1-hydroxyoctan-2-one

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:

Sept 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

This is a Klimisch 1 rated OECD 201 study conducted on the registered substance according to GLP

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Batch/Lot number: 1203/16/100

Analytical monitoring:

yes

Details on sampling:

Two samples of 6 mL were taken from both additional vessels (without test organisms in order to not disturb the TOC analysis) of treatment A, C, E and NC after 0 h, 24 h, 48 h and 72 h exposure for TOC analysis. Of these 4 samples per treatment and time, 2 were analysed directly after sampling and 2 were stored as retain samples in the freezer (≤ -18 °C) until finalisation of the study. For treatment C at 48 h, the two retain samples were measured, including the corresponding
NC samples, because the wrong calibration curve was used for the first two samples which resulted in implausible data.

Vehicle:

no

Details on test solutions:

The stock solution was prepared by adding 111.1 mg test item (including a factor of 1.11 to take into account the dilution caused by addition of the algal inoculum) to 1000 mL test medium and shaking for 0.5 h using an overhead shaker. This stock solution was used as highest test item concentration in the test.

Into each test vessel for the test item treatment and the negative control (NC; test medium), 50 mL test solution (including algal inoculum) was transferred. The further test item concentrations were prepared by diluting the stock solution with test medium according to the following scheme (dilution factor of 2):

Treatment Group NC A B C D E
Nominal test item concentration [mg/L]* 0 6.25 12.5 25 50 100
Stock solution [mL] 0 25 50 100 200 400
Test medium [mL] 400 375 350 300 200 0
Test vessels (replicates) 6 3 3 3 3 3
Total vol per test vessel [mL] 50 50 50 50 50 50
Test Solution/Test Medium [mL] 45 45 45 45 45 45
Algal inoculum suspension [mL] 5 5 5 5 5 5
Additional Vessels for TOC analysis 2 2 - 2 - 2
Total vol per test vessel [mL]** 60 60 - 60 - 60
Test Solution/Test Medium [mL] 54 54 - 54 - 54
Test Medium [mL] 6 6 - 6 - 6

"*Due to weighting tolerance and measuring inaccuracy of the analytical balance, the nominal test item concentrations
can deviate < 2 % from the target values.
** Due to the volume loss caused by the sampling, the volume in the additional vessels for TOC-analysis was increased to obtain similar volumes as in the test vessels during the exposure period.

Test organisms (species):

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

Details on test organisms:

The test organism Raphidocelis subcapitata (Strain No. 61.81 SAG) originates from the Culture Collection of Algae at the University of Goettingen. The strain used for this study has been cultured in suspension culture at Hydrotox GmbH since May 2018. Twice a week, the stock suspension is inoculated into fresh Holm-Hansen medium (composition: 496 mg/L NaNO3, 39 mg/L K2HPO4, 75 mg/L MgSO4×7H2O, 36 mg/L CaCl2×2H2O, 58 mg/L Na2CO3, 10 mg/L Na2EDTA×2H2O, 3 mg/L citric acid, 3 mg/L iron citrate, 0.1144 mg/L H3BO3, 0.0724 mg/L MnCl2×4H2O, 0.0088 mg/L ZnSO4×7H2O, 0.0032 mg/L CuSO4×5H2O, 0.0010 mg/L Na2MoO4×2H2O, 0.0016 mg/L CoCl2×6H2O) under axenic conditions to keep it in exponential growth.

Quality assurance takes place at regular intervals by testing the sensitivity of the test organisms to the reference item potassium dichromate (Honeywell GmbH, Seelze, Germany, Lot: H1030). The recent quality testing was performed in July 2018 which resulted in an ErC50 (72 h) of 1.05 mg/L (CL 95 %: 0.78 - 1.41 mg/L; interlaboratory test result for ErC50: mean of 1.19 mg/L with SD of 0.27 mg/L) and an EyC50 (72 h) of 0.21 mg/L (CL 95 %: 0.12 – 0.39 mg/L).

