1,3-diethenyl-1,1,3,3- tetramethyldisiloxane and its platinum(0) complexes

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

documentation insufficient for assessment

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

Rangefinder only

Principles of method if other than guideline:

Rangefinder test for algal study

GLP compliance:

no

Analytical monitoring:

yes

Details on sampling:

- Concentrations: All test concentrations at test start and end
- Sample storage conditions before analysis: Pt samples were acidified with HNO3 (2.5 mL concentrated HNO3, final concentration presumably 10 %) and stored in a refrigerator (about 4°C) until further analysis. Samples for analysis of the organic ligand were analysed on the day of sampling.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: The highest test concentration was prepared by adding 10.01 mg of the test item into 1 L sterile growth medium under sterile conditions to obtain a nominal concentration of 10 mg test item/L. The solution was stirred vigorously using a magnetic stirring bar for about 1 h at room temperature (ca. 20°C). This solution was filtered with a PES filter. An aliquot of the clear test solution was then diluted with sterile growth medium to obtain the other two test concentrations.
- Controls: Sterilised growth medium

Test organisms (species):

other: Raphidocelis subcapitata

Details on test organisms:

TEST ORGANISM
- Source: SAG, Culture Collection of Algae at Pflanzenphysiologisches Institut of the University at Göttingen, Albrecht von Haller Institut, Untere Klarspüle 2, D-37073 Göttingen, Catalog No 61.81 SAG.
- Pre-culture: Prior to testing a pre-culture was established in standard OECD growth medium to obtain exponentially-growing algae for the test. The culture duration of the pre-cultures was 3 days.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

21.5 °C

pH:

Test start: 7.61 (control) 7.60 - 7.75 (treatments)
Test end: 8.03 (control) 8.03 - 8.28 (treatments)

Nominal and measured concentrations:

Nominal concentrations: 0.1, 1 and 10 mg/L
Measured Pt concentrations: Measured organic ligand concentrations:

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 mL conical glass flasks covered with air-permeable silicone-sponge caps
- Initial cells density: 10,000 cells/mL
- No. of vessels per control: 8
- No. of vessels per vehicle control: 4

GROWTH MEDIUM
- Standard medium used: Yes
- Detailed composition: Sterilisied synthetic growth medium according to OECD 201

OTHER TEST CONDITIONS
- Light intensity and quality: 4440 and 8880 lux


EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: Cell concentrations were determined in the inoculum culture prior to the addition to the test vessels at test start and after 24, 48 and 72 h in the test cultures using an electronic particle counter

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 10
- Range finding study
- Test concentrations: 0.1, 1, 10 mg/L

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol tested twice a year

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: Range-finder only

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: yield

Remarks on result:

other: Range-finder only

Details on results:

No significant effects at the highest test concentration

Validity criteria fulfilled:

yes

Conclusions:

At the highest test concentration of 10 mg L-1, no significant effects on growth rate and yield were observed.

Executive summary:

Wenzel (2016) is a non-GLP rangefinder study with Raphidocelis subcapitata. A 72 -hour static study was conducted. Analytical verification of both platinum and the organic ligand showed that platinum was only detected in very low concentrations and the organic ligand was only detected in one sample at test start. At the highest test concentration of 10 mg L-1, no effects on growth rate or yield were observed. As the test item was shown to be very poorly soluble in the range-finder, and it was not possible to get higher amounts of test item into solution following further solubility trials, and no effects were observed at the highest nominal concentration tested, a definitive test was not conducted.

Description of key information

A range-finder study showed no toxicity at nominal concentrations up to 10 mg L^-1(highest concentration tested). Analytical monitoring of both the organic ligand and platinum showed very low concentrations of platinum and the organic ligand could be detected in solution. As the test item is very poorly soluble, and it was not possible to get more of the test item into solution, aquatic toxicity is not expected at the limit of solubility and this was demonstrated in the range-finding study.

Additional information

A range-finder study showed no toxicity at nominal concentrations up to 10 mg L^-1 (highest concentration tested). Analytical monitoring of both the organic ligand and platinum showed very low concentrations of platinum and the organic ligand could be detected in solution. As the test item is very poorly soluble and it was not possible to get more of the test item into solution, aquatic toxicity is not expected at the limit of solubility and this was demonstrated in the range-finding study.

