Diphenyl carbonate

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

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.3 (Algal Inhibition test)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

TOC measurement

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

23 +/- 2 °C

pH:

pH value after 0 h: 7.8 - 8.2
pH value after 72 h: 7.3 - 10.3

Nominal and measured concentrations:

The following initial nominal concentrations were tested:
0.63, 1.25, 2.5 and 5.0 mg/l
For nominal concentrations equal or lower than 2.5 mg/l the corresponding measured values were below the limit of quantification (LOQ = 2 mg/l TOC). For a nominal concentration of 5 mg/l measured values of 4 mg/l after 0 h and and 7 mg/l after 72 h was observed.

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

1.4 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.31 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

0.63 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

2.4 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.63 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

1.25 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.5 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: Estimation based on half-life (40 hours)

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.11 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: Estimation based on half-life (40 hours)

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

< 0.22 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: Estimation based on half-life (40 hours)

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.9 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: Estimation based on half-life (40 hours)

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.22 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: Estimation based on half-life (40 hours)

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

0.44 mg/L

Nominal / measured:

estimated

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: Estimation based on half-life (40 hours)

Since the measured effect concentrations found (EC10 and EC50) were lower than LOQ, following results refer to
nominal concentrations.
Results were given for 10, 50 and 90 % growth inhibition. After 72 h the following effect concentrations were observed:
- Biomass
EbC10= 0.64 mg/l        EbC50= 1.4 mg/l         Eb90= 3.2 mg/l
- Growth rate
ErC10= 1.0 mg/l         ErC50= 2.4 mg/l         Er90= 5.8 mg/l
Due to the hydrolyses of diphenyl carbonate in the presence of water, forming phenol and carbon dioxide, the effective 

concentrations of diphenyl carbonate are estimated for each test concentration. With the assumption that the half-life 

of diphenyl carbonate is about 40 hours under abiotic conditions in a buffered medium, and a water solubility of 

13 mg/l, the geometric mean over time (inclusive 24 hours of stirring before the test) is 1.77 mg/l, 0.88 mg/l, 

0.44 mg/l and 0.22 mg/l at the nominal test concentrations of 5 mg/l, 2.5 mg/l, 1.25 mg/l and 0.63 mg/l. The 

resulting effective ErC50 (72h) is 0.9 mg/l and 0.5 mg/l for the EbC50 (72h). The corresponding 72h-NOEC, obtained 

from growth rate, is 0.22 mg/l and the 72h-LOEC is 0.44 mg/l.
The corresponding 72h-NOEC, obtained from biomass, is <0.22 mg/l and the 72h-LOEC is <0.22 mg/l.

Conclusions:

Under the conditions of the study the 72 hour ErC50 was calculated to be 0.9 mg/L. The corresponding effective 72h NOEC for growth rate was 0.22 mg/L.

Executive summary:

The toxicity of the test material to Desmodesmus subspicatus was investigated in accordance with the standardised guideline EU Method C.3 under GLP conditions.

The algae were exposed to the test material at nominal concentrations of 0.63, 1.25, 2.5 and 5.0 mg/L for 72 hours under static conditions. Analytical monitoring (TOC measurement) was performed during the course of the study. However, since the effect concentrations observed were lower than the limit of quantification of the method (LOQ = 2 mg/L TOC) and because the analytical method could not distinguish between diphenyl carbonate and its hydrolysis product phenol, only nominal concentrations could be given. Due to the hydrolysis of diphenyl carbonate in the presence of water, forming phenol and carbon dioxide, the effective concentrations were estimated for each test concentration. With the assumption that the half-life of diphenyl carbonate is 39.9 hours under abiotic conditions in a buffered medium, and a water solubility of 13 mg/L, the geometric mean over time (inclusive 24 hours of stirring before the test) is 1.77, 0.88, 0.44 and 0.22 mg/L at the nominal test concentrations of 5, 2.5, 1.25 and 0.63 mg/L, respectively. The resulting effective ErC50 (72 h) is 0.9 mg/L and 0.5 mg/L for the EbC50 (72 h). The corresponding 72 h-NOEC, obtained from growth rate, is 0.22 mg/L and the 72 h-LOEC is 0.44 mg/L. The corresponding 72 h-NOEC, obtained from biomass, is <0.22 mg/L and the 72h-LOEC is <0.22 mg/L.

Description of key information

The EC50 of diphenyl carbonate towards algae is considered be > 1 mg/L.

Additional information

As agreed in the OECD ICCA/HPV-program, a half-life of 39.9 hours and a water solubility of 13 mg/L were used for the interpretation of aquatic data. The nominal diphenyl carbonate concentrations were converted to effective concentrations by approximation as geometric means over time. It is considered that the observed effects cover both the toxicity of diphenyl carbonate and the toxicity of the degradation products.

Toxicity to Aquatic Algae

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

In the key study (Bayer, 1999b) the toxicity of the test material to Desmodesmus subspicatus was investigated in accordance with the standardised guideline EU Method C.3 under GLP conditions.

The algae were exposed to the test material at nominal concentrations of 0.63, 1.25, 2.5 and 5.0 mg/L for 72 hours under static conditions. Analytical monitoring (TOC measurement) was performed during the course of the study. However, since the effect concentrations observed were lower than the limit of quantification of the method (LOQ = 2 mg/L TOC) and because the analytical method could not distinguish between diphenyl carbonate and its hydrolysis product phenol, only nominal concentrations could be given. Due to the hydrolysis of diphenyl carbonate in the presence of water, forming phenol and carbon dioxide, the effective concentrations were estimated for each test concentration. With the assumption that the half-life of diphenyl carbonate is 39.9 hours under abiotic conditions in a buffered medium, and a water solubility of 13 mg/L, the geometric mean over time (inclusive 24 hours of stirring before the test) is 1.77, 0.88, 0.44 and 0.22 mg/L at the nominal test concentrations of 5, 2.5, 1.25 and 0.63 mg/L, respectively. The resulting effective ErC50 (72 h) is 0.9 mg/L and 0.5 mg/L for the EbC50 (72 h). The corresponding 72 h-NOEC, obtained from growth rate, is 0.22 mg/L and the 72 h-LOEC is 0.44 mg/L. The corresponding 72 h-NOEC, obtained from biomass, is <0.22 mg/L and the 72h-LOEC is <0.22 mg/L.

Given the uncertainties in the original extrapolation of the half-life value of 39.9 hours, as well as its use in the interpretation of aquatic data, particular consideration is appropriate during the use of the algae study results when determining the classification of diphenyl carbonate. In particular, higher NOEC and EC50 values would be derived if the half-life of 73.5 hours is taken for the interpretation of aquatic data.

In the supporting study (Smithers, 2010), the toxicity of the test material to algae was calculated using ECOSAR v1.00 (EPI Suite v4.0) March 2009.

The applicability domain and adequacy of the QSAR for short-term toxicity to aquatic algae have been assessed. The use of a predicted value appears relevant for registration in accordance with the REACH Regulation and relevant ECHA guidance. Currently there is no definition of model domain other than being applicable to organic molecules, though particularly high or low log Kow values may potentially be outside the applicability domain.

The investigated substance is not highly complex. The log Kow and the chemical structure appear appropriate given the chemical structures and compounds used to develop the QSAR. The result is considered adequate for the purpose of providing supplementary information that can be used in the assessment of the short-term aquatic toxicity of diphenyl carbonate to algae; the predicted EC50 for green algae is 3.66 mg/L (96 h).

As a conclusion, when both the key and supporting data are taken into consideration, the EC50 of diphenyl carbonate towards algae is considered be > 1 mg/L.