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Bioaccumulation: terrestrial

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Endpoint:
bioaccumulation: terrestrial
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
Accumulation data in earthworms were obtained after use in a toxicity study conducted according to modified ISO 11268-1 (Effects of Pollutants on Earthworms. 1. Determination of Acute Toxicity Using Artificial Soil Substrate), with sufficient information presented on materials and methods to adequately evaluate bioaccumulation results. Insufficient information was available on the levels of background tungsten, other metals, and environmental contaminants in the soil tested. No data on the behavior of tungsten dioxide in the environment are available. Concentration data for tungsten metal are appropriate for read-across for this endpoint as the soluble species released are expected to be similar for each of the compounds, and are thus expected to behave similarly in the environment. For more details refer to the attached description of the read across approach.
Justification for type of information:
REPORTING FORMAT FOR THE CATEGORY APPROACH
1. HYPOTHESIS FOR THE ANALOGUE APPROACH: The hypothesis is that properties are likely to be similar or follow a similar pattern because of the presence of a common metal ion, in this case tungstate.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES):
Source: Tungsten Metal
Target: Tungsten Dioxide
3. CATEGORY APPROACH JUSTIFICATION: See Annex 1 in CSR
4. DATA MATRIX: See Annex 1 in CSR
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
other: modified ISO 11268-1 (Effects of Pollutants on Earthworms. 1. Determination of Acute Toxicity Using Artificial Soil Substrate.)
GLP compliance:
not specified
Radiolabelling:
no
Details on sampling:
- Sampling intervals/frequency for test organisms: After the 80 day exposure period, the surviving worms were collected and placed in jars containing wet filter paper and no soil.
- Sample storage conditions before analysis: worms were placed in jars containing wet filter paper and no soil for 2 days.
- Details on sampling and analysis of test organisms and test media samples (e.g. sample preparation, analytical methods): Worms were frozen in liquid nitrogen, acid digested, and tungsten concentration measured by ICP.
Vehicle:
no
Details on preparation and application of test substrate:
- Method of mixing into soil (if used): mixed manually with tungsten powder
- Controls: Non-treated highway soil
Test organisms (species):
Eisenia fetida
Details on test organisms:
- Common name: Earthworm
- Source: Worm Farm Inc. Monroe Twp, NJ
- Age at test initiation (mean and range, SD): Not specified
- Weight at test initiation (mean and range, SD): Not specified
Total exposure / uptake duration:
80 d
Total depuration duration:
2 d
Test temperature:
Room temperature
pH:
Varied with tungsten concentration, 4.80-7.25.
TOC:
- Organic carbon (%): 2 %
Moisture:
Not specified; DI water added daily.
Details on test conditions:
TEST SYSTEM
- Test container (material, size): glass jar, covered with filter paper
- Amount of soil or substrate: 750 g
- No. of organisms per container (treatment): 10
- No. of replicates per treatment group: 3 or 4
- No. of replicates per control: 3 or 4
- One set of replicates ammended with 10,000 mg/kg CaCO3 in addition to the toxicant to buffer pH change.

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographic location: Highway soil (Exit 40, Hwy 78, The Plainfields, NJ)
- Pesticide use history at the collection site: Not specified
- Sampling depth (cm): 1-5 cm
- Organic carbon (%): 2 %
- Pretreatment of soil: Homogenized, plant roots and large particles removed, sieved through a 1 mm sieve.
- Storage (condition, duration): 4degree C until use- more than 1 year.





Nominal and measured concentrations:
Nominal-Control, 10, 100 and 10,000 mg/kg tungsten.
Kinetic parameters:
No data
Metabolites:
No data
Details on results:
Test with non-aged soil
- Mortality of test organisms: All worms in the 10 and 100 mg W/kg soil levels survived for 80 days. All worms in the 10,000 mg/kg soil died after 80 days.
- Other biological observations: All worms in all concentrations survived after 80 days in the soils amended with 10,000 mg/kg CaCO3. The pH of the soil decreased over time from its initial value of 5.6 in all soils without a CaCO3 supplement. The largest drop observed for the highest W concentration where a final soil pH of 4.80 was measured. However, for the replicates containing the same W concentration and supplemented with CaCO3, the pH after 80 days was 7.25.
- Mortality and/or behavioural abnormalities of control: all worms in the control group survived.
- Worms took up and accumulated tungsten in their tissue. Dry weight tissue concentrations were 1.52, 3.24, and 193.2 mg/kg tungsten
for the 10, 100, and 10,000 mg W/kg soil concentrations, respectively.

