Docusate sodium

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to microorganisms, other

Type of information:

experimental study

Adequacy of study:

key study

Study period:

27 to 30 April 1993

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Guideline compliant GLP study

Qualifier:

according to guideline

Guideline:

DIN 38412-8 (Pseudomonas Zellvermehrungshemmtest)

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

Pseudomonas putida

Details on inoculum:

- Laboratory culture: Pseudomonas putida MIGULA
- Method of cultivation: in a glass vial
- Preparation of inoculum for exposure: In the first experiment, the pre-culture had an optical density of 0.302. This pre-culture was adjusted to an optical density of 0.145. In the second experiment the optical density was adjusted from 0.285 to 0.138. The optical density as measured with a Zeiss-Photometer PM 6 and a 1 cm path length.
- Initial biomass concentration: not provided, but the inoculum was diluted 1:10.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

16.5 h

Test temperature:

21.4°C for both experiments

pH:

See tables 2 and 3

Duration:

16 h

Dose descriptor:

EC10

Effect conc.:

122 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

growth inhibition

Duration:

16 h

Dose descriptor:

EC10

Effect conc.:

190 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth inhibition

Duration:

16 h

Dose descriptor:

EC50

Effect conc.:

164 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

growth inhibition

Duration:

16 h

Dose descriptor:

EC50

Effect conc.:

256 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth inhibition

Details on results:

- Effect concentrations exceeding solubility of substance in test medium: Since a 5 g/L stock solution was prepared and no insolubility was reported, it is likely that the test concentrations were below the solubility limit in the test medium

Reported statistics and error estimates:

Calculation of the mean optical density per test group and the percent inhibition were performed using the MULTIPLAN software "MIGULA". The ECx values and their corresponding probit values were calculated using the MULTIPLAN software "Programm ZZ". "Programm ZZ" calculates the ECx values by regression analysis of probit transformed % inhibition vs. log concentration.

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

SERWET WH 170	pH	pH
mg/L	start of exposure	end of exposure
0	not provided	not provided
40	6.2	6.8
80	6.2	6.8
160	6.3	6.8
240	6.4	6.8
320	6.6	6.8
400	7.3	6.6

Table 3 pH-values at the start and end of the exposure of the second experiment

SERWET WH 170	pH	pH
mg/L	start of exposure	end of exposure
0	not provided	not provided
40	5.8	6.8
80	5.8	6.8
160	5.9	6.8
240	6.1	6.8
320	6.6	6.8
400	7.1	6.7

Table 4 Optical density (OD) at 436 nm (1cm path length) in the first and second experiment

Note: % inhibition was calculated as: 100*(mean increase of control OD - (mean OD of test culture-initial control OD)/(mean increase of control OD) )

SERWET WH 170	replicate	Experiment 1	Experiment 2
mg/L		initial optical density controls 0.017	initial optical density controls 0.016
0	1	1.705	1.806
	2	1.784	0.706*
	3	1.806	1.796
	4	1.709	1.776
	5	1.745	1.821
	mean	1.750	1.800
	increase of optical density	1.733	1.784
40	1	1.781	1.833
	2	1.786	1.838
	3	1.806	1.813
	mean	1.791	1.828
	% inhibition	-2.4	-1.5
80	1	1.792	1.833
	2	1.806	1.828
	3	1.803	1.821
	mean	1.800	1.827
	% inhibition	-2.9	-1.5
160	1	1.703	1.779
	2	1.681	1.767
	3	1.797	1.775
	mean	1.727	1.774
	% inhibition	1.3	1.5
240	1	1.194	1.329
	2	1.030	1.358
	3	1.254	1.280
	mean	1.159	1.322
	% inhibition	34.1	26.8
320	1	0.183	0.180
	2	0.218	0.183
	3	0.224	0.188
	mean	0.208	0.184
	% inhibition	89.0	90.7
400	1	0.082	0.076
	2	0.075	0.075
	3	0.077	0.085
	mean	0.078	0.079
	% inhibition	96.5	96.5

* not used for calculations

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

Experiment	Effect parameter	based on SERWET WH 170	based on Docusate Sodium
		mg/L	mg /L
Experiment 1	EC10	189	121
Experiment 2	EC10	191	123
Mean	EC10	190	122
Experiment 1	EC50	255	164
Experiment 2	EC50	256	164
Mean	EC50	256	164

Validity criteria fulfilled:

yes

Conclusions:

The EC50 as determeined in a Pseudomonas growth inhibition test according to DIN 38412 is 164 mg Docusate Sodium/L.

