Isooctadecanoic acid, mixed esters with oxybis[propanediol]

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Refer to the Analogue Approach Justification document provided in Section 13

Reason / purpose for cross-reference:

read-across source

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 250 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

based on nominal loading rate (WAF)

Basis for effect:

growth rate

Remarks on result:

other: Source: CAS 67938-21-0

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

> 250 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

based on nominal loading rate (WAF)

Basis for effect:

growth rate

Remarks on result:

other: Source: CAS 67938-21-0

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 250 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

based on nominal loading rate (WAF)

Basis for effect:

other: yield

Remarks on result:

other: Source: CAS 67938-21-0

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

> 250 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

based on nominal loading rate (WAF)

Basis for effect:

other: yield

Remarks on result:

other: Source: CAS 67938-21-0

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

11 Jan - 31 Jan 2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

GLP guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

2006

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Staatliches Gewerbeaufsichtsamt, Hildesheim, Germany

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Five water accommodated fractions (WAF): 6.40 - 16.0 - 40.0 - 100 - 250 mg/L
- Sampling method: All test item loadings and the control were analytically verified via analysis of organic carbon (TOC, according to DIN EN 1484) at the start and at the end of the test. Separate replicates for the test item analysis after 0 and 72 hours were prepared without algae and incubated under test conditions.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Five water accommodated fractions (WAF) were prepared with nominal loadings of the test item in the range of 6.40 to 250 mg/L set up in a geometric series with a factor of 2.5: 6.40 - 16.0 - 40.0 - 100 - 250 mg/L. For each loading level, an appropriate amount of the test item was weighed out. The test item was applied onto a glass slide. The glass slide with the test item was inserted in a brown glass flask with an appropriate amount of dilution water. These dispersions were stirred for at least 72 hours with 1100 rpm at room temperature. After a separation phase of 1 hour, the aqueous phase or WAF was removed by siphoning (from the approximate centre of the glass flask) to give the loading rate WAF.
- Controls: Six replicates (without test item) were tested under the same test conditions as the test vessels.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Common name: Freshwater algae
- Strain: SAG 86.61
- Source (laboratory, culture collection): SAG Pflanzenphysiologisches Institut der Universitaet Goettingen, Nikolausberger Weg 18, D-37073 Goettingen, Germany
- Age of inoculum (at test initiation): 3 days
- Method of cultivation: Fresh stocks were prepared every month on Z-Agar. Light intensity amounted to 35 - 70 μE x m-2 x s-1 for 24 h per day.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

0.24 mmol Ca+Mg/l

Test temperature:

min.: 21.5 max.: 22.5, mean value: 22.0

pH:

at test start: 7.58 - 8.10
at test end: 7.92 - 8.21

Nominal and measured concentrations:

nominal (WAF): control, 6.40, 16.0, 40.0, 100 and 250 mg/L
measured at test start: < 2.00, < 2.00, < 2.00, 11.8. 5.38 and 3.38 mg/L
measured at test end: < 2.00, < 2.00, < 2.00, 7.62, 3.04 and 2.45 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 mL Erlenmeyer flasks
- Type: open, cotton wool plugs
- Material, size, headspace, fill volume: sterile 250 mL Erlenmeyer flasks, test volume 100 mL
- Aeration: Test containers were placed on a rotary shaker and oscillated at appr. 70 rpm
- Initial cells density: Nominal: approximately 2 - 5 x 103 cells/mL, Actual: mean 4910 cells/mL
- Control end cells density: Mean 776146 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
Composition of Dilution Water according to the guideline
Component Concentration [mg/L]
NH4Cl 15
MgCl2 x 6 H2O 12
CaCl2 x 2 H2O 18
MgSO4 x 7 H2O 15
KH2PO4 1.6
FeCl3 x 6 H2O 0.064
Na2EDTA x 2 H2O 0.1
H3BO3 0.185
MnCl2 x 4 H2O 0.415
ZnCl2 3 x 10-3
Na2MoO4 x 2 H2O 7 x 10-3
CoCl2 x 6 H2O 1.5 x 10-3
CuCl2 x 2 H2O 1 x 10-5
NaHCO3 50

pH 8.1 +/- 0.2

OTHER TEST CONDITIONS
- Photoperiod: 24 h light
- Light intensity and quality: 60 - 120 μE x m-2 x s-1, mean value: 67.9

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: fluorimeter, Cell density and self fluorescence was measured daily via Chlorophyll-a- fluorescence, excitation at 436 nm, emission at 685 nm. Dilution water was used as background signal.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2.5
- Test concentrations of the range findign study: 2.56, 6.40, 16.0, 40.0 and 100 mg/L
- Results used to determine the conditions for the definitive study: 12% growth inhibition at the highest loading rate; 3% growth increase at the lowest loading rate

