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Short-term toxicity to aquatic invertebrates

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Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH

Substances whose physicochemical, toxicological and ecotoxicological properties are likely to be similar as a result of structural similarity may be considered as analogue substances. In this case, experimental data of one substance may provide indications for specific physico-chemical properties and the (eco-) toxicological profile of another, based on a read-across approach (ECHA (2012); ECHA (2013), ECHA (2017a)).

In the present situation an “analogue approach” has been chosen because the target and the source substance are structurally similar substances. The target substance is a mono-constituent substance consisting of a linear C7 chain and two hydroxyl groups. The source substance hexane-1,2-diol consists of a linear C6 chain with two hydroxyl groups at the same positions. The molecules only differ by one methylene group in the terminal C chain.

Hence, target and source substances share same chemical structures and functional groups. For the REACH information requirement under consideration, the effects obtained in a study conducted with the source substances are used to predict the effects that would be observed in a study with the target substance if it were to be conducted (ECHA 2017b).

This read-across is based on the hypothesis that source and target substances have the same type of toxicological effects based on common underlying mechanisms. This prediction is supported by physicochemical and (eco-)toxicological data on the substances.

Therefore, the effects of the target substance are predicted to be similar to the effects of the source substance. The exposure to target and source substances causes the same type of effects through a common mechanism.


References:

ECHA (2012) Practical guide 6: How to report read-across and categories. ECHA-10-B-11.1-EN, December 2012.

ECHA (2013) Grouping of substances and read-across approach, part 1: Introductory note. ECHA-13-R-02-EN, April 2013.

ECHA (2017a) Read-Across Assessment Framework (RAAF), Reference: ECHA-17-R-01-EN, Date: March 2017.

ECHA (2017b) Read-Across Assessment Framework (RAAF), Appendix B: Scenario 2.

2. SOURCE AND TARGET CHEMICAL
1) Target chemical
- IUPAC name: 1,2-Heptanediol
- CAS no.: 3710-31-4
- EC no.: 855-780-2
- Molecular formula: C7H16O2
- SMILES notation: CCCCCC(CO)O
- Purity: >= 99 < 100 % (w/w), typical concentration ca 99.8 % (w/w)

2) Source chemical
- IUPAC name: hexane-1,2-diol
- CAS no.: 6920-22-5
- EC no.: 230-029-6
- Molecular formula: C6 H14 O2
- SMILES notation: OCC(O)CCCC
- Purity: 99.6% (w/w)

3. ANALOGUE APPROACH JUSTIFICATION
Read-across from (eco-)toxicity studies on the source substances is considered as an appropriate adaptation to the standard information requirements of Annex VII of the REACH Regulation for the target substance, in accordance with the provisions of Annex XI, 1.5 of Regulation (EC) No 1907/2006 (REACH).
Reason / purpose for cross-reference:
read-across source
Duration:
48 h
Dose descriptor:
EC10
Effect conc.:
> 110 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 110 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
EC100
Effect conc.:
> 110 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
>= 110 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
LOEC
Effect conc.:
>= 110 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
08.08.2012-03.10.2012
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)
Qualifier:
according to guideline
Guideline:
EU Method C.2 (Acute Toxicity for Daphnia)
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
yes
Details on sampling:
For the determination of the actual test item concentrations, duplicate samples were taken from each treatment at the start and at the end of the test (after 48 hours).
For the 48-hour stability samples, the contents of the respective replicates were combined prior to sampling.
The concentration of the test item was analytically measured in one of the duplicate test medium samples of the single test concentration taken at the start and end of the test.
From the control, one of the duplicate samples was analyzed per sampling time, too.
Vehicle:
no
Details on test solutions:
The test medium was prepared by dissolving 110.2 mg of test item completely in 1000 mL of test water using ultrasonic treatment for 15 minutes and intense stirring for 15 minutes at room temperature. The test medium was prepared just before introduction of the daphnids (i.e. start of the test).
Test organisms (species):
Daphnia magna
Details on test organisms:
The study was performed with young daphnids of the species Daphnia magna Straus. A clone of this species (defined by the supplier as clone 5) was originally supplied by the University of Sheffield / UK in 1992. Since that time, the clone has been bred at Harlan Laboratories in reconstituted water of the quality identical to the water quality used in the tests (in respect to pH, main ions, and total hardness) and under temperature and light conditions identical to those of the test.
During breeding, daphnids are generally fed three times a week with an algal suspension of the green algae Desmodesmus subspicatus CHODAT, Strain No. 86.81 SAG, supplied by the Collection of Algal Cultures (SAG, Institute for Plant Physiology, University of Göttingen, 37073 Göttingen / Germany) and cultivated at Harlan Laboratories under standardized conditions or a mixture of this algal suspension and a commercial fish diet (Tetra Min®, Hauptfutter, supplied by TETRA-Werke, 49304 Melle / Germany).
For each treatment, 20 daphnids were used divided into four replicates of five daphnids each.
The volume of test solution provided for each daphnid was 10 mL. Thus, the requirement of the test guidelines for the minimum volume of 2 mL test medium per daphnid was fulfilled. The daphnids were randomly distributed to the test vessels at initiation of the test.
Test duration was 48 hours.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
48 h
Hardness:
Water Hardness: 2.5 mmol/L, 250 mg/L as CaCO3
Test temperature:
The water temperature was maintained at 20-21°C.
pH:
7.8
Dissolved oxygen:
The test water was aerated prior to the start of the study until oxygen saturation was reached.
During the test period, the test water was not aerated.
Oxygen: 8.1 - 8.5 mg/L
Salinity:
Reconstituted test water according to ISO 6341 [ISO, 1996] was used in the study. It consisted of analytical grade salts dissolved in purified water at the following nominal concentrations.
[mmol/L] [mg/L]
CaCl2 × 2H2O: 2.0 mmol/L , 294 mg/L
MgSO4 × 7H2O: 0.5 mmol/L, 123 mg/L
NaHCO3: 0.75 mmol/L, 65 mg/L
KCl: 0.075 mmol/L, 5.8 mg/L
Water Hardness: 2.5 mmol/L, 250 mg/L as CaCO3
Alkalinity 0.8 mmol/L
Nominal and measured concentrations:
Based on the results of a range-finding test a limit test with the nominal concentration of 110 mg/L was carried out. The measured concentrations of the test item in the test medium were 93 and 94% of the nominal value at the start and end of the test, respectively.
Details on test conditions:
A 16-hour light to 8-hour dark cycle with a 30-minute transition period was used. Light intensity
during the light period was approximately between 400 and 540 Lux.
The daphnids were not fed during the test.
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Duration:
48 h
Dose descriptor:
EC10
Effect conc.:
> 110 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 110 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
EC100
Effect conc.:
> 110 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
>= 110 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
LOEC
Effect conc.:
>= 110 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Details on results:
The test item had no acute toxic effects on Daphnia magna up to the nominal concentration of 110 mg/L (measured 93 to 94%) under the conditions of the test.
Results with reference substance (positive control):
For evaluation of the quality of the daphnia clone and the experimental conditions, potassium dichromate is tested as a positive control twice a year. The result of the latest positive control test in February 2012 (48-hour EC 50 : 0.63 mg/L, Harlan Laboratories Study D50585) showed that the sensitivity of the test organisms was within the internal historical range (48-hour EC 50 from 2000 to 2012: 0.43-1.1 mg/L).

