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Endpoint:
toxicity to terrestrial plants: long-term
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
2008-10-31 to 2008-04-14
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
Well documented, scientifically sound study that follows GLP and OECD Guideline 208. The reliability of this study for the substance tested is a K1, but in application of read-across to a different substance ECHA’s guidance specifies that the score can be a maximum of K2. Due to similar or lower transformation/dissolution results for tungsten trioxide (the target substance) than sodium tungstate (the source substance), the resulting toxicity potential would also be expected to be similar or lower, so read-across is appropriate. In addition, read-across is justified because the classification and labelling is the same or less severe for the target substance PBT/vPvB profile is the same. Finally, the dose descriptors are, or are expected to be, sufficiently similar or higher for the target substance, and read-across to the source chemical is adequately protective. 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 trioxide
3. CATEGORY APPROACH JUSTIFICATION: See Annex 1 in CSR
4. DATA MATRIX: See Annex 1 in CSR
Reason / purpose:
read-across: supporting information
Reason / purpose:
reference to same study
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
OECD Guideline 208 (Terrestrial Plants Test: Seedling Emergence and Seedling Growth Test)
Deviations:
yes
Remarks:
homogeneity and stability of the test substance within the soil matrix was not confirmed- analytical samples were not taken for this study.
GLP compliance:
yes
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
no data
Analytical monitoring:
no
Vehicle:
yes
Details on preparation and application of test substrate:
To prepare the soil for the seedling emergence test, 18.479 kilograms (18.0 kg dry soil equivalent) of the soil matrix was weighed into a steel pan for the control and each treatment level. A 27.2729 mg a.i./mL primary standard solution was prepared by adding 27.3002 g (27.2729 g corrected for purity) of the test substance to a 1,000-mL volumetric flask and bringing the flask to volume with deionized water. A 3-fold dilution series of the primary standard was used to prepare lower treatment level dosing solutions, by transferring 330-mL volumes of the primary standard and subsequent dilutions to a 1-L mixing cylinder and bringing the cylinder to a volume of 990 mL with deionized water, resulting in final concentrations of 0.0374, 0.1122, 0.3367, 1.0101, 3.0303, and 9.0910 mg a.i./mL. The control solution consisted only of deionized water. The soil was dosed by adding 660 mL volumes of control or test substance solution to 18.0 kg (dry) soil and mixing with a rotary mixer for 5-10 minutes. The control soil batch was prepared first, followed by the highest treatment level (1,000 mg/kg) and then proceeding downward in test material concentration. The rotary mixer was cleaned out between treatments by inversion, continued rotation, and rapid oscillation to dislodge adhering soil. The nominal soil concentrations after preparation were 0 (control), 1.37, 4.11, 12.3, 37.0, 111, 333, and 1,000 mg/kg dry soil.
Species:
Avena sativa
Plant group:
Monocotyledonae (monocots)
Details on test organisms:
- Common name: oat
- Plant family: Gramineae
- Source of seed: Ohio Seed Foundation Croton, OH
- Germination Rate (%): 99.5 (provided by supplier)
Test type:
seedling emergence toxicity test
Study type:
laboratory study
Substrate type:
natural soil
Limit test:
no
Total exposure duration:
21 d
Test temperature:
11.4 to 38.3 degree C
pH:
7.8
Moisture:
10.1 (at 1/3 Bar)
Details on test conditions:
TEST SYSTEM
- Testing facility: The test was conducted in a greenhouse at ABC Laboratories, Inc. in Columbia, Missouri
- Test container (type, material, size): The test pots for oat were square plastic pots measuring 10 x 10 cm in rim opening area, and 12 cm in depth. Each pot was filled with the control or dosed test soil and labeled with the species code, treatment code, and replicate number.
- Amount of soil: depth of approximately 20 mm
- No. of seeds per container: 5
- No. of replicates per treatment group: 4
- No. of replicates per control: not specified
- No. of replicates per vehicle control: not specified

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographic location: Troth Farms, Hartsburg, Missouri.
- Pesticide use history at the collection site: Not expected to have received direct application of pesticides or herbicides prior to the collection of the soil.
- Sampling depth (cm): collected at a depth of approximately 6-10"
- Soil texture (if natural soil): The test soil used in the test (Lot no. GM82107MO) was characterized as a sandy loam soil, based upon the USDA textural classification. The soil was a mixture of two topsoils (G82107MOSAND and G82107MOSILT).
- % sand: 66
- % silt: 26
- % clay: 8
- Organic carbon (%): 0.4
- Organic Matter (%): 0.6
- Bulk density: 1.35 g/cc disturbed
- Cation Exchange Capacity: 10.2 meq/100 g

NUTRIENT MEDIUM (if used)
- Description: oat was fertilized twice, with commercial fertilizer (i.e., ½ tablespoon Peter’s 20-20-20 to one gallon of water) during this test.

