Octadecyl 3-mercaptopropionate

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:

2018-06-14 to 2018-09-21

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Qualifier:

according to guideline

Guideline:

other: OECD No 23, Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Name: ODMP
Chemical Name: Octadecyl 3-Mercaptopropionat
CAS No.: 31778-15-1
Batch No.: 0061486
Purity: 98.5 % according to certificate of analysis
Manufacturing Date: December 21, 2017
CoA Reference Number P907/2016
Aggregate State at Room Temperature: Solid
Colour: Colourless
Expiry Date: December 20, 2018
Storage Conditions at Test Facility: At 4 +/- 4 °C, in the dark

Analytical monitoring:

yes

Remarks:

GC-MS

Details on sampling:

Four samples from the freshly prepared test media (containing algae) of all test concentrations and from the control were taken at the start of the test.
For the determination of the stability of the test item under the test conditions and of the maintenance of the test item concentrations during the test period, four samples from the test media of all test concentrations and the control (containing algae) were taken at the end of the test (after the 72 hours test period) by pouring together the contents of the test beakers of each treatment.

Vehicle:

no

Details on test solutions:

Test Concentrations: A filtrate of nominal 100 mg/L and dilutions of 1:3.16, 1:10, 1:31.65 and 1:100 and a control. Control: In the control, test water was used without addition of the test item.
Dosage of Test Item: The test item was not well soluble in test water. In this study, only the inhibitory effects of dissolved test item was tested and thus no concentrations above the solubility limit of the test item in test water were tested. Therefore, a supersaturated stock solution of nominal 100 mg test item/L was prepared by suspending 50 mg test item in 500 mL test water for preparing the test concentrations. The stock suspension was stirred for 24 hours at room temperature in the dark to dissolve as much test item as possible. Then non-dissolved fractions of the test item were separated from the test medium by membrane filtration (0.45 µm cellulose acetate filter). The solution with dissolved test item was used as the test medium of the highest test concentration and to prepare the desired 1:3.16, 1:10, 1:31.65 and 1:100 dilutions. The test media were prepared just before introduction of the algae (= start of the test).

Test organisms (species):

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

Details on test organisms:

Species: Pseudokirchneriella subcapitata, Strain No. 61.81 SAG
Origin: The algae were supplied by the "Sammlung von Algenkulturen, Pflanzenphysiologisches Institut der Universität Göttingen", 37073 Göttingen, Germany.
Breeding Conditions: The algae were cultivated in the laboratories of IBACON under standardised conditions according to the test guidelines.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

Calculated water hardness of the test water: 0.24 mmol/L (= 24 mg/L) as CaCO3

Test temperature:

22 to 23°C

pH:

7.7 to 7.9 at test start and 9.2 to 9.4 at test end

Nominal and measured concentrations:

A filtrate of nominal 100 mg/L and dilutions of 1:3.16, 1:10, 1:31.65 and 1:100 and a control.

Details on test conditions:

Water Temperature: The temperature was measured daily in an Erlenmeyer flask filled with water and incubated under the same conditions as the test flasks.
Water temperature was: 22.4 to 22.6 °C
pH-Values: The pH was measured in all test item concentrations and the control at the start and the end of the test. pH was: 7.7 to 7.9 at test start and 9.2 to 9.4 at test end
Light Regime: Continuous illumination
Light Intensity: The light intensity was measured once during the test at 6 positions distributed over the experimental area at the surface of the test media.
Mean light intensity: 6392 lux (range: 5820 to 6730 lux)

Reference substance (positive control):

yes

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

The 72-hour EC50 and the 72-hour EC10 for the parameters growth rate and yield could not be calculated due to the absence of effects of the test item. Therefore the 72-hour EC50 and the 72-hour EC10 was determined to be higher than the limit of water solubility of the test item, represented by the filtrate of nominal 100 mg test item/L, the highest concentration tested.
The 72-hour NOEC was determined to be at least the filtrate of nominal 100 mg test item/L for the parameters growth rate and yield and the associated 72-hour LOEC was determined to be higher than the filtrate of nominal 100 mg test item/L for both parameters.

Results with reference substance (positive control):

The influence of Potassium dichromate on the growth of the freshwater green algae Pseudokirchneriella subcapitata was assessed in a static concentration-response test.
The 72-hour EyC50 was calculated to be 0.402 mg test item/L, the 72-hour EbC50was calculated to be 0.414 mg test item/L and the 72-hour ErC50 value was calculated to be 0.963 mg test item/L. The 72-hour NOEyC was determined to be 0.094 mg test item/L and the associated 72-hour LOEyC was 0.21 mg test item/L. The 72-hour NOErC was determined to be 0.094 mg test item/L and the associated 72-hour LOErC was 0.21 mg test item/L. The 72-hour NOEbC was determined to be 0.094 mg test item/L and the associated 72-hour LOEbC was 0.21 mg test item/L.

Reported statistics and error estimates:

Based on the calculated cell densities, the 72 hours ErC50 and the 72 hours EyC50 could not be calculated by statistical analysis due to the lack of effects and were therefore determined directly from the raw data.
For the determination of the 72 hours LOEC and the 72 hours NOEC, the calculated growth rates and yields at each test concentration were tested for significant differences compared to the control values by Dunnett's t-test.
The software used to perform the statistical analysis was ToxRat Professional, Version 3.2.1, ToxRat Solutions GmbH.