Test with aged soil
-The results of the second test are consistent with the results of the first test where all worms survived the 14-days exposure to soils amended with 10-1000 mg W/kg soil and all of them died at the 10,000 mg W/kg soil level.
- Tissue concentrations of 3.45 to 25.9 mg tungsten/kg dry weight were observed for tungsten soil concentrations ranging from 10 to 1000 mg/kg, respectively.
Conclusions:
Accumulation data in earthworms were obtained after use in a toxicity study conducted according to modified ISO 11268-1 (Effects of Pollutants on Earthworms. 1. Determination of Acute Toxicity Using Artificial Soil Substrate). Earthworms were exposed to nominal tungsten concentrations of 0 (control), 10, 100 and 10,000 mg/kg tungsten. Soil (non-treated highway soil, 2 % organic carbon, pH varied with tungsten concentration between 4.80 and 7.25) was mixed manually with tungsten powder. To one set of replicates ammended with 10,000 mg/kg CaCO3 was added in addition to the toxicant to buffer the pH change. Animals were exposed to the substance for a total of 80 days. In a second test, soils were amended with tungsten as above, and aged 1 year before the introduction of the worms.

In the test with non-aged soil all animals died within the 80 day exposure period at 10,000 mg W/kg, however, all worms in all concentrations survived after 80 days in the soils amended with 10,000 mg/kg CaCO3. Worms took up and accumulated tungsten in their tissue. Dry weight tissue concentrations were 1.52, 3.24, and 193.2 mg/kg tungsten for the 10, 100, and 10,000 mg W/kg soil concentrations, respectively.
 
The results from the test using aged soil are consistent with the results of the first test described above. All worms survived the 14-days exposure to soils amended with 10-1000 mg W/kg soil and all of them died at the 10,000 mg W/kg soil level. Tissue concentrations of 3.45 to 25.9 mg tungsten/kg dry weight were observed for tungsten soil concentrations ranging from 10 to 1000 mg/kg, respectively.
 
 No data on the behavior of tungsten dioxide in the environment are available. Concentration data for tungsten metal are appropriate for read-across for this endpoint as the soluble species released are expected to be similar for each of the compounds, and are thus expected to behave similarly in the environment.

Worms took up and accumulated tungsten in their tissue. Dry weight tissue concentrations were 1.52, 3.24, and 193.2 mg/kg tungsten for the 10, 100, and 10,000 mg W/kg soil concentrations, respectively, in the test with unaged soils. In the test with tungsten-aged soil, tissue concentrations of 3.45 to 25.9 mg tungsten/kg dry weight were observed for tungsten soil concentrations ranging from 10 to 1000 mg/kg, respectively.
Executive summary:

No terrestrial bioaccuumulation data of sufficient quality are available for tungsten dioxide (target substance). However, terrestrial bioccumulation data are available for tungsten metal (source substance), which will be used for reading across. Due to similar water solubility and lower toxicity for the target substance compared to the source substance, the resulting read across from the source substance to the target substance is appropriate. In addition, read across is appropriate because the classification and labelling is similar for the source substance than the target substance, the PBT/vPvB profile is the same, and the dose descriptors are, or are expected to be, lower for the source substance. For more details, refer to the read-across category approach included in the Category section of this IUCLID submission and/or as an Annex in the CSR.

Endpoint:
bioaccumulation: terrestrial
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
Well documented study, with accumulation results obtained during toxicity testing. No data on the behavior of tungsten dioxide in the environment are available. Concentration data for tungsten metal are appropriate for read-across for this endpoint as the soluble species released are expected to be similar for each of the compounds, and are thus expected to behave similarly in the environment. For more details refer to the attached description of the read across approach.
Justification for type of information:
REPORTING FORMAT FOR THE CATEGORY APPROACH
1. HYPOTHESIS FOR THE ANALOGUE APPROACH: The hypothesis is that properties are likely to be similar or follow a similar pattern because of the presence of a common metal ion, in this case tungstate.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES):
Source: Tungsten Metal
Target: Tungsten Dioxide
3. CATEGORY APPROACH JUSTIFICATION: See Annex 1 in CSR
4. DATA MATRIX: See Annex 1 in CSR
Reason / purpose:
reference to same study
Reason / purpose:
read-across: supporting information
Principles of method if other than guideline:
Accumulation of tungsten in plant tissues obtained during toxicity testing.
GLP compliance:
not specified
Radiolabelling:
no
Details on sampling:
-Leaves were harvested several times over the 9 month vegetation period

