m-phenylenediamine

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

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:

comparable to guideline study with acceptable restrictions

Remarks:

The purity of the test substance was reported to be as received from Akzo Nobel Fibres, Amhem.

Justification for type of information:

Additional documentation, provided within the IUCLID Assessment Reports (Section 13), supports the read-across approach.

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

yes

Remarks:

The test was performed according to a slightly modified OECD test guideline.

GLP compliance:

not specified

Analytical monitoring:

no

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION:
- Method: The test substance was added to the incubation vessels using a stock solution of 1.0 g/L.
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): Deionised water containing no more than 0.01 mg Cu/L and 1 mg/L non-purgeable organic carbon

Test organisms (species):

activated sludge of a predominantly industrial sewage

Details on inoculum:

- Laboratory culture: Secondary activated sludge was obtained from the WWTP Kleefse Waard in Arnhem. The WWTP Kleefse Waard is an activated sludge plant treating industrial waste water of the site Kleefse Waard.
- Preparation of inoculum for exposure: the activated sludge was diluted 5 times in the test. The influent used as substrate and effluent used to dilute the sludge were also obtained from the WWTP Kleefse Waard

Test type:

not specified

Water media type:

freshwater

Limit test:

no

Total exposure duration:

30 min

Test temperature:

20°C

pH:

ranged from 8.7-8.9

Nominal and measured concentrations:

Nominal: 0, 3.1, 6.3, 12.5, 25, 50, 100 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 200 mL Erlenmeyers
- Other: Homogenized activated sludge was incubated in a shaking water bath (100 Hz, 20°C) for 30 minutes.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2

Reference substance (positive control):

no

Duration:

30 min

Dose descriptor:

other: 30% reduction in respiration rate

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: EC50 could not be calculated

Details on results:

The validity of the test is shown by the control respiration rates which are within 16% of each other. The respiration rates and inhibition percentages calculated are in Table 1. At 100 mg/L, a 30% reduction of the respiration rate was observed and EC50 values could therefore not be calculated.

Respiration Rates, Inhibition Percentages, pH

Concentration (mg/L)	Activity (mg O2/min.litre)	Inhibition (%)	pH
Control	0.31	-	8.7
Control	0.26	-	8.7
3.1	0.31	0	8.7
6.3	0.28	2	8.7
12.5	0.29	0	8.7
25	0.27	5	8.7
50	0.28	2	8.8
100	0.20	30	8.9

Validity criteria fulfilled:

yes

Conclusions:

At 100 mg test substance/L, a 30% reduction of the respiration rate was observed and EC50 values could therefore not be calculated. The test substance will not have any adverse effects on the WWTP Kleefe Waard at concentration <10 mg/L.

Executive summary:

The toxicity of the test substance to activated sludge of the WWTP Kleefse Waard was determined by measuring the respiration rate after a contact time of 30 minutes at various concentrations of the test substance. The inhibitory effect of the test substance at a particular concentration was expressed as a percentage of the two controls. At 100 mg test substance/L, a 30% reduction of the respiration rate was observed and EC50 values could therefore not be calculated. The results demonstrate that the test substance will not have any adverse effects on the WWTP Kleefe Waard at concentration <10 mg/L.

Additional information

Microbiological respiration inhibition data is provided on p-phenylenediamine in activated sludge of predominantly industrial sewage. A 30% reduction in respiration rate (30 min): 100 mg/L (nominal) based on respiration rate was observed. Additional supporting data is provided for o-phenylenediamine, a structurally related analogue, in activated sludge for predominantly domestic sewage. The EC10 (3 h) and EC50 (3 h) values were 100 mg/L and 580 mg/L respectively. Data from the study with p-phenylenediamine are consistent with the results from the study with o-phenylenediamine.