Sodium p-chloro-m-cresolate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

11 Aug 2008

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Ministerium für Umwelt und Naturschutz, Landwirtschaft und Verbraucherschutz des Landes Nordrhein-Westfalen

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Direct weighting
- Differential loading: yes
- Controls: blank control
- Eluate: no

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Laboratory culture: no
- Name and location of sewage treatment plant where inoculum was collected: STP, Cologne-Stammheim, Germany (aeration tank)
- Method of cultivation: Aeration of the activated sludge at 20 °C ± 2 °C, daily feed with synthetic medium.
- Preparation of inoculum for exposure: First, the sludge is settled and supernatant is decanted. After centrifuging (15 min at 4000 rpm and 20°C) the supernatant is decanted again. 1 g of wet sludge is dried in order to calculate the amount of wet sludge to achieve a concentration of activated sludge of 3 g/L (dry wet) suspended solids. The calculated amount of sludge is first dissolved in synthetic medium and then filled up to a defined end volume with de-ionized water.
- Pretreatment: none
- Concentration of Inoculum: 3 g/L (dry weight).

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20.7 - 20.9 °C

pH:

7.7 - 7.9

Dissolved oxygen:

See "Any other information on results incl. tables"

Nominal and measured concentrations:

nominal: control, 10, 18, 32, 56 and 100 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 300 mL glass Erlenmeyer flasks
- Aeration: yes
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2
- Sludge concentration (weight of dry solids per volume): 800 mg/L suspended solids

TEST MEDIUM / WATER PARAMETERS
- Preparation of test medium: according to guideline

OTHER TEST CONDITIONS
- Adjustment of pH: yes, adjusted to pH 7±0.5 using HCl

EFFECT PARAMETERS MEASURED: respiration inhibition after 3 h of incubation

TEST CONCENTRATIONS
- Range-finding test : 10, 100 and 1000 mg/L
- Results used to determine the conditions for the definitive study: The range-finding test revealed inhibition rates of 20.1%, 74.2% and 100% for test substances concentrations of 10, 10 and 100 mg/L, respectively.

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

5.7 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: respiration rate

Remarks:

95% CL: 1.6 - 10.2 mg/L

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

41.4 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: respiration rate

Remarks:

95% CL: 30.8 - 58.7 mg/L

Details on results:

- Effect concentrations exceeding solubility of substance in test medium: no
- Blank controls oxygen uptake rate: no physico-chemical oxygen consumption was observed

Results with reference substance (positive control):

- Results with reference substance valid? yes, the EC50 of 3,5-dichlorophenol is in the accepted range 5 to 30 mg/L
- EC50 (3 h): 7.2 mg/L (95% CI: 3.8 - 13.2 mg/L)

Reported statistics and error estimates:

Inhibitory effect of the test item: Percentage of the mean of the respiration rates of two controls. EC50 values: Determined by probit analysis of the respiration rates at different test substance concentrations.

Table 1: Main test (test substance CMK): Oxygen content, temperature and pH values during exposure phase

	Test item concen-tration [mg/L]	O2 start [mg O2/L]	O2 end [mg O2/L]	Time (start-end) [min.]	Temp. [°C]	pH
Test item	10	5.7	2.6	7	20.6	7.7
	18	5.5	2.8	7	20.5	7.7
	32	5.8	2.7	9	20.7	7.7
	56	5.9	3.9	8	20.8	7.6
	100	6.2	5.0	9	20.9	7.5
Control 1		5.7	2.8	5	21.1	7.7
Control 2		5.4	2.7	5	20.6	7.7
Physico-chemical oxygen consumption control *		7.5	7.5	9	20.8	7.3

  Comments: * Data obtained in the range finding test. The test item was added to about 130 mL deionized water and stirred overnight before testing (equilibration phase).

