Zinc bis(dibenzyldithiocarbamate)

Toxicity to microorganisms

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:

guideline study

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test organisms (species):

activated sludge, domestic

Details on inoculum:

type: mixed population of aquatic microorganisms (activated sludge)
origin: aeration tank of a domestic sewage treatment plant (municipal STP Cologne-Stammheim).
microbial inoculum: the sludge was settled and the supernatant was decanted. After centrifuging (15 min at 3500/4500rpm and 20°C) the supernatant was decanted. Approx. 1g of the wet sludge was dried in order to calculate the amount of wet sludge of 3 g/l (dry weight)suspended solids.
The calculated amount of sludge was first dissolved in synthetic medium and than filled up to a defined end volume with deionised water.
storage of sludge: aeration of the activated sludge at 20°C daily fed with synthetic medium. (peptone, meat extract, urea, NaCl, CaCl2, MgSO4, K2HPO4)

Test type:

static

Water media type:

saltwater

Limit test:

yes

Total exposure duration:

3 h

Test temperature:

20°C

pH:

pH ogf the suspension before application: 7.6
pH of the synthetic sewage feed 7.5

Dissolved oxygen:

1000mg/L

Nominal and measured concentrations:

10,100 and 1000mg/l of test item
5,10 and 20mg/l of 3,5-dichlorophenol

Details on test conditions:

method: direct weighing
test vessel: 300ml glass Erlenmeyer flasks
test concentration of the activated sludge 800mg/l suspended solids
sitrring period of the test item before start of incubation time: 16h

Reference substance (positive control):

yes

Remarks:

3,5 dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

> 1 000 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

since some substances may consume oxygen by chemical reactivity, a physicochemical oxygen consumption control was carried out additionally. In order to be able to differentiate between physico-chemical oxygen consumption and biological oxygen consumption, at least the maximum concentration of the test item was tested without activated sludge. The respiration rate for each concentration was determined graphically from the linear part of the curve of O2 content veruss time. The inhibitory effect of the test item at a particular concentration is expressed as a percentage of the mean of the respiration rates of two controls. An EC50 value was calculated from the respiration rates at different test item concentrations.

Results with reference substance (positive control):

two controls without test item were included in the test design, one at the start and the other at the end of the test series. Each batch of activated sludge was checked using 3,5-Dichlorophenol as a reference compound.

Zinc dibenzyldithiocarbamate (ZBEC) showed 6,4 % respiration inhibition of activated sludge at the highest test item concentration of 1000mg/L

Description of key information

The 3-h EC10 of >1,000 mg/L in activated sludge will be used in the assessment.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L

Additional information

3-h EC50 and EC10 values of >1,000 mg/L are available from a GLP-compliant, OECD 209 guideline study with activated sludge (Currenta GmbH & Co., 2010e) for zinc bis(dibenzyldithiocarbamate). The 3-h EC50 value is used in the assessment. The 3-h EC10 was therefore determined to be 1000 mg/L