4,4'-diamino[1,1'-bianthracene]-9,9',10,10'-tetraone

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

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

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Guideline study. According to the ECHA guidance document "Practical guide 6: How to report read-across and categories (March 2010)", the reliability was changed from RL1 to RL2 to reflect the fact that this study was conducted on a read-across substance.

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The substance 6,15-dihydroanthrazine-5,9,14,18-tetrone with the EC-no. 201-375-5 (PB60), which CINIC has not REACH-registered, is a structurally similar anthraquinone pigment. Due to the structural similarity, they are assessed in an analogue approach. The analogue approach is reported according to chapter R.6.2.6.1 of the ‘Guidance on information requirements and chemical safety assessment - Chapter R.6: QSARs and grouping of chemicals’ (ECHA, 2008). In addition, the respective analogue approach scenario (Appendix A: Scenario 2) of the Read-Across Assessment Framework (RAAF; ECHA, 2017) has been used as guidance to facilitate the assessment.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The source substance is 6,15-dihydroanthrazine-5,9,14,18-tetrone (EC-no. 201-375-5), referred to here as PB60. PB60 is an organic mono-constituent substance with a typical purity of > 99.0% (w/w). It is not classified, is not a PBT/vPvB and does not contain any impurity relevant for the analogue approach. The structure of PB60 is shown in Figure 1B.
The target substance is 4,4'-diamino[1,1'-bianthracene]-9,9',10,10'-tetraone (EC-no. 223-754-4), referred to here as PR177. Also, PR177 is an organic mono-constituent substance with a typical purity of > 99.0% (w/w). It is not classified, is not a PBT/vPvB and does not contain any impurity relevant for the analogues approach.
The substance identities and all information on physicochemical properties, environmental fate, ecotoxicity and toxicity are summarised in Annex 1 of the below attached justification.

3. ANALOGUE APPROACH JUSTIFICATION
Both substances consist basically of two connected anthraquinone groups. For PR177, the connection is a single carbon bond connection. In addition, PR177 has one amino group at each of the two connected aromatic rings. Both substances form internal N-H-O hydrogen bridges which keep the molecules in perfect planar shape and reduce surface polarity leading to low solubility in water.

4. DATA MATRIX
Please refer to Annex 1 of the below attached justification.

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): inoculum taken from a sewage treatment plant of the city of Reinach, Switzerland.

Duration of test (contact time):

28 d

Initial conc.:

11 mg/L

Based on:

test mat.

Initial conc.:

20.6 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: An emulsifier was used to increase the solubility of the test substance (Nonylphenol)
- Test temperature: 22 ± 2 °C
- Test vessels: 2 L flasks (dark brown glass) equipped with gas inlet and magnetic stirrer

Reference substance:

aniline

Parameter:

% degradation (CO2 evolution)

Value:

3

Sampling time:

28 d

Remarks on result:

other: At concentration of 11 mg/L

Parameter:

% degradation (CO2 evolution)

Value:

1

Sampling time:

28 d

Remarks on result:

other: At concentration of 20.6 mg/L

Results with reference substance:

Biodegradation of reference substance: 84 % in 28 days

Interpretation of results:

other: not readily biodegradable

Description of key information

Not readily biodegradable (according to OECD criteria).

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Additional information

Since no data on the registered substance are available a read-across to a similar pigment (CAS 81-77-6) is used to cover this endpoint. The ready biodegradability of the analogue substance was tested in a guideline study according to OECD 301B. The biodegradation rate was determined by measuring the CO2 evolution of domestic activated sludge at test substance concentrations of 11 mg/L and 20.6 mg/L, respectively. After the 28 day incubation period a degradation rate of < 10 % was observed [Ciba-Geigy Ltd., 1989].

This result supports one model calculation which was conducted with CATALOGIC v5.11.5. The calculation with CATALOGIC v5.11.5 (BOD 28 days MITI (OECD 301C) v06.07) resulted in ca. 0.04 % biodegradation after 28 d. Even though the structural domain was correct with only 52.94 % (47.06 % unknown) the results support the overall conclusion that the pigment is "not readily biodegradable".

Moreover, the pigment is practically insoluble and therefore considered to be essentially not bioavailable. Due to the large molecular size, cellular uptake of the pigment is unlikely. Hence intracellular biodegradation, which is the main degradation route of bacteria, is probably low. It can be concluded that the substance is likely to persist in the environment.