GROWTH CONDITIONS
- Photoperiod: 16-hours light/8-hours dark
- Light source: natural sunlight and grow lights
- Light intensity and quality: 33.68 to 68.47 k lux (measured using a Li-Cor Model LI-198 light meter equipped with a quantum sensor)
- Relative humidity (%): 7 to 75%
- Watering regime and schedules:
- Water source/type: All watering was done with ABC well water
- Method of application: After the pots were filled with the control and treated soils, the soil was misted to a point near saturation and left to settle in the pots overnight. The following day seeds were planted and the pots were watered from the top. The pots were also watered from the top the first day after planting. From that point forward the plants were watered from the bottom using sub-irrigation trays.


EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Observations of seedling emergence were first performed on test day 6 and then on a weekly basis for all species. A seedling was considered emerged upon complete emergence of the cotyledons or coleoptile from the soil. The in-life phase was terminated 21 days after introduction of the test substance and 20 days after planting of seeds which corresponded to 14 days of exposure after 50% of the control seedlings had emerged. Shoot heights were measured from the base of the stem to the tip of the longest leaf for all of the species tested. Shoot heights were recorded to the nearest millimeter. After the length measurements, the shoot portions were harvested. Shoots were composited by replicate, dried in a drying oven, and replicate dry weights were recorded.


- Phytotoxicity rating system (if used): phytotoxicity ratings (i.e., visual injury assessments) were first performed on test day 6 and then on a weekly basis for all species. Visual injury assessments were made on a scale of 0 to 100 with 0 indicating no injury and 100 indicating maximum effect (100% non-emergence or mortality). At test termination, the numbers of live and dead plants, if observed, were recorded along with the visual assessments. If there was any visible normal coloration of the emergent seedling, that plant was reported as alive.
Nominal and measured concentrations:
Nominal soil concentrations of 0 (control), 1.37, 4.11, 12.3, 37.0, 111, 333, and 1,000 mg/kg dry soil.
Reference substance (positive control):
no
Species:
Avena sativa
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: % Emergence, Shoot Height, and Individual Shoot Weight
Species:
Avena sativa
Duration:
21 d
Dose descriptor:
EC25
Effect conc.:
> 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: % Emergence, Shoot Height, and Individual Shoot Weight
Species:
Avena sativa
Duration:
21 d
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: % Emergence, Shoot Height, and Individual Shoot Weight
Details on results:
SEEDLING EMERGENCE
- Percent seedling emergence: values ranged from 90 to 100% in all treated soils
- Percent survival: Two oat plants died in the control, but this test still met the minimum test acceptablility criteria for control post-emergent survival of 90%.
- Plant height: The percent inhibition in the shoot heights for the treated oat seedlings in comparison to the control seedlings ranged from -1% to 15% for all treatment levels. Oat showed a significant difference from the control at the 4.11 mg/kg level for shoot height, but the overall data manifested no dose dependent response. Since none of the 5 higher treatment levels tested, up to 1,000 mg/kg, showed a significant difference compared to the control, this lower treatment level significance was regarded as an anomaly, and the NOEC for oat was interpreted as 1,000 mg/kg dry soil. The EC25 and EC50 values for oat were >1,000 mg/kg dry soil, the highest concentration tested.
- Dry weight: The percent inhibition in the replicate dry weights for the treated oat seedlings in comparison to the control seedlings ranged from -15% to 11% for all treatment levels. The NOEC for oat shoot dry weight was 1,000 mg/kg dry soil. The EC25 and EC50 values for oat were >1,000 mg/kg dry soil, the highest concentration tested.
- Other effects: All visual injury ratings recorded for oat were less than 10 for the duration of the test.