Validity criteria fulfilled:

yes

Remarks:

Cell Density Increase: 170.1-fold increase within 72 hours; Coefficient of Variation of Sectional (Daily) Growth Rates: 10.4 %; Coefficient of Variation of Average Growth: 0.9 %

Conclusions:

The influence of ODMP on the growth of the freshwater green algae Pseudokirchneriella subcapitata was assessed in a static concentration-response test, which was performed using nominal concentrations of up to 100 mg test item/L. The filtrate of this solution was used as highest test concentration, but analytical verification of the concentrations was below the limit of detection of 0.02 mg test item/L.
The 72-hour NOEC was determined to be at least the filtrate of nominal 100 mg test item/L. The NOEC might even be higher than this concentration, but concentrations in excess of nominal 100 mg test item/L or the limit of solubility have not been tested according to the recommendations of the test guidelines.
The 72-hour LOEC and the 72-hour EC50 were clearly higher than the filtrate of nominal 100 mg test item/L. These values could not be quantified due to the absence of toxicity of ODMP up to the filtrate of nominal 100 mg test item/L, the concentration representing the limit of solubility.

Executive summary:

An algal toxicity study was conducted according to OECD TG 201 to determine the inhibitory effect of the test item ODMP on the growth of the freshwater green algae Pseudokirchneriella subcapitata. For this purpose, exponentially growing cultures of unicellular green algal species were exposed to various concentrations of the test item under defined conditions. The inhibition of growth in relation to control cultures was determined over a test period of 72 hours, and thus over several algal generations. The test method of application and the test system are recommended by the test guidelines and Pseudokirchneriella subcapitata is one of the recommended test species. The purpose of the analytical part of this study was to verify the concentrations of the test item in the test medium.

This study encompassed 6 treatment groups (5 dose rates of the test item and a control) with three replicates per test concentration and six replicates for the control. At test start 50 mL of the test concentrations were inoculated with approx. 5000 algal cells per mL test medium and defined volumes of the algal suspensions were sampled after 24, 48 and 72 hours for determination of cell densities by spectrophotometrical measurement.

Biological Results:

Yield and growth rate of the algae:

72-hour EC50: > filtrate of 100 mg test item/L

72-hour NOEC: ≥filtrate of 100 mg test item/L

72-hour LOEC: > filtrate of 100 mg test item/L

 

The influence of ODMP on the growth of the freshwater green algae Pseudokirchneriella subcapitata was assessed in a static concentration-response test, which was performed using nominal concentrations of up to 100 mg test item/L. The filtrate of this solution was used as highest test concentration, but analytical verification of the concentrations was below the limit of detection of 0.02 mg test item/L. The 72-hour NOEC was determined to be at least the filtrate of nominal 100 mg test item/L. The NOEC might even be higher than this concentration, but concentrations in excess of nominal 100 mg test item/L or the limit of solubility have not been tested according to the recommendations of the test guidelines. The 72-hour LOEC and the 72-hour EC50 were clearly higher than the filtrate of nominal 100 mg test item/L. These values could not be quantified due to the absence of toxicity of ODMP up to the filtrate of nominal 100 mg test item/L, the concentration representing the limit of solubility. The initial concentrations and the maintenance of the exposure concentrations during the test could not be verified in the analytical part. The analytical verification of the concentrations was below the limit of detection of 0.02 mg test item/L.

This study is classified acceptable and satisfies the guideline requirements for growth inhibition algae studies.

Description of key information

The 72-hour ErC10 and the 72-hour ErC50 were higher than the filtrate of nominal 100 mg test item/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

100 mg/L

EC10 or NOEC for freshwater algae:

100 mg/L

Additional information

An algal toxicity study was conducted according to OECD TG 201 to determine the inhibitory effect of the test item ODMP on the growth of the freshwater green algae Pseudokirchneriella subcapitata. For this purpose, exponentially growing cultures of unicellular green algal species were exposed to various concentrations of the test item under defined conditions. The inhibition of growth in relation to control cultures was determined over a test period of 72 hours, and thus over several algal generations. The test method of application and the test system are recommended by the test guidelines and Pseudokirchneriella subcapitata is one of the recommended test species. The purpose of the analytical part of this study was to verify the concentrations of the test item in the test medium.

This study encompassed 6 treatment groups (5 dose rates of the test item and a control) with three replicates per test concentration and six replicates for the control. At test start 50 mL of the test concentrations were inoculated with approx. 5000 algal cells per mL test medium and defined volumes of the algal suspensions were sampled after 24, 48 and 72 hours for determination of cell densities by spectrophotometrical measurement.

Biological Results:

Yield and growth rate of the algae:

72-hour EC50: > filtrate of 100 mg test item/L

72-hour NOEC: ≥filtrate of 100 mg test item/L

72-hour LOEC: > filtrate of 100 mg test item/L

 

The influence of ODMP on the growth of the freshwater green algae Pseudokirchneriella subcapitata was assessed in a static concentration-response test, which was performed using nominal concentrations of up to 100 mg test item/L. The filtrate of this solution was used as highest test concentration, but analytical verification of the concentrations was below the limit of detection of 0.02 mg test item/L. The 72-hour NOEC was determined to be at least the filtrate of nominal 100 mg test item/L. The NOEC might even be higher than this concentration, but concentrations in excess of nominal 100 mg test item/L or the limit of solubility have not been tested according to the recommendations of the test guidelines. The 72-hour LOEC and the 72-hour EC50 were clearly higher than the filtrate of nominal 100 mg test item/L. These values could not be quantified due to the absence of toxicity of ODMP up to the filtrate of nominal 100 mg test item/L, the concentration representing the limit of solubility. The initial concentrations and the maintenance of the exposure concentrations during the test could not be verified in the analytical part. The analytical verification of the concentrations was below the limit of detection of 0.02 mg test item/L.