Ziram

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

Study period:

15 February 1999 - 17 May 1999

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method:
Test substance: a stock dispersion of the test substance was prepared by dispering 0.2010 g of Ziram in 1000 mL of BOD dilution water
Reference substance: a stock solution of the reference substance was prepared according to the OECD guideline by dissolving 0.1251 g in 5 mL NaOH solution, adjusting the pH to 7.7 with HCl solution, and the making up to 250 mL with Nanopure water
- Controls: yes

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Source: oxidation ditch treating domestic sewage, Berkel en Rodenrijs, The Netherlands
- Preparation of inoculum for exposure: the sample was centrifugated and the supernatant discarded. Activated sludge was washed three times by centrifugation (10 min at 2000 rpm = max. 1218 g) and resuspension in tap water twice and in dilution water once. The dry weight of the sludge suspension was determined and the suspension diluted to approximately 4 g/L of mixed liquor suspended solids (MLSS) by addition of dilution water. Then, it was aerated vigorously and kept at approximately 20°C in the dark.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20°C

pH:

7.9

Nominal and measured concentrations:

Nominal concentrations: 0.10, 0.32, 1, 3.2, 10, 32 and 100 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 1 L glass beakers containing 16 mL of synthetic sewage feed, 284 mL of control (dilution water) or treatment solutions and 200 mL of activated sludge
- Aeration: 0.5 to 1 L/min
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: the dilution water was prepared according to NEN standard No. 6634.
- Synthetic sewage feed was prepared according to OECD guideline

EFFECT PARAMETERS MEASURED: respiration inhibition

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.2

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

19.2 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

0.32 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Results with reference substance (positive control):

The EC50 for 3,5-dichlorophenol was determined to be 13.2 mg/L, value within the validity range of the OECD guideline (5 to 30 mg/L)

Validity criteria fulfilled:

yes

Description of key information

EC50 (3 h) = 19.2 mg/L (nominal, activated sludge, OECD 209)

Key value for chemical safety assessment

EC50 for microorganisms:

19.2 mg/L

Additional information

The effect of zinc bis dimethyldithiocarbamate (CAS No. 137-30-4) on aquatic microorganisms activity was investigated by Hanstveit et al. (1999). This test was conducted according to OECD Guideline 209, Activated Sludge, Respiration Inhibition Test (1984), under GLP conditions. After 3 hours of exposure to the test substance at 20°C, respiration rate inhibition in activated sludge microorganisms was reported, resulting in a EC50 (3 h) value of 19.2 mg/L.