Results with reference substance (positive control):
no data
Reported statistics and error estimates:
The means and standard deviations were calculated for the percent emergence, survival, shoot height, and replicate dry weight data. Statistical analysis of the concentration versus effect data was performed using SAS. Emergence and survival data, as well as shoot height and dry weight data, was analyzed using analysis of variance (ANOVA) and a one-way Dunnett’s comparison (p < 0.05) of means less than the control to determine no observable effect concentrations (NOEC). Prior to the ANOVA and Dunnett’s tests, a Shapiro-Wilk’s test and a Levene’s test were conducted to test for normality and homogeneity of variance, respectively. If either of these tests were negative, subsequent analysis was done using nonparametric analysis on ranks of data. In most cases the no observable effect concentration (NOEC) was the highest concentration tested that was not statistically different from the control, the exceptions are discussed in the test results sections.

Since there were no significant effects compared to the control observed for any treatment level for emergence or survival, and no greater than an 11% reduction in seedling emergence or survival as compared to the controls was observed, EC25 and EC50 estimates for emergence and survival data were not calculated. The twenty-five percent (EC25), and fifty percent (EC50) estimates for shoot height and dry weight were calculated by using a four-parameter logistic (sigmoid-shaped) model with two parameters fixed (100 and 0% inhibition) fit to the data with percent inhibition as the dependent variable and log concentration as the independent variable. If there was no convergence of the effects versus log concentration data, the EC25 and EC50 values were estimated as greater than the highest soil concentration tested.

 

Conclusions:
The NOEC, EC25, and EC50 values for oat plant emergence, shoot height, and shoot weight based on nominal concentrations (mg/kg dry soil) of sodium tungstate were 1,000 (NOEC), >1,000 (EC25), and >1,000 (EC50), for the three endpoints evaluated.
Executive summary:

No toxicity to terrestrial plants data of sufficient quality are available for tungsten trioxide (target substance). However, toxicity to terrestrial plants 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.

Endpoint:
toxicity to terrestrial plants: long-term
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
2008-10-31 to 2009-04-14
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
Well documented, scientifically sound study that follows GLP and OECD Guideline 208. The reliability of this study for the substance tested is a K1, but in application of read-across to a different substance ECHA’s guidance specifies that the score can be a maximum of K2. Due to similar or lower transformation/dissolution results for tungsten trioxide (the target substance) than sodium tungstate (the source substance), the resulting toxicity potential would also be expected to be similar or lower, so read-across is appropriate. In addition, read-across is justified because the classification and labelling is the same or less severe for the target substance PBT/vPvB profile is the same. Finally, the dose descriptors are, or are expected to be, sufficiently similar or higher for the target substance, and read-across to the source chemical is adequately protective. 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 trioxide
3. CATEGORY APPROACH JUSTIFICATION: See Annex 1 in CSR
4. DATA MATRIX: See Annex 1 in CSR
Reason / purpose:
read-across: supporting information
Reason / purpose:
reference to same study
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
OECD Guideline 208 (Terrestrial Plants Test: Seedling Emergence and Seedling Growth Test)
Deviations:
yes
Remarks:
homogeneity and stability of the test substance within the soil matrix was not confirmed- analytical samples were not taken for this study.
GLP compliance:
yes
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
no data
Analytical monitoring:
no
Vehicle:
yes
Details on preparation and application of test substrate:
To prepare the soil for the seedling emergence test, 18.479 kilograms (18.0 kg dry soil equivalent) of the soil matrix was weighed into a steel pan for the control and each treatment level. A 27.2729 mg a.i./mL primary standard solution was prepared by adding 27.3002 g (27.2729 g corrected for purity) of the test substance to a 1,000-mL volumetric flask and bringing the flask to volume with deionized water. A 3-fold dilution series of the primary standard was used to prepare lower treatment level dosing solutions, by transferring 330-mL volumes of the primary standard and subsequent dilutions to a 1-L mixing cylinder and bringing the cylinder to a volume of 990 mL with deionized water, resulting in final concentrations of 0.0374, 0.1122, 0.3367, 1.0101, 3.0303, and 9.0910 mg a.i./mL. The control solution consisted only of deionized water. The soil was dosed by adding 660 mL volumes of control or test substance solution to 18.0 kg (dry) soil and mixing with a rotary mixer for 5-10 minutes. The control soil batch was prepared first, followed by the highest treatment level (1,000 mg/kg) and then proceeding downward in test material concentration. The rotary mixer was cleaned out between treatments by inversion, continued rotation, and rapid oscillation to dislodge adhering soil. The nominal soil concentrations after preparation were 0 (control), 1.37, 4.11, 12.3, 37.0, 111, 333, and 1,000 mg/kg dry soil.
Species:
Lactuca sativa
Plant group:
Dicotyledonae (dicots)
Details on test organisms:
- Common name: lettuce
- Plant family: Compositae
- Source of seed: Meyer Seed Company, Baltimore MD
- Germination Rate (%): 85 (provided by supplier)
Test type:
seedling emergence toxicity test
Study type:
laboratory study
Substrate type:
natural soil
Limit test:
no
Total exposure duration:
21 d
Test temperature:
11.4 to 38.3 degree C
pH:
7.8
Moisture:
10.1 (at 1/3 Bar)
Details on test conditions:
TEST SYSTEM
- Testing facility: The test was conducted in a greenhouse at ABC Laboratories, Inc. in Columbia, Missouri
- Test container (type, material, size): The test pots for lettuce were round plastic pots measuring 16.5 cm diameter x 11.5 cm in depth. Each pot was filled with the control or dosed test soil and labeled with the species code, treatment code, and replicate number.
- Amount of soil: depth of approximately 6 mm
- No. of seeds per container: 10
- No. of replicates per treatment group: 4
- No. of replicates per control: not specified
- No. of replicates per vehicle control: not specified

