Methanesulfonamide, N-[2-[(4,6-dimethoxy-1,3,5-triazin-2-yl)carbonyl]-6-fluorophenyl]-1,1-difluoro-N-methyl-

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:

22 Oct - 12 Dec 2014

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Version / remarks:

2010 and considered the Question-and-Answer Document by the German Federal Environment Agency (Version 2012-03-02).

Qualifier:

equivalent or similar to guideline

Guideline:

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

Version / remarks:

2008

GLP compliance:

yes (incl. QA statement)

Remarks:

Ministerium für Arbeit, Gesundheit und Soziales des Landes Nordrhein-Westfalen

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
A direct weighing was prepared to give the test item concentrations. The test item was added into Erlenmeyer flasks (incubation vessels) to about 130 mL deionised water and was stirred before testing (equilibration phase) overnight for 17 hours. The pH was measured was adjusted with NaOH.

Test organisms (species):

activated sludge, domestic

Details on inoculum:

- Origin: Aeration tank of a domestic waste water treatment plant (Municipal WWTP Cologne-Stammheim)
- Date of collection: 2014-10-27
- Pretreatment: The sludge was settled and the supernatant was decanted. After centrifuging the sludge (15 min at 4500 rpm and 20°C) the supernatant was decanted again.
- Method of cultivation: Approximately 1 g of the wet sludge was dried in order to calculate the amount of wet sludge to achieve a concentration of activated sludge of 3 g/L (dry weight) suspended solids. The sludge was aerated at 20 ± 2 °C and daily fed with synthetic medium*
- Initial biomass concentration: Before use the wet weight/dry weight relationship of the activated sludge was determined by drying 10 mL of sludge suspension. Subsequently, a sludge suspension of 2 g (dry weight)/L was prepared. 8 mL of the synthetic medium and 100 mL of activated sludge were added to the dissolved test item. The mixture was filled up with deionised water to 250 mL and aerated at 20 ± 2 °C. The inoculum concentration in the test was equal to 800 mg/L suspended solids.


* Synthetic medium:
16.0 g/L peptone
11.0 g/L meat extract
3.0 g/L urea
0.7 g/L NaCl
0.4 g/L CaCl2 x 2H2O
0.2 g/L MgSO4 x 7H2O
2.8 g/L K2HPO4

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Test temperature:

20 ± 2 °C

pH:

7.2-8.0

Nominal and measured concentrations:

Test item concentration (nominal): 100 mg/L
Reference substance concentrations (nominal): 2.5, 5, 10, 20 and 40 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 300 mL glass Erlenmeyer flasks
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6
- Additional control to determine the physico-chemical oxygen consumption: 1
- Additional control of heterotrophic oxidation (replicates): 2 (100 mg/L test item, containing 1.25 mL of ATU-solution (N-allylthiourea), which equals to a final concentration of 11.6 mg ATU/L)

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: deionised water and synthetic medium

OTHER TEST CONDITIONS
- Adjustment of pH: Initial to pH 6-8

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

>= 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

As no significant inhibitory effect was measured at a limit test item concentration of 100 mg/L no statistical analysis was required to determine the EC50.

Results with reference substance (positive control):

EC50 (3h) for 3,5-Dichlorophenol = 8.36 mg/L
The EC50 of the reference compound 3,5-Dichlorophenol should be in the range of 2 – 25 mg/L for total respiration; thus the test is validity criterion is fulfilled

The respiration rate is classified into two processes of oxidation. The oxidation of organic carbon and the ammonium oxidation (nitrification). The use of the specific nitrification inhibitor, ATU (N-allylthiourea), enables the direct assessment of the inhibitory effects of test substances on heterotrophic oxidation, and by subtracting the oxygen uptake rate in the presence of ATU from the total uptake rate, the effects on the rate of nitrification may be calculated.

The oxygen uptake rates of two additional controls and one replicate of the test item concentration 100 mg/L all in the presence of N-allylthiourea were measured after the exposure period. These values represent the heterotrophic respiration.

Description of key information

 Activated sludge respiration inhibition (OECD 209) NOEC >= 100 mg/L (nominal)

Additional information

One study is available on the toxicity of triafamone (CAS No. 874195-61-6) to activated domestic sludge (Neuhahn, 2014). The study was performed according to OECD guideline 209 and GLP. The test was conducted as limit test with a test item concentration of 100 mg/L. After 3 hours incubation, no statistically significant difference in respiration was determined between the 3 replicates with 100 mg/L triafamone and the 6 control vessels. Thus the NOEC (3h) for respiration inhibition of activated sludge is >= 100 mg/L triafamone.