Molybdenum, bis(dibutylcarbamodithioato)di-μ-oxodioxodi-, sulfurized

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

key study

Study period:

26 May 2017 to 31 August 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.1 (Acute Toxicity for Fish)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

- Physical state/Appearance: Yellow powder
- Purity: This substance has an Unknown or Variable composition, is a Complex reaction product, or a Biological material (UVCB).

Analytical monitoring:

yes

Details on sampling:

Water samples were taken from the control and 100 mg/L loading rate WAF test vessels at 0 and 72 hours from fresh media and at 24 and 96 hours from old media for quantitative analysis. The samples were stored frozen prior to analysis.
Duplicate samples and samples at 24 (fresh media), 48 (old and fresh media) and 72 hours (old media) were taken and stored frozen for further analysis if necessary.

Preparation of Test Samples
The test samples (100 mL) were thawed in a water bath and then an aliquot (0.5 mL) of formic acid was added to the test samples. The test item was extracted from the test samples using a solid phase extraction cartridge, which was pre-conditioned with 10 mL of acetonitrile and 10 mL of water. The samples were drawn through the cartridge under reduced pressure. Subsequently, the cartridge was eluted with 10 mL of acetonitrile into a 10 mL volumetric and made up to the mark with acetonitrile.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
Due to the low aqueous solubility and the complex nature of the test item, the test medium was prepared as Water Accommodating Fraction ((WAF).

A nominal amount of test item (2200 mg) was added to the surface of 22 liters of test water to give the 100 mg/L loading rate. After the addition of the test item, the test water was stirred by magnetic stirrer using a stirring rate such that a vortex was formed to give a dimple at the water surface. The stirring was stopped after 23 hours and the mixture was left to stand for 1-Hour. Visual observations made on the WAF indicated that a significant amount of dispersed test item was present in the water column and hence it was considered justifiable to remove the WAF by filtering through a glass wool plug (2-4 cm in length). A wide bore glass tube, covered at one end with Nescofilm was submerged into the vessel, sealed end down, to a depth of approximately 5 cm from the bottom of the vessel. A length of Tygon tubing was inserted into the glass tube and pushed through the Nescofilm seal. A glass wool plug was inserted into the opposite end of the tubing and the WAF removed by mid-depth siphoning (the first 75-100 mL discarded) to give the 100 mg/L loading rate WAF. After filtration through the glass wool plug, dispersed material was observed in the filtrate, therefore it was considered appropriate to filter through filter paper. Microscopic observations of the WAF were performed after passing through filter paper and showed no undissolved test item present.

Test organisms (species):

Pimephales promelas

Details on test organisms:

Test System and Supporting Information
The test was carried out using juvenile fathead minnow (Pimephales promelas). Fish were obtained bred in house on the 08 May 2017. Fish were maintained in a glass tank with a "single pass" water renewal system. Fish were acclimatized to test conditions from 12 June 2017 to 19 June 2017. The lighting cycle was controlled to give a 16 hours light and 8 hours darkness cycle with 20 minute dawn and dusk transition periods.
The water temperature was controlled at 21 to 22 ºC with a dissolved oxygen content of greater than or equal to 8.8 mg O2/L. These parameters were recorded daily. The stock fish were fed commercial GM 300 which was discontinued approximately 24 hours prior to the start of the definitive test. There was no mortality in the 7 days prior to the start of the test and the fish had a mean standard length of 2.8 cm (sd = 0.20) and a mean weight of 0.15 g (sd = 0.040) at the end of the definitive test. Based on the mean weight value this gave a loading rate of 0.23 g bodyweight/liter.
The diet and diluent water are considered not to contain any contaminant that would affect the integrity and outcome of the study.

Test Water
The test water used for the definitive test was the same as that used to maintain the stock fish.
Laboratory tap water was dechlorinated by passage through an activated carbon filter (Purite Series 500) and partly softened, with a commercially available water softener, giving water with a total hardness of approximately 140 mg/L as CaCO3. After dechlorination and softening the water was passed through a series of computer controlled plate heat exchangers to achieve the required temperature.

Test type:

semi-static

Water media type:

other: Water Accommodated Fraction (WAF)

Limit test:

yes

Total exposure duration:

48 h

Hardness:

140 mg/L as CaCO3

Test temperature:

Ranged from 22 to 23 ºC

pH:

Ranged from 7.7 to 8.3

Dissolved oxygen:

Ranged from 8.2 to 9.0 mg O2/L

Details on test conditions:

Experimental Preparation
The concentration and stability of the test item in the test preparations were verified by chemical analysis at 0 and 48 hours (fresh media) and at 24 and 72 hours (old media).

