α-trimethylsilanyl-ω-trimethylsiloxypoly[oxy(methyl-3-(2-(2-methoxypropoxy)propoxy)propylsilanediyl]-co-oxy(dimethylsilane))

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

23 April - 04 June, 2002

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study performed according to GLP.

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2002

Report date:

2002

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

α-trimethylsilanyl-ω-trimethylsiloxypoly[oxy(methyl-3-(2-(2-methoxypropoxy)propoxy)propylsilanediyl]-co-oxy(dimethylsilane))

EC Number:

406-420-4

EC Name:

α-trimethylsilanyl-ω-trimethylsiloxypoly[oxy(methyl-3-(2-(2-methoxypropoxy)propoxy)propylsilanediyl]-co-oxy(dimethylsilane))

Cas Number:

69430-40-6

Molecular formula:

Unspecified example: C18.3H46.8O5.8Si4.1

IUPAC Name:

2,2,4,4,6,12,15-heptamethyl-6-[(trimethylsilyl)oxy]-3,5,10,13,16-pentaoxa-2,4,6-trisilaheptadecane

Details on test material:

- Name of test material (as cited in study report): DOW CORNING 2-5067 Surfactant
- Substance type: Reaction mass (mixture)
- Physical state: Liquid
- Analytical purity: > 99%
- Lot/batch No.: 0000771635
- Expiration date of the lot/batch: December 13, 2003
- Stability under test conditions: Stable
- Storage condition of test material: In the original container at room temperature in the dark
- Other:

Sampling and analysis

Analytical monitoring:

yes

Test solutions

Vehicle:

no

Test organisms

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Study design

Test type:

flow-through

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Results and discussion

Effect concentrations

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

other: Water accomodated fractions used due to poor water solubility of the test substance..

Basis for effect:

growth rate

Remarks on result:

other: n/a

Any other information on results incl. tables

Combined Limit/range-finding test:

The mean cell densities measured during the combined limit/range-finding test are presented in Table 1. Table 2 presents the percentages growth inhibition and growth rate reduction per concentration. No significant treatment related effects on algal growth rate were observed during the test period.

Table 1: Mean cell densities (x 10⁴ cells/ml) during the combined limit/range finding test.

DOW CORNING®   2-5067 SURFACTANT   WAF at x mg/l		Exposure Time (hours)
		0	24	48	72
Blank-control		1.0	2.2	24.5	105.2
0.1*		1.0	2.6	26.0	106.9
1		1.0	3.0	22.2	90.2
10		1.0	2.3	21.8	93.7
100		1.0	2.8	20.8	82.8

* Ten-fold dilution from the WAF prepared at 1 mg/l

Table 2: Percentage reduction of growth rate and inhibition of total growth during

the combined limit/range finding test

DOW CORNING®   2-5067 SURFACTANT   WAF at x mg/l		Cell growth (0 - 72 hrs)		Mean growth rate
		Mean area (A)	Inhibition (%)	µ (0 - 72 hours)	Reduction (%)
Blank-control		1843.54		0.06444
0.1*		1909.57	-3.6	0.06486	-0.7
1		1626.44	11.8	0.06234	3.3
10		1644.35	10.8	0.06306	2.2
100		1493.97	19.0	0.06101	5.3

* Ten-fold dilution from the WAF prepared at 1 mg/l

Analyses of samples taken at the highest tested concentration, being a Water Accomodated Fraction (WAF) prepared at 100 mg/l, did not result in reliable resuIts. As a cansequence, the Analytical (extraction) method was improved. After the extraction procedure was improved, the project was continued with a limit test as no significant effects were expected.

Hence, both the EL₅₀, for cell growth lnhibition and growth rate reduction were expected to be above the concentration reached after preparation of a WAF at a nominal loading of 100 mg/l.

Limit test:

The mean cell densities measured during the limit test are presented in Table 3. Table 4 presents the percentages growth inhibition and growth rate reduction per concentration. Unexpectedly, algal cell growth was more inhibited (46%) than observed during the combined limit/range-finding test (19%). Simultaneously, growth rate was biologically significantly reduced (14%). No clear founded reason for this inconsistency could be given. It was thought that the differences in effects were related to the nature of the test substance, i.e. a mixture with various components with various solublllty limits. Hence, one or more components could have been present in different concentrations when comparing the test solutions in the limit test with those prepared in the combined limit/range-finding test. This problem often rises when testing WAFs. It was decided to continue testing with a range of WAFs prepared at loadings between 5.6 and 56 mg/l in order to be able to define a NOELR.

Analyses of the samples was based on the two major peaks that were observed in the chromatograms. No correlation could be given between the observed peaks and the various test substance components. The measured concentration in the WAF prepared at 100 rng/l corresponded with approximately 20 mg/l at the start and decreased to ca. 10 m/l at the end of the test period (results were comparable for both peaks; see Tables 4 and 5 of the appended Analytical report). Temperalure and pH were maintained within the optimum limits for testing with algae.

Table 3: Mean cell densities (x 10⁴ cells/ml) during the limit test.

DOW CORNING®   2-5067 SURFACTANT   WAF at x mg/l		Exposure Time (hours)
WAF at mg/l	Actual (mg/l)	0	24	48	72
Blank-control		1.0	5.0	37.6	150.2
100	20 - 10	1.0	5.8	22.0	73.7

Actual (mg/l) based on analyses of the two major peaks at t=0 and t= 72 hours

Table 4: Percentage reduction of growth rate and inhibition of total growth during the limit/range test

DOW CORNING®   2-5067 SURFACTANT   WAF at x mg/l		Cell growth (0 - 72 hrs)		Mean growth rate
WAF at mg/l	Actual (mg/l)	Mean area (A)	Inhibition (%)	µ (0 - 72 hours)	Reduction (%)
Blank-control		2763.50		0.06959
100	20 - 10	1493.27	46.0	0.05969	14.2

Actual (mg/l) based on analyses of the two major peaks at t=0 and t= 72 hours

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Remarks:

details see attached study report, p.6

Conclusions:

Under the conditions of the present study wiih Selenastrum capricornutum, no significant reduction of growth rate was recorded at any of the loadings of DOW CORNING(R) 2-5067 SURFACTANT tested. The NOELR equalled a WAF loaded at 100 mg/l.

Executive summary:

Selenastrum capricornutum, Fresh Water Algal Growth Inhibition Test with DOW CORNING(R) 2-5067 SURFACTANT.

The batch of DOW CORN ING(R) 2-5067 SURFACTANT tested was a slightly yellowish coloured liquid. DOW CORNING(R) 2-5067 SURFACTANT is a mixture consisting of at last 9 different components. The test substance was not completely soluble in test medium at the concentrations tested. Owing to the poor solubifity of the test substance and the fact that the test substance was a mixture, it was decided to separately prepare Water Accomodated Fractions (WAFs) at various nominal loadings. A 24-hour magnetic stirring period was followed by phase separation for either 4 or 24 hours. The water fractions were then tested.

A limit test and a range-finding test combined with a limit test were conducted. The initial cell density was 10⁴ cells/ml. The total test period was 72 hours. Samples for determination of actual exposure concentrations were in general taken at the start, after 24 hours and at the end of the test period. Analyses were based on the two major peaks observed in the chromatograms of the DOW CORNING(R) 2 -5067 SURFACTANT mixture. Results are presented in tables 1 - 4 under Results and Discussions.