Vehicle:
no
Details on preparation and application of test substrate:
- Method of mixing into soil (if used): Manually mixed with powder in different proportions to achieve metal concentrations ranging from 0.0001% to 10% on a mass basis.
- Controls: Non-amended urban soil

Test organisms (species):
other: Ryegrass
Details on test organisms:
- Common name: Ryegrass
- Plant family: Poaceae
- Source of seed: Ward's Biology (Rochester, NY)
Total exposure / uptake duration:
ca. 36 wk
Test temperature:
20 deg. C or room temperature (not specified)

pH:
No data
TOC:
urban: 5.3%

Moisture:
35%
Details on test conditions:
TEST SYSTEM
- Test container (type, material, size): Plastic jars
- Amount of soil: 100-200 g (held constant within each experiment)
- No. of seeds per container: 5
- No. of replicates per treatment group: three
- No. of replicates per control: Not specified

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographic location: urban soil (Stevens Institute of Technology campus, Hoboken, NJ, USA)
- Pesticide use history at the collection site: Not specified
- Sampling depth (cm): 1-5 cm
- Pretreatment of soil: Homogenized, large particles and plant roots removed, sieved through a 1 mm sieve.
- Storage (condition, duration): Stored at 4 deg. C until use.

GROWTH CONDITIONS
- Photoperiod: 12/12 or natural light (held constant within each experiment)
- Light source: no data
- Light intensity and quality: no data
- Day/night temperatures: no data
- Watering regime and schedules: daily
- Water source/type: DI water
- Volume applied: 15 g/ day


EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Growth and tungsten concentration in plant tissue.

VEHICLE CONTROL PERFORMED: no

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 10x
Nominal and measured concentrations:
0.1-10000 mg W/kg soil

Kinetic parameters:
No data
Metabolites:
No data
Details on results:
-Mean concentrations of W in ryegrass leaves (mg/kg) after 9 months were 5.67, 9.13, 10.5, 42.2, 201.7, and 13,535 (only 2 months) corresponding to W concentrations in soil (mg/kg) of 0.1, 1.0, 10, 100, 1000, and 10,000; respectively.
-The W uptake for the highest W concentration in soil was 13500 mg/kg (standard deviation 6100 mg/kg). These plants died off after 2 months of
incubation.
-Most significant uptake of tungsten by plants occurs at concentrations greater than 1000 mg/kg.

Conclusions:
In a non-guideline study, the accumulation of tungsten in plant tissues was obtained during toxicity testing. Soil (non-amended urban soil) was manually mixed with powder in different proportions to achieve metal concentrations ranging from 0.0001% to 10% on a mass basis, corresponding to 0.1-10000 mg W/kg soil.

Ryegrass seeds were exposed to the substance for total exposure duration of 36 weeks and growth as well as tungsten concentration in plant tissue was determined. The leaves, harvested several times during the 9 month vegetation period, were dried, and tungsten concentrations were determined.

Mean concentrations of W in ryegrass leaves (mg/kg) were 5.67, 9.13, 10.5, 42.2, 201.7, and 13,535 corresponding to W concentrations in soil (mg/kg) of 0.1, 1.0, 10, 100, 1000, and 10,000; respectively. Ryegrass takes up significant amounts of tungsten from the soil over a 9 month period at high soil W concentrations.
Executive summary:

No terrestrial bioaccuumulation data of sufficient quality are available for tungsten dioxide (target substance). However, terrestrial bioccumulation data are available for tungsten metal (source substance), which will be used for reading across. Due to similar water solubility and lower toxicity for the target substance compared to the source substance, the resulting read across from the source substance to the target substance is appropriate. In addition, read across is appropriate because the classification and labelling is similar for the source substance than the target substance, the PBT/vPvB profile is the same, and the dose descriptors are, or are expected to be, lower for the source substance. For more details, refer to the read-across category approach included in the Category section of this IUCLID submission and/or as an Annex in the CSR

 

 

No data on the behavior of tungsten dioxide in the environment are available. Concentration data for tungsten metal are appropriate for read-across for this endpoint as the soluble species released are expected to be similar for each of the compounds, and are thus expected to behave similarly in the environment.