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

The temperature during the exposure was 22.1 – 23.2 °C (required: 21 - 24 °C, constant within ± 2 °C).

pH:

The pH was 7.5 – 7.9 in the control and 7.6 – 8.0 in the test item treatment (requirement: increase ≤ 1.5).

Nominal and measured concentrations:

Nominal Concentrations: 0; 6.25; 12.5; 25; 50; 100 mg/L
Geometric Mean Measured Concentrations (0h, 24h, 48h and 72h): X; 5.57; X; 23.78; X; 97.2 mg/L (only 3 out of 5 concentration series was subjected to TOC analysis)

Details on test conditions:

The test vessels were sealed with stainless steel caps and kept in the light incubator (specified temperature: 21 – 24 °C, constant within ± 2 °C). They were placed on the shaking table with adhesive mats and continuously shaken with 100 rpm and an orbital diameter of 5 cm.

The test vessels were continuously illuminated by LEDs (warm white) with a light intensity of 78.0 μE m-² s-1 ± 3.0 %. The pH was measured at the start (0 h) and at the end (72 h) of the test. The temperature was measured continuously.

Reference substance (positive control):

no

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

105.1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

39.26 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

12.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

45.53 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

17.6 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

25 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Details on results:

The measured TOC concentrations in the test item treatments were 79.6 – 98.7 % of the nominal TOC concentrations. As the measured test item concentrations are within ± 20 % of the nominal concentrations, according to OECD 201 (2006) and OECD 23 (2000), all results are given in relation to the nominal test item concentrations.

Reported statistics and error estimates:

See results table for 95% Confidence Limits on 72h EC50 and EC10 values

Parameter	Nominal test item concentration [mg/L]
	Yield (72h)	Growth rate (72h)
EC50	45.53	105.1
95% CL	42.74-48.53	100.18-111.05
EC10	17.58	39.26
95% CL	15.14-19.81	35.47-42.64
LOEC	50	25
NOEC	25	12.5

Validity criteria fulfilled:

yes

Conclusions:

The 72h EC50 value for algae exposed to 1-hydroxyoctan-2-one was determined to be 105.1 mg/L and 45.53 mg/L based on growth rate and yield, respectively. 72h EC10 values were 39.3 and 17.6 mg/L for effects on growth rate and yield, respectively. The 72h NOEC based on growth rate was determined to be 12.5 mg/L.

Executive summary:

The toxicity of 1 -hydroxyoctan-2 -one towards the aquatic plant algae species raphidocelis supcapitata was investigated in an OECD 201 guideline study conducted in accordance with GLP including TOC chemical analysis to confirm exposure concentrations (Klimisch 1).

The 72h EC50 value for algae exposed to 1-hydroxyoctan-2-one was determined to be 105.1 mg/L and 45.53 mg/L based on growth rate and yield, respectively. 72h EC10 values were 39.3 and 17.6 mg/L for effects on growth rate and yield, respectively. The 72h NOEC based on growth rate was determined to be 12.5 mg/L. As the measured test item concentrations are within ± 20 % of the nominal concentrations, according to OECD 202 (2004), all results are given in relation to the nominal test item concentrations.

Description of key information

The toxicity of 1 -hydroxyoctan-2 -one towards the aquatic plant algae species raphidocelis supcapitata was investigated in an OECD 201 guideline study conducted in accordance with GLP including TOC chemical analysis to confirm exposure concentrations (Klimisch 1).

The 72h EC50 value for algae exposed to 1-hydroxyoctan-2-one was determined to be 105.1 mg/L and 45.53 mg/L based on growth rate and yield, respectively. 72h EC10 values were 39.3 and 17.6 mg/L for effects on growth rate and yield, respectively. The 72h NOEC based on growth rate was determined to be 12.5 mg/L. As the measured test item concentrations are within ± 20 % of the nominal concentrations, according to OECD 202 (2004), all results are given in relation to the nominal test item concentrations.

Key value for chemical safety assessment

EC50 for freshwater algae:

45.5 mg/L

EC10 or NOEC for freshwater algae:

12.5 mg/L