Disodium wolframate

Toxicity to soil macroorganisms except arthropods

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2008-12-30 to 2009-07-23

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Well documented, scientifically sound study that was conducted in accordance to GLP and OECD guideline 222. A deviation in the protocol included the prepared diet was provided first to the test organisms on the day of test initiation rather than one day later as specified by the protocol. This had no significant effect on the integrity of the study.

Qualifier:

according to guideline

Guideline:

OECD Guideline 222 (Earthworm Reproduction Test (Eisenia fetida/Eisenia andrei))

Deviations:

yes

Remarks:

the prepared diet was provided first to the test organisms on the day of test initiation rather than one day later as specified by the protocol, this had no significant effect on the integrity of the 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:

yes

Details on sampling:

no data

Vehicle:

no

Details on preparation and application of test substrate:

A 2.69 mg/mL primary standard was prepared on March 4, 2009, by transferring 5.3755 g of sodium tungstate (5.73 g corrected for purity) to a 2-L volumetric flask and bringing the flask to volume with deionized water. The 2.69 mg/mL primary standard was serially diluted with 2,000 mL volumes of deionized water to prepare working standards at concentrations of 0.169, 0.338, 0.675, and 1.35 mg/mL. A 931 mL aliquot of each working standard solution and the primary standard were added to 2,533.8 grams of air dry soil (equivalent to 2.5 kg of oven dry soil). The soil from the control and each treatment batch was mixed for approximately two to three minutes in a Hamilton Beach commercial mixer. This produced dosed soils with nominal concentrations of 0 (control), 62.9, 126, 251, 503, and 1,000 mg sodium tungstate/kg dry soil and a hydration level of approximately 60% of the soil water holding capacity (i.e., 38.6% moisture). Approximately 831 g of hydrated soil (approximately 600 g dry weight equivalent) was added to each replicate test vessel.

Test organisms (species):

Eisenia fetida

Animal group:

annelids

Details on test organisms:

TEST ORGANISM
- Common name: Earthworms (clitellate adults)
- Source: Vicker’s Farms, Orlando, Florida
- Age at test initiation (mean and range, SD): The adult animals selected for acclimation and testing were approximately 3 months of age with a developed clitellum.
- Weight at test initiation (mean and range, SD): 337 to 595 mg wet weight; initial mean weight of the treatment worms used in this exposure ranged from 411 to 450 mg/worm, based upon the replicate weights of ten worms.
- Weight of control worms at test initiation (mean and range, SD): initial mean weight of the control earthworms used for the definitive exposure was 462 mg/worm based upon the mean of the replicate weights of ten worms in each control replicate.
- The worms were maintained in commercial worm bedding prior to testing.
- An invertebrate diet similar to the diet utilized in the test was provided during the culture period.

ACCLIMATION
- Acclimation period: The adult animals selected for acclimation and testing were approximately 3 months of age with a developed clitellum. Four days prior to test initiation, adult earthworms were removed from the culture bedding and placed in artificial soil to acclimate the worms to the test conditions.
- Acclimation conditions (same as test or not): Same as test
- Health during acclimation (any mortality observed): No mortality observed

Study type:

extended laboratory study

Substrate type:

artificial soil

Limit test:

no

Total exposure duration:

56 d

Post exposure observation period:

no data

Test temperature:

19 to 21 degree C

pH:

Soil pH (day 0): 6.09 to 6.45
Soil pH (day 56): 5.59 to 5.73

Moisture:

Soil Moisture (day 0): 37.04 to 38.92%
Soil Moisture (day 56): 44.60 to 48.22%
Soil Moisture at 60% WHC: 38.6%

Details on test conditions:

TEST SYSTEM
- Test container (material, size): The test chambers were glass containers that have an approximate volume of 1.8 L.
- Amount of soil or substrate: A total of 500 or 600 g (dry weight) of prepared soil was added to each test chamber.
- No. of organisms per container (treatment): 10; Each replicate test chamber contained ten worms for a total of 40 worms per test substance treatment.
- No. of replicates per treatment group: four
- No. of replicates per control: Eight replicate test chambers were prepared for the control treatment; Each replicate test chamber contained ten worms for a total of 80 control worms.

