2-hydroxy-3-(prop-2-enoyloxy)propyl 2-methyl-2-propylhexanoate

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:

From October 24, 2016 to October 28, 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Deviations:

yes

Remarks:

temperature of the stock solution but it was judged uncritical

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

yes

Remarks:

temperature of the stock solution but it was judged uncritical

Qualifier:

according to guideline

Guideline:

other: OECD guidance document no.43

Version / remarks:

Guidance document on aquatic toxicity testing of difficult substances and mixtures (adopted Dec. 2000)

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Batch no.: JBGJ0045R
Purity: 100% (UVCB)
Appearance: clear yellowish liquid

Analytical monitoring:

yes

Remarks:

HPLC

Details on sampling:

The water-accommodated fraction (WAF) was prepared for the test. This was done by pipetting 100 µL/L corresponding to the nominal load 100 mg/L (based on a density of 1.01 g/mL, stated in the MSDS provided by the sponsor) on the surface of algal medium (demineralised water enriched with minerals but without algae) and stirring slowly for 24 hours. The lower phase was used as test solution. The lower treatments were prepared by dilution of this WAF with nutrient medium. This procedure was in agreement with the OECD guidance document no. 23 for the testing of mixtures which are toxic at very low loading rates. Nearly complete inhibition of algal growth was observed in a non-GLP pre-test at a loading rate of 1 mg/L.

Vehicle:

no

Details on test solutions:

Samples of the nominal concentration 32 mg/L and 100 mg/L were diluted with drinking water in a ratio 1:4 and 1:9, respectively. Samples of the other concentrations were not diluted before measurement. Filtration using 0.45 µm PTFE filters was not possible (it leads to erroneous results during the validation of the method) and was therefore not done. For elimination of the algal cells before analytical determination, samples were centrifuged using 4500 rounds per minute for a period of 10 minutes.
As deviation of QC samples was less than 3%, the recovery was not taken into account for the analytical determinations.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

The culture of Desmodesmus subspicatus was obtained in January 2016 by MBM Sciencebridge GmbH (Institut für Pflanzenphysiologie of Universität Göttingen). The algae are kept as stock culture on solid agar at 2 - 8°C. Three days before the start of each test, an aliquot of the permanent culture was brought into nutrient medium and incubated under continuous lighting for 72 hours. The resulting cuture grew exponentially. Before usage, the pre-culture was checked for the absence of cell aggregates and the cell number of culture was determined.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

250 mg CaCO3/L

Test temperature:

22.4 – 22.6 °C

pH:

7.5-7.6

Salinity:

-

Conductivity:

-

Nominal and measured concentrations:

1.0 to 100 mg/L nominal concentration

Details on test conditions:

cfr "Any other information on materials and methods incl. tables"

Reference substance (positive control):

yes

Remarks:

potassium dichromate (K2Cr2O7, CAS No. 7778-50-9)

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

4.6 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: growth rate yield

Remarks on result:

other: 1.14 mg/L (measured)

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: growth and yield

Remarks on result:

other: 3.08 mg/L (measured)

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

6.2 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 1.5 mg/L (measured)

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

8.9 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: yield

Remarks on result:

other: 2.6 mg/L (measured)

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

21 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 11 mg/L (measured)

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

9.9 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: yield

Remarks on result:

other: 3.0 mg/L (measured)

Details on results:

One valid experiment was performed. The study was performed using 5 concentrations ranging from 1.0 to 100 mg/L nominal concentrations. Significant inhibition of algal growth was observed at the three highest concentrations, i.e.10, 32 and 100 mg/L (nominal).

Results with reference substance (positive control):

The 72h-EC50s of potassium dichromate (K2Cr2O7, CAS No. 7778-50-9) were determined. The values lay within the range of the laboratory (growth rate 0.73 - 1.10 mg/L, yield 0.21 – 0.66 mg/L).

Table 1. Endpoints (measured values)

Endpoints	NOEC	LOEC	EC10	EC50
Growth rate	1.14 mg/L	3.08 mg/L	1.5 mg/L	11 mg/L
Yield	1.14 mg/L	3.08 mg/L	2.6 mg/L	3.0 mg/L

Table 2. Endpoints (nominal values)

Endpoints	NOEC	LOEC	EC10	EC50
Growth rate	4.6 mg/L	10.0 mg/L	6.2 mg/L	21 mg/L
Yield	4.6 mg/L	10.0 mg/L	8.9 mg/L	9.9 mg/L

Note: NOEC and LOEC were determined by comparing the respective treatment with the blank control. Statistically insignificant variation is considered as “no observed effect”, although the EC values which were read from the graph toxicity vs. concentration may lie lower. 

Analytical determination:

At the start and at the end of the test, the content of the test substance in the test solutions was determined using HPLC. The measured concentrations lay between 39% and 58% of the nominal concentrations at the beginning of the test and between 24% and 46% of the nominal concentrations at the end of the test. Therefore, the geometric mean of the measured concentration was used for the determination of the results. Geometric mean is calculated by multiplication of the n participating concentrations and taking the nth root.