Endpoint:
bioaccumulation: terrestrial
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
Well documented, scientifically sound study that provided a sufficient amount of information on materials and methods to adequately evaluate results. No data on the behavior of tungsten dioxide in the environment are available. Concentration data for tungsten metal are appropriate for read-across for this endpoint as the soluble species released are expected to be similar for each of the compounds, and are thus expected to behave similarly in the environment. For more details refer to the attached description of the read across approach.
Justification for type of information:
REPORTING FORMAT FOR THE CATEGORY APPROACH
1. HYPOTHESIS FOR THE ANALOGUE APPROACH: The hypothesis is that properties are likely to be similar or follow a similar pattern because of the presence of a common metal ion, in this case tungstate.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES):
Source: Tungsten Metal
Target: Tungsten Dioxide
3. CATEGORY APPROACH JUSTIFICATION: See Annex 1 in CSR
4. DATA MATRIX: See Annex 1 in CSR
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study
Reason / purpose:
read-across: supporting information
Qualifier:
no guideline available
Principles of method if other than guideline:
The study examined the uptake and bioavailability of tungsten in sunflower leaves, stems, and roots.
GLP compliance:
not specified
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
no data
Radiolabelling:
no
Details on sampling:
no data
Vehicle:
not specified
Details on preparation and application of test substrate:
- Method of mixing into soil (if used): Grenada-Loring soil was spiked with 6500 mg/kg of metallic tungsten powder, tumble-mixed overnight, and then aged for approximately six months to oxidize the metallic tungsten.
- The spiked soil was diluted with clean field soil to generate six log-spaced doses ranging from 0 to 6500 mg W/kg soil and were amended with 0.2 L perlite/kg soil and hydrated to field capacity (0.295 L/kg soil).
Test organisms (species):
other: Helianthus annuus
Details on test organisms:
TEST ORGANISM
- Common name: Sunflower
Total exposure / uptake duration:
14 d
Test temperature:
24+/- 2.0 degree C
pH:
no data
TOC:
no data
Moisture:
no data
Details on test conditions:
TEST SYSTEM
- Test container (type, material, size): set-up in 3.8 cm x 14 cm Cone-Tainers tubes; a 6 cm x 6 cm square fiberglass mesh screen was placed into the bottom of the tube.
- Amount of soil: The tube was filled with soil to within 2 cm of the top (approximately 80 g).
- No. of organisms per container (treatment): four seeds per tube
- No. of replicates per treatment group: Five replicates per treatment
- No. of replicates per control: Not specified

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographic location: The silty loam Grenada-Loring field soil (Alfisol order) was collected from the Brown Loam Experiemental Station (Learned, MS).
- Sampling depth (cm): 12 cm

OTHER TEST CONDITIONS
- Photoperiod: 14:10 hour light:dark
- Plants were given 6 mL of water per day
Nominal and measured concentrations:
Grenada-Loring soil was spiked with 6500 mg/kg metallic tungsten powder.
Type:
BCF
Value:
0.05
Basis:
other: sunflower leaves
Remarks on result:
other: Tungsten bioaccumulation in leaves appeared to plateau at approximately 138 mg/kg W in the 3900 mg/kg soil.
Kinetic parameters:
n/a
Metabolites:
n/a
Details on results:
- Tungsten bioaccumulation was only analyzed in plants grown at ≤3900 mg/kg, despite additional time to grow, because insufficient biomass was produced due to tungsten’s effects on sunflower growth at higher concentrations. Sunflower leaves showed a significant dose-dependent increase in tungsten bioaccumulation at all soil tungsten concentrations. Tungsten bioaccumulation in leaves appeared to plateau at approximately 138 mg/kg W in the 3900 mg/kg soil. Sunflower roots showed a significant dose dependent increase in tungsten bioaccumulation at ≥1300 mg/kg. Tungsten bioaccumulation in roots did not plateau at the concentrations studied, and at 3900 mg/kg W soil, average tungsten concentrations in roots were 6455 mg/kg, over 46 times greater than leaf concentrations. When the data were expressed as biota–soil bioaccumulation factors (BSAF), sunflower leaves had significantly lower BSAF values (0.05) at ≥1300 mg/kg, whereas BSAF in sunflower roots, ranging from 1.6 to 2, did not differ from controls.
- Tungsten was identified in the plant tissues as either tungstate, polytungstate, or an unknown tungsten species. Each sunflower tissue displayed a differential pattern of tungsten species bioaccumulation at each tungsten soil concentration.
- In leaves, polytungstate and an unknown tungsten species increased in a dose-dependent manner, but tungstate peaked at 1,300 mg W/kg soil and declined at higher tungsten soil concentrations.
- In stems, all three tungsten species followed the same trend, with all three peaking in tissue concentrations at 2,600 mg W/kg soil, with tungstate and unknown tungsten species being the most abundant. At higher concentrations, all three species decreased in stem tissue.
- All three tungsten species had dramatically higher concentrations in sunflower roots than in leaves or stems; all three species increased in a dose-dependent manner, plateauing in the 2,600 mg W/kg soil. Tungstate was the most abundant species in sunflower roots, followed by unknown tungsten species and polytungstate.

