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activated sludge respiration inhibition testing
Type of information:
migrated information: read-across based on grouping of substances (category approach)
Adequacy of study:
key study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Well documented report but with some deviations from standard method and no analytical monitoring reported.
according to
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
GLP compliance:
Analytical monitoring:
not specified
Details on test solutions:
Test substance added to test vessels and dispersed by slight stirring with a glass rod.
Test organisms (species):
activated sludge
Details on inoculum:
Strain/source: activated sludge from laboratory plant
Breeding method: bacteria fed with synthetic sewage consisting of peptone meat extract urea and some inorganic salts as in guideline.
Control: yes.
Test type:
Water media type:
Limit test:
Total exposure duration:
3 h
Post exposure observation period:
Test parameter: inhibition of respiration.
Nominal and measured concentrations:
1, 10 and 100 mg/l.
Details on test conditions:
no details provided.
Reference substance (positive control):
3 h
Dose descriptor:
Effect conc.:
> 100 mg/L
Nominal / measured:
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
respiration rate
Details on results:
Exposed: 0% inhibition of respiration with any of the tested concentrations. (respiration rate 0.5 mg/l min).
Control: respiration rate: 0.5 mg/l min
Results with reference substance (positive control):
Respiration rate with 1 mg/l: 0.4 mg/l min
respiration rate with 100 mg/l: 0 mg/l min

Description of key information

Based on the respiration rate using activated sludge, the 3h-EC50 for the test substance  was found to be >100 mg/L (Caspers et al, 1986), following an OECD 209 Activated Sludge, Respiration Inhibition Test. 

Key value for chemical safety assessment

EC50 for microorganisms:
100 mg/L

Additional information

The test substance is covered by the category approach of methylenediphenyl diisocyanates (MDI). Hence, data of the category substances can be used to cover this endpoint. The read-across category justification document is attached in IUCLID section 13. It is important to note that the MDI category approach for read-across of environmental and human hazards between the MDI substances belonging to the MDI category is work in progress under REACH. Therefore the read-across document should be considered a draft.

An OECD 209 Activated Sludge, Respiration Inhibition Test is available for PMDI. Based on the respiration rate using activated sludge, the 3h-EC50 was found to be >100 mg/L, which was the highest concentration tested (Caspers et al, 1986). This value may be used for the derivation of a PNECstp.