The measured concentrations of the test item in the test medium were 93 and 94% of the nominal value at the start and end of the test, respectively. Thus, the correct dosage of the test item was confirmed. The test item was stable in the test media over the test period of 48 hours. The biological results were related to the nominal concentrations of the test item.

In the control and at the test concentration of 110 mg/L, no immobilized test organisms were observed during the test period of 48 hours. Therefore, the 48-hour NOEC of the test item to Daphnia magna was determined to be at least 110 mg/L. The 48-hour NOEC might even be higher, but concentrations above 110 mg/L were not tested, in accordance with the test guidelines. The 48-hour EC 10 , EC 50 and EC 100 were clearly higher than 110 mg/L.

Validity criteria fulfilled:
yes
Conclusions:
In the negative control and at the test concentration of 110 mg/L, no immobilized test organisms were observed during the test period of 48 hours. Thus, NOEC (daphnia magna, 48h) is greater or equal 110 mg/L.
Executive summary:

In the negative control and at the test concentration of 110 mg/L, no immobilized test organisms were observed during the test period of 48 hours. Thus, NOEC (daphnia magna, 48h) is greater or equal 110 mg/L. The test is considered to be valid, as in the negative control no daphnids showed immobilization or other signs of disease or stress (e.g. discoloration or unusual behavior such as trapping at the surface water). Furthermore, the dissolved oxygen concentration at the end of the test was ≥3 mg/L in the control and test vessels.

Description of key information

In a limit test according to OECD TG 202 with Daphnia magna the 48-hour EC50 of the read across source substance hexane-1,2-diol (CAS 3710-31-4) was determined to be > 110 mg/L (nominal). Based on this result the 48-hour EC50 of the target substance heptane-1,2-diol is considered to be > 110 mg/L.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
110 mg/L

Additional information

No experimental data on the toxicity of the registration substance to aquatic invertebrates is available, but for the structural analogue substance hexane-1,2-diol. Therefore, a read across approach was applied.


 


Key information


The acute toxicity of the read across source substance hexane-1,2-diol was studied in a valid GLP test according to OECD TG 202. The test was performed under static conditions over a period of 48 hours. Based on the results of a range-finding test a limit test with the nominal concentration of 110 mg/L was carried out. The measured concentrations of the substance in the test medium were 93 and 94 % of the nominal value at the start and end of the test, respectively and thus the effects levels were based on the nominal concentration.In the control and at the test item concentration of 110 mg/L, no immobilized test organisms were observed during the test period of 48 hours.Thus, the test item had no acute toxic effects on Daphnia magna up to the nominal concentration of 110 mg/L under the conditions of the test (NOEC >= 110 mg/L). The 48 hour EC50 was hence determined to be > 110 mg/L.


Conclusion
In a limit test according to OECD TG 202 with Daphnia magna the 48-hour EC50 of the read across source substance hexane-1,2-diol (CAS 3710-31-4) was determined to be > 110 mg/L. By applying a read across approach the 48-hour EC50 of the target substance heptane-1,2-diol is considered to be > 110 mg/L.