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Ecotoxicological information

Toxicity to microorganisms

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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Year of publication: 1981
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study without detailed documentation
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
GLP compliance:
no
Analytical monitoring:
not specified
Vehicle:
not specified
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
The sludge used by the different laboratories (5 laboratories) was domestic for 4 laboratories. One laboratory however used industrial sludge.
Preparation and amount of sludge used was as specified by OECD 209.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
3 h
Test temperature:
20 +- 2°C
pH:
pH: between 7 and 8
Nominal and measured concentrations:
Limit test: 100 mg/L nominal concentration
Details on test conditions:
Identical to OECD-guideline 209, as this publication was the basis for the development of the guideline.
For those chemicals whose respiration rate was at least 80% of the control, the IC50 (concentration for 50% inhibition of respiration rate) is recorded as >100 mg/L.
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Key result
Duration:
3 h
Dose descriptor:
IC50
Effect conc.:
> 100 mg/L
Nominal / measured:
not specified
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
The respiration rate for the submission substance at a concentration of 100 mg/L was >= 80% of the control samples without test item.
Results with reference substance (positive control):
Concentration of 3,5-dichlorophenol [mg/L] :: mean inhibition [%]:

100 :: 90%
50 :: 91%
25 :: 78%
10 :: 36%
1 :: 6%
Validity criteria fulfilled:
not specified
Remarks:
However, as validity criteria for guideline OECD 209 were specified, these criteria were probably fulfilled for the reported test results.
Conclusions:
In a publication regarding the development of a screening test for inhibitory effects of dye-stuffs on aerobic waste-water bacteria, later used as the methodical basis of the OECD 209 activated sludge respriation inhibition test, the toxicity of the submission substance to aerobic waste water bacteria had been tested. The EC50 (3 hours) had been determined as > 100 mg/L (defined as at least 80% respiration rate of the control) . This is probably a nominal concentration, however no specific indication is given. The sludge used by the different laboratories was predominantly domestic (4 laboratories used domestic, one of five laboratories however used industrial sludge). It is not clear, which type of sludge had been used with the submission substance. No information on substance purity is given.
However, as this interlaboratory study formed the basis for OECD guideline 209, the data are judged to be reliable (reliability category 2). From these data, the submission substance would be regarded as not harmful to aerobic microorganisms of sewage treatment plants.
Executive summary:

In a publication regarding the development of a screening test for inhibitory effects of dye-stuffs on aerobic waste-water bacteria, later used as the methodical basis of the OECD 209 activated sludge respriation inhibition test, the toxicity of the submission substance to aerobic waste water bacteria had been tested. The EC50 (3 hours) had been determined as > 100 mg/L (defined as at least 80% respiration rate of the control) . This is probably a nominal concentration, however no specific indication is given. The sludge used by the different laboratories was predominantly domestic (4 laboratories used domestic, one of five laboratories however used industrial sludge). It is not clear, which type of sludge had been used with the submission substance. No information on substance purity is given.

However, as this interlaboratory study formed the basis for OECD guideline 209, the data are judged to be reliable (reliability category 2). From these data, the submission substance would be regarded as not harmful to aerobic microorganisms of sewage treatment plants.

Description of key information

In a publication regarding the development of a screening test for inhibitory effects of dye-stuffs on aerobic waste-water bacteria, later used as the methodical basis of the OECD 209 activated sludge respriation inhibition test, the toxicity of the submission substance to aerobic waste water bacteria had been tested. The EC50 (3 hours) had been determined as > 100 mg/L (defined as at least 80% respiration rate of the control) . This is probably a nominal concentration, however no specific indication is given. The sludge used by the different laboratories was predominantly domestic (4 laboratories used domestic, one of five laboratories however used industrial sludge). It is not clear, which type of sludge had been used with the submission substance. No information on substance purity is given.

However, as this interlaboratory study formed the basis for OECD guideline 209, the data are judged to be reliable (reliability category 2). From these data, the submission substance would be regarded as not harmful to aerobic microorganisms of sewage treatment plants.

Key value for chemical safety assessment

EC50 for microorganisms:
100 mg/L

Additional information

To assess the possible impact of substances of the Pigment Yellow 12 and its strucutral analogues, the Diarylide Yellow Pigments, on sewage treatment plant microbial activity, a reliable Activated Sludge Respiration Inhibition Test for Pigment Yellow 13 is available (reliability category 2). At a pigment concentration far above the solubility limit, no respiration inhibition was observed (≥ 80% of the control). This is supported by a non-guideline study which focussed on possible long term microbial degradation of Pigment Yellow 13. By light microscopy different microorganisms growing on the particle surface could be detected, arguing against microbial toxicity of the pigment.

Judging from these experimental results, Diarylide Yellow Pigments are nontoxic to sewage treatment plant microorganisms.