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographic location: Troth Farms, Hartsburg, Missouri.
- Pesticide use history at the collection site: Not expected to have received direct application of pesticides or herbicides prior to the collection of the soil.
- Sampling depth (cm): collected at a depth of approximately 6-10"
- Soil texture (if natural soil): The test soil used in the test (Lot no. GM82107MO) was characterized as a sandy loam soil, based upon the USDA textural classification. The soil was a mixture of two topsoils (G82107MOSAND and G82107MOSILT).
- % sand: 66
- % silt: 26
- % clay: 8
- Organic carbon (%): 0.4
- Organic Matter (%): 0.6
- Bulk density: 1.35 g/cc disturbed
- Cation Exchange Capacity: 10.2 meq/100 g

NUTRIENT MEDIUM (if used)
- Description: lettuce was fertilized once, with commercial fertilizer (i.e., ½ tablespoon Peter’s 20-20-20 to one gallon of water) during this test.

GROWTH CONDITIONS
- Photoperiod: 16-hours light/8-hours dark
- Light source: natural sunlight and grow lights
- Light intensity and quality: 33.68 to 68.47 k lux (measured using a Li-Cor Model LI-198 light meter equipped with a quantum sensor)
- Relative humidity (%): 7 to 75%
- Watering regime and schedules:
- Water source/type: All watering was done with ABC well water
- Method of application: After the pots were filled with the control and treated soils, the soil was misted to a point near saturation and left to settle in the pots overnight. The following day seeds were planted and the pots were watered from the top. The pots were also watered from the top the first day after planting. From that point forward the plants were watered from the bottom using sub-irrigation trays.


EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Observations of seedling emergence were first performed on test day 6 and then on a weekly basis for all species. A seedling was considered emerged upon complete emergence of the cotyledons or coleoptile from the soil. The in-life phase was terminated 21 days after introduction of the test substance and 20 days after planting of seeds which corresponded to 14 days of exposure after 50% of the control seedlings had emerged. Shoot heights were measured from the base of the stem to the tip of the longest leaf for all of the species tested. Shoot heights were recorded to the nearest millimeter. After the length measurements, the shoot portions were harvested. Shoots were composited by replicate, dried in a drying oven, and replicate dry weights were recorded.


