3-[3-(1,1,1,3,5,5,5-heptamethyltrisiloxan-3-yl)propoxy]propane-1,2-diol

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:

16 June- 03 July 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study was performed according to OECD Guidelines and in compliance with GLP principles.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2015

Report date:

2015

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

other: Guidance document on aquatic toxicity testing of difficult substances and mixtures, OECD series on testing and assessment number 23, December 14, 2000.

Deviations:

no

Test guideline 4

Qualifier:

according to guideline

Guideline:

other: Food and Agricultural Materials Inspection Centre (FAMIC), 12 Nousan, Notification No 9147, April 2011.

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

3-[3-(1,1,1,3,5,5,5-heptamethyltrisiloxan-3-yl)propoxy]propane-1,2-diol

EC Number:

807-413-2

Cas Number:

70280-68-1

Molecular formula:

C13H34O5Si3

IUPAC Name:

3-[3-(1,1,1,3,5,5,5-heptamethyltrisiloxan-3-yl)propoxy]propane-1,2-diol

Test material form:

other: Liquid

Details on test material:

- Name (as cited in study report): X-22-1927
- Appearance: clear light yellow liquid
- Storage conditions: at room temperature

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

15 mL samples were taken from all test concentrations and the control at t=0 h, t=24h and t=72 h and were analyzed on the day of sampling.

Test solutions

Vehicle:

no

Details on test solutions:

Individual loading rates ranging from 1.0 to 100 mg/L were prepared. A two-day period of magnetic stirring was applied and followed by an one-hour settlement period. The aqueous Water Accommodated Fractions (WAFs) were siphoned off and were used as test concentrations. The final test solutions were all clear and colourless. After preparation, volumes of 50 mL were added to each replicate of the respective test concentration. Subsequently, 1 mL of an algal suspension was added to each replicate providing a cell density of 10^4 cells/mL.

Test organisms

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata
- Strain: NIVA CHL 1
- Source (laboratory, culture collection): In-house laboratory culture.
- Method of cultivation: Algae stock cultures were started by inoculating growth medium with algal cells from a pure culture on agar. The suspensions were continuously aerated and exposed to light in a climate room at a temperature of 21-24°C.

ACCLIMATION
- Acclimation period: 4 days before the start of the test, cells from the algal stock culture were inoculated in culture medium at a cell density of 1 x 10^4 cells/ml. The pre-culture was maintained under the same conditions as used in the test.
- Culturing media and conditions (same as test or not): yes

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test conditions

Hardness:

24 mg CaCO3/L

Test temperature:

between 22 and 24°C

pH:

8.0-8.2

Dissolved oxygen:

Not measured.

Salinity:

Not applicable.

Nominal and measured concentrations:

WAFs prepared at a loading rate of 1.0, 3.2, 10, 32 and 100 mg/L.
At the start of the test concentrations were below nominal (18 – 73% of nominal), except for the loading rate of 3.2 mg/L which was within nominal (88% of nominal). Stability of the samples varied between the concentrations (68 – 112% of initial, 14 – 81% of nominal). Based on these results, the TWA concentrations were calculated (see table in results below).

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Material, size, headspace, fill volume: 100 mL, all-glass, containing 50 mL of test solution
- Aeration: no
- Initial cells density: 1 x 10^4 cells/mL.
- Control end cells density: 83 x 10^4 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Culture medium different from test medium: stock culture medium was M1, pre-culture medium was M2

OTHER TEST CONDITIONS
- Adjustment of pH: no data
- Photoperiod: Continuously
- Light intensity and quality: TLD-lamps with a light intensity within the range of 79 to 91 μE.m^-2.s^-1

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: At the beginning of the test, cells were counted using a microscope and a counting chamber. Thereafter cell densities were determined by spectrophotometric measurement of samples at 720 nm using a spectrophotometer with immersion probe (pathlength =20 mm). Algal medium was used as blank.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.2
- Limit/Range finding study
- Test concentrations: Three replicates per concentration were exposed to WAFs prepared at a loading rate of 1.0 and 10 mg/L.
- Results used to determine the conditions for the definitive study: The inhibition of growth rate increased with increasing loading rate ranging from 2% at 1.0 mg/L to 16% at 100 mg/L.

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 17 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 2

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

7.2 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 3

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

9.9 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 8.8-11 mg/L

Details on results:

Growth rates were in the range of the controls at the TWA concentrations from 0.63 to 7.2 mg/L during the 72-hour test period. Statistically significant inhibition of growth rate was found at test concentrations of 2.5 mg/L and higher however it should be noted that the effects up to a concentration of 7.2 mg/L were below 10% and therefore considered not biologically relevant.
Although the procedural recoveries of the analytical method were mostly outside the range of 70-110%, the effect concentrations are located in the range of the 10 mg/L procedural samples which were in line with the range of the criteria or which gave a slight overestimation of the concentration and thus are considered worst-case.

Results with reference substance (positive control):

The EC50 for growth rate inhibition (72h-ErC50) was 1.3 mg/L with a 95% confidence interval ranging from 1.2 to 1.5 mg/L. The historical ranges for growth rate inhibition lie between 0.82 and 2.3 mg/L. Hence, the 72h-ErC50 for the algal culture tested corresponds with this range.

Any other information on results incl. tables

Measured concentrations versus nominal concentrations

X-22-1927 WAF prepared at (mg/l)	Measured concentration (mg/l)			TWA (mg/l)
	t=0h	t=24h	t=72 h
1.0	0.713	0.649	0.561	0.63
3.2	2.81	2.93	1.90	2.5
10	7.27	8.13	5.87	7.2
32	9.94	9.80	8.34	9.3
100	17.9	17.9	14.2	17

 

Percentage inhibition of growth rate (total test period) during the final test

X-22-1927 TWA Concentration (mg/l)	Mean	Std. Dev.	n	%Inhibition
Control	1.473	0.0309	6
0.63	1.488	0.0110	3	-1.0
2.5	1.436	0.0193	3	2.5*^#
7.2	1.388	0.0144	3	5.7*^#
9.3	1.286	0.0290	3	12.7*
17	1.266	0.0200	3	14.1*

* - effect was statistically significant

^#- effect biologically insignificant (<10%)

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The 72h- ErC50 of > 17 mg/L and a 72h- ErC10 of 9.9 mg/L based on TWA measured concentrations.

Executive summary:

Toxicity of the test substance to fresh water algae was investigated in the algae growth inhibition test according to OECD 201 Guidelines and GLP principles. The test substance showed an 72h- ErC50 of > 17 mg/L and a 72h- ErC10 of 9.9 mg/L based on TWA measured concentrations.