because tungsten zirconium oxide has an extremely low water solubility, only small amounts of tungsten and zirconium may become available for uptake when the substance is released to the environment. Experimental data for zirconium (key BCF of 0.064 L/kg ww for microalgae and cyanobacteria, Garnham et al., 1993) confirm that there is no concern for bioaccumulation of this element. No data are included in the dossier on bioaccumulation of tungsten. However, since zirconium is the most dominant element in tungsten zirconium oxide on a weight by weight basis, and because tungsten is expected to be released only to a very limited extent in environmental media, it was considered sufficient to cover the endpoint by data on zirconium alone. Based on the available information, it can be concluded that there is no concern for bioaccumulation resulting from environmental exposure to tungsten zirconium oxide.

Key value for chemical safety assessment

Additional information

1. Information on zirconium (dioxide)

The accumulation of zirconium by cyanobacteria and microalgae was characterised by Garnham et al. (1993). In this study the organisms were exposed to solutions of zirconium dichloride oxide. Actual exposure however was rather to zirconium dioxide, since zirconium dichloride oxide hydrolyses rapidly in aqueous solutions at environmentally relevant pH, resulting in the precipitation of zirconium as zirconium dioxide or hydroxide. In all cyanobacterial and microalgal species examined, accumulation consisted of a single rapid energy-independent phase ("biosorption"). No energy-dependent accumulation was observed. Biosorption of zirconium was concentration-dependent, followed a Freundlich adsorption isotherm, and was dependent on pH, showing decreasing accumulation with decreasing pH. Zirconium desorption from microalgae and cyanobacteria was increased by increasing external cation concentrations or by decreasing the pH of the desorption agent. Overall, biosorption/bioaccumulation was very limited. BCF values between 0.0525 and 0.64 L/kg dw were obtained. Assuming 90% water content in the organisms, the highest value can be recalculated to a BCF of 0.064 L/kg ww. Since no bioconcentration/bioaccumulation data are available for zirconium for other groups of organisms, this BCF can be considered as the key BCF for zirconium.

2. Information on tungsten (oxide)

No data are included in the dossier on the potential bioconcentration/bioaccumulation of tungsten in aquatic organisms.

3. Conclusion on tungsten zirconium oxide

Tungsten zirconium oxide has an extremely low water solubility and only small amounts of tungsten and zirconium may become available for uptake when the substance is released to the environment (Buchholz, 2018; Ablitt, 2018; Vryenhoef, 2018). For zirconium, experimental data confirm that there is no concern for bioaccumulation. For tungsten, no data are included in the dossier. However, since zirconium is the most dominant element in tungsten zirconium oxide on a weight by weight basis, and because tungsten is expected to be released only to a very limited extent in environmental media, it was considered sufficient to cover the endpoint by data on zirconium alone. Based on the available information, it can be concluded that there is no concern for bioaccumulation resulting from environmental exposure to tungsten zirconium oxide.