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)
- Composition (if artificial substrate): The artificial soil used for both definitive exposures was prepared to approximate a sandy loam soil by mixing the following ratio of constituents: 70% silica sand, 20% kaolin clay, and 10% sphagnum peat based on dry weight equivalents. Calcium carbonate, CaCO3, was added to the soil to adjust the pH to fall within the 6.5 ± 0.5 range specified by the protocol. The peat moss was sieved to a finely ground consistency and did not contain any visible plant remains.
- Organic carbon (%): low total content
- Maximum water holding capacity (in % dry weigth): The water holding capacity (WHC) was determined to be 64.4 mL per 100 grams dry soil for the soil used in the definitive exposure.
- Storage (condition, duration): After preparation, the soil was stored at room temperature.

OTHER TEST CONDITIONS
- Photoperiod: 16-hr light to 8-hr dark
- Light intensity: 560.8 to 708.1 lux

TEST CONCENTRATIONS
- Range finding study
- Test concentrations: A 28-day range-finding test was conducted using nominal concentrations of 0 (control), 1.0, 10, 100, and 1,000 mg/kg dry soil. Two replicates were used for the control and test substance treatments with 10 worms added per replicate.
- Results used to determine the conditions for the definitive study: After 28 days there was no mortality or sublethal effects observed in the control or test substance treatments. At the termination of the range-finding test there was an average of 34, 33, 31, 30, and 28 cocoons per replicate for the control, 1.0, 10, 100, and 1,000 mg/kg dry soil treatments, respectively. Based on these results, a definitive test was performed at target nominal
concentrations of 0 (control), 62.5, 125, 250, 500, and 1,000 mg/kg dry soil.

Nominal and measured concentrations:

Calculated Nominal Soil Concentrations: 0 (Control), 62.9, 126, 251, 503, and 1,000 mg/kg dry soil

Reference substance (positive control):

yes

Remarks:

Tungsten ICP Standard

Key result

Duration:

56 d

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks on result:

other: The highest concentration tested

Key result

Duration:

56 d

Dose descriptor:

LOEC

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks on result:

other: The highest concentration tested

Key result

Duration:

56 d

Dose descriptor:

EC10

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks on result:

other: The highest concentration tested

Duration:

56 d

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

reproduction

Remarks on result:

other: The highest concentration tested

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: survival

Remarks on result:

other: The highest concentration tested

Duration:

28 d

Dose descriptor:

LOEC

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: suvival

Remarks on result:

other: The highest concentration tested

Duration:

28 d

Dose descriptor:

EC10

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: survival

Remarks on result:

other: The highest concentration tested

Duration:

28 d

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: survival

Remarks on result:

other: The highest concentration tested

Details on results:

- Mortality at end of exposure period: After 28 days of exposure to sodium tungstate, percent mortality of the adult worms was 0% in the control and all treatment.
- Other biological observations: Observations of general health and behavior of the worms were also noted (i.e., normal, lethargic, softness, absence of burrowing, and discoloration). All of the live earthworms were normal in appearance and behavior with the exception of five lethargic worms in the 1,000 mg/Kg dry soil treatment. No abnormal burrowing or avoidance behaviors were recorded during testing.
- The weights of surviving earthworms were measured on a replicate basis. The control worms gained an average of 2.164 g per replicate or 47% in replicate mass during the 28-day exposure . The treatment worms also gained weight during the study. The mean replicate weight gain of the surviving treatment animals ranged from 2.004 to 2.671 grams. The mean percent weight gain for the treatment animals ranged from 47 to 65% in replicate animal mass over the initial 28 days of exposure.
- At test termination, the number of juvenile worms will be determined by rinsing the test soil through a series of sieves (e.g., 710, 500, and 425 um mesh), collecting and enumerating the animals retained within the sieves.
- The average reproduction for the control animals was 547 juveniles per replicate. The percent coefficient of variation (%CV) for the control data was 14%. The average reproduction values were 447, 447, 483, 459, and 518 juveniles for nominal concentrations of 62.9, 126, 251, 503, and 1,000 mg sodium tungstate per kilogram dry soil treatments, respectively. There was no statistically significant reduction (p < 0.05) in the reproductive output of the adult worms exposed to the test substance. The EC10 and EC50 for reproduction was > 1,000 mg sodium tungstate/kg dry soil, the highest concentration tested. The NOEC and LOEC for reproduction was 1,000 and > 1,000 mg sodium tungstate/kg dry soil, respectively.
- The survival of the control adult animals was 100%, which met the acceptability of the test protocol and guidance document. Each control replicate containing 10 adult worms after the first 28 days of exposure produced more than the minimum acceptability criterion of 30 juvenile worms and the %CV value for the control reproduction was less than the maximum acceptability of 30% as specified by the protocol and the test guideline.