Reported statistics:
Data were expressed as mean ± standard deviation (SD). Data were analyzed for normality and equal variance, using the Shapiro–Wilks test and the Levene’s test, respectively. Data that failed either test were transformed to normalized ranks (rankits) (Conover and Imam 1981). Comparisons with controls on either the raw data or rankits, as appropriate, were conducted with one-way analysis of variance (ANOVA), followed by Dunnett’s post hoc test (SAS, Cary, NC).
Conclusions:
A study was conducted to examine the uptake and bioavailability of tungsten in sunflower leaves, stems, and roots. Tungsten metal was used as test substance. This study was not conducted according to specific standard guidelines, however, the study was evaluated to be scientifically sound. Sufficient information on materials and methods are available to adequately evaluate the results.
 
In the experiment Grenada-Loring soil was spiked with up to 6500 mg/kg metallic tungsten powder on which Sunflower (Helianthus annuus) was grown for 14 days. After 14-d, however, there was not sufficient tissue to complete the analysis, so additional sunflowers were grown for a total of 28 days.
 
Under the conditions of this study, tungsten was bioaccumulated in both sunflower roots and leaves in a dose-dependent manner, with roots having a bioaccumulation factor of approximately two-fold from soil to plant tissue. Sunflowers showed differential bioaccumulation of tungsten species in leaves, stems and roots, based on tungsten soil concentrations.
 
Tungsten bioaccumulation was only analyzed in plants grown at ≤3900 mg/kg, despite additional time to grow, because insufficient biomass was produced due to tungsten’s effects on sunflower growth at higher concentrations. The BCF value of tungsten in Sunflower leaves was determined to be 0.05. Tungsten bioaccumulation in leaves appeared to plateau at approximately 138 mg/kg W in the 3900 mg/kg soil. No data on the behavior of tungsten dioxide in the environment are available. Concentration data for tungsten metal are appropriate for read-across for this endpoint as the soluble species released are expected to be similar for each of the compounds, and are thus expected to behave similarly in the environment. For more details refer to the attached description of the read across approach.

Under the conditions of this study, tungsten was bioaccumulated in both sunflower roots and leaves in a dose-dependent manner, with roots having a bioaccumulation factor of approximately two-fold from soil to plant tissue. Sunflowers showed differential bioaccumulation of tungsten species in leaves, stems and roots, based on tungsten soil concentrations.
Executive summary:

No terrestrial bioaccuumulation data of sufficient quality are available for tungsten dioxide (target substance). However, sterrestrial bioccumulation data are available for tungsten metal (source substance), which will be used for reading across. Due to similar water solubility and lower toxicity for the target substance compared to the source substance, the resulting read across from the source substance to the target substance is appropriate. In addition, read across is appropriate because the classification and labelling is similar for the source substance than the target substance, the PBT/vPvB profile is the same, and the dose descriptors are, or are expected to be, lower for the source substance. For more details, refer to the read-across category approach included in the Category section of this IUCLID submission and/or as an Annex in the CSR.

