Docusate sodium

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

24 - 26 November 1992

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

GLP and in general guideline compliant study, minor shortcommings were: dose-verification analysis not performed, actual temperature readings not provided. Based on information provided in the endpoint summary, this study is considered to be supporting.

Qualifier:

according to guideline

Guideline:

other: EG 84/449, Nov 1989

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Deviations:

yes

Remarks:

no dose verification analysis, test conducted in darkness

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 SERWET WH 170/L was prepared. The stock solution was used to prepare the test solutions.
- Controls: blank control
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): no vehicle used
- Concentration of vehicle in test medium (stock solution and final test solution): not applicable

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water flea, Daphnia magna Straus
- Strain: Klon 5 (="clone 5")
- Source: "own culture" (eigene Zucht),
- Age at study initiation (mean and range, SD): younger than about 24 hours
- Method of breeding: the parent animals are cultured in 1 L beakers in Elendt M4 medium every 2 -3 days, the water was exchanged and the juveniles are removed. Every 4 weeks the culture was started with new offspring. The culture conditions provided pathogenetic reproduction.
- Feeding during test: the test animals were not fed during the test.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

not provided, but the sum of Ca2+ and Mg2+ ions was 2.5 mmol.

Test temperature:

The test temperature was not reported, but the target water temperature was provided as 20 +/- 1°C. Since it was not stated that this target was not reached, it can be assumend that the actual water temperature was within the target range.

pH:

see table 1

Dissolved oxygen:

see table 1

Nominal and measured concentrations:

Nonimal concentrations: 0 (control), 2.5, 3.5, 5.0, 7.0, 10, 14, 20, 28 and 40 mg SERWET EWH 170/L corresponding to 0 (control), 1.61, 2.25, 3.21, 4.49, 6.42, 8.99.12.84, 17.98 and 25.68 mg Docusate Sodium/L

Details on test conditions:

TEST SYSTEM
- Test vessel: glass vessels with rounded bottom
- Type (delete if not applicable): not provided
- Material, size, headspace, fill volume: glass vessels with rounded bottom, filled with 10 mL test solution.
- Aeration: none
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- No. of vessels per vehicle control (replicates): NA
- Biomass loading rate: 2 mL per test organism


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: synthetic test medium prepared with following amounts of salts:
CaCl2*2 H2O: 294 mg/L
MgSO4*7 H2O: 123 mg/L
NaHCO3: 63 mg/L
KCl: 5.5 mg/L

- Ca/Mg ratio: 4:1
- Culture medium different from test medium: Yes, the parents were cultured in Elendt M4 medium, the test was performed with the above mentioned test solution.
- Intervals of water quality measurement: water quality parameters were determined at the end of the exposure


OTHER TEST CONDITIONS
- Photoperiod: the test was performed in darkness
- Light intensity: NA


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Immobilization at 24 and 48 hours


TEST CONCENTRATIONS
- Spacing factor for test concentrations: 1.4
- Justification for using less concentrations than requested by guideline: NA

Reference substance (positive control):

yes

Remarks:

Potasium dichromate, the test was performed as separate 24 h test

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

24.8 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: immobilization

Remarks on result:

other: 95% CI: 14.2 - 43.7 mg/L

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

38.7 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: immobilization

Remarks on result:

other: 95% CI: 22.1 - 68.0 mg/L

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

6.6 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: immobilization

Remarks on result:

other: 95% CI: 5.3 - 8.2 mg/L

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

10.3 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: immobilization

Remarks on result:

other: 95% CI: 8.3 - 12.8 mg/L

Details on results:

- Behavioural abnormalities: not reported
- Observations on body length and weight: not provided
- Other biological observations: not provided
- Mortality of control: 5% (immobilization)
- Other adverse effects control: not reported
- Abnormal responses: not reported
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: The concentration dependent decline of the dissolved oxygen concentration may indicate biodegradation of the test material during the test.
- Effect concentrations exceeding solubility of substance in test medium: A 1.0 g/L stock solution was prepared and no insolubility was reported. Therefore, the concentrations of the test solutions are likely below the limit of water solubility.