Validity criteria fulfilled:

yes

Conclusions:

Under the study conditions, the 72h ErC50 (growth rate) and EYC50 (yield inhibition) for Desmodesmus subspicatus based on measured concentrations were determined to be 11.0 and 3.0 mg/L, respectively (i.e., corresponding to 21 and 9.9 mg/L nominal concentration), while the NOEC for both the parameters was 1.14 mg/L (i.e., corresponding to 4.6 mg/L nominal concentration). Further, the 72h ErC10 and EyC10 were determined to be at 1.5 and 2.6 mg/L, respectively (i.e., corresponding to 6.2 and 8.9 mg/L nominal concentrations), respectively.

Executive summary:

A study was conducted to determine the toxicity to aquatic algae and cyanobacteria of the test substance according to OECD Guideline 201 and EU Method C.3, in compliance with GLP. Desmodesmus subspicatus were exposed to Water Accomodated Fractions (WAF; using an orbital shaker) of the substance at loading rates of 0, 1, 3.2, 10, 32 and 100 mg/L (nominal) and incubated in open (covered with perforated plastic foil) for 72 h in triplicates. The cell concentration of each replicate was determined by measuring the cell numbers every 24 h with an electronic particle counter. Growth rate and the yield were determined from the cell number at the respective observation times (i.e., at 0, 24, 48 and 72 h). At the start and at the end of the test, the content of the test substance in the test solutions was determined using HPLC. The measured concentrations lay between 39% and 58% of the nominal concentrations at the beginning of the test and between 24% and 46% of the nominal concentrations at the end of the test. Therefore, the geometric mean of the measured concentration was used for the determination of the result. Significant inhibition of algal growth was observed at the three highest concentration of 10, 32 and 100 mg/L nominal concentrations. The 72 h EC50 of positive control (potassium dichromate) were determined to be within the range of the laboratory (growth rate: 0.73 - 1.10 mg/L; yield: 0.21–0.66 mg/L). All validity criteria were met. Under the study conditions, the 72 h ErC50 (growth rate) and EyC50 (yield inhibition) for Desmodesmus subspicatus based on measured concentrations were determined to be 11.0 and 3.0 mg/L, respectively (i.e., corresponding to 21 and 9.9 mg/L nominal concentration), while the NOEC for both the parameters was 1.14 mg/L (i.e., corresponding to 4.6 mg/L nominal concentration). Further, the 72 h ErC10 and EyC10 were determined to be at 1.5 and 2.6 mg/L, respectively (i.e., corresponding to 6.2 and 8.9 mg/L nominal concentrations), respectively (Bangert, 2016).

Description of key information

The 72h ErC50 and ErC10 values for Desmodesmus subspicatus due to the test substance was determined to be 11 and 1.5 mg/L (measured) respectively.

Key value for chemical safety assessment

EC50 for freshwater algae:

11 mg/L

EC10 or NOEC for freshwater algae:

1.5 mg/L

Additional information

A study was conducted to determine the toxicity to aquatic algae and cyanobacteria of the test substance according to OECD Guideline 201 and EU Method C.3, in compliance with GLP. Desmodesmus subspicatus were exposed to Water Accomodated Fractions (WAF; using an orbital shaker) of the substance at loading rates of 0, 1, 3.2, 10, 32 and 100 mg/L (nominal) and incubated in open (covered with perforated plastic foil) for 72 h in triplicates. The cell concentration of each replicate was determined by measuring the cell numbers every 24 h with an electronic particle counter. Growth rate and the yield were determined from the cell number at the respective observation times (i.e., at 0, 24, 48 and 72 h). At the start and at the end of the test, the content of the test substance in the test solutions was determined using HPLC. The measured concentrations lay between 39% and 58% of the nominal concentrations at the beginning of the test and between 24% and 46% of the nominal concentrations at the end of the test. Therefore, the geometric mean of the measured concentration was used for the determination of the result. Significant inhibition of algal growth was observed at the three highest concentration of 10, 32 and 100 mg/L nominal concentrations. The 72 h EC50 of positive control (potassium dichromate) were determined to be within the range of the laboratory (growth rate: 0.73 - 1.10 mg/L; yield: 0.21–0.66 mg/L). All validity criteria were met. Under the study conditions, the 72 h ErC50 (growth rate) and EyC50 (yield inhibition) for Desmodesmus subspicatus based on measured concentrations were determined to be 11.0 and 3.0 mg/L, respectively (i.e., corresponding to 21 and 9.9 mg/L nominal concentration), while the NOEC for both the parameters was 1.14 mg/L (i.e., corresponding to 4.6 mg/L nominal concentration). Further, the 72 h ErC10 and EyC10 were determined to be at 1.5 and 2.6 mg/L, respectively (i.e., corresponding to 6.2 and 8.9 mg/L nominal concentrations), respectively (Bangert, 2016).