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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
from Feb. 19, 1997 to May 15, 1997
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Remarks:
Similar to OECD guidance with GLP compliance
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
GLP compliance:
yes (incl. QA statement)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
Collection: Feb. 19, 1997
The activated sludge was screened through a 2 mm sieve prior to determining the total suspended solids. Based on this result approximately three liters of the sludge was adjusted to a target solids level of 2500 mg/L. The adjusted sludge was areated in semi-continuous activated sludge units until used on the same day in the preparation of the inoculum.
Duration of test (contact time):
28 d
Initial conc.:
10 mg/L
Based on:
other: TOC
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
Test concentration: 10 mg C/L
Two replicates for test suspention and blank control. And one replicate for reference control.
The flasks were placed on a rotary platform shaker and mixed at 110 ±10 rpm for the duration of the study.
Reference substance:
benzoic acid, sodium salt
Remarks:
Sodium Benzoate
Preliminary study:
no data
Test performance:
no data
Key result
Parameter:
% degradation (CO2 evolution)
Value:
82.9
Sampling time:
28 d
Remarks on result:
other: mean value derived from measured biodegradation (%) in replicate 1 and 2
Parameter:
% degradation (CO2 evolution)
Value:
82.1
Sampling time:
28 d
Remarks on result:
other: replicate 1
Parameter:
% degradation (CO2 evolution)
Value:
83.7
Sampling time:
28 d
Remarks on result:
other: replicate 2
Details on results:
no data
Results with reference substance:
28 d biodegradation: 89.3 %
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The final TCO2 results for the two flasks dosed with test substance were 82.1 and 83.7 percent respectively for an average of 82.9. The pass value was achieved within a 10-d window. Therefore, the test substance is readily biodegradable.
Executive summary:

The study was conducted with a CO2 evolution test on test substance under GLP compliance. Each solution was used to volumetrically dose duplicate flasks at a concentration of 10 mg C/L. The final TCO2 results for the two flasks dosed with test substance were 82.1 and 83.7 percent respectively for an average of 82.9. The pass value was achieved within a 10-d window. Therefore, the test substance is readily biodegradable.

Endpoint:
biodegradation in water: ready biodegradability
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
Key result
Parameter:
% degradation (CO2 evolution)
Value:
82.1
Sampling time:
28 d
Key result
Parameter:
% degradation (CO2 evolution)
Value:
83.7
Sampling time:
28 d
Interpretation of results:
readily biodegradable

Description of key information

In a CO2 Evolution Test according to OECD TG 301 B the read across source substance hexane-1,2-diol (CAS 6920-22-5) was determined to be readily biodegradable (82.9 % biodegradation in average after 28 days fulfilling the 10-day window criterion). Based on this information the read across target substance heptane-1,2-diol is considered to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information

No experimental data on the ready biodegradability of the registration substance is available, but for the structural analogue hexane-1,2-diol (CAS 6920-22-5). Therefore, a read across approach was applied.


 


Key information


The ready biodegradability of the read across source substance hexane-1,2-diol  was assessed in a CO2 Evolution Test according to OECD TG 301 B in compliance with GLP principles. Each test solution was used to volumetrically dose duplicate flasks at a concentration of 10 mg C/l. The final TCO2 results for the two flasks dosed with test substance were 82.1 and 83.7 % after 28 days respectively for an average of 82.9 %. The pass value was achieved within a 10-d window. Therefore, the source substance was determined to be readily biodegradable.


 


Conclusion


Based on valid experimental data for the read across source substance hexane-1,2-diol (CAS 6920-22-5) the target substance heptane-1,2-diol is considered to be readily biodegradable. The provided information is regarded reliable and sufficient to cover the data requirements according to REACH Annex VII.