Tetrakis(diethyldithiocarbamato-S,S')tellurium

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:

05 Jul 2018 to 09 Jul 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)

Version / remarks:

July 1992

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.1075 (Freshwater and Saltwater Fish Acute Toxicity Test)

Version / remarks:

2016

Qualifier:

according to guideline

Guideline:

other: ASTM Standard E 729-96: Standard Guide for Conducting Acute Toxicity Tests on Test Materials with Fishes, Macroinvertebrates, and Amphibians

Version / remarks:

2014

GLP compliance:

yes

Specific details on test material used for the study:

- Name of test material (as cited in study report): Perkacit® TDEC pdr
- Batch No.: 60701019
- Appearance: Solid
- Tellurium content: 17.6%
- Date of manufacture: 09 Feb 2017
- Storage conditions: Ambient

Analytical monitoring:

yes

Details on sampling:

Test water samples were collected from one test chamber of each treatment and control group three days prior to the start of exposure to confirm concentrations after conditioning the diluter system for two days. Test water samples also were collected from one replicate test chamber in each treatment and control group at the beginning of the test and at 96 hours (± 1 hour) to measure concentrations of the test substance. Sampling alternated between the replicate test chambers in each group at each sampling interval. The samples (10.0 mL) were collected from mid-depth, placed in glass vials containing 10.0 mL of acetonitrile and processed immediately for analysis.

Vehicle:

yes

Remarks:

0.1 mL/L HPLC-grade dimethylformamide (DMF)

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
Individual stock solutions were prepared for each of the five concentrations tested. The primary stock solution was prepared once during the test. The secondary stock solutions were prepared daily during the test. Test solution concentrations were not adjusted for the active ingredient of the test substance during preparation and are based on the test substance as received. A 1000-mL primary stock solution was prepared
by mixing a calculated amount of test substance into HPLC-grade dimethylformamide (DMF) at a nominal concentration of 6340 μg/mL. The primary stock solution was partially brought to volume and sonicated for approximately 15 minutes. The stock solution was then brought to final volume and stirred on a magnetic stir plate for approximately 15 minutes. The stock solution appeared clear and orange. Four secondary stock
solutions (30 mL each) were prepared in DMF at nominal concentrations of 400, 790, 1590 and 3170 μg/mL by proportional dilution of the primary stock after it had been sonicated for approximately 10 minutes. The secondary stock solutions were mixed by stirring on a magnetic stir plate for approximately 15 minutes and appeared clear with increasing orange color as the concentration increased.

The primary stock solution was held at room temperature in a glass amber bottle. Fresh aliquots of each stock were placed on the delivery system pump every day during the test. During the exposure period, the stock solutions were pumped into the diluter mixing chambers assigned to the treatment groups at a target rate of 20.0 μL/minute and were mixed with dilution water in the mixing chambers, delivered at a target rate of 200 mL/minute to achieve the desired nominal test concentrations. The negative control received dilution water only. The solvent control was prepared by delivering HPLC-grade DMF to the mixing chamber for the solvent control at the same rate as the test substance stock solutions. The concentration of DMF in the solvent control and all treatment groups was 100 μL/L.

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

TEST ORGANISM
- Common name: Rainbow trout
- Source: Rainbow trout used in the test were received as juveniles from Thomas Fish Company LLC of Anderson, California.
- Length at study termination in controls: 6.2 cm, with a range of 5.2 to 6.9 cm
- Dry weight at study termination in controls: 2.706 grams, with a range of 1.215 to 3.776 grams

ACCLIMATION
- Acclimation period: The fish were held for at least 14 days prior to the test in water from the same source and at approximately the same temperature as used during the test.
- Acclimation conditions: During the 2-week period immediately preceding the test, water temperatures in the cultures ranged from 11.9 to 14.7 °C, the pH of the water ranged from 8.2 to 8.6, and the dissolved oxygen concentrations were ≥ 9.6 mg/L (≥ 91% of saturation).
- Feeding: Daily during the holding period, except during periods of fasting prior to testing, the fish were fed a commercially-prepared diet supplied by Zeigler Brothers, Inc., Gardners, Pennsylvania. The fish were not fed for at least two days prior to the test or during the test.
- Health during acclimation: During the 7-day period prior to the test, the fish in the lot used for the test showed no signs of disease or stress and there were no mortalities.