Exposure Conditions
In the definitive test a 5 liter glass exposure vessel containing 4.5 liters of test media was used for each control and test concentration. At the start of the test, seven fish were placed in each test vessel at random. The test vessels were then covered to reduce evaporation and maintained at 22 C to 23 ºC in a temperature controlled room with a photoperiod of 16 hours light and 8 hours darkness with 20 minute dawn and dusk transition periods for a period of 96 hours. The test vessels were aerated via narrow bore glass tubes. The fish were not individually identified and received no food during exposure.
The control group was maintained concurrently under identical conditions but was not exposed to the test item.
A semi-static test regime was employed in the test involving a daily renewal of the test preparations to aid in maintaining exposure levels and to prevent the build-up of nitrogenous waste products.

Key result

Duration:

48 h

Dose descriptor:

LL50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

other: loading rate WAF

Basis for effect:

mortality (fish)

Key result

Duration:

48 h

Dose descriptor:

NOELR

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

other: loading rate WAF

Basis for effect:

mortality (fish)

Details on results:

Analysis of the freshly prepared 100 mg/L loading rate WAF test solutions at 0 and 48 hours showed that measured concentrations of 0.031 and 0.018 mg/L were obtained, respectively. Analysis of the expired test solutions at 24 and 72 hours showed that measured concentrations of 0.024 mg/L and less than the limit of quantification of the analytical method (0.013 mg/L) were obtained, respectively.

Given that the toxicity in this study cannot be attributed to a single component or a mixture of components, but to the test item as a whole, the results were based on nominal loading rates only. No mortality or sublethal effects were observed among the 7 fish exposed to 100 mg/L loading rate WAF for a period of 96 hours.

Exposure of fathead minnow to the test item for 96 hours resulted in LL50 values of greater than 100 mg/L loading rate WAF. The No Observed Effect Loading Rate (NOELR) for 96 hours was 100 mg/L loading rate WAF.

It was considered unnecessary and unrealistic to test at loading rates in excess of 100 mg/L loading rate WAF.

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of the acute toxicity study, exposure of the fathead minnow to the test item resulted in LL50 values greater than 100 mg/L loading rate WAF. The No Observed Effect Loading Rate was 100 mg/L loading rate WAF.

Executive summary:

A study was performed to assess the acute toxicity of the test item to fathead minnow (Pimephales promelas).  The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (1992) No. 203, "Fish, Acute Toxicity Test" and Method C.1 “Acute Toxicity for Fish”, of Commission Regulation (EC) No. 440/2008.

Due to the low aqueous solubility and complex nature of the test item, the test medium was prepared as a Water Accommodated Fraction (WAF).

In accordance with the recommendations of REACh, the test was conducted according to the threshold approach recommended by ECHA.  Using this approach the lowest EL50 value from the Algal Growth Inhibition study or Acute Toxicity to Daphnia magna study is set as the threshold loading rate and a “Limit test” is conducted at this threshold loading rate.  If no mortalities are observed this indicates that fish are not the most sensitive species and that the LL50 is greater than the threshold loading rate. Therefore, as the EL50 values obtained for both the Algal Growth Inhibition study and the Acute Toxicity to Daphnia magna study (Envigo Study Numbers MB69HS and FJ69VW, respectively) were greater than 100 mg/L loading rate WAF, the test was conducted at a single loading rate of 100 mg/L loading rate WAF to ensure that toxicity was not observed at this loading rate.

Seven fish were exposed to a Water Accommodated Fraction (WAF) of the test item, at a single nominal loading rate of 100 mg/L for a period of 96 hours at a temperature of 22 ºC to 23 ºC under semi-static test conditions.  The number of mortalities and any sub-lethal effects of exposure in each test and control vessel were determined 3 and 6 hours after the start of exposure and then daily throughout the test until termination at 96 hours.

Analysis of the freshly prepared 100 mg/L loading rate WAF test solutions at 0 and 48 hours showed that measured concentrations of 0.031 and 0.018 mg/L were obtained, respectively.  Analysis of the old or expired test solutions at 24 and 72 hours showed that measured concentrations of 0.024 mg/L and less than the limit of quantification of the analytical method, (0.013 mg/L) were obtained, respectively.

Given that the toxicity in this study cannot be attributed to a single component or a mixture of components, but to the test item as a whole, the results were based on nominal loading rates only.

Exposure of fathead minnow to the test item for 96 hours resulted in an LL50 value of greater than 100 mg/L loading rate WAF. The No Observed Effect Loading Rate was 100 mg/L loading rate WAF.

It was considered unnecessary and unrealistic to test at loading rates in excess of 100 mg/L loading rate WAF.

Description of key information

Under the conditions of the study, exposure of fathead minnow to the test item gave LL50 values of greater than 100 mg/L loading rate WAF. The No Observed Effect Loading Rate was 100 mg/L loading rate WAF.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

100 mg/L