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Diss Factsheets

Ecotoxicological information

Toxicity to microorganisms

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Administrative data

Link to relevant study record(s)

Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
comparable to guideline study
Remarks:
under GLP, validity criteria met. 1993 OECD guideline version.
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Version / remarks:
1993
GLP compliance:
yes
Analytical monitoring:
no
Test organisms (species):
activated sludge, domestic
Details on inoculum:
Test mixture contained test substance (1g/l), sewage feed (as prescribed by OECD 209) and activated sludge from laboratory wastewater treatment plants treating municipal wastewater.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
30 min
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Duration:
30 min
Dose descriptor:
other: EC20
Effect conc.:
ca. 27 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Key result
Duration:
30 min
Dose descriptor:
EC50
Effect conc.:
800 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Results with reference substance (positive control):
The EC20 for the reference 3,5-dichlorophenyl was 2.5 mg/l and the EC50 was 15 mg/l. The EC50 for the reference is valid because of ranging between 5 and 30 mg/l as validity criteria. 
Respiration rate          Inhibition
                        (mgO2/l*h)               (%)
Test substance
           20 mg/l          13                   -19
          100 mg/l          12                   -25
          250 mg/l          11                   -31
          500 mg/l          10                   -38
         1000 mg/l           7                   -56

Inoculum blank              16                    -
Reference substance
            1 mg/l          15                   -6
           10 mg/l           9                   -44
          100 mg/l           1                   -94

A significant inhibition of the respiration rate was observed.  Disturbances in the biodegradation process of activated sludge are  possible.

Description of key information

The toxicity to microorganisms was investigated in an OECD209 (1993) guideline test under GLP. Activated sludge from a municipal waste water treatment was used and respiration rate was measured after 30 minutes of exposure. Concentrations tested were 20, 100, 250, 500 and 1000 mg/L. The EC20 and EC50 values were approximately 27 and 800 mg/L respectively.

Key value for chemical safety assessment

EC50 for microorganisms:
800 mg/L

Additional information