Sodium 2-biphenylate

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:

other: GLP guideline study

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

Concentration of test material was reduced to 0.2 and 1.0 mg/L.

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: A sample of activated sludge mixed Iiquor was obtained from the Midland Municipal Wastewater Treatment Plant (Midland, Michigan. USA) on April 28, 1997.
- Concentration of sludge: mixed liquor suspended solids (MLSS) concentration of the activated sludge sample was determined to be 2190 ± 160 mg/L: Based on this determination, the mineral medium (3 liters) was inoculated with 41 ml of activated sludge to yield a final MLSS concentration of 30 ± 1 mg/L.

Duration of test (contact time):

28 d

Initial conc.:

0.2 mg/L

Based on:

test mat.

Initial conc.:

1 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: according to guideline
- Test temperature: 23 ± 1°C
- pH adjusted: yes, the pH of the inoculated mineral medium was adjusted from 7.01 to 7.37 with 5N NaOH.

TEST SYSTEM
- Culturing apparatus: 1 L flasks were sealed with rubber stoppers fitted with CO2 traps containing 4 ml of 1N NaOH.


CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: yes
- Toxicity control: yes
- Other: non labelled control

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (CO2 evolution)

Value:

33.5

St. dev.:

1.5

Sampling time:

3 d

Remarks on result:

other: 0.2 mg [14C]-OPP

Parameter:

% degradation (CO2 evolution)

Value:

62.5

St. dev.:

0.5

Sampling time:

11 d

Remarks on result:

other: 0.2 mg [14C]-OPP

Parameter:

% degradation (CO2 evolution)

Value:

70.8

St. dev.:

0.3

Sampling time:

28 d

Remarks on result:

other: 0.2 mg [14C]-OPP

Parameter:

% degradation (CO2 evolution)

Value:

35.2

St. dev.:

0.2

Sampling time:

3 d

Remarks on result:

other: 1.0 mg [14C]-OPP

Parameter:

% degradation (CO2 evolution)

Value:

67.7

St. dev.:

0.8

Sampling time:

11 d

Remarks on result:

other: 1.0 mg [14C]-OPP

Parameter:

% degradation (CO2 evolution)

Value:

75.7

St. dev.:

0.5

Sampling time:

28 d

Remarks on result:

other: 1.0 mg [14C]-OPP

Details on results:

70.8 and 75.7% biodegradation (CO2 formation as percentage of theoretical value) after 28 days at low (0.2 mg/L) and high (1.0 mg/L) concentration

Results with reference substance:

Kinetic of control substance: 81% after 2 days

Biodegradation rates of o-phenylphenol (percentage of added radioactivity mineralized to 14CO2):

Day	Abiotic control	Biodegradation at different OPP concentrations
	1.0 mg [14C]-OPP	0.2 mg [14C]-OPP	1.0 mg [14C]-OPP
0	0.0%	0.0%	0.0%
3	0.2%	33.5% (± 1.5)	35.2% (± 0.2)
11	0.3%	62.5% (± 0.5)	67.7% (± 0.8)
28	0.6%	70.8% (± 0.3)	75.7% (± 0.5)

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

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

Justification for type of information:

Please refer to analogue justification provided in IUCLID section 13

Reason / purpose for cross-reference:

read-across source

Parameter:

% degradation (CO2 evolution)

Value:

75.7

St. dev.:

0.5

Sampling time:

28 d

Remarks on result:

other: 1.0 mg [14C]-OPP

Interpretation of results:

readily biodegradable

Description of key information

Readily biodegradable: 70.8 – 75.7% in 28 days (OECD 301B); read across

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

Reliable experimental data on the biodegradability of sodium 2-biphenylate are not available. The assessment was therefore based on a study conducted with the analogue substance 2-phenylphenol (CAS 90-43-7). The read across approach is in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5. Please refer to the analogue justification attached to IUCLID section 13 for a detailed justification.

The biodegradability of the source substance 2-phenylphenol (CAS 90-43-7) was tested according to OECD 301B under GLP conditions using non-adapted activated sludge as inoculum (Gonsior and Tryska, 1997). To avoid potential inhibitory effects the tested substance, concentrations were lower than specified in the guideline (i.e. 0.2 mg and 1 mg test material/L). The test substance was radiolabelled (¹⁴C-OPP) and the degradation was followed by measuring the amount of evoluted¹⁴CO₂. Furthermore the concentration of the test substance was determined at day 28 by HPLC. Based on the CO₂evolution a biodegradation rate of 70.8% was determined at a test substance concentration of 0.2 mg/L. The determined degradation rate at a substance concentration of 1 mg/L was 75.7%.The 10-day window was met (degradation rate at day 11: > 60%). Thus the substance is considered as readily biodegradable.

The results are supported by data available for sodium 2-biphenylate. The ready biodegradability of the substance was tested based on the oxygen consumption in a study design similar to OECD 301D (Hamburger, 1976). At a test substance concentration of 2.4 mL/L a degradation rate of 84% was determined after 20 days. The results were not considered for assessment because of insufficient study documentation. However, the results are a further indication of a ready biodegradability of the substance.

Based on the results for the source substance (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5) sodium 2-biphenylate is considered as readily biodegradable.