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

132 mg/L as CaCO3 at Day 0

Test temperature:

12.7 - 13.6 °C

pH:

7.9 - 8.3

Dissolved oxygen:

8.3 - 9.3 mg O2/L

Conductivity:

350 μS/cm at Day 0

Nominal and measured concentrations:

- Nominal concentrations: 0 (blank control), 0 (solvent control), 40, 79, 159, 317 and 634 μg/L.
- Mean measured concentrations:

Details on test conditions:

TEST SYSTEM
- Test vessel: Test chambers were 25-L Teflon®-lined stainless steel aquaria filled with approximately 15 L of test water. The depth of the test water in a representative chamber was 16.8 cm and was maintained by a standpipe within the test chamber. All test chambers were labeled with the project number, test concentration and replicate designation. The test chambers were impartially positioned in a temperature-controlled water bath to maintain the target water temperature throughout the test period.
- Aeration: No
- No. of organisms per vessel: 5
- No. of vessels per concentration: 2
- No. of vessels per control: 2
- No. of vessels per vehicle control: 2
- Biomass loading rate: Loading was defined as the total wet weight of fish per liter of test solution and was 0.094 g fish/L that passed through the test chamber in 24 hours. Instantaneous loading was 0.902 g fish/L of test water present in the test chambers at any given time.

FLOW-THROUGH SYSTEM
The toxicity test was conducted using a continuous-flow diluter system to provide each concentration of the test substance, a negative control (dilution water only) and a solvent control (100 μL dimethylformamide/L) to test chambers. A syringe pump (Harvard Apparatus, Holliston, Massachusetts) was used to deliver volumes of test substance stock solutions to mixing chambers impartially assigned to each
treatment group. Dimethylformamide (DMF) was delivered to a separate mixing chamber assigned to the solvent control. The stock solutions or solvent were mixed with well water in the mixing chambers in order to prepare the test solutions at the appropriate nominal concentrations prior to delivery to the test chambers. Well water alone was delivered to a mixing chamber for the negative control. Impellors were located in the mixing chambers to facilitate mixing of the stock solutions with dilution water. The flow of dilution water into each mixing chamber was controlled using rotameters and was adjusted to provide approximately 10 volume additions of test solution in each test chamber per day. After mixing, the test water in each mixing chamber was delivered in approximately equal volumes to two replicate test chambers in each control and treatment group.

The pumps used to deliver stock solutions or solvent to the mixing chambers, and the rotameters used to control the flow of dilution water to the mixing chambers, were calibrated prior to exposure initiation and verified at the end of the test. The proportion of the test water that was delivered to each replicate test chamber was checked to ensure that flow rates varied by no more than ± 10% of the mean flow rate for the
two replicates. Delivery of test water to the test chambers was initiated five days prior to the introduction of the test organisms to the test water in order to establish equilibrium concentrations of the test substance. The general operation of the exposure system was checked visually at least once on the first and last days of the test and at least two times per day during the test.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The water used for organism holding and testing was freshwater obtained from a well approximately 40 meters deep located on the EAG Laboratories site in Easton, Maryland. The well water was passed through a sand filter to remove particles greater than approximately 25 µm and pumped into a 37,800-L storage tank where the water was aerated with spray nozzles. Prior to use in the test system, the water was filtered to 0.45 µm to remove fine particles and was passed through an ultraviolet (UV) sterilizer.
- Alkalinity: 176 mg/L as CaCO3 at Day 0

OTHER TEST CONDITIONS
- Adjustment of pH: No
- Photoperiod: The lights were controlled by an automatic timer to provide a photoperiod of 16 hours of light and 8 hours of darkness. A 30-minute transition period of low light intensity was provided when lights went on and off to avoid sudden changes in light intensity.
- Light quality: The test systems were illuminated using fluorescent tubes that emit wavelengths similar to natural sunlight.
- Light intensity: Light intensity at the beginning of the test was 707 lux at the surface of the water of one representative test chamber. Light intensity was measured at the water surface of one representative test chamber at the beginning of the test using a SPER Scientific Model 840006 light meter.