- Phytotoxicity rating system (if used): phytotoxicity ratings (i.e., visual injury assessments) were first performed on test day 6 and then on a weekly basis for all species. Visual injury assessments were made on a scale of 0 to 100 with 0 indicating no injury and 100 indicating maximum effect (100% non-emergence or mortality). At test termination, the numbers of live and dead plants, if observed, were recorded along with the visual assessments. If there was any visible normal coloration of the emergent seedling, that plant was reported as alive.
Nominal and measured concentrations:
Nominal soil concentrations of 0 (control), 1.37, 4.11, 12.3, 37.0, 111, 333, and 1,000 mg/kg dry soil.
Reference substance (positive control):
no
Species:
Lactuca sativa
Duration:
21 d
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: % Emergence and shoot height
Species:
Lactuca sativa
Duration:
21 d
Dose descriptor:
EC50
Effect conc.:
534 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Individual Shoot Weight
Species:
Lactuca sativa
Duration:
21 d
Dose descriptor:
EC25
Effect conc.:
> 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: % Emergence
Species:
Lactuca sativa
Duration:
21 d
Dose descriptor:
EC25
Effect conc.:
831 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Shoot Height
Species:
Lactuca sativa
Duration:
21 d
Dose descriptor:
EC25
Effect conc.:
93.9 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Individual Shoot Weight
Species:
Lactuca sativa
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
37 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: % Emergence, Shoot Height and Weight
Details on results:
SEEDLING EMERGENCE
- Percent seedling emergence: The percent emergence for lettuce in the control was 73% and ranged from 65 to 88% in all treated soils.
- Percent survival: Lettuce met the 90% post-emergent survival acceptability criteria for the control seedlings. One lettuce plant died in the 4.11 mg/kg dry soil treatment, but this did not result in a statistically significant reduction in survival.
- Plant height: The percent inhibition in the shoot heights for the treated lettuce seedlings in comparison to the control seedlings ranged from 1% to 44% for all treatment levels. Lettuce shoot height showed significant treatment effects at 111 and 333 mg/kg, but lacked a statistically significant response at 1,000 mg/kg. Since the prominent effects at 111 and 333 mg/kg seemed to follow a dose-response in conjunction with the lower levels, and since significance was observed for lettuce dry weight at all three treatment levels (111, 333, and 1,000 mg/kg), the lack of significance for shoot height at 1,000 mg/kg was interpreted as an anomaly. The NOEC for lettuce shoot height was interpreted as the 37.0 mg/kg dry soil treatment. The EC25 value for lettuce shoot height was 831 mg/kg dry soil (95% confidence limits of 0 and 2,690 mg/kg dry soil), and the EC50 value was >1,000 mg/kg dry soil, the highest concentration tested.
- Dry weight: The percent inhibition in the individual dry weights for the treated lettuce seedlings in comparison to the control seedlings ranged from -12% to 64% for all treatment levels. The NOEC for lettuce shoot dry weights was 37.0 mg/kg dry soil. The EC25 and EC50 values for lettuce were 93.9 mg/kg dry soil (95% confidence limits of 0 and 195 mg/kg dry soil) and 534 mg/kg dry soil (95% confidence limits of 14.5 and 1,050 mg/kg dry soil) respectively.
- Other effects: Lettuce displayed mean visual injury ratings of 10, 28, and 10 for the 111, 333, and 1,000 mg/kg levels, and ratings <10 for all lower levels. Treatment level mean visual injuries of 10 or greater observed on the final day of the exposure were manifested as stunting and chlorosis for lettuce.



Results with reference substance (positive control):
no data
Reported statistics and error estimates:
The means and standard deviations were calculated for the percent emergence, survival, shoot height, and replicate dry weight data. Due to the variation in the number of lettuce seedlings, individual dry weights were calculated by dividing the replicate dry weight by the number of surviving plants. Statistical analysis of the concentration versus effect data was performed using SAS. Emergence and survival data, as well as shoot height and dry weight data, was analyzed using analysis of variance (ANOVA) and a one-way Dunnett’s comparison (p < 0.05) of means less than the control to determine no observable effect concentrations (NOEC). Prior to the ANOVA and Dunnett’s tests, a Shapiro-Wilk’s test and a Levene’s test were conducted to test for normality and homogeneity of variance, respectively. If either of these tests were negative, subsequent analysis was done using nonparametric analysis on ranks of data. In most cases the no observable effect concentration (NOEC) was the highest concentration tested that was not statistically different from the control, the exceptions are discussed in the test results sections.

Since there were no significant effects compared to the control observed for any treatment level for emergence or survival, and no greater than an 11% reduction in seedling emergence or survival as compared to the controls was observed, EC25 and EC50 estimates for emergence and survival data were not calculated. The twenty-five percent (EC25), and fifty percent (EC50) estimates for shoot height and dry weight were calculated by using a four-parameter logistic (sigmoid-shaped) model with two parameters fixed (100 and 0% inhibition) fit to the data with percent inhibition as the dependent variable and log concentration as the independent variable. If there was no convergence of the effects versus log concentration data, the EC25 and EC50 values were estimated as greater than the highest soil concentration tested.