Results with reference substance (positive control):

- Results with reference substance valid? The reference test was performed as separate 24 hour test on 29 September 1992. No detailed test information provided and hence the validity cannot be assessed.
- Mortality: 5% immobilization at 0.9 mg/L and 95% immobilization at 1.9 mg/L
- EC50/LC50: not provided
- Other:

Reported statistics and error estimates:

Probit analysis according to Cavalli-Sforza (1972)

Table 2 Water quality parameters at the end of the exposure

SERWET WH 170	Dissolved oxygen concentration	pH
mg/L	% of air saturation value
0	94	7.3
2.5	93	7.4
3.5	92	7.4
5.0	91	7.4
7.0	88	7.4
10	85	7.3
14	83	7.3
20	80	7.3
28	76	7.3
40	75	7.2

Table 3 Observation and cummulative number of immobilized daphnids per test group

	24-hour	obervation		48 hour	observation
nominal concentration	Number		%	Number		%
mg SERWET WH 170/L	mobile	immobilized	immobilized	mobile	immobilized	immobilized
0	20	0	0	19	1	5
2.5	20	0	0	20	0	0
3.5	20	0	0	18	2	10
5.0	20	0	0	13	7	35
7.0	20	0	0	13	7	35
10	18	2	10	9	11	55
14	15	5	25	10	10	50
20 *	16	5	24	6	15	71
28	10	10	50	3	17	85
40	12	8	40	0	20	100
* inadvertantly started with 21 daphnids

Table 4 EC50 values based on immobilization

	For SERWET WH 170
	EC50	95% C.I.
Time interval	mg/L	lower	upper
24 h	38.7	22.1	68
48 h	10.3	8.3	12.8
	For Docusate Sodium
	EC50	95% C.I.
Time interval	mg/L	lower	upper
24 h	24.8	14.2	43.7
48 h	6.6	5.3	8.2

Validity criteria fulfilled:

yes

Remarks:

but actual temperature readings were not provided

Executive summary:

The acute toxicity of SERWET WH 170 - which contains 64.2% Docusate Sodium - to Daphnia magna was determined in a static GLP compliant test. The test was performed according to guideline EG 84/449 which is similar to EEC C.2. The test was started with a control and nominal 2.5, 3.5, 5, 7, 10, 14, 20, 28 and 40 mg SERWET WH 170/L corresponding to 0 (control), 1.61, 2.25, 3.21, 4.49, 6.42, 8.99, 12.84, 17.98 and 25.68 mg Docusate Sodium/L. For each test concentration and the control, 4 replicates with 5 daphinds each were set up in 10 mL vessels. The test was performed in darkness. Dose-verification analysis was not performed and hence, the concentrations were reported as nominal concentrations. After 48 hours of exposure, 5, 0, 10, 35, 35, 55, 50, 71, 85 and 100 % of the daphnids were immobilized at 0 (control), 1.61, 2.25, 3.21, 4.49, 6.42, 8.99, 12.84, 17.98 and 25.68 mg Docusate Sodium/L. The corresponding 48 h EC50 value is 6.6 mg Docusate Sodium/L (95% C.I. 5.3 to 8.2 mg Docusate Sodium/L).

This study is considered to be acceptable for the risk assessment.

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1985

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Well documented study, no GLP statement, no dose verification analysis

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method C.2 (Acute Toxicity for Daphnia)

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

no

GLP compliance:

not specified

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Water flea (Daphnia magna Straus)
- Source: Environmental Research Laboratory Duluth, obtained in May 1984
- Age at study initiation (mean and range, SD): less than 24 hours old
- Method of breeding: The Daphnia were cultured in media consiting of reconstituted fresh water containing live Selenastrum algal cells and trout food suspension. The daphnids were kept at a density of one adult per 100 mL culture medium. The temperature was 20°C and the light:dark cycle was 16:8 hours. The light intensity in the culture area was 100 food candles, for testing the light intensity was 80 food candles..
- Feeding during test: not fed during the test


ACCLIMATION
- Acclimation conditions (same as test or not): similar
- Type and amount of food: Selenastrum capricornutum algal cells and trout food suspension

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

184 mg/L as CaCO3

Test temperature:

20°C (SD: 0.5°C)

pH:

8.42 - 8.47

Dissolved oxygen:

not provided

Nominal and measured concentrations:

Nominal concentrations: 5, 10, 20, 40 and 80 mg DSS/L corresponding to 4.95, 9.9, 19.8, 39.6 and 79.2 mg Docusate Sodium/L

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Type (delete if not applicable): 100 mL glass beakers
- Material, size, headspace, fill volume: 80 mL fill volume
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- No. of vessels per vehicle control (replicates): NA
- Biomass loading rate: NA


