Docusate sodium

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

10 to 13 November 1992

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

This GLP study is considered to be acceptable for the risk assessment despite the shortcomings in the reported documentation. Major criticism points are the lack of individual temperature measurement data and the lack of the calibration curve used to calculate the cell density.

Qualifier:

according to guideline

Guideline:

other: EWG 88/302

Deviations:

yes

Remarks:

lack of individual temperature measurement data and the lack of the calibration curve used to calculate the cell density.

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

yes

Remarks:

lack of individual temperature measurement data and the lack of the calibration curve used to calculate the cell density.

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: a stock solution with 1 g/L test material was prepared in deionized water
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): not applicable
- Concentration of vehicle in test medium (stock solution and final test solution(s) including control(s)): not applicable

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Common name: Scenedesmus subspicatus (new name: Desmodesmus subspicatus)
- Strain: SAG 86.81
- Source (laboratory, culture collection): Institut für Wasser-, Boden- und Lufthygiene, Berlin, Germany, thereafter own culture.
- Age of inoculum (at test initiation): 3 days
- Method of cultivation: static

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

not provided

Test temperature:

The temperature was 24 +/- 2°C, however, temperature readings for individual time intervals were not provided.

pH:

See table 2

Nominal and measured concentrations:

Nonimal concentrations: 0 (control), 10, 17, 30, 50, 90 and 150 mg SERWET WH 170/L corresponding to 0 (control), 6.42, 10.91, 19.26, 32.10, 57.78 and 96.30 mg Docusate Sodium/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer flasks
- Type (delete if not applicable): closed, but allowing air exchange under sterile conditions.
- Aeration: the stopper allowed air exchange
- Type of flow-through (e.g. peristaltic or proportional diluter): not applicable
- Renewal rate of test solution (frequency/flow rate): static test and hence no renewal
- Initial cells density: 20'000 cells/mL
- Control end cells density: 910'000 cells/mL
- No. of vessels per concentration (replicates): 5
- No. of vessels per control (replicates): 8
- No. of vessels per vehicle control (replicates): not applicable


GROWTH MEDIUM
- Standard medium used: yes (medium according to EWG 88/302)


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: medium according to EWG 88/302
- Intervals of water quality measurement: the pH was measured at start and the end of the exposure.


OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: no
- Photoperiod: not provided
- Light intensity and quality: about 8'000 lux, white


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: spectrophotometer at 685 nm, the photometer readings were subsequently converted to cell density using an established calibration curve (not provided in the report), measurements were performed at 24, 48 and 72 hours


TEST CONCENTRATIONS
- Spacing factor for test concentrations: about 1.7

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

12.4 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

19.3 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

39.3 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

61.2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

22 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

34.3 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

82.5 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

128.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

- Exponential growth in the control (for algal test): yes
- Any stimulation of growth found in any treatment: no
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: no information provided
- Effect concentrations exceeding solubility of substance in test medium: a stock solution was prepared with 1 g/L and no insolubility was reported. Therefore, it is highly likely that the test material was water soluble at the concentration levels tested.

Reported statistics and error estimates:

The EC-values were calculated with probit transformed (%) inhibition values. These values were subsequently used for probit analysis according to Cavalli-Sforza (1972).

Table 2 pH-values at the start and end of the exposure

SERWET WH 170	pH	pH
mg/L	start of exposure	end of exposure
0	8.9	9.5
10	8.8	9.6
17	8.8	9.5
30	8.7	9.4
50	8.5	9.2
90	8.5	9.3
150	8.6	7.8

Table 3 Cell densities in 10^4 cells/mL at the individual observation intervals (the test was started with 2*10^4 cells/mL)

SERWET WH 170	replicate	24 hours	48 hours	72 hours
mg/L
0	1	7	28	94
	2	7	28	101
	3	8	33	89
	4	8	31	91
	5	7	30	88
	6	7	30	90
	7	7	31	92
	8	7	28	85
	mean	7.25	29.875	91.25
	SD	0.46	1.81	4.77
10	1	7	27	82
	2	7	30	89
	3	7	30	87
	4	8	26	95
	5	7	27	89
	mean	7.2	28	88.4
	SD	0.45	1.87	4.67
17	1	7	29	80
	2	7	29	81
	3	7	30	84
	4	8	30	83
	5	7	29	86
	mean	7.2	29.4	82.8
	SD	0.45	0.55	2.39
30	1	7	24	73
	2	7	25	69
	3	8	28	68
	4	7	26	70
	5	7	26	74
	mean	7.2	25.8	70.8
	SD	0.45	1.48	2.59
50	1	7	22	48
	2	7	21	48
	3	7	19	45
	4	7	23	51
	5	7	24	57
	mean	7	21.8	49.8
	SD	0.00	1.92	4.55
90	1	6	10	16
	2	6	11	17
	3	6	11	18
	4	6	13	19
	5	6	12	19
	mean	6	11.4	17.8
	SD	0.00	1.14	1.30
150	1	5	7	7
	2	5	7	10
	3	4	7	8
	4	5	7	13
	5	5	8	24
	mean	4.8	7.2	12.4
	SD	0.45	0.45	6.88