 

Karstedt concentrate was tested in range-finder studies with fish, Daphnia and algae (Eilebrecht 2016, Simon 2016, Wenzel 2016). The highest nominal test concentration used in the range-finders was 10 mg L^-1. The highest concentration test solutions were prepared by adding the test item to test media (20 mg in 2 litres), stirring for one hour and then passing the resulting ‘solution’ through a 0.2 µm PES filter. The filtrate was used directly as the highest test concentration (nominally 10 mg L^-1), while the lower test concentrations were prepared by appropriate dilution of the filtrate. This procedure ensured that only soluble components of the test item were assessed for toxicity. The resulting test solution at the highest concentration used in the range-finder is considered to be at the limit of solubility for the substance. Analytical monitoring of the test solutions was conducted, with both the organic ligand and platinum measured. In the range-finding studies, only very low concentrations of platinum were detected and the organic ligand was present close to or below the LOQ in all samples. No toxicity was observed for fish,Daphniaor algae.

 

As the substance was shown to be poorly soluble in test media and therefore only small amounts of platinum could be detected in the range-finder studies, further solubility trials were conducted in order to determine if it is possible to increase the concentrations of the test item components in solution. Although higher solubility was determined for the test item in a water solubility study, the water solubility result was based on analysis of platinum only, and similar levels of solubility were not observed with ecotoxicity test media. 96-hour solubility trials were conducted using the same media used in the fish andDaphniastudies, adjusted to pH 6, and with three different separation techniques trialled (decanting, filtering and centrifugation). An initial concentration of 4.3 mg L^-1 Karstedt concentrate was used. The test solutions were analysed after 0, 24, 48, 72 and 96 hours. The organic ligand was present close to or below the LOQ in all samples (LOQ 2.16 µg L^-1), suggesting it is highly insoluble and therefore unlikely to be toxic to aquatic organisms. Platinum was detected in the solutions but measured concentrations were low, ranging from 3.90 to 9.43 µg Pt L^-1over the course of the test for filtered and centrifuged solutions. Measured concentrations were higher for the decanted solutions (45.16 µg Pt L^-1at 0 hours to 7.03 µg Pt L^-1at 96 h), however it is believed that this is likely to be due to some of the undissolved test material being included during the decanting phase.

 

Based on the solubility trials, it was not possible to get the organic ligand into solution and only small amounts of platinum were in solution. The platinum concentrations in solution are unlikely to lead to aquatic toxicity. Comparing the measured concentrations of platinum from the filtered and centrifuged solutions against the acute environmental reference values (ERV) for other platinum substances (481 µg L^-1for dihydrogen hexahydroxyplatinate, 117 µg L^-1 for dihydrogen hexahydroxyplatinate, compound with 2-aminoethanol, 108 µg L^-1 for diammonium hexachloroplatinate, 7600 µg L^-1 for tetraammineplatinum hydrogencarbonate, 9750 µg L^-1 for platinum tetraamine diacetate and 20.5 µg L^-1for hexachloroplatinic acid) shows that measured platinum concentrations released from Karstedt concentrate are lower than the ERVs and therefore aquatic toxicity is not expected. The most toxic platinum substance, hexachloroplatinic acid, is expected to release platinum in the form of chloroplatinate anions and, although the exact form of platinum released from Karstedt concentrate is not known, it is not expected to be chloroplatinate. Any platinum released from Karstedt concentrate is therefore likely to be in a less toxic form than that released from hexachloroplatinic acid. However, even comparing the platinum release from the solubility trial against the acute ERV for hexachloroplatinic acid, as a worst case approach, aquatic toxicity from Karstedt concentrate is not expected.

 

Analysis of the organic ligand showed that it was present close to or below the LOQ in all samples, although the fate of the ligand is not clear. The ligand may be very poorly soluble and therefore removed during filtering of the solutions (it appears that solubility of Karstedt concentrate in test media is lower than solubility of the organic ligand alone), it may be strongly adsorbing to the test vessels or filters, although several different methods for preparing the test solutions have been trialled in order to reduce this possibility, or it may hydrolyse leading to breakdown products that are not detected in the analysis. If breakdown products are present these are not considered to contribute to the toxicity of the test item as the breakdown products would also have been present in the range-finder tests in which no toxicity was observed.

 

Based on the results from solubility trials it is concluded that neither the organic ligand nor the platinum component of Karstedt concentrate will enter solution in high enough amounts to lead to aquatic toxicity. This is supported by the results of the range-finder studies conducted with three trophic levels at a highest nominal concentration of 10 mg L^-1. As it is not possible to get more of the test item in solution, conducting definitive ecotoxicity studies is not considered to be necessary. To conclude on environmental classification, the standard approach would be to test up to a nominal concentration of 100 mg L^-1. However, for this substance testing at a nominal concentration of 100 mg L^-1 is considered to be unnecessary, as the limit of solubility appears to have been reached at the nominal concentration of 10 mg L^-1, and testing at higher concentrations would not lead to additional test item in solution. As no toxicity was observed at the limit of solubility in the range-finder studies, neither an acute or chronic environmental classification is considered to be required for the substance.