Diphenyl carbonate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Duration of test (contact time):

28 d

Initial conc.:

3.3 mg/L

Based on:

test mat.

Parameter:

% degradation (O2 consumption)

Value:

37

Sampling time:

28 d

Details on results:

The amount of oxygen taken up by the test substance is expressed as a percentage of ThOD.
Degradation products: not analysed

Validity criteria fulfilled:

yes

Interpretation of results:

other: not readily biodegradable

Executive summary:

Diphenyl carbonate is not readily biodegradable. After 28 days 37 % of the test substance had been degraded in a closed bottle test according to Directive 92/69/EEC, C.4-E.

Description of key information

Diphenyl carbonate is not readily biodegradable, C.4-E (Bayer, 2000b)

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable, not fulfilling specific criteria

Additional information

This endpoint is addressed using one key study and three supporting studies. The key study was awarded a reliability score of 1 in accordance with the criteria for assessing data quality as set forth by Klimisch et al. (1997). All three supporting studies were awarded a reliability score of 2 in accordance with the criteria for assessing data quality as set forth by Klimisch et al. (1997).

The key study was selected on the basis that it is a modern, guideline-compliant study conducted under GLP conditions. This study and the supporting study conducted using non-adapted sludge both find the test material to be non-readily biodegradable. Tests using adapted bacteria were not taken into consideration, as the inoculant does not occur in the environment.

Biodegradation of the hydrolysis product phenol was assessed in a European Union Risk Assessment Report (European Chemicals Bureau, 2006). Phenol was classified as readily biodegradable.

 

The key study (Bayer, 2000b) was performed in accordance with the standardised guideline EU Method C.4-E under GLP conditions. Domestic activated sludge (non-adapted) was exposed to an initial concentration of the test material of 3.3 mg/L under aerobic conditions for a period of 28 days. Degradation was followed by analysis of dissolved oxygen.

After 28 days 37 % of the test material was degraded. Considering the corresponding results on biodegradability for the hydrolysis product phenol, a higher degradation rate was expected than observed. Possible effects influencing the biodegradation rate can be explained with regard to the kinetic results of degradation: in the first 21, days no more than 11 - 12 % of diphenyl carbonate was degraded. As an adsorption potential is expected for diphenyl carbonate, adsorption to organic matter in the test medium takes place. At test start, the material is therefore not available for hydrolysis and not available to microorganisms for degradation.

As a consequence of desorption processes, the hydrolysis is delayed and the biodegradation of the hydrolysis product phenol is lagged. This effect corresponds to the kinetic results of the degradation study. In the last 7 days of the experiment biodegradation increased rapidly up to 37 % degradation.

 

In the first supporting study (Bayer, 1979, adapted) a closed bottle test comparable to the standardised guideline OECD 301 D was performed. Predominantly domestic sewage (adapted) was exposed to an initial concentration of the test material of 2.4 mg/L under aerobic conditions for a period of 20 days. Degradation was assessed via oxygen consumption.

After 20 days 99.5 % of the test material had been degraded, which indicates a potential of inherent biodegradability of the material.

 

In the second supporting study (Bayer, 1979, non-adapted) a closed bottle test comparable to the standardised guideline OECD 301 D was performed. Predominantly domestic sewage (non-adapted) was exposed to an initial concentration of the test material of 2.4 mg/L under aerobic conditions for a period of 20 days. Degradation was assessed via oxygen consumption.

After 20 days 48 % of the test material had been degraded.

 

In the third supporting study (Andreoni et al. 1990) the biodegradability of diphenyl carbonate with enriched mixed cultures was investigated. Adapted activated sludge from a waste water treatment plant was exposed to the test material under aerobic conditions at an initial test material concentration of 833 mg/L.

For enrichment flasks containing 100 mL liquid mineral medium (M9) were used. Phenyl-2-octyl carbonate served as sole carbon and energy source and was supplied directly to the medium at 0.1 % (w/v). The cultures were incubated by shaking at 30 °C. For isolation serial dilutions were plated on Difco nutrient agar and incubated at 30 °C, the material was added to the enriched mixed culture at a concentration of 50 mg to 60 mL M9 mineral medium (test concentration = 833 mg/L).

100 % biodegradation was determined turbidimetrically after 2.7 days. Enriched mixed cultures and the isolated strain Acinetobacter calcoaceticus showed good growth in the presence of diphenyl carbonate. Degradation/hydrolysis was complete after 65 hours.