2-methoxy-2-methylheptane

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

15 Dec 2017 - 18 Jan 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Principles of method if other than guideline:

Guidance document on aquatic toxicity testing of difficult substances and mixtures, OECD series on testing and assessment number 23, 2000.

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

2-methoxy-2-methylheptane

EC Number:

816-311-7

Cas Number:

76589-16-7

Molecular formula:

C9H20O

IUPAC Name:

2-methoxy-2-methylheptane

Test material form:

liquid

Specific details on test material used for the study:

Identification: DAIKON ETHER
Appearance: Colorless liquid
Test item storage: At room temperature

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

Test samples were stored in the freezer (≤ -15°C). On the day of analysis, the test samples were thawed at room temperature. The samples were extracted in a 3:1 (v:v) ratio with n-hexane and analyzed. The shaking time was 30 seconds. If necessary, the samples were further diluted with n-hexane to obtain concentrations within the calibration range.

Test solutions

Vehicle:

no

Test organisms

Test organisms (species):

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

Details on test organisms:

Species: Raphidocelis subcapitata (formerly known as Pseudokirchneriella subcapitata), strain: NIVA CHL 1
Source: In-house laboratory culture.
Reason for selection: This system is a unicellular algal species sensitive to toxic items in the aquatic ecosystem and has been selected as an internationally accepted species.

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test conditions

Test temperature:

21-24°C

pH:

7.3 - 8.0

Nominal and measured concentrations:

Nominal concentration: 1.0, 3.2, 10, 32 and 100% of the SS prepared at a loading rate of 100 mg/L
Actual concentration: 0.59, 1.4, 5.5, 19 and 70 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel:glass vials, closed airtight, with no headspace to prevent any loss of test item due to volatilization
- Type: closed
- Material, size, headspace, fill volume: 40 mL
- Initial cells density: 1 x 10^4 cells/mL.
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6
- No. of vessels per vehicle control (replicates): 1 or 2 replicates of each test concentration without algae.

GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Phtoperiod: continuous light
- Light intensity and quality: 60 to 120 μE/m2/s at 400 to 700 nm

EFFECT PARAMETERS MEASURED :
- Determination of cell concentrations: counting chamber

TEST CONCENTRATIONS
- Range finding study
- Test concentrations: 0, 1.0,10 100% SS prepared at 100 mg/L

Reference substance (positive control):

yes

Results and discussion

Effect concentrations

Effect concentrations 1

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

23 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 2

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

1.1 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: based on statistical significance

Effect concentrations 3

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

4 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: based on biological relevance

Details on results:

The EC50 for yield inhibition (72h-EYC50) was 8.0 mg/L with a 95% confidence interval ranging from 7.3 to 8.7 mg/L.
The 72h-NOEC for yield inhibition was 1.1 mg/L based on statistical significance and based on biological relevance.
See Attachment.

Results with reference substance (positive control):

Potassium dichromate
Start of first exposure: 02 Jan 2018
Completion last exposure: 05 Jan 2018
The EC50 for growth rate inhibition (72h-ERC50) was 0.86 mg/L with a 95% confidence interval ranging from 0.84 to 0.88 mg/L. The historical ranges for growth rate inhibition lie
between 0.82 and 2.3 mg/L. The observed 72h-ERC50 for the algal culture tested corresponds with this range.
The EC50 for yield inhibition (72h-EYC50) was 0.34 mg/L with a 95% confidence interval ranging from 0.34 to 0.35 mg/L. The historical ranges for yield inhibition lie between 0.20
and 1.1 mg/L. The observed 72h-EYC50 for the algal culture tested corresponds with this range.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

In conclusion, under the conditions of the present study with Raphidocelis subcapitata (formerly known as Pseudokirchneriella subcapitata), the test substance reduced growth rate and inhibited the yield of this fresh water algae species significantly at average concentrations of 4.0 mg/L and higher.
The EC50 for growth rate inhibition (72h-ERC50) was 23 mg/L with a 95% confidence interval ranging from 23 to 24 mg/L.
The EC50 for yield inhibition (72h-EYC50) was 8.0 mg/L with a 95% confidence interval ranging from 7.3 to 8.7 mg/L.
The 72h-NOEC for growth rate inhibition was 1.1 mg/L based on statistical significance.
The 72h-NOEC for growth rate inhibition was 4.0 mg/L based on biological relevance.
The 72h-NOEC for yield inhibition was 1.1 mg/L based on statistical significance and based on biological relevance.