 

Conclusions:
The NOEC values based on nominal concentrations (mg/kg dry soil) for the effects of sodium tungstate on lettuce for plant emergence, shoot height and individual shoot weight were >1,000, 37.0, and 37.0 mg/kg, respectively. The EC25 values based on nominal concentrations (mg/kg dry soil) for the effects of sodium tungstate on lettuce for plant emergence, shoot height and individual shoot weight were >1,000, 831, and 93.9 mg/kg, respectively. The EC50 rates based on nominal concentrations (mg/kg dry soil) for the effects of sodium tungstate on lettuce for plant emergence, shoot height and individual shoot weight were >1,000, >1,000 and 534 mg/kg, respectively.
Executive summary:

No toxicity to terrestrial plants data of sufficient quality are available for tungsten trioxide (target substance). However, toxicity to terrestrial plants 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

Endpoint:
toxicity to terrestrial plants: long-term
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
2008-10-31 to 2009-04-14
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
Well documented, scientifically sound study that follows GLP and OECD Guideline 208. The reliability of this study for the substance tested is a K1, but in application of read-across to a different substance ECHA’s guidance specifies that the score can be a maximum of K2. Due to similar or lower transformation/dissolution results for tungsten trioxide (the target substance) than sodium tungstate (the source substance), the resulting toxicity potential would also be expected to be similar or lower, so read-across is appropriate. In addition, read-across is justified because the classification and labelling is the same or less severe for the target substance PBT/vPvB profile is the same. Finally, the dose descriptors are, or are expected to be, sufficiently similar or higher for the target substance, and read-across to the source chemical is adequately protective. 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 trioxide
3. CATEGORY APPROACH JUSTIFICATION: See Annex 1 in CSR
4. DATA MATRIX: See Annex 1 in CSR
Reason / purpose:
read-across: supporting information
Reason / purpose:
reference to same study
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
OECD Guideline 208 (Terrestrial Plants Test: Seedling Emergence and Seedling Growth Test)
Deviations:
yes
Remarks:
homogeneity and stability of the test substance within the soil matrix was not confirmed- analytical samples were not taken for this study.
GLP compliance:
yes
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
no data
Analytical monitoring:
no
Vehicle:
yes
Details on preparation and application of test substrate:
To prepare the soil for the seedling emergence test, 18.479 kilograms (18.0 kg dry soil equivalent) of the soil matrix was weighed into a steel pan for the control and each treatment level. A 27.2729 mg a.i./mL primary standard solution was prepared by adding 27.3002 g (27.2729 g corrected for purity) of the test substance to a 1,000-mL volumetric flask and bringing the flask to volume with deionized water. A 3-fold dilution series of the primary standard was used to prepare lower treatment level dosing solutions, by transferring 330-mL volumes of the primary standard and subsequent dilutions to a 1-L mixing cylinder and bringing the cylinder to a volume of 990 mL with deionized water, resulting in final concentrations of 0.0374, 0.1122, 0.3367, 1.0101, 3.0303, and 9.0910 mg a.i./mL. The control solution consisted only of deionized water. The soil was dosed by adding 660 mL volumes of control or test substance solution to 18.0 kg (dry) soil and mixing with a rotary mixer for 5-10 minutes. The control soil batch was prepared first, followed by the highest treatment level (1,000 mg/kg) and then proceeding downward in test material concentration. The rotary mixer was cleaned out between treatments by inversion, continued rotation, and rapid oscillation to dislodge adhering soil. The nominal soil concentrations after preparation were 0 (control), 1.37, 4.11, 12.3, 37.0, 111, 333, and 1,000 mg/kg dry soil.
Species:
Raphanus sativus
Plant group:
Dicotyledonae (dicots)
Details on test organisms:
- Common name: radish
- Plant family: Cruciferae
- Source of seed: Meyer Seed Company, Baltimore, MD
- Germination Rate (%): 85 (provided by supplier)
Test type:
seedling emergence toxicity test
Study type:
laboratory study
Substrate type:
natural soil
Limit test:
no
Total exposure duration:
21 d
Test temperature:
11.4 to 38.3 degree C
pH:
7.8
Moisture:
10.1 (at 1/3 Bar)
Details on test conditions:
TEST SYSTEM
- Testing facility: The test was conducted in a greenhouse at ABC Laboratories, Inc. in Columbia, Missouri
- Test container (type, material, size): The test pots for radish were round plastic pots measuring 16.5 cm in diameter, and 11.5 cm in depth. Each pot was filled with the control or dosed test soil and labeled with the species code, treatment code, and replicate number.
- Amount of soil: depth of approximately 12 mm
- No. of seeds per container: 5
- No. of replicates per treatment group: 4
- No. of replicates per control: not specified
- No. of replicates per vehicle control: not specified