Endpoint:
bioaccumulation: terrestrial
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
weight of evidence
Reliability:
4 (not assignable)
Rationale for reliability incl. deficiencies:
documentation insufficient for assessment
Remarks:
Insufficient information provided on methods or results to accurately evaluate the study. Bioaccumulation was not the main objective of this study. No data on the behavior of tungsten dioxide in the environment are available. Concentration data for sodium tungstate are appropriate for read-across for this endpoint as the soluble species released are expected to be similar for each of the compounds, and are thus expected to behave similarly in the environment. For more details refer to the attached description of the read across approach.
Justification for type of information:
REPORTING FORMAT FOR THE CATEGORY APPROACH
1. HYPOTHESIS FOR THE ANALOGUE APPROACH: The hypothesis is that properties are likely to be similar or follow a similar pattern because of the presence of a common metal ion, in this case tungstate.
2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES):
Source: Sodium Tungstate
Target: Tungsten Dioxide
3. CATEGORY APPROACH JUSTIFICATION: See Annex 1 in CSR
4. DATA MATRIX: See Annex 1 in CSR
Reason / purpose:
read-across source
Qualifier:
no guideline followed
Principles of method if other than guideline:
Wet tissue weight tungsten concentrations were measured in earthworms following 28-day exposure to sodium tungstate.
GLP compliance:
not specified
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
N/A
Radiolabelling:
no
Details on sampling:
- Sampling intervals/frequency for test organisms: after 28 days
- Sampling intervals/frequency for test medium samples: after 28 days
- Sample storage conditions before analysis: earthworms frozen at -80 degrees C until analysis
- Details on sampling and analysis of test organisms and test media samples (e.g. sample preparation, analytical methods): Samples were digested according to U.S.EPA Method 3050B for metals analysis, and analyzed by modified Method 6010 (ICP) and 6020 (ICP-MS).
Vehicle:
no
Details on preparation and application of test substrate:
- Method of mixing into soil (if used): Aqueous solution, hand-mixed into test soil.
- Controls: Untreated soil.
Test organisms (species):
Eisenia fetida
Details on test organisms:
TEST ORGANISM
- Common name: Earthworm
- Source: Laboratory brood stock, original source Carolina, Burlington, NC
- Age at test initiation (mean and range, SD): Adult
-Weight at test initiation:0.3-0.6 g

ACCLIMATION
- Acclimation period: Soils were allowed to sit for one week after dosing before the addition of test organisms.
- Acclimation conditions (same as test or not): Yes
Total exposure / uptake duration:
28 d
Total depuration duration:
ca. 8 h
Test temperature:
21 ± 1 C
pH:
6.5-7.0
TOC:
Field soil-0.7%
Artificial soil-2.6%
Moisture:
85% of holding capacity at test initiation.
Details on test conditions:
TEST SYSTEM
- Test container (material, size): Clear glass pint jars
- Amount of soil or substrate: 250 g
- No. of organisms per container (treatment): 5
- No. of replicates per treatment group: 5
- No. of replicates per control / vehicle control: 5

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographical reference of sampling site (latitude, longitude): Brown Loam Experimental Station, Learned, MS. Grenada-Loring silty loam
- Vegetation cover: top 12 cm removed prior to sampling to remove vegetation.
- Depth of sampling: beginning at 12 cm, collected with a front-end loader.

Natural soil
- Soil texture
- % sand: 3
- % silt: 72
- % clay: 26
- Soil taxonomic classification: Grenada-Loring silty loam
- Soil classification system: N/A
- Composition (if artificial substrate): Natural soil
- pH water: N/A
- pH soil: 6.72
- Organic carbon (%): 0.7
- Moisture (%): 85% holding capacity
- Maximum water holding capacity (in % dry weigth): 0.295 ml/g
- Stability and homogeneity of test material in the medium: N/A

OTHER TEST CONDITIONS
- Adjustment of pH: No
- Photoperiod: continuous
- Light intensity: N/A

VEHICLE CONTROL PERFORMED: no


Nominal and measured concentrations:
Nominal -Control, 704, 909, 1174, 1517, 1959, 2530, 3267, 4220, 5450, and 7039 mg/L
Kinetic parameters:
N/A
Metabolites:
N/A
Details on results:
See below
Reported statistics:
N/A

Bioaccumulation results:

-Body burden data is from adult worms exposure to sodium tungstate for 28 days.

-Wet weight tissue was analyzed for tungsten in the Control, 704, 1517, 3267, and 5450 mg/kg nominal concentrations only.