Results with reference substance (positive control):

- The analytical reference substance, Tungsten ICP Standard (1,000 ppm W) was received from Ricca Chemical Company on September 11, 2008, and was stored at room temperature. The sample was assigned ABC reference no. PS-22260. A certificate of analysis reported the concentration of solution to be 1,000 ppm W. This material was used to prepare analytical reference standard solutions. All solutions were corrected for the purity of the reference substance.

The reference substance (i.e., toxic standard) was carbendazim (received from Chem Service (West Chester, Pennsylvania)). The certificate of analysis showed the purity to be 99.4%

Reported statistics and error estimates:

All statistical analyses were performed using SAS software. Inferences of statistical significance were based upon p <= 0.05. Since there was no mortality in the control or treatments the noobserved-effect concentration (NOEC) for the survival data was equal to the highest level tested. The reproduction NOEC value was estimated using a one-way analysis of variance (ANOVA) procedure and a one-tailed Dunnett's test. Prior to the Dunnett's test, a Shapiro-Wilk’s and the Levene’s tests were performed to determine data normality and homogeneity of the treatment variances. The reproductive data met the criterion for normality and homogeneity of variance, therefore a parametric analysis was performed on the reproductive data.

The soil moisture and pH were measured in samples collected from the parent control and treatment soils on day 0. At test termination (study day 56), the moisture content and soil pH were determined from samples of test medium collected from a single replicate test chamber (i.e., replicate A) for all treatment levels. The soil samples were collected prior to the enumeration of the juvenile worms. The pH was measured using a WTW Model pH 330i pH meter. The percent moisture was calculated as the difference between the wet and dry soil samples and presented as percent of the soil dry weight using a Mettler Toledo HR73 Halogen Moisture Analyzer. A continuous temperature record was measured with an electronic data logger in a chamber containing moistened control soil and placed in the water bath. Light intensity was measured at test initiation with a LI-COR Model LI-189 light meter equipped with a photometric sensor.

Validity criteria fulfilled:

yes

Conclusions:

The survival of the control adult animals was 100%, which met the acceptability of the test protocol and guidance document. Each control replicate containing 10 adult worms after the first 28 days of exposure produced more than the minimum acceptability criterion of 30 juvenile worms and the %CV value for the control reproduction was less than the maximum acceptability of 30% as specified by the protocol and the test guideline.

Under the conditions of this study and based upon nominal concentrations, the 56-day reproduction NOEC value was 1,000 mg sodium tungstate/kg dry soil and the estimated EC10 and EC50 value for average reproduction was > 1,000 mg sodium tungstate/kg, the highest concentration tested.

Reference 2

Endpoint:

toxicity to soil macroorganisms except arthropods: short-term

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

Well documented, scientifically sound study conducted similarly to OECD Guideline 207 with some deviations.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 207 (Earthworm, Acute Toxicity Tests)

GLP compliance:

not specified

Analytical monitoring:

yes

Vehicle:

no

Details on preparation and application of test substrate:

Artificial soils were prepared following Organization for Economic Cooperation and Development protocols and consisted of 70% sand, 20% kaolin clay, and 10% sieved peat moss, with pH adjusted to between 6.5 to 7.0 through addition of calcium carbonate. Sand, clay, and peat moss were obtained from local suppliers, and peat moss was sieved (mesh size, 2 mm) before its use in preparing artificial soils. The field soil used in these experiments was a silty loam soil of the Grenada–Loring soil series and was collected from the Brown Loam Experimental Station (Learned, MS, USA). The soil was collected with a front-end loader after the top 12 cm were removed to eliminate unwanted vegetation. The soil was air-dried, processed through a hammer mill, and sieved (mesh size, 1.4 mm) before use. Both field soil and artificial soil were sent to A&L Laboratories (Memphis, TN, USA) for characterization before use in the tests; all analyses were conducted on triplicate aliquots. Soil characterization included texture analysis (percentage sand, silt, and clay), total organic carbon (Walkley–Black method), percentage organic matter (loss-on-ignition), pH, and cation-exchange capacity. Sodium tungstate was prepared as serially diluted aqueous solution and was added to the soils one week before addition of earthworms; soils were mixed by hand after addition of the solution. Spiking solutions were analyzed for metal content and, in all cases, were within 5% of the target concentrations. The solution was added in amounts sufficient to hydrate the soil to 85% of its water-holding capacity (0.350 ml/g for artificial soil and 0.295 ml/g for field soil)

Test organisms (species):

Eisenia fetida

Animal group:

annelids

Details on test organisms:

Earthworm cultures originally were obtained from Carolina (Burlington, NC, USA). They were maintained as a brood stock in our acclimation laboratory in peat moss neutralized with calcium carbonate to pH of between 6.5 and 7.0 and were fed a grain-based food (MagicWorm Food; Magic Products, Amherst Junction, WI, USA).

Study type:

laboratory study

Substrate type:

other: Natural or artificial soil

Limit test:

no

Total exposure duration:

14 d

Test temperature:

21±1 degree C

Moisture:

soil hydrated to 85% of its water-holding capacity

Details on test conditions:

- Each of the 10 concentrations and the control contained 10 individual jars with one worm per jar.

Nominal and measured concentrations:

- Nominal soil concentrations ranged between 2,560 to 10,240 mg/kg for artificial soil and from 4,500 to 10,500 mg/kg for field soil.
- Measured soil concentrations ranged between 1,940 to 3,830 mg/kg for artificial soil and from 2,820 to 6,557 mg/kg for field soil.

Reference substance (positive control):

yes

Remarks:

lead nitrate

Key result

Duration:

14 d

Dose descriptor:

LC50

Effect conc.:

6 250 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: Field soil

Key result

Duration:

14 d

Dose descriptor:

LC50

Effect conc.:

3 960 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality

Remarks on result:

other: Artificial soil

Details on results:

- Toxicity was greater in the OECD artificial soil compared to the field soil (LC50s of 3,960 and 6,250 mg/kg soil, respectively). Chemical analysis of soils from the acute toxicity exposures resulted in measured tungsten concentrations averaging 63% of nominal concentrations.

Results with reference substance (positive control):

LC50 value for lead nitrate in field soil was 2,490 mg/kg soil. No deaths were observed in artificial soils with nominal lead concentrations as high as 10,000 mg/kg.

Reported statistics and error estimates:

Statistical analysis was conducted with SigmaStatt 2.0 and graphics and associated curvefittingwere conducted with SigmaPlott 8.0. The LC50s were determined by plotting log dose versus percentage survival and fitting a sigmoidal curve.

-Spiking solutions were analyzed for metal content and, in all cases, were within 5% of the target concentrations.

Conclusions:

Under the conditions of this study, the 14-day LC50 was 6,250 mg/kg soil for tungsten in earthworms exposed to sodium tungstate spiked field-collected soil. The 14-day LC50 was 3,960 mg/kg soil for tungsten in earthworms exposed to sodium tungstate spiked artificial soil.

Reference 3

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Guideline study with limited documentation on the preparation of test solutions and test conditions provided. Analytical confirmation of test solutions was not performed.

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

OECD Guideline 207 (Earthworm, Acute Toxicity Tests)

Deviations:

yes

Remarks:

: no analytical confirmation performed

Qualifier:

according to guideline

Guideline:

OECD Guideline 222 (Earthworm Reproduction Test (Eisenia fetida/Eisenia andrei))

Deviations:

yes

Remarks:

: no analytical confirmation performed

GLP compliance:

not specified

Analytical monitoring:

no

Details on sampling:

N/A

Vehicle:

no

Details on preparation and application of test substrate:

- Method of mixing into soil: Dry components of the artificial soils were mixed thoroughly and then tungsten salts were introduced with water and mixed again
- Controls: no data

Test organisms (species):

Eisenia fetida

Animal group:

annelids

Details on test organisms:

TEST ORGANISM
- Common name: red earthworms
- Source: Worm Farms Inc., NJ
- Age at test initiation (mean and range, SD): 4-5 cm
- Weight at test initiation (mean and range, SD): 250-350 mg with a clitellum


ACCLIMATION
- Acclimation period: No data
- Acclimation conditions (same as test or not): No data
- Health during acclimation (any mortality observed): No data

Study type:

other: Acute and chronic studies performed

Substrate type:

artificial soil

Limit test:

no

Total exposure duration:

180 d

Post exposure observation period:

none

Test temperature:

Room temperature

pH:

5.8 (peat)

Moisture:

50% of maximum water holding capacity

Details on test conditions:

TEST SYSTEM
- Test container (material, size): 1 L glass jars
- Amount of soil or substrate: 700 g moist soil
- No. of organisms per container (treatment): 10
- No. of replicates per treatment group: 3


SOURCE AND PROPERTIES OF SUBSTRATE
- Composition: 10% finely ground sphagnum peat moss (pH 5.8), 20% kaolin clay with kaolinite content above 40%, 70% fine sand.
- Organic carbon (%): 10 approx
- Maximum water holding capacity (in % dry weigth): No data
- CEC: No data
- Pretreatment of soil: all components thoroughly mixed, toxicants added with water, mixed again.



OTHER TEST CONDITIONS
- Photoperiod: No data
- Light intensity: No data


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : mortality and reproduction

Nominal and measured concentrations:

Nominal-seven concentrations up to 10,000 mg/kg soil

Reference substance (positive control):

no

Key result

Duration:

180 d

Dose descriptor:

LC50

Effect conc.:

> 10 other: g W/kg soil

Nominal / measured:

nominal

Conc. based on:

other: tungsten concentration

Basis for effect:

mortality

Key result

Duration:

180 d

Dose descriptor:

NOEC

Effect conc.:

1.125 other: g W/kg soil

Nominal / measured:

nominal

Conc. based on:

other: tungsten concentration

Basis for effect:

reproduction

Key result

Duration:

180 d

Dose descriptor:

LOEC

Effect conc.:

2.25 other: g W/kg soil

Nominal / measured:

nominal

Conc. based on:

other: tungsten concentration

Basis for effect:

reproduction

Details on results:

- Mortality at end of exposure period: none

Reported statistics and error estimates:

LC50 values and their confidence intervals were calculated by the EPA Probit Analysis Program version 1.5. Other statistical calculations have been performed using Statistica 7.0 software.

Additional observations:

-No mortality occurred for 6 months.

-Worm eggs first appeared at 2 months.

-At 6 months, Controls, 0.02625, 0.5625, and 1.125 g/kg concentrations contained numerous old and new eggs and small worms.

-Jars of 2.25 and 4.5 g/L concentrations contained about 100 times fewer offspring than the lower concentrations.

-Worms exposed to greater than 9.0 g/kg concentration did not produce eggs or offspring during the test.

-Therefore, concentrations less than 1.125 g/kg did not affect reproduction.

Conclusions:

The 180 day LC50 of sodium tungstate to E. fetida is > 10 g W/kg soil. The 180 day NOEC for reproduction is 1.125 g W/kg soil, and the LOEC is 2.25 g w/kg soil.

Reference 4

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

Well documented, scientifically sound study similar to OECD Guideline 222 with some deviations, including use of fewer earthworms per replicate container.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 222 (Earthworm Reproduction Test (Eisenia fetida/Eisenia andrei))

Deviations:

yes

Remarks:

Only 5 worms per replicate

GLP compliance:

not specified

Analytical monitoring:

yes

Vehicle:

no

Details on preparation and application of test substrate:

The field soil used in these experiments was a silty loam soil of the Grenada–Loring soil series and was collected from the Brown Loam Experimental Station (Learned, MS, USA). The soil was collected with a front-end loader after the top 12 cm were removed to eliminate unwanted vegetation. The soil was air-dried, processed through a hammer mill, and sieved (mesh size, 1.4 mm) before use. The field soil was sent to A&L Laboratories (Memphis, TN, USA) for characterization before use in the tests; all analyses were conducted on triplicate aliquots. Soil characterization included texture analysis (percentage sand, silt, and clay), total organic carbon (Walkley–Black method), percentage organic matter (loss-on-ignition), pH, and cation-exchange capacity. Sodium tungstate was prepared as serially diluted aqueous solution and was added to the soils one week before addition of earthworms; soils were mixed by hand after addition of the solution. Spiking solutions were analyzed for metal content and, in all cases, were within 5% of the target concentrations. The solution was added in amounts sufficient to hydrate the soil to 85% of its water-holding capacity (0.295 ml/g).