WATER QUALITY MEASUREMENTS
- Temperature: Temperature was measured in each
test chamber at the beginning and end of the test using a digital thermometer. Water temperature also was monitored continuously in one negative control test chamber using a validated environmental monitoring system (AmegaView Central Monitoring System). The system measurements were calibrated prior to exposure initiation with a digital thermometer.
- Dissolved oxygen and pH: Dissolved oxygen and pH were measured in each test chamber at the beginning of the test, at approximately 24-hour intervals during the test, and at the end of the test. Dissolved oxygen was measured using a Thermo Scientific Orion Star A213 Benchtop RDO/DO meter, and measurements of pH were made using a Thermo Scientific Orion DUAL STAR pH/ISE meter. When 100% mortality occurred in a test chamber, measurements of temperature, dissolved oxygen and pH were taken in that test chamber and then
discontinued.
- Hardness, alkalinity and specific conductance: Hardness, alkalinity and specific conductance in the dilution water were measured at the beginning of the test. Hardness and alkalinity measurements were made by titration. Specific conductance was measured using a Thermo Scientific Orion Star A122 Portable Conductivity meter.

EFFECT PARAMETERS MEASURED: mortality, sublethal effects
Prior to test initiation, juvenile rainbow trout were collected from the holding tanks. To initiate the test, the fish were impartially distributed one or two at a time to the test chambers until each contained five fish. All organisms were observed periodically during the test to determine the number of mortalities in each treatment group. Mortality was defined as the lack of visible movement (e.g., lack of fin or opercular movement) and the lack of response to gentle prodding in the fish. Dead fish were removed from the test chambers at each observation interval. The numbers of individuals exhibiting signs of toxicity or abnormal behavior also were evaluated. Observations were made approximately 4, 24, 48, 72 and 96 hours after test initiation.

RANGE-FINDING STUDY
The range-finding study was conducted at nominal concentrations of 2.5, 9.9, 40, 159 and 634 μg/L for 96 hours under flow-through test conditions. Percent mortality in the 2.5, 9.9, 40, 159 and 634 μg/L treatment groups at test termination was 0, 0, 0, 0 and 100%, respectively. Sublethal effects at test termination included discoloration where the fish appeared almost jet black in color. The results were used to determine the target concentrations in the definitive test.

Reference substance (positive control):

no

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

344 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Remarks on result:

other: 95% C.I.: 151 - 570 μg/L.

Details on results:

Daily observations of mortality and other signs of toxicity observed during the test are presented in 'Any information on results incl. tables'.

There was one fish that escaped from a solvent control test chamber before the 48-hour observation interval. All other fish in the negative and solvent control groups appeared normal throughout the test. All fish in the 35 and 71 μg/L treatment groups also appeared normal throughout the test, with no mortalities or overt signs of toxicity observed. Percent mortality in the 35, 71, 151, 273 and 570 μg/L treatment groups at test termination was 0, 0, 0, 20 and 100%, respectively. Signs of toxicity observed among the surviving fish in the 151 and 273 μg/L treatment groups at test termination included discoloration (i.e., fish with a white mark on head) and lethargy. Therefore in this study, the no-mortality concentration was 151 μg/L, the 100% mortality concentration was 570 μg/L and the NOEC was 151 μg/L.

Reported statistics and error estimates:

The mortality data were analyzed using the computer program of C. E. Stephan. The program was designed to calculate the LC50 value and the 95% confidence interval by probit analysis, the moving average method, and binomial probability with nonlinear interpolation. Based on the mortality pattern in this study, nonlinear interpolation was used to calculate the 48, 72 and 96-hour LC50 values and binominal probability was used to calculate the 95% confidence intervals. Since there was <50% mortality at 24 hours, the 24-hour LC50 value was estimated to be greater than the highest concentration tested. Due to the method used to calculate the 96-hour LC50 value, the slope of the concentration-response curve could not be calculated. The no-mortality concentration and 100% mortality concentration were determined by visual interpretation of the mortality data. The no-observed-effect concentration (NOEC) based on mortality was analyzed using Cochran-Armitage (O) Trend Step-Down Test in CETIS™ v1.9.3.0.