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 250 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

based on nominal loading rate (WAF)

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

> 250 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

based on nominal loading rate (WAF)

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 250 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

based on nominal loading rate (WAF)

Basis for effect:

other: yield

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

> 250 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

based on nominal loading rate (WAF)

Basis for effect:

other: yield

Details on results:

- Exponential growth in the control (for algal test): yes

Results with reference substance (positive control):

- Results with reference substance valid? yes
- EC50, based on growth rate: 0.631 mg/L (95% CI = 0.583 - 0.687 mg/L)
- EC50, based on yield: 0.256 mg/L (95% CI = 0.247 - 0.265 mg/L)

Table 1: Cell densities

Nominal test item loading rate [mg/L]	Replicate No.	Cell density [cells/mL]
		0 h	24 h	48 h	72 h
250	1	4332	23013	157619	939592
	2	4332	18364	136654	1105931
	3	4332	18154	133698	936981
	Mean	4332	19844	142657	994168
100	1	4332	18588	115727	725323
	2	4332	13968	142076	894964
	3	4332	14072	133232	755452
	Mean	4332	15543	130345	791913
40.0	1	4332	16742	136862	642515
	2	4332	15691	123124	737117
	3	4332	16327	101418	619273
	Mean	4332	16253	120468	666302
16.0	1	4332	20207	87542	527251
	2	4332	14537	139567	306894
	3	4332	11615	111356	553165
	Mean	4332	15453	112822	561437
6.40	1	4332	17824	145863	1013719
	2	4332	23859	147265	1128984
	3	4332	19078	126974	999630
	Mean	4332	20254	140034	1047444
Control	1	4332	21047	138579	836970
	2	4332	18305	146360	815427
	3	4332	21201	127433	860479
	4	4332	15122	127622	663461
	5	4332	19591	128075	780109
	6	4332	13845	128741	700430
	Control	4332	18185	132802	776146

Table 2: Validity criteria

Criterion from the guideline	Outcome	Validity criterion fulfilled
The biomass in the control cultures should have increased exponentially by a factor of at least 16 within the 72-hour test period.	factor of 179	yes
The mean coefficient of variation for section-by-section specific growth rates (days 0-1, 1-2 and 2-3, for 72-hour tests) in the control cultures must not exceed 35%	17.6%	yes
The coefficient of variation of average specific growth rates during the whole test period in replicate control cultures must not exceed 7% in tests with Pseudokirchneriella subcapitata and Desmodesmus subspicatus. For other less frequently tested species, the value should not exceed 10%.	2.00%	yes

Additional information

Since no studies investigating the toxicity of Isooctadecanoic acid, mixed esters with oxybis[propanediol] to algae are available, in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5, a read-across to the structurally related source substance Di(isooctadecanoic) acid, diester with oxydi(propanediol) (CAS 67938-21-0) was conducted. The source substance is representative to evaluate the toxicity of the target substance to algae.

The target substance Isooctadecanoic acid, mixed esters with oxybis[propanediol] exists as two different grades. Grade One is characterized by mainly triesters of C18 iso fatty acids of the alcohol component diglycerol. Grade Two is characterized by mainly tetraesters of C18 iso fatty acids of the alcohol component diglycerol.

The source substance Di(isooctadecanoic) acid, diester with oxydi(propanediol) (CAS 67938-21-0) is characterized by the alcohol component diglycerol which is esterified by C18 iso fatty acids and consists only of diesters.

This read-across is justified in detail in the analogue justification in IUCLID section 13. In this case of read-across, the best suited (highest degree of structural similarity, nearest physico-chemical properties) read-across substance was used for the assessment.

The study with the source substance Di(isooctadecanoic) acid, diester with oxydi(propanediol) (CAS 67938-21-0) was performed according to OECD 201. Due to the low water solubility of the test material, WAFs ("water accommodated fractions") prepared with algae test medium were used to prepare the five test material loading rates. The test was performed under GLP conditions. Algae (Desmodesmus subspicatus) were exposed to five different loading rates (6.40, 16.0, 40.0, 100 and 250 mg/L) over a period of 72 h in a static freshwater system. After 72 h, the effects of the test material on algae growth rate and yield was assessed.The NOEC and EL₅₀(72 h) for growth rate and yield were determined at > 250 mg/L based on nominal loading rates.

Based on the results for the structurally related read-across substance (in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5) which is characterized by a similar ecotoxicological profile and comparable structure, it can be concluded that no toxicity of Isooctadecanoic acid, mixed esters with oxybis[propanediol] to algae is expected up to the limit of the water solubility (< 0.15 mg/L).