Table 2: Results of test item

Test item concen-tration [mg/L]	Respiratory ratetest item [mg/L h]	Phys.-chem. O2 consumption [mg/L⋅h]	Respiratory rate - phys.-chem. O2 consumption [mg/L⋅h]	Inhibition [%]
10	26.6	0.0*	26.6	20.9
18	23.1	0.0*	23.1	31.1
32	20.7	0.0*	20.7	38.5
56	15.0	0.0*	15.0	55.4
100	8.0	0.0	8.0	76.2
Control. Mean	33.6
Control 1	34.8
Control 2	32.4

* The physico-chemical oxygen consumption has been determined at 1000 mg/L test item concentration. As no physico-chemical oxygen consumption was observed at that test item concentration this observation also holds true for the lower test item concentrations.

Table 3: Validity criteria

Criterion from the guideline	Outcome	Validity criterion fulfilled
The two control respiration rates are within 15 per cent of each other.	Respiratory rates of the 2 controls differ less than 15 %	yes
The EC 50 (3 hours) of 3,5-dichlorophenol is in the accepted range 5 to 30 mg/L.	EC50 of the reference compound 3.5-Dichlorophenol is in the range 5 – 30 mg/L	yes

Validity criteria fulfilled:

yes

Remarks:

For further details please refer to “Any other information on results incl. tables”.

Conclusions:

EC 50 (3 h) = 41.4 mg/L
EC 10 (3 h) = 5.7 mg/L

Executive summary:

The effect of p-chloro-m-cresol on aquatic micro-organism was investigated by Neuhahn (2008) in accordance with the OECD guideline 209 and EC Method C.11. P-chloro-m-cresol showed inhibitory effects on activated sludge. 50% inhibition of microbial activity was determined at 41.4 mg/L. The EC10 was determimed at 5.7 mg/L.

Reference 2

Endpoint:

activated sludge respiration inhibition testing

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

Refer to analogue justification document provided in IUCLID section 13.

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

5.7 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: respiration rate

Remarks:

95% CL: 1.6 - 10.2 mg/L

Remarks on result:

other:

Remarks:

source, CAS 59-50-7, key rel 1, Neuhahn 2008

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

41.4 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: respiration rate

Remarks:

95% CL: 30.8 - 58.7 mg/L

Remarks on result:

other:

Remarks:

source, CAS 59-50-7, key rel 1, Neuhahn 2008

Description of key information

EC50 (3 h) = 41.4 mg/L (nominal, activated sludge microorganisms), read-across

EC10 (3 h) = 5.7 mg/L (nominal, activated sludge microorganisms), read-across

Key value for chemical safety assessment

EC50 for microorganisms:

41.4 mg/L

EC10 or NOEC for microorganisms:

5.7 mg/L

Additional information

No study investigating the toxicity of sodium p-chloro-m-cresolate (CAS 15733-22-9) to aquatic microorganisms is available. Therefore, in accordance to Regulation (EC) No. 1907/2006 Annex XI, 1.5 a read-across to the source substance (p-chloro-m-cresol, CAS 59-50-7) which is the main transformation product of the target substance sodium p-chloro-m-cresolate (CAS 15733-22-9) is applied.

The source substance p-chloro-m-cresol is the common compound in this analogue approach and is solely responsible for the (absence of) effects. Thus, the source substance is considered a suitable representative for the evaluation of the toxicity of the target substance to aquatic organisms. The read-across approach is justified in detail within the analogue justification in IUCLID section 13.

One experimental study is available investigating the effect of p-chloro-m-cresol on aquatic microorganism (Neuhahn, 2008). The test was conducted according to OECD guideline 209 and EC Method C.11. Activated sludge microorganisms were exposed for 3 hours to nominal concentrations of 10, 18, 32, 56 and 100 mg/L. The inhibition of respiration was measured at the end of the study. P-chloro-m-cresol showed inhibitory effects on activated sludge microorganisms. 50% inhibition of microbial activity was determined at 41.4 mg/L. Therefore the EC50 (3 h) was 41.4 mg/L. The EC10 (3 h) was determined to be 5.7 mg/L.

Based on the available results from a structurally similar source substance (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5) which is the main transformation product of the target substance and is characterized by a similar ecotoxicological profile and comparable structure, it can be concluded that sodium p-chloro-m-cresolate has effects in the same range as the target substance.