Table 4 Areas under the growth curves (AUC), growth rates and corresponding % inhibition

SERWET WH 170	AUC	% inhibition of AUC
mg/L
0	77.5	-
10	74.0	4.5
17	72.5	6.5
30	63.5	18.1
50	49.0	36.8
90	21	72.9
150	13	83.2
SERWET WH 170	growth rate	% inhibition of growth rate
mg/L
0	1.273	-
10	1.3	0.9
17	1.2	2.4
30	1.2	6.5
50	1.1	15.7
90	0.732	42.5
150	0.597	53.1

Table 5 72-hour ECx-values based on SERWET WH 170 and Docusate Sodium

Parameter	based on SERWET WH 170	based on Docusate Sodium
	mg/L	mg /L
AUC
EbC10	19.3	12.4
EbC50	61.2	39.3
EbC90	-*	-*
Growth rate
ErC10	34.3	22.0
ErC50	128 .5	82.5
ErC90	-*	-*

* the EbC90 and ErC90 are significantly higher than the highest tested concentration and were therefore not calculated

Executive summary:

The growth inhibition of SERWET WH 170 (which contains 64.2% Docusate Sodium) to Scenedesmus subspicatius was determined in a 72 h static GLP algae growth inhibition test. The test design was based on the EWG 88/302 guideline which is similar to the EEC C.1 guideline. The nominal test concentrations were 0 (control), 10, 17, 30, 50, 90 and 150 mg SERWET WH 170/L, corresponding to 0 (control), 6.42, 10.91, 19.26, 32.10, 57.78 and 96.30 mg Docusate Sodium/L. Eight control replicates and 5 replicates from each test solution were set up. Dose verification analysis was not performed. In order to determine the growth of the cultures, the optical density was measured by photometry at 685 nm. The cell density was calculated using an calibration curve (not provided in the report). The cell density was determined at 0, 24, 48 and 72 hours. The growth of the control cultures fulfilled the validity criteria from OECD 201 (2006). The 72 -hour ErC10 and ErC50 are 22 and 82.5 mg Docusate Sodium/L based on the nominal concentration.

This study is considered to be acceptable for the risk assessment despite minor shortcomings in the reported documentation. Minor criticism points are the lack of individual temperature measurement data and the lack of the calibration curve used to calculate the cell density.

Description of key information

ErC10 freshwater algae = 22 mg Docusate Sodium/L

ErC50 freshwater algae = 82.5 mg Docusate Sodium/L

Key value for chemical safety assessment

EC50 for freshwater algae:

82.5 mg/L

EC10 or NOEC for freshwater algae:

22 mg/L

Additional information

For the data endpoint “Toxicity to aquatic algae and cyanobacteria” 2 experimental studies are available: 1 Klimisch 2 key-study and 1 disregarded Klimisch 3 study.

The study from Elementis (Scholz 1993) was classified as Klimisch 2 key study. In this study the growth inhibition of formulated product (which contains 64.2% Docusate Sodium) to Scenedesmus subspicatius was determined in a 72 h static GLP algae growth inhibition test. The test design was based on the EWG 88/302 guideline which is similar to the EEC C.1 guideline. The nominal test concentrations were 0 (control), 10, 17, 30, 50, 90 and 150 mg formulated product/L, corresponding to 0 (control), 6.42, 10.91, 19.26, 32.10, 57.78 and 96.30 mg Docusate Sodium/L. Eight control replicates and 5 replicates from each test solution were set up. Dose verification analysis was not performed. In order to determine the growth of the cultures, the optical density was measured by photometry at 685 nm. The cell density was calculated using a calibration curve (not provided in the report). The cell density was determined at 0, 24, 48 and 72 hours. The growth of the control cultures fulfilled the validity criteria from OECD 201 (2006). The 72 -hour ErC10 and ErC50 are 22 and 82.5 mg Docusate Sodium/L based on the nominal concentration. This study is considered to be acceptable for the risk assessment despite minor shortcomings in the reported documentation. Criticism points are the lack of individual temperature measurement data and the lack of the calibration curve used to calculate the cell density.

In addition to the Klimisch 2 study, there is one Klimisch 3 study for toxicity to aquatic algae and cyanobacteria available. Due to the poor reliability of this study, it is disregarded and not discussed here.

The ErC50 value of the key study from Elementis (Scholz 1993) is 82.5 mg Docusate Sodium/L. The ErC50 value of the disregarded study from Cognis (Rieche 1994), i. e., 127 mg Docusate Sodium/L, is considered to be less reliable since the validity criteria of the OECD 201 (2006) were not met. Furthermore, the results of the key study are more protective than the results from the disregarded study. The ErC10 and ErC50 of 22 and 82.5 mg Docusate Sodium/L, respectively, are considered to be reliable and will be used for the further risk assessment of Docusate Sodium.