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Geographic location: Troth Farms, Hartsburg, Missouri.
- Pesticide use history at the collection site: Not expected to have received direct application of pesticides or herbicides prior to the collection of the soil.
- Sampling depth (cm): collected at a depth of approximately 6-10"
- Soil texture (if natural soil): The test soil used in the test (Lot no. GM82107MO) was characterized as a sandy loam soil, based upon the USDA textural classification. The soil was a mixture of two topsoils (G82107MOSAND and G82107MOSILT).
- % sand: 66
- % silt: 26
- % clay: 8
- Organic carbon (%): 0.4
- Organic Matter (%): 0.6
- Bulk density: 1.35 g/cc disturbed
- Cation Exchange Capacity: 10.2 meq/100 g

NUTRIENT MEDIUM (if used)
- Description: radish were fertilized twice, with commercial fertilizer (i.e., ½ tablespoon Peter’s 20-20-20 to one gallon of water) during this test.

GROWTH CONDITIONS
- Photoperiod: 16-hours light/8-hours dark
- Light source: natural sunlight and grow lights
- Light intensity and quality: 33.68 to 68.47 k lux (measured using a Li-Cor Model LI-198 light meter equipped with a quantum sensor)
- Relative humidity (%): 7 to 75%
- Watering regime and schedules:
- Water source/type: All watering was done with ABC well water
- Method of application: After the pots were filled with the control and treated soils, the soil was misted to a point near saturation and left to settle in the pots overnight. The following day seeds were planted and the pots were watered from the top. The pots were also watered from the top the first day after planting. From that point forward the plants were watered from the bottom using sub-irrigation trays.


EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Observations of seedling emergence were first performed on test day 6 and then on a weekly basis for all species. A seedling was considered emerged upon complete emergence of the cotyledons or coleoptile from the soil. The in-life phase was terminated 21 days after introduction of the test substance and 20 days after planting of seeds which corresponded to 14 days of exposure after 50% of the control seedlings had emerged. Shoot heights were measured from the base of the stem to the tip of the longest leaf for all of the species tested. Shoot heights were recorded to the nearest millimeter. After the length measurements, the shoot portions were harvested. Shoots were composited by replicate, dried in a drying oven, and replicate dry weights were recorded.


- Phytotoxicity rating system (if used): phytotoxicity ratings (i.e., visual injury assessments) were first performed on test day 6 and then on a weekly basis for all species. Visual injury assessments were made on a scale of 0 to 100 with 0 indicating no injury and 100 indicating maximum effect (100% non-emergence or mortality). At test termination, the numbers of live and dead plants, if observed, were recorded along with the visual assessments. If there was any visible normal coloration of the emergent seedling, that plant was reported as alive.
Nominal and measured concentrations:
Nominal soil concentrations of 0 (control), 1.37, 4.11, 12.3, 37.0, 111, 333, and 1,000 mg/kg dry soil.
Reference substance (positive control):
no
Species:
Raphanus sativus
Duration:
21 d
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: % Emergence, shoot height and weight
Species:
Raphanus sativus
Duration:
21 d
Dose descriptor:
EC25
Effect conc.:
> 1 000 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: % Emergence
Species:
Raphanus sativus
Duration:
21 d
Dose descriptor:
EC25
Effect conc.:
787 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Shoot Height
Species:
Raphanus sativus
Duration:
21 d
Dose descriptor:
EC25
Effect conc.:
259 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Dry Shoot Weight
Species:
Raphanus sativus
Duration:
21 d
Dose descriptor:
NOEC
Effect conc.:
111 mg/kg soil dw
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Shoot Height and weight
Details on results:
SEEDLING EMERGENCE
- Percent seedling emergence: values ranged from 90 to 100% in all treated soils
- Percent survival: There was 100% survival in the radish control and treatments. Radish met the 90% post-emergent survival acceptability criteria for the control seedlings.
- Plant height: The percent inhibition in the shoot heights for the treated radish seedlings in comparison to the control seedlings ranged from -7% to 24% for all treatment levels. The NOEC for radish shoot height was 111 mg/kg dry soil. The radish shoot height EC25 value was 787 mg/kg dry soil (95% confidence limits of 0 and 1,620 mg/kg dry soil), and the EC50 value was >1,000 mg/kg dry soil.
- Dry weight: The percent inhibition in the replicate dry weights for the treated radish seedlings in comparison to the control seedlings ranged from -28% to 41% for all treatment levels. The NOEC for radish shoot dry weight was 111 mg/kg dry soil. The EC25 and EC50 values for radish were 259 mg/kg dry soil (95% confidence limits of 0 and 565 mg/kg dry soil) and >1,000 mg/kg dry soil, the highest concentration tested, respectively.
- Other effects: Radish displayed visual ratings of 23 and 25 for the 333 and 1,000 mg/kg levels, and <10 for all lower levels. Treatment level mean visual injuries of 10 or greater observed on the final day of the exposure were manifested as stunting, chlorosis and leaf curl for radish.