Test organisms (species):

Eisenia fetida

Animal group:

annelids

Details on test organisms:

Earthworm cultures originally were obtained from Carolina (Burlington, NC, USA). They were maintained as a brood stock in authors' acclimation laboratory in peat moss neutralized with calcium carbonate to pH of between 6.5 and 7.0 and were fed a grain-based food (MagicWorm Food; Magic Products, Amherst Junction, WI, USA).

Study type:

laboratory study

Substrate type:

natural soil

Limit test:

no

Total exposure duration:

56 d

Post exposure observation period:

No data

Test temperature:

21±1 degree C

pH:

6.72

Moisture:

Soil hydrated to 85% of its water-holding capacity

Details on test conditions:

- Each of the 10 concentrations and the control had five replicate containers with five worms per container.
- Dried fermented alfalfa (2 g/container) was provided for food.
- After 28 d, the adult worms were removed, and survival was recorded.
- Adult worms were allowed to depurate overnight on wetted filter paper, weighed, and then frozen and stored at -80 degrees C until chemical analysis.
- The soil was returned to the environmental chamber for another 28 d to allow cocoons to hatch, and an additional 2-g aliquot of dried fermented alfalfa was added at this time.
- After the additional 28 d, containers were removed from the environmental chamber and placed in a water bath heated to 40 degrees C, and juvenile worms were collected as they moved to the surface.
- A subsample of soil was removed for chemical analysis, and the remaining soil was sieved to recover the cocoons.

Nominal and measured concentrations:

Nominal tungsten concentrations ranged from 704 to 7,039 mg/kg soil (dry-wt basis).
Measured tungsten concentration ranged from 923 to 6,173 mg/kg soil (dry-wt basis).

Reference substance (positive control):

yes

Remarks:

lead nitrate

Key result

Duration:

28 d

Dose descriptor:

EC100

Effect conc.:

> 704 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

other: tungsten concentration

Basis for effect:

reproduction

Key result

Duration:

56 d

Dose descriptor:

EC100

Effect conc.:

>= 704 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

other: tungsten concentration

Basis for effect:

reproduction

Details on results:

- For 28-d exposures, lethality was observed at the higher doses of tungsten.
- Tungsten did not cause a significant decreases in growth.
- No cocoons or juveniles were observed in any of the tungsten exposures.
- Body burden analysis of tissues showed a mean tungsten body burden of 11 mg/kg wet tissue associated with complete shutdown of reproduction and concentrations of 41 mg/kg wet wt associated with decreased adult survival.

Results with reference substance (positive control):

Lead nitrate was used as a reference toxicant, with nominal concentrations ranging from 165 to 1,650 mg/kg soil. 100% survival at all doses was obtained after 28-days. Statistically significant differences in the number of cocoons/replicate and the number of juveniles/replicate were observed relative to the control group at doses as low as 213 mg/kg soil. Cocoon production was still observed at the highest lead nitrate concentration tested.

Reported statistics and error estimates:

Statistical analysis was conducted with SigmaStatt 2.0 and graphics and associated curve fitting were conducted with SigmaPlott 8.0.

-Spiking solutions were analyzed for metal content and, in all cases, were within 5% of the target concentrations.

Conclusions:

Under the conditions of this study, sodium tungstate completely inhibited reproduction in 28- and 56-day earthworm assays at all tested concentrations greater than or equal to 704 mg/kg soil.

Description of key information

The 56-day NOEC for earthworms (Eisenia fetida) found in a test conducted according to OECD 222, under GLP standards, and with analytical verification of the test concentrations was ≥1000 mg sodium tungstate/kg soil dw.

Key value for chemical safety assessment

Short-term EC50 or LC50 for soil macroorganisms:

1 000 mg/kg soil dw