- Corresponding tungsten values were 2.9 ± 4.3 (<2 mg W/kg soil), 10.9 ± 3.7(923 ± 23 mg W/kg soil), 18.0 ± 7.8(1783 ± 210 mg W/kg soil), 36.2 ± 19.2 ( 3250 ± 289 mg W/kg soil), and 41.3 ± 28.3(4643 ± 265 in soil) mg/kg, respectively.

Conclusions:
A 28-d study on the effects of sodium tungstate to earthworm (Eisenia fetida) reproduction was conducted. In the course of this study, wet tissue weight tungsten concentrations were measured in earthworms following the 28-day exposure to sodium tungstate.
 
Applied sodium tungstate nominal concentrations in aqueous solution were 0 (control), 704, 909, 1174, 1517, 1959, 2530, 3267, 4220, 5450, and 7039 mg/L. These solutions were then hand-mixed into the test soil (Grenada-Loring silty loam, pH 6.5 – 7.0, moisture at 85% of holding capacity at test initiation, 0.7 % organic carbon). Wet weight tissue analysis and measurements of tungsten content were conducted for Control, 704, 1517, 3267, and 5450 mg/kg nominal concentrations only.

The 28 day exposure of the earthworm, Eisenia fetida to sodium tungstate (0-5450 mg W/kg nominal concentration) in soil, resulted in wet weight tissue tungsten concentrations of 2.9-41.3 mg W/kg wet tissue. 28 day exposure of the earthworm, Eisenia fetida to sodium tungstate (0- 5450 mg W/kg nominal concentration) in soil, resulted in wet weight tissue tungsten concentrations of 2.9-41.3 mg W/kg wet tissue.
Executive summary:

No terrestrial bioaccuumulation data of sufficient quality are available for tungsten dioxide (target substance). However, terrestrial bioccumulation data are available for sodium tungstate (source substance), which will be used for reading across. Due to lower water solubility and lower toxicity for the target substance compared to the source substance, the resulting read across from the source substance to the target substance is appropriate as a conservative estimate of potential toxicity for this endpoint. In addition, read across is appropriate because the classification and labelling is more protective for the source substance than the target substance, the PBT/vPvB profile is the same, and the dose descriptors are, or are expected to be, lower for the source substance. For more details, refer to the read-across category approach included in the Category section of this IUCLID submission and/or as an Annex in the CSR.

Description of key information

No data on the behavior of tungsten dioxide in the environment are available. Bioconcentration data for tungsten metal and sodium tungstate are presented in this section. The soluble species released are expected to be similar for each of the compounds, and are thus expected to behave similarly in the environment. However, the amount of soluble species resulting from tungsten metal and sodium tungstate is different, with sodium tungstate being much more soluble. Therefore, data for sodium tungstate and tungsten metal are expected to adequately capture the range of bioavailability of tungsten trioxide in the environment. For more details, refer to the attached read-across document (see Annex 1).

Relatively low bioaccumulation of tungsten is observed in sunflower leaves at soil concentrations of 3900 mg W/kg soil, with calculated concentration factors plateauing at approximately 0.05 (Johnson et al., 2009). Tungsten concentrations factors calculated for ryegrass were higher and ranged from 56.1-0.202 (Strigul et al., 2005). However, it should be noted that, in this study, background levels of tungsten in the collected soils used for testing were not determined prior to testing. Tungsten concentrations measured in earthworm tissue ranged from 1.52-193.2 mg/kg wet weight in soils with tungsten concentrations of 10-10000 mg/kg soil, respectively (non-aged soil) (Strigul et al., 2005). Additionally, tungsten concentrations of 10 and 10000 mg/kg soil yielded earthworm tissue concentrations of 3.45 and 25.9 mg/kg wet weight, respectively (Strigul et al., 2005). Using these paired concentration data, the BCFs for earthworms in non-aged soils ranged 0.152-0.019 and BCFs for aged soils ranged from 0.345 - 0.00259. Tungsten concentrations measured in earthworm tissue in another study with soil spiked with sodium tungstate (Inouye et al., 2006) ranged from 2.9 - 41.3 mg/kg wet weight in soils with tungsten concentrations of <2 – 4643 mg/kg soil, respectively. These data would indicate concentration factors ranging from 1.45 – 0.008, respectively, with only the lowest tungsten concentration resulting in a BCF of > 1. Therefore, tungsten compounds such as tungsten dioxide are not expected to bioaccumulate in terrestrial organisms.

Key value for chemical safety assessment

BCF (terrestrial species):
0.345 dimensionless

Additional information