7,7-dimethyl-3-oxa-6-azaoctan-1-ol

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:

July 2001

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study conducted in accordance with generally accepted scientific principles, possibly with incomplete reporting or methodological deficiencies, which do not affect the quality of relevant results.

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

no

GLP compliance:

not specified

Analytical monitoring:

yes

Details on sampling:

For each test concentration, after a 3 hour incubation period the respiration rates were measured in each vessel.

Details on test solutions:

Nominal test concentrations (mg/l) of: 0 (control), 3.2, 10, 32, 100, 320, 1000 were prepared.

Test organisms (species):

activated sludge, domestic

Details on inoculum:

Activated sludge, freshly obtained from a sewage treatment plant receiving largely domestic sewage, used as the microbial source.

Test type:

static

Water media type:

not specified

Limit test:

no

Total exposure duration:

3 h

Post exposure observation period:

After a 3 hour incubation period the concentration of dissolved oxygen (mg/l) was measured every minute in each vessel for 10 minutes.

Hardness:

Not known.

Test temperature:

The test was performed at a temperature of 19.0ºC

pH:

Not known.

Dissolved oxygen:

The concentration of dissolved oxygen (mg/l) was measured every minute in each vessel for 10 minutes (after 3 hour incubation).

Salinity:

Not known.

Nominal and measured concentrations:

Nominal test conentrations (mg/l): 0 (control), 3.2, 10, 32, 100, 320, 1000

Details on test conditions:

See table below for test treatments.

The reference stock (0.5 g/l) was prepared in deionised water as described in OECD test guideline 209.

The appropriate volume of dilution water was measured into each test vessel and vigorously aerated. At time zero the required volume of synthetic sewage feed and activated sludge was added to the dechlorinated tap water in the first flask. The appropriate amount of test material was added (if required) and the aeration restored. This process was repeated at 15 minute intervals for the remaining flasks, using the volumes previously indicated.

After a 3 hour incubation period the respiration rates were measured in each vessel as follows. The contents were poured into 250ml glass BOD bottles and the oxygen electrode inserted. The probe displaced liquid and thus any air from the measuring apparatus. The contents were stirred continuously using the probes built in stirrer and the concentration of dissolved oxygen (mg/l) was measured every minute in each vessel for 10 minutes. The test was performed at a temperature of 19.0ºC

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol (3,5-DCP)

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

>= 320 - <= 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

dissolved

Remarks:

oxygen

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

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:

Between 3.2 and 100 mg/l test substance there was no apparent dose related response. However, for 320 mg/l and 1000 mg/l a response was observed with 18 and 63% inhibition respectively. The data clearly indicates that the EC50 lies between 320 mg/l and 1000 mg/l although an exact value could not be calculated with so few data.

The EC80 and EC20 values of the test substance, equally, could not be calculated.

The results of the abiotic control flask (test without addition of inocula) indicated that there would be no reduction in oxygen concentration in any of the test vessels up to, and including, 1000 mg/l of the test substance, attributable to processes in the test system other than those due to the activity of the activated sludge.

Results with reference substance (positive control):

The EC50 for the reference substance 3,5-DCP was 5.62 mg/l, satisfying the OECD validity condition that the EC50 for this substance be in the range 5 to 30 mg/l. The second validity condition, given in OECD 209, that the two control flasks had respiration rates within 15% of each other was also satisfied in this test.

Treatment	Respiration rate (R) (mg O2/l/hr)	Percentage respiration inhibition (I)
Control	30.51
Abiotic 1000 mg/l	0.40	99
DCP 5 mg/l	15.99	48
DCP 15 mg/l	9.02	71
DCP 30 mg/l	3.96	87
3.2 mg/l	32.24	-5
10 mg/l	32.82	-7
32 mg/l	32.20	-5
100 mg/l	31.05	-1
320 mg/l	25.14	18
1000 mg/l	11.45	63
Control	30.74

 

Validity criteria fulfilled:

yes

Conclusions:

Between 3.2 and 100 mg/l of the test substance there was no apparent dose related response. However, for 320 mg/l and 1000 mg/l a response was observed with 18 and 63% inhibition respectively. The data clearly indicates that the EC50 lies between 320 mg/l and 1000 mg/l although an exact value could not be calculated with so few data.

The EC80 and EC20 values of the test substance, equally, could not be calculated.

Executive summary:

This report describes a study to determine the effect of the test substance on activated