Executive summary:

The growth inhibition of SERWET WH 170 (which contains 64.2% Docusate Sodium) to Pseudomonas putida MIGULA was determined in a 16 h static GLP Pseudomonas growth inhibition test. The test design was based on the DIN 38412.The nominal test concentrations were 0 (control), 40, 80, 160, 240, 320 and 400 mg SERWET WH 170/L, corresponding to 0 (control), 25.7, 51.4, 102.7, 154.1, 205.4 and 256.8 mg Docusate Sodium/L. Five control replicates and 3 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 436 nm. The optical density was determined at 0 hours in the control and about 16 hours after start of the exposure in the control and all test solutions. The EC10 and EC 50 values were calculated by regression of the log transformed concentration vs. probit transformed percent inhibition relative to the average control density. Two experiments were preformed. In the first experiment, the EC10 and EC50 were 121 and 164 mg Docusate Sodium/L, respectively. In the second experiment, the EC10 and EC50 were 123 and 164 mg Docusate Sodium/L, respectively. The mean values for the of the calculated EC10 and EC50 values of both experiments deviated at the maximum of less than 1 % from their mean values and hence, both experiments can be considered to be reliable. The 16 -hour EC10 is 122 mg Docusate Sodium/L and the EC50 is 164 mg Docusate Sodium/L.

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

Description of key information

EC10 = 122 mg Docusate Sodium/L

Key value for chemical safety assessment

EC50 for microorganisms:

164 mg/L

EC10 or NOEC for microorganisms:

122 mg/L

Additional information

For the data endpoint “Toxicity to microorganisms” in total 2 experimental studies are available: 1 key-study and 1 disregarded study.

The study from Elementis (Schöberl 1993) was classified as Klimisch 1 key study. In this study the growth inhibition of formulated product (which contains 64.2% Docusate Sodium) to Pseudomonas putida MIGULA was determined in a 16 h static GLP Pseudomonas growth inhibition test. The test design was based on the DIN 38412.The nominal test concentrations were 0 (control), 40, 80, 160, 240, 320 and 400 mg formulated product/L, corresponding to 0 (control), 25.7, 51.4, 102.7, 154.1, 205.4 and 256.8 mg Docusate Sodium/L. Five control replicates and 3 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 436 nm. The optical density was determined at 0 hours in the control and about 16 hours after start of the exposure in the control and all test solutions. The EC10 and EC 50 values were calculated by regression of the log transformed concentration vs. probit transformed percent inhibition relative to the average control density. Two experiments were preformed. In the first experiment, the EC10 and EC50 were 121 and 164 mg Docusate Sodium/L, respectively. In the second experiment, the EC10 and EC50 were 123 and 164 mg Docusate Sodium/L, respectively. The mean values for the of the calculated EC10 and EC50 values of both experiments deviated at the maximum of less than 1 % from their mean values and hence, both experiments can be considered to be reliable. The 16 -hour EC10 is 122 mg Docusate Sodium/L and the EC50 is 164 mg Docusate Sodium/L. This study is considered to be acceptable for the risk assessment.

In addition to the Klimisch 1 study, there is one Klimisch 3 study for toxicity to microorganisms available. Due to the poor reliability of this study, it is disregarded and not discussed here.

Therefore, the EC10 (122 mg Docusate Sodium/L) and EC50 (164 mg Docusate Sodium/L) reported by Elementis (Schöberl 1993) (Klimisch 1 key study) will be used for the risk assessment.