Hexan-4-olide

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

GLP compliance:

yes

Analytical monitoring:

yes

Vehicle:

not specified

Details on test solutions:

Dilution water
Top prepare the dilution water, 4 vials (1, 2, 3, 4) of different concentrated salts “ISO medium" (purchased from ECOTOX LOS), were used; each vial contains a concentrated salt solution enough to prepare 2 I of dilution water. The composition of each salt solution is given below.
Batch used: ISOD140617
Expiration date: 14/06/2019

NRI: 171VIT/2018 and 214VIT/2018
Vial 1: NaHC03 129.5 mg - dissolved in 2 I - final concentration 64. 75 mg/I
Vial 2: CaCl2’ 2H20 588 mg - dissolved in 2 I - final concentration 294 mg/I
Vial 3: MgS04 · 7H20 264.5 mg - dissolved in 2 I - final concentration 123.25 mg/I
Vial 4: KCI 11.5 mg - dissolved in 2 I - final concentration 5. 75 mg/I
The dilution water was prepared as follows:
A volumetric flask (2 I capacity) was filled with approximately 1 l of distilled water;
The content of each vial (from vial 1 to 4) was poured in the volumetric flask;
The flask was filled up to 2 I with distilled water and mixed.
The dilution water was transferred in dark glass containers and stored in the refrigerator (5°C+-3 °C), in the dark, for no longer than one month.
The pH of the dilution water was in the acceptable range of 7.8+-0.5. Before using the dilution water for the hatching of ephippia or for the p「eparation of the test solutions, it was g「adually brought to room temperature, and it was aerated for 30 minutes.
At the beginning of each test, pH and dissolved oxygen of the dilution water were measured. Dissolved oxygen was >7 mg/I (minimum acceptable value).
The compliance of pH and dissolved oxygen values was reported in the raw data of the Study.

K2Cr2O7
The sensitivity to potassium dichromate (K2Cr2O7) of the batch of ephippia employed in the assay, as indicated in the certificate, was assessed preliminarily The results are reported in the control chart Mod. 775/GxP.

Reagents for TOC analysis
Sucrose
1,4-Benzoquinone
Nitric acid concentrate 70% (for washing volumetric flasks employed in the Tl-0016031 analysis)
Sucrose solutions were freshly prepared prior to begin with the analysis at each time point.
At first the sucrose was heated in a oven for at least 3 hours at 105 °C and afterwards dried for at least 1 hour. Then a 5000 ppm working solution (RSO) was prepared by solving the sucrose in MilliQ H20.
From the RSO solution, 1 ml was transferred in a new 100 ml volumetric flask and brought to volume with MillliQ H20 in order to prepared the RS0-50 ppm solution.
The other dilutions were prepared as follows:
RS (0.2 ppm) = 0.4 ml of RS0-50 ppm were transferred into a 100 ml volumetric flask and brought to volume with milliQ H20;
RS2 (1 ppm)= 2 ml of RS0-50 ppm were transferred into a 100 ml volumetric flask and brought to volume with milliQ H20;
RS3 (2.5 ppm) = 5 ml of RS0-50 ppm were transferred into a 100 ml volumetric flask and brought to volume with milliQ H20;
RS4 (5 ppm)= 10 ml of RS0-50 ppm were transferred into a 100 ml volumetric flask and brought to volume with milliQ H20;
RS5 (1 O ppm) = 20 ml of RS0-50 ppm were transferred into a 100 ml volumetric flask and brought to volume with milliQ H20;
RS6 {20 ppm} = 40 ml of RS0-50 ppm were transferred into a 100 ml volumetric flask and brought to volume with milliQ H20.
A 5000 ppm 1.4-Benzoquinone stock solution (BQO-5000 ppm) was prepared in MilliQ H20 and the solution was then sonicated for 10 minutes.
Afterwards BQ1 (50 ppm) solution was prepared by transferring 1 ml of BQO into a new 100 ml volumetric flask and bringing to volume with MilliQ H20.
Finally BQ2 (0.5 ppm) solution was prepared by transferring 1 ml of 801 into a new 100 ml volumetric flask and flask and bringing to volume with MilliQ H20.

Test organisms (species):

Daphnia magna

Details on test organisms:

As test system Daphnia magna Straus (Cladocera, Crustacea) was employed in the assay, as described by the guideline OECD 202:2004. The animals were less than 24 hours old at the start of the test, and they were not first brood progeny. They derived from Daρhnia magna ephippia, supplied by the qualified provider ECOTOX LDS. Ephippia are a quiescent form of animals which can be hatched when needed.

Test type:

not specified

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

48 h

Test temperature:

21°C

pH:

7.38-7.70

Dissolved oxygen:

>3mg/L

Nominal and measured concentrations:

The definitive test was carried out, since in the preliminary assay the test substance at the concentration 100 mg/I induced > 10% animal immobilization. The definitive test was carried out on 5 concentrations (from C1to C5) which, on the basis of the preliminary test results, allowed the EC50 calculation. The selected nominal concentrations were:
C1: 25 mg/I
C2: 12.5 mg/I
C3: 6.25 mg/I
C4: 3.125 mg/I
CS: 1.562 mg/I

Reference substance (positive control):

yes

Remarks:

K2Cr2O7

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

ca. 3.176 mg/L

Nominal / measured:

nominal

Details on results:

At the end of the definitive test, EC50 was calculated using the EPA software PROBIT, 95%confidence limits were also calculated. The PROBIT elaboration is attached to the raw data. EC50: 3.176 mg/I (confidence limits 2.478 mg/I-4.001 mg/I).
The graph of the fitted model used for the calculation of the EC50 is attached to the raw data.

Results with reference substance (positive control):

Prior to routine use of the batch of Daphnia magna, the sensitivity toward K2Cr2O7 was verified by carrying out a
test with 5 concentrations of this chemical; the concentrations used in this test were: 3.2 mg/I - 1.8 mg/I - 1 mg/I -
0.56 mg/I -0.32 mg/I. Results of the tests were reported in the control chart 775/GxP. The calculated ECso resulted
between 0.6 mg/1 and 2.1 mg/I.

Validity criteria fulfilled:

yes

Conclusions:

According to OECD 202:2004, under the test conditions applied, the EC50 of the test substance is calculated as 3.176 mg/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

EC50

Effect concentration:

3.176 mg/L