Sublethal observations / clinical signs:

Table: Cumulative mortality and observations

Mean measured concentration (µg/L)	Rep.	No. Exposed	~4 Hours		24 Hours		48 Hours		72 Hours		96 Hours		Cumulative percent mortality
			No. Dead(1)	Observations(2)	No. Dead(1)	Observations(2)	No. Dead(1)	Observations(2)	No. Dead(1)	Observations(2)	No. Dead(1)	Observations(2)
Negative control	A	5	0	5 AN	0	5 AN	0	5 AN	0	5 AN	0	5 AN	0
	B	5	0	5 AN	0	5 AN	0	5 AN	0	5 AN	0	5 AN
Solvent control	A	5	0	5 AN	0	5 AN	0	5 AN	0	5 AN	0	5 AN	0
	B	5	0	5 AN	0	5 AN	1 EX	4 AN	1 EX	4 AN	1 EX	4 AN
35	A	5	0	5 AN	0	5 AN	0	5 AN	0	5 AN	0	5 AN	0
	B	5	0	5 AN	0	5 AN	0	5 AN	0	5 AN	0	5 AN
71	A	5	0	5 AN	0	5 AN	0	5 AN	0	5 AN	0	5 AN	0
	B	5	0	5 AN	0	5 AN	0	5 AN	0	5 AN	0	5 AN
151	A	5	0	5 AN	0	1 D; 4 AN	0	1 D; 4 AN	0	1 D; 4 AN	0	1 D; 4 AN	0
	B	5	0	5 AN	0	5 AN	0	5 AN	0	1 C; 4 AN	0	1 C; 4 AN
273	A	5	0	5 AN	0	5 AN	1	1 C; 3 AN	1	1 C; 3 AN	2	3 AN	20
	B	5	0	5 AN	0	5 AN	0	5 AN	0	5 AN	0	1 C; 4 AN
570	A	5	0	5 AN	0	5 AN	5	--	5	--	5	--	100
	B	5	0	5 AN	2	1 C; 2 AN	5	--	5	--	5	--

1) Cumulative number of dead fish. Any mortalities were removed from the test chambers at each observation interval.

2) Observations of surviving organisms: AN = appear normal; D = white mark on head; C = lethargy; EX = escaped from test chamber.

Validity criteria fulfilled:

yes

Remarks:

See 'Any other information on materials and methods incl. tables'

Description of key information

The 96-h LC50 was determined to be 344 μg/L in freshwater species Oncorhynchus mykiss, according to OECD TG 203 and GLP criteria.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

344 µg/L

Additional information

The short-term toxicity to freshwater fish was determined in a study according to OECD TG 203 and in compliance with GLP criteria. In this study, groups of 10 (5 per replicate) rainbow trout (Oncorhynchus mykiss) were exposed for 96 hours to nominal concentrations of0 (blank control), 0 (solvent control), 40, 79, 159, 317 and 634 μg/L under flow-through conditions.Test concentrations were analytically verified at the start and end of the test and determined to be<LOQ (blank control), LOQ (solvent control), 35, 71, 151, 273 and 570 μg/ (mean measured).Incidences of mortality and clinical effects were recorded after approximately 4, 24, 48, 72 and 96 hours exposure. All OECD validity criteria were met.

All fish in the controls and 35 and 71 μg/L treatment groups appeared normal throughout the test, with no mortalities or overt signs of toxicity observed. Percent mortality in the 35, 71, 151, 273 and 570 μg/L treatment groups at test termination was 0, 0, 0, 20 and 100%, respectively. Signs of toxicity observed among the surviving fish in the 151 and 273 μg/L treatment groups at test termination included discoloration and lethargy. Based on these findings, the 96-h LC50 was determined to be 344 μg/L, with a 95% confidence interval of 151 to 570 μg/L.