2,6-dibromo-4-cyanophenyl heptanoate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

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 301 B (Ready Biodegradability: CO2 Evolution Test)

Version / remarks:

1992

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): A mixed population of activated sewage sludge micro-organisms was obtained on 18 September 2000 from the aeration stage of the Severn Trent Water Pic sewage treatment plant at Helper, Derbyshire, UK, which treats predominantly domestic sewage.
- Storage conditions: The sample of activated sewage sludge was maintained under continuous aeration upon receipt.
- Preparation of inoculum for exposure: A sample of the activated sewage sludge was washed three times by settlement and resuspension in culture medium to remove any excessive amounts of dissolved organic carbon (DOC) that may have been present. A sub-sample of the washed sewage sludge was then removed and the concentration of suspended solids determined.
- Initial cell/biomass concentration: 30 mg suspended solids (ss)/L
- Water filtered: no

Duration of test (contact time):

>= 0 - <= 29 d

Initial conc.:

22.4 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: Solution a (KH2PO4 8.50 g/L, K2HPO4 21.75 g/L, Na2HP04.2H2O 33.40 g/L, NH4Cl 0.50 g/L, pH = 7.4); Solution b (CaCl2 27.50 g/L); Solution c (MgS04.7H20 22.50 g/L); Solution d (FeCl3.6H2O 0.25 g/L). To 1 litre (final volume) of purified water was added the following volumes of solutions a - d. 10 mL of Solution a, 1 mL of Solution b, 1 mL of Solution c and 1 mL of Solution d.
- Solubilising agent (type and concentration if used): The test material was dispersed directly in culture medium.
- Test temperature: 21 °C
- pH: 7.4
- pH adjusted: no
- Suspended solids concentration: 30 mg suspended solids (ss)/L
- Continuous darkness: yes
- Other: For the purpose of the definitive study the test material was dispersed directly in culture medium. An amount of test material (67.2 mg) was dispersed in approximately 200 mL of culture medium and subjected to ultrasonication for approximately 30 minutes prior to dispersal in inoculated culture medium. The volume was adjusted to 3 litres to give a final concentration of 22.4 mg/L equivalent to 10 mg carbon/L.

TEST SYSTEM
- Culturing apparatus: The test solutions were prepared and inoculated in 5 litre glass culture vessels each containing 3 litres of solution.
- Method used to create aerobic conditions: The culture vessels were sealed and CO2-free air bubbled through the solution at a rate of approximately 40 mL/minute and stirred continuously by magnetic stirrer.
- Measuring equipment: The samples were analysed for CO2 using a Tekmar-Dohrmann Apollo 9000 TOC analyser and an Ionics 1555B TOC analyser. The samples were analysed for DOC using a Shimadzu TOC-5050A TOC analyser.
- Test performed in closed vessels due to significant volatility of test substance: The culture vessels were sealed.
- Details of trap for CO2 and volatile organics if used: The CO2 produced by degradation was collected in two 500 mL Dreschel bottles containing 350 mL of 0.05 M NaOH. The CO2 absorbing solutions were prepared using purified de-gassed water.

SAMPLING
- Sampling frequency: Samples (2 mL) were taken from the first CO2 absorber vessel on days 0, 1, 2, 3, 6, 8. 10, 12. 14. 16, 18, 20, 22, 24, 27, 28 and 29. The second absorber vessel was sampled on days 0 and 29.
- Sampling method: 2 mL samples were taken for CO2 analysis at each sampling time. Samples (20 mL) were removed from the test material and toxicity control vessels on day 0 prior to the addition of the test material in order to calculate the IC/TC ratio in the test media.
- Sample storage before analysis: The samples taken on days 0, 1, 2, 3, 6, 8, 10, 14, 16, 20, 22, 24, 27, 28 and 29 were analysed for CO2 immediately. The samples taken on days 12 and 18 were stored deep frozen at -20°C.

CONTROL AND BLANK SYSTEM
- Inoculum blank: A control, in duplicate, consisting of inoculated culture medium.
- Toxicity control: A toxicity control (BROMOXYNIL OCTANOATE and sodium benzoate) was included in the study to assess any toxic effect of the test material on the sewage sludge micro-organisms used in the study.

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (CO2 evolution)

Value:

37

Sampling time:

28 d

Results with reference substance:

Sodium benzoate attained 78% degradation after 28 days thereby confirming the suitability of the inoculum and test conditions.

For detailed information on the percentage biodegradation values of the test substance during the test, see Table 2 in the "Attached background material".

Table 1: Validity criteria for OECD 301B.

 

Criterion from the guideline	Outcome	Validity criterion fulfilled
Difference of extremes of replicate values of the removal of the test chemical at the plateau, at the end of the test or at the end of the 10-d window, as appropriate, is less than 20%.	Difference of extremes of replicate values were less than 20%.	yes
Percentage degradation of the reference compound reached the pass level by day 14 (≥ 60%).	69%	yes
The toxicity control should degrade to at least 35% (based on DOC) or at least 25% (based on ThOD or ThCO2) within 14 d.	64% after 28 days	yes
The IC content of the test substance suspension in the mineral medium at the beginning of the test must be less than 5% of the TC.	2%	yes
The total CO2 evolution in the inoculum blank at the end of the test should not normally exceed 40 mg/L medium.	24.17 mg/L at day 28	yes

Validity criteria fulfilled:

yes

Remarks:

Please refer to Table 1 in "Any other information on results incl. tables".

Interpretation of results:

not readily biodegradable

Conclusions:

The test material attained 37% degradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No 301B.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

20 Jue 2000 - 27 Nov 2000

Justification for type of information:

Please refer to the Analogue Justification provided in IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Parameter:

% degradation (CO2 evolution)

Value:

37

Sampling time:

28 d

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The test material attained 37% degradation after 28 days and therefore cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No 301B.

Description of key information

37 % biodegradation in 28 days (OECD 301B); based on RA to 2,6-dibromo-4-cyanophenyl octanoate (CAS 1689-99-2)

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater

Additional information

Reliable data on the biodegradation of 2,6-dibromo-4-cyanophenyl heptanoate (CAS 56634-95-8) is not available. In accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5 “Grouping of substances and read-across” and in accordance with the read across assessment framework (RAAF, ECHA 2017), the assessment was based on reliable and adequate read-across data available for the structural analogue 2,6-dibromo-4-cyanophenyl octanoate (CAS 1689-99-2).

 

In the key study, the ready biodegradability of 2,6-dibromo-4-cyanophenyl octanoate was assessed under aerobic conditions according to GLP and OECD Guideline No 301B. The test substance attained 37% degradation after 28 days and therefore cannot be considered to be readily biodegradable according to OECD criteria.