Yttrium chloride hexahydrate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

3 August 2017 - 28 March 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))

Deviations:

yes

Remarks:

In some instances, the initial and final dissolved oxygen concentrations were outside those recommended in the test guidelines. This was not considered to have affected the results and interpretation of the study.

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Test water: The water used for the test was deionised reverse osmosis water containing less than 1 mg/L Dissolved Organic Carbon.
- Method: Nominal amounts of test item (77, 138.6, 246.4, 431.2 and 770 mg (triplicate replicates of each )) were each separately dispersed in approximately 200 mL of deionised reverse osmosis water and subjected to ultrasonication for approximately 15 minutes followed by magnetic stirring for 24 hours, at room temperature, in order to maximise the dissolved test item concentration. All test vessels were shielded from the light during mixing. Synthetic sewage (16 mL), activated sewage sludge (250 mL) and water were added to a final volume of 500 mL to give the required concentrations of 100, 180, 320, 560 and 1000 mg anhydrous YCl3/L (3 replicates of each).

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Name and location of sewage treatment plant where inoculum was collected: Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK (aeration stage)
- The activated sewage sludge sample was maintained on continuous aeration in the laboratory at a temperature of approximately 21ºC overnight prior to use in the test.
- On the day of collection the activated sewage sludge (12.6 liters) was fed synthetic sewage (630 mL).
- Determination of the suspended solids level of the activated sewage sludge was carried out by filtering a sample (100 mL) of the activated sewage sludge by suction through a pre-weighed GF/A filter paper (rinsed three times with 20 mL deionised reverse osmosis water prior to drying in an oven) using a Buchner funnel which was then rinsed 3 times with 10 mL of deionised reverse osmosis water and filtration continued for 3 minutes. The filter paper was then dried in an oven at approximately 105ºC for at least one hour and allowed to cool before weighing. This process was repeated until a constant weight was attained.
- Initial biomass concentration: 3.0 g/L

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Hardness:

cannot be determined based on the available information

Test temperature:

20-21°C

pH:

7.1 - 7.9 (after 0 hours exposure)
7.3 - 8.4 (after 3 hours exposure)

Dissolved oxygen:

The dissolved oxygen concentrations after 30 minutes contact time in all vessels were above 60% of the dissolved oxygen saturation level of 8.9 mg O2/L (i.e. 5.68-8.46 mg/L).
Dissolved oxygen concentrations after 3 h of exposure ranged from 4.2 to 8.9 mg/L.
Final readings (for determination of oxygen consumption rate) ranged from 1.7 to 6.7 mg/L.
In some instances, the initial and final dissolved oxygen concentrations were outside those recommended in the test guideline (7 mg O2/L and 2 mg O2/L respectively). This was considered to have had no adverse effect on the results of the study given that in all cases the oxygen consumption rate was determined over the linear portion of the oxygen consumption trace.

Salinity:

not applicable

Nominal and measured concentrations:

Nominal test concentrations:
- Range finder: Control + 10, 100 and 1000 mg YCl3/L.
- Definitive test: Control + 100, 180, 320, 560 and 1000 mg YCl3/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 500-mL conical flasks containing 500 mL of incubation mixture
- No. of vessels per concentration (replicates): 3
- No. of vessels per blank control (replicates): 6
- Dry matter in the test: 3 g suspended solids/L

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: deionised reverse osmosis water containing < 1 mg/L DOC

OTHER TEST CONDITIONS
- Adjustment of pH: The pH of test item stock solutions and test solutions was adjusted to between 7.0 and 8.0 if necessary.
- Photoperiod: normal laboratory lighting

EFFECT PARAMETERS MEASURED
- After 3 hours contact time, an aliquot was removed from each flask and poured into the measuring vessel (250-mL darkened glass Biological Oxygen Demand (BOD) bottle) and the rate of respiration measured using a Yellow Springs dissolved oxygen meter fitted with a BOD probe.
- The contents of the measuring vessel were stirred constantly by magnetic stirrer.
- The rate of respiration for each flask was measured over the linear portion of the oxygen consumption trace (where possible between 7 mg O2/L and 2 mg O2/L). In the case of a rapid oxygen consumption, measurements may have been outside this range but the oxygen consumption was always within the linear portion of the respiration curve. In the case of low oxygen consumption, the rate was determined over an approximate 10 minute period.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 1.8
- Range finding study: yes, control + 10, 100 and 1000 mg YCl3/L
- Results used to determine the conditions for the definitive study: significant inhibition (86-89%) observed at 1000 mg YCl3/L

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

470 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr. (total fraction)

Remarks:

yttrium trichloride anhydrous

Basis for effect:

inhibition of total respiration

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

214 mg/L

Nominal / measured:

nominal

Conc. based on:

element (total fraction)

Basis for effect:

inhibition of total respiration

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

180 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr. (total fraction)

Remarks:

yttrium trichloride anhydrous

Basis for effect:

inhibition of total respiration

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

82 mg/L

Nominal / measured:

nominal

Conc. based on:

element (total fraction)

Basis for effect:

inhibition of total respiration

Results with reference substance (positive control):

The following results were obtained:

3-h EC10 = 0.82 mg/L
3-h EC20 = 1.3 mg/L
3-h EC50 = 5.6 mg/L (95% Confidence Limits 4.1-7.7 mg/L)
3-h EC80 = 24 mg/L

The validation criterion for the reference item EC50 value was fulfilled.

Reported statistics and error estimates:

In order to determine the NOEC, one way analysis of variance incorporating Bartlett's test for homogeneity of variance (Sokal and Rohlf, 1981) and Dunnett's multiple comparison procedure for comparing several treatments with a control (Dunnett, 1955) was carried out on the oxygen consumption data after 3 hours for the control and all test concentrations to determine any statistically significant differences between the test and control groups. All statistical analyses were performed using the SAS computer software package (SAS, 1999 - 2001).

Validity criteria fulfilled:

yes

Conclusions:

This activated sludge respiration inhibition test with yttrium trichloride yielded a NOEC and EC50 of 180 and 470 mg YCl3/L, respectively, corresponding to a NOEC and EC50 of 82 and 214 mg Y/L.

Description of key information

The key study from Bayliss (2018) yielded a 3-h EC50 and NOEC of 470 and 180 mg YCl3/L, respectively, which is equivalent to 214 and 82 mg Y/L, respectively.

Key value for chemical safety assessment

EC50 for microorganisms:

470 mg/L

EC10 or NOEC for microorganisms:

180 mg/L

Additional information

Bayliss (2018) performed an activated sludge respiration inhibition test with yttrium trichloride according to OECD guideline 209 and conform GLP requirements. In this study, a 3-h EC50 and NOEC of 470 and 180 mg YCl3/L were obtained, respectively, which is equivalent to 214 and 82 mg Y/L, respectively. This study is considered reliable without restrictions (Klimisch 1).