Results with reference substance (positive control):
no data
Reported statistics and error estimates:
The means and standard deviations were calculated for the percent emergence, survival, shoot height, and replicate dry weight data. Statistical analysis of the concentration versus effect data was performed using SAS. Emergence and survival data, as well as shoot height and dry weight data, was analyzed using analysis of variance (ANOVA) and a one-way Dunnett’s comparison (p < 0.05) of means less than the control to determine no observable effect concentrations (NOEC). Prior to the ANOVA and Dunnett’s tests, a Shapiro-Wilk’s test and a Levene’s test were conducted to test for normality and homogeneity of variance, respectively. If either of these tests were negative, subsequent analysis was done using nonparametric analysis on ranks of data. In most cases the no observable effect concentration (NOEC) was the highest concentration tested that was not statistically different from the control, the exceptions are discussed in the test results sections.

Since there were no significant effects compared to the control observed for any treatment level, within any species, for emergence or survival, and no greater than an 11% reduction in seedling emergence or survival as compared to the controls was observed, EC25 and EC50 estimates for emergence and survival data were not calculated. The twenty-five percent (EC25), and fifty percent (EC50) estimates for shoot height and dry weight were calculated by using a four-parameter logistic (sigmoid-shaped) model with two parameters fixed (100 and 0% inhibition) fit to the data with percent inhibition as the dependent variable and log concentration as the independent variable. If there was no convergence of the effects versus log concentration data, the EC25 and EC50 values were estimated as greater than the highest soil concentration tested.

 

Conclusions:
The NOECs based on nominal concentrations (mg/kg dry soil) for the effects of sodium tungstate on radish for plant emergence, shoot height and individual shoot weight were 1,000, 111, and 111 mg/kg, respectively. The EC25 values based on nominal concentrations (mg/kg dry soil) for the effects of sodium tungstate on radish for plant emergence, shoot height and individual shoot weight were >1,000, 787, and 259 mg/kg, respectively. The EC50 rates based on nominal concentrations (mg/kg dry soil) for the effects of sodium tungstate on radish for plant emergence, shoot height and individual shoot weight were >1,000, >1,000, and >1,000 mg/kg respectively.
Executive summary:

No toxicity to terrestrial plants data of sufficient quality are available for tungsten trioxide (target substance). However, toxicity to terrestrial plants 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

Tungsten trioxide was not tested for toxicity to terrestrial plants, and read across to sodium tungstate was used for this endpoint. In a Seedling Emergence and Seedling Growth Testusing Avena sativa, Raphanus sativus and Lactuca sativa and testing sodium tungstate, Lactuca sativa (lettuce) was found to be the most sensitive species, with an identified NOEC of 37 mg/kg soil d.w. sodium tungstate (nominal) (approximately 22 mg W/L) based on: Individual Shoot Weight.

Key value for chemical safety assessment

Long-term EC10, LC10 or NOEC for terrestrial plants:
37 mg/kg soil dw

Additional information

Due to similar or lower transformation/dissolution results for tungsten trioxide (the target substance) than sodium tungstate (the source substance), the resulting toxicity potential would also be expected to be similar or lower, so read-across is appropriate. In addition, read-across is justified because the classification and labeling is the same or less severe for the target substance PBT/vPvB profile is the same. Finally, the dose descriptors are, or are expected to be, sufficiently similar or higher for the target substance, and read-across to the source chemical is adequately protective. For more details refer to the attached description of the read across approach.