2,6-dimethyloct-7-en-2-yl acetate

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:

May 10, 2016 to October 25, 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:

no

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

Principles of method if other than guideline:

There were no Amendments or Deviations to the Study Plan.

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Vehicle:

no

Test organisms (species):

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

Details on test organisms:

The test organism used for the study was Pseudokirchneriella subcapitata (formerly Selenastrum capricornutum), Strain No. 61.81 SAG, supplied by the Collection of Algal Cultures (SAG, Institute for Plant Physiology, University of Göttingen, 37073 Göttingen / Germany). The algae were cultivated at IES Laboratories under standardized conditions according to the test guidelines. An inoculum culture was set up three days before the start of the exposure. The algae were cultivated under the test conditions and were kept in the exponential growth phase until inoculation of the test solutions.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

0.15 mmol/L (= 15 mg/L as CaCO3).

Test temperature:

The water temperature during the test was maintained at 23 °C.

pH:

The pH of the test media was in the range of 7.9 to 8.3 during the test period

Nominal and measured concentrations:

At the start of the test, the analytically measured concentrations of Dihydro Myrcenyl Acetate in the dilutions 1:32, 1:10, 1:3.2 and in the undiluted test medium with a loading rate of 100 mg/L were 0.50, 1.6, 5.1 and 18 mg/L. At the end of the test, 79 to 91% of the initially measured values were found, in the samples with algae. The mean measured concentrations were calculated to be 0.4, 1.4, 4.7 and 16 mg/L respectively.

The measured concentrations for the lower treatment dilutions, 1:320 and 1:100, were not analyzed since they were below the NOEC determined in this test.

Details on test conditions:

As the test item is a volatile substance, the test was performed using glass stoppered Erlenmeyer flasks (closed system) completely filled with test medium, minimizing the air space in the flasks and avoiding potential losses of test item by evaporation.Due to the low water solubility of the test item, the test media were prepared as follow: The test item was added into test water in a requisite amount at a loading rate of 100 mg/L. Thereafter slow stirring was applied for 96 hours in a closed vessel to reach a maximum concentration of dissolved test item in the test water. After stirring, the lower equilibrated aqueous phase of the solution was carefully separated from the non-dissolved upper test item phase and was used as highest test concentration. This highest test concentration was further diluted with test water to obtain the test media with the lower test item concentrations.

Reference substance (positive control):

no

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

5.4 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

2.9 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

Effects based on yield were also reported (see attached full study report). However, the preferred observational endpoint in the algal inhibition study is growth rate because it is not dependent on the test design (ECHA guidance Chapter R.7b v1.1). The EU CLP regulation (No 1272/2008 and its adaption 286/2011) also states that classification should be based on the ErC50. Thus only the effects based on growth rate are presented in the above "effects concentration" table. Furthermore, the preferred observational endpoint in long-term studies is the EC10 value because it is derived from the dose response curve. In contrast the NOEC strongly depends on the experiment design (e.g. the concentrations used in the test). Thus, only the EC10 is presented in the above "effects concentration" table. The NOEC values are available in the full study report.

Validity criteria fulfilled:

yes

Conclusions:

According to this test,
The 72-hour ErC50 was determined to be 5.4 mg/L (95% confidence interval : 5.1-6.0) based on mean measured concentrations
The 72-hour ErC10 was determined to be 2.9 mg/L (95% confidence interval : 2.2-3.4) based on mean measured concentrations

Executive summary:

The impact of the test item Dihydro Myrcenyl Acetate on the growth of the freshwater green algal species Pseudokirchneriella subcapitata was investigated in a 72-hour static test according to the OECD Guideline 201 (2006) and the Commission Regulation (EU) No 2016/266, C.3. As the test item is a volatile substance, the test was performed using glass stoppered Erlenmeyer flasks (closed system) completely filled with test medium, minimizing the air space in the flasks and avoiding potential losses of test item by evaporation. Due to the low water solubility of the test item, the test media were prepared as follow: The test item was added into test water in a requisite amount at a loading rate of 100 mg/L. Thereafter slow stirring was applied for 96 hours in a closed vessel to reach a maximum concentration of dissolved test item in the test water. After stirring, the lower equilibrated aqueous phase of the solution was carefully separated from the non-dissolved upper test item phase and was used as highest test concentration. This highest test concentration was further diluted with test water to obtain the test media with the lower test item concentrations. These were the dilutions 1:320, 1:100, 1:32, 1:10 and 1:3.2. Additionally, a control (test water without test item) was tested in parallel. The preparation of the test media was based on the OECD Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures, 2000.

At the start of the test, the analytically measured concentrations of Dihydro Myrcenyl Acetate in the dilutions 1:32, 1:10, 1:3.2 and in the undiluted test medium with a loading rate of 100 mg/L were 0.50, 1.6, 5.1 and 18 mg/L. At the end of the test, 79 to 91% of the initially measured values were found, in the samples with algae. This loss is likely due to adsorption of the test item to the growing algal biomass since measured concentrations at the end of the test in samples without algae were 94-100% initial. In such cases, it may be appropriate to base the analysis of the results on the initialmeasured concentrations. However, in order to give a “worse case” analysis of the data, biological results were based on the mean measured concentrations (calculated as the geometric mean of the test item concentrations measured at the start and end of the test).

The biological test results (based on mean measured concentrations) were as follows: EC50 (0-72 h) Growth rate = 5.4 mg/L ( 95% confidence interval: 5.1-6.0) and the

EC10 (0-72 h) Growth rate = 2.9 mg/L ( 95% confidence interval: 2.2-3.4).

Description of key information

The impact of the test item Dihydro Myrcenyl Acetate on the growth of the freshwater green algal species Pseudokirchneriella subcapitata was investigated in a 72-hour static test according to the OECD Guideline 201 (2006) and the Commission Regulation (EU) No 2016/266, C.3. As the test item is a volatile substance, the test was performed using glass stoppered Erlenmeyer flasks (closed system) completely filled with test medium, minimizing the air space in the flasks and avoiding potential losses of test item by evaporation. Due to the low water solubility of the test item, the test media were prepared as follow: The test item was added into test water in a requisite amount at a loading rate of 100 mg/L. Thereafter slow stirring was applied for 96 hours in a closed vessel to reach a maximum concentration of dissolved test item in the test water. After stirring, the lower equilibrated aqueous phase of the solution was carefully separated from the non-dissolved upper test item phase and was used as highest test concentration. This highest test concentration was further diluted with test water to obtain the test media with the lower test item concentrations. These were the dilutions 1:320, 1:100, 1:32, 1:10 and 1:3.2. Additionally, a control (test water without test item) was tested in parallel. The preparation of the test media was based on the OECD Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures, 2000.

At the start of the test, the analytically measured concentrations of Dihydro Myrcenyl Acetate in the dilutions 1:32, 1:10, 1:3.2 and in the undiluted test medium with a loading rate of 100 mg/L were 0.50, 1.6, 5.1 and 18 mg/L. At the end of the test, 79 to 91% of the initially measured values were found, in the samples with algae. This loss is likely due to adsorption of the test item to the growing algal biomass since measured concentrations at the end of the test in samples without algae were 94-100% initial. In such cases, it may be appropriate to base the analysis of the results on the initialmeasured concentrations. However, in order to give a “worse case” analysis of the data, biological results were based on the mean measured concentrations (calculated as the geometric mean of the test item concentrations measured at the start and end of the test).

The biological test results (based on mean measured concentrations) were as follows: EC50 (0-72 h) Growth rate = 5.4 mg/L ( 95% confidence interval: 5.1-6.0) and the EC10 (0-72 h) Growth rate = 2.9 mg/L ( 95% confidence interval: 2.2-3.4).

Key value for chemical safety assessment

EC50 for freshwater algae:

5.4 mg/L

EC10 or NOEC for freshwater algae:

2.9 mg/L