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Ecotoxicological information

Toxicity to microorganisms

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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
From March 15, 1999 to March 18, 1999
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Remarks:
RA study
Reason / purpose:
read-across: supporting information
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Qualifier:
according to
Guideline:
other: Commission Directive 88/302/EEC; Official Journal of the EC L 133, Part C: Biodegradability: Test for inhibition of oxygen consumption
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Remarks:
direct weighing
Details on test solutions:
Test concentrations: 0, 100, 1000 and 10000 mg/L
The test substance has been added to about 130 mL deionized water and stirred overnight before testing (equilbrium phase)
Test organisms (species):
activated sludge
Details on inoculum:
Origin: aeration tank of a waste water plant treating predominantly domestic sewage (Wupper area water authority)
Pretreatment: none
Test concentration of the activated sludge: 560 mg/L
pH of the suspension before application: 6.8
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Test temperature:
20 +/- 2°C
pH:
7.1 - 8.2
Nominal and measured concentrations:
0, 100, 1000 and 10000 mg/L (nominal)
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol (purity: 97%; stock solution: 500 mg/L) at concentrations of 5, 10 and 20 mg/L
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 10 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Key result
Duration:
3 h
Dose descriptor:
EC10
Effect conc.:
> 10 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Details on results:
There was no physico-chemical oxygen consumption at the highest test substance concentration, therefore no physico-chemical oxygen consumption has been determined at the lower concentrations.

Table 1. Results for the test substance

 Test concentration (mg/L)  Respiratory rate test substance (mg/L*h)  Phys. chem. O2 -consumption (mg/L*h)  Respiratory rate - phys. chem. O2 - consumption (mg/L*h) Inhibition (%) 
 100  27.8 0.0   27.8  1.1
 1000  28.3 0.0  28.3  0.0
 10000  24.8 0.0  24.8  11.7

Control mean: 28.1 mg/L*h (respiratory rate)

Table 2. Results for the reference substance

 Test concentration (mg/L)  Respiratory rate (mg/L*h)  Inhibition (%)  
 5 22.3  20.6   
 10 15.0  46.6   
 20 6.8  75.8   
Validity criteria fulfilled:
yes
Conclusions:
Under the study conditions, the nominal 3 h EC50 of the substance in activated sludge was determined to be greater than 10000 mg/L.
Executive summary:

A study was conducted to determine the toxicity of the read-across substance to the respiration of activated sludge microorganisms according to a method equivalent to OECD Guideline 209. Activated sludge (at 560 mg/L suspended solids level) was exposed to the test substance at nominal concentrations of 0, 100, 1000 and 10000 mg/L for 3 h. The reference substance3,5 -dichlorophenol was run in parallel at 5, 10 and 20 mg/L. Temperature and pH were recorded at test end. Under the study conditions, the nominal 3 h EC50 of the substance in activated sludge was determined to be greater than 10000 mg/L (Müller, 1999).

Description of key information

Key value for chemical safety assessment

EC50 for microorganisms:
10 000 mg/L
EC10 or NOEC for microorganisms:
10 000 mg/L

Additional information

A study was conducted to determine the toxicity of the read-across substance to the respiration of activated sludge microorganisms according to a method equivalent to OECD Guideline 209. Activated sludge (at 560 mg/L suspended solids level) was exposed to the test substance at nominal concentrations of 0, 100, 1000 and 10000 mg/L for 3 h. The reference substance 3,5 -dichlorophenol was run in parallel at 5, 10 and 20 mg/L. Temperature and pH were recorded at test end. Under the study conditions, the nominal 3 h EC50 of the substance in activated sludge was determined to be greater than 10000 mg/L (Müller, 1999).