Bromo(hexahydro-2H-azepin-2-onato-N)magnesium

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

01/2008 to 06/2008

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2008

Report date:

2008

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Bromo(hexahydro-2H-azepin-2-onato-N)magnesium

EC Number:

241-158-2

EC Name:

Bromo(hexahydro-2H-azepin-2-onato-N)magnesium

Cas Number:

17091-31-5

Molecular formula:

C6H10BrMgNO

IUPAC Name:

magnesium(2+) ion 2-oxoazepan-1-ide bromide

additive 1

Reference substance name:

ε-caprolactam

EC Number:

203-313-2

EC Name:

ε-caprolactam

Cas Number:

105-60-2

Molecular formula:

C6H11NO

IUPAC Name:

azepan-2-one

Test material form:

solid: particulate/powder

Specific details on test material used for the study:

Batch No.: 07072601

Sampling and analysis

Analytical monitoring:

not required

Test solutions

Vehicle:

yes

Details on test solutions:

water

Test organisms

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

The sludge was taken from the activation basin of the ESN (Stadtentsorgung Neustadt)
sewage treatment plant, Im Altenschemel, 67 435 NW-Lachen-Speyerdorf. It was collected
on the same day as the respective experiment was performed and aerated during transport.
Upon arrival in the test facility, the sludge was washed with tap water three times, then
c~ntrifuged and re-suspended in tap water.

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test conditions

Hardness:

2.01 mmol/L

Test temperature:

20 ± 2 °C

pH:

7.2 to 7.9

Nominal and measured concentrations:

2000, 1000, 500, 250 and 125 mg/L.

Details on test conditions:

First, a limit-test with two replicates using the nominal concentration 1000 mg/L was performed.
Duration of the test was three hours. Activated sludge was used as inoculum. It
was taken from a domestic sewage treatment plant and washed t?efore usage. The dry
matter was determined as 4.3 g suspended solids/L, giving a concentration of 1.72 g suspended
solids/L in the test.

3,5-Dichloro-phenole was used as reference item. Five concentrations were tested; an
EC50 of 8.8 mg/L (95% confidence interval: 7.2 - 10.5 mg/L) was tjetermined, which lies
within the range of 5 - 30 mg/L.
The treatment 1000 mg/L showed a mean inhibition of the respiration rate of the activated
sludge of 42 %.

Then, a main study was performed using five treatments (ranging from nominally 2000 to
125 mg/L). The dry matter of the activated sludge was determined as 3.8 g suspended
solids/L, giving a concentration of 1.52 g suspended solids/L in the test. The EC50 of the
reference item was determined as 6.8 mg/L (95% confidence interval: 5.9 - 7.7 mg/L).

Reference substance (positive control):

yes

Remarks:

3,5-Dichloro-phenole

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 2 018 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Effect concentrations 2

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

126 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

At
2000 mg/L and 1 OOO mg/L 40 %, at 500 mg/L 38 %, at 250 mg/L 31 % and at 125 mg/L
12% inhibition were detected. The test item showed inhibition values which were not correlated
to its concentration: at nominal concentrations 2000, 1 OOO and 500 mg/L, approx.
the same inhibition was found. It is believed that the test system, consisting of a wide variety
of micro-organisms, is not uniformly affected by the test item.

Results with reference substance (positive control):

3,5-Dichloro-phenole was used as reference item. Five concentrations were tested; an
EC50 of 8.8 mg/L (95% confidence interval: 7.2 - 10.5 mg/L) was tjetermined, which lies
within the range of 5 - 30 mg/L.
The treatment 1000 mg/L showed a mean inhibition of the respiration rate of the activated
sludge of 42 %.

Reported statistics and error estimates:

O2 consumption was calculated from the linear regression equations of the measured O2
values of the respective test vessel. For all regressions, r2 of 0.99 or more were found.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

In both studies, the inhibition which was caused by the test item Bromo(hexahydro-2H-
azepin-2-onato-N)magnesium did not rise above approx. 40 %, which were observed in
the treatments 2000, 1000 and 500 mg/L. It might be possible that the test item shows
inhibitory action only to part of the micro-organisms which are present in the activated
sludge, so that respiration of these micro-organisms is nearly completely inhibited by
approx. 500 mg/L test item concentration. The micro-organisms which are not susceptible
to toxic effects of the test item are not inhibited at all up to the highest concentrations
tested. The inhibition values of the concentrations 1000 and 2000 mg/L do not correlate
with those of the lower concentrations. If the 3h EC50 value were extrapolated from the
lower concentrations, a value of 600 mg/L would be obtained. Experimentally, a 3h-EC50
of > 2000 mg/L (nominal; real: 2018 mg/L) was found.

At the lowest concentration (126 mg/L), 12 % inhibition were observed. As this inhibition
lies below the recommended limit for variation within the controls, 126 mg/L can be stated
as NOEC.

All validity criteria were met. The respiration rate of the activated sludge lay within the
normal range of 0.5 - 0.9 mg/(L*min.).

Therefore, the result of the test can be considered valid.

Executive summary:

In a test on the inhibition of the respiration of Activated Sludge an EC50 over 3 hours of >2018 mg/l was determined.