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: reconstituted fresh water
- Alkalinity: 121.1 to 128.7 mg/L as CaCO3
- Intervals of water quality measurement: at start and 48 hours


OTHER TEST CONDITIONS
- Photoperiod: 16:8 hours light dark cycle
- Light intensity: 80 food candles


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
EC50 at 24 and 48 hours

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2
- Justification for using less concentrations than requested by guideline: NA

Reference substance (positive control):

yes

Remarks:

48 hour LC50 with pentachlorphenol: 0.736 mg/L

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

40.3 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: Immobilization

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

41.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Immobilization

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

34.9 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

other: Immobilization

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

36 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Immobilization

Details on results:

- Behavioural abnormalities: See table
- Mortality of control: none
- Other adverse effects control: none
- Abnormal responses: none

Results with reference substance (positive control):

- EC50/LC50: 48-hour EC50 0.752 mg PCP/L

Reported statistics and error estimates:

Spearman Karber estimation

Table 1 Immobilization of Daphnids exposed to DSS

Concentration [mg DSS/L]	24 hour observation Percent mortality	24 hour observationOrientation	48 hour observation Cumulative Percent mortality	48 hour observation Orientation
0 (control)	0	N	0	N
5	0	N	0	N
10	0	N	0	N
20	0	N	5	AB (5%)
40	50	AB (25%)	60	AB (25%)
80	90	AB (100%)	100	-

AB(x) Percentage of living Daphnids orientating at the bottom of the test vessel

Validity criteria fulfilled:

yes

Conclusions:

48-hour EC50 = 34.9 mg Docusate Sodium/L

Executive summary:

The acute toxicity of DSS - which contains 99% Docusate Sodium - to Daphnia magna was determined in a static test. GLP compliance was not stated. The test was performed similar to EEC C.2 and OECD 202. The test was started with a control and nominal 5, 10, 20, 40 and 80 mg DSS/L corresponding to 0 (control), 4.95, 9.9, 19.8, 39.6 and 79.2 mg Docusate Sodium/L. For each test concentration and the control, 4 replicates with 5 daphinds each were set up in 100 mL vessels filled with 80 mL test solution. The test was performed in a 16:8 hour light dark cycle. Dose-verification analysis was not performed and hence, the concentrations were reported as nominal concentrations. After 48 hours of exposure, 0, 0, 0, 5, 60 and 100 % of the daphnids were immobilized at 0 (control), 4.95, 9.9, 19.8, 39.6 and 79.2 mg Docusate Sodium/L. The corresponding 48 h EC50 value is 34.9 mg Docusate Sodium/L.

This study is considered to be acceptable for the risk assessment.

Description of key information

EC50  freshwater invertebrates = 15.2 mg Docusate Sodium/L

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

15.2 mg/L

Additional information

For the data endpoint “Short-term toxicity to aquatic invertebrates” 4 experimental studies are available: two of them are Klimisch 2 studies and two of them are Klimisch 3 and 4 studies. The Klimisch 3 and 4 studies are part of the IUCLID dossier but are disregarded and not discussed in detail here.

First the two Klimisch 2 studies will be introduced. Thereafter, the Klimisch 3 and 4 studies will be discussed.

The study from Elementis (Scholz 1993) was classified as Klimisch 2 study. In this study the acute toxicity of formulated product - which contains 64.2% Docusate Sodium, ~ 24% water and ~ 10% ethanol- to Daphnia magna was determined in a static GLP compliant test. The test was performed according to guideline EG 84/449 which is similar to EU method C.2 and OECD 202. The test was started with a control and nominal 2.5, 3.5, 5, 7, 10, 14, 20, 28 and 40 mg formulated product/L corresponding to 0 (control), 1.61, 2.25, 3.21, 4.49, 6.42, 8.99, 12.84, 17.98 and 25.68 mg Docusate Sodium/L. For each test concentration and the control, 4 replicates with 5 daphnids each were set up in 10 mL vessels. The test was performed in darkness. Dose-verification analysis was not performed and hence, the concentrations were reported as nominal concentrations. After 48 hours of exposure, 5, 0, 10, 35, 35, 55, 50, 71, 85 and 100 % of the daphnids were immobilized at 0 (control), 1.61, 2.25, 3.21, 4.49, 6.42, 8.99, 12.84, 17.98 and 25.68 mg Docusate Sodium/L. The corresponding 48 h EC50 value is 6.6 mg Docusate Sodium/L (95% C.I. 5.3 to 8.2 mg Docusate Sodium/L).

The study from Cytec (Goodrich and Lech 1985) was classified as Klimisch 2 study. In this study the acute toxicity of the test substance - which contains 99% Docusate Sodium - to Daphnia magna was determined in a static test. GLP compliance was not stated. The test was performed similar to EEC C.2 and OECD 202. The test was started with a control and nominal 5, 10, 20, 40 and 80 mg test substance /L corresponding to 0 (control), 4.95, 9.9, 19.8, 39.6 and 79.2 mg Docusate Sodium/L. For each test concentration and the control, 4 replicates with 5 daphnids each were set up in 100 mL vessels filled with 80 mL test solution. The test was performed in a 16:8 hour light dark cycle. Dose-verification analysis was not performed and hence, the concentrations were reported as nominal concentrations. After 48 hours of exposure, 0, 0, 0, 5, 60 and 100 % of the daphnids were immobilized at 0 (control), 4.95, 9.9, 19.8, 39.6 and 79.2 mg Docusate Sodium/L. The corresponding 48 h EC50 value is 34.9 mg Docusate Sodium/L. This study is considered to be acceptable for the risk assessment.

In addition to the Klimisch 2 studies, there is one Klimisch 3 and one Klimisch 4 study for short-term toxicity to aquatic invertebrates available. EC50 values of 10.2 and 23 mg Docusate Sodium/L were reported by Dow (Raghuram 1992) and Cognis (Wierich 2001), respectively. Due to the poor reliability of these studies, they are not discussed here.

 

The EC50 values of the two Klimisch 2 studies from Scholz (1993) and Goodrich and Lech (1985) were 6.6 and 34.9 mg Docusate Sodium/L, respectively. The evaluation which of the EC50 values is more reliable and relevant for the risk assessment will be made based on (1) the test design, (2) the test material used, and (3) if there is further evidence from disregarded acute studies with lower Klimisch scores and (4) from a long-term Daphnia reproduction study.

(1): Both guideline compliant studies were of comparable quality and hence no decision which study is more relevant could be made based on the test design.

(2): The higher purity of the test material (99% vs. 64%) in the study from Cytec (Goodrich and Lech 1985) when compared to Elementis (Scholz 1993) could indicate that the study from Cytec (Goodrich and Lech 1985) is more relevant. On the other hand, the further constituents of the test material used by Elementis (Scholz 1993) were water (~24%) and ethanol (~10%), both not toxic at 100 mg/L. Therefore, these constituents are not expected to have an effect on the toxicity of the test material.

(3): In the two Klimisch 3 and 4 studies (these studies are part of the IUCLID dossier, were disregarded and will not be further discussed here), EC50 values of 10.2 and 23 mg Docusate Sodium/L were reported by Dow (Raghuram 1992) and Cognis (Wierich 2001), respectively. Therefore, the disregarded studies give no clear indication which of the Klimisch 2 studies is more reliable.

(4) Based on the results of a long-term study with Daphnids resulting in an EC10 of 9 mg/L and in combination with the other acute Daphnia studies, the EC50 of 6.6 mg/L seems to be too low. It is unclear why this test resulted in higher immobilization. However, as worst case scenario, this

 

Considering items 1-4, no clear decision could be made which of the available studies is the most reliable one. The Guidance on information requirements and chemical safety assessment Chapter R.10: Characterisation of dose [concentration]-response for environment: R.10.2.2 Evaluation and interpretation of data states that " When there is more than one set of data on the same species, (strain if known), endpoint, duration, life stage and testing condition the greatest weight is attached to the most reliable and relevant one. When there is more than one set of data with the same reliability rating, it might be necessary to look into more detail at the study reports to see whether a specific reason could explain the difference. If no explanation can be found and the results are for the same species and endpoints and are not more than one order of magnitude apart, they can be harmonised by a geometric mean."

 

As outlined in items 1-4 no clear decision could be made for a key study for scientific reasons or other arguments for reliability and the difference of the EC50 values of both Klimisch 2 studies is less than one order of magnitude. Therefore, the geometric mean was calculated. The geometric mean EC50 is 15.2 mg/L when both Klimisch 2 studies were considered. This value will not change when the two disregarded studies are considered as well. Therefore, this geometric mean EC50 is considered to be robust and reliable.

 

Based on the above argumentation, the geometric mean EC50 of 15.2 mg Docusate Sodium/L was used for the further risk assessment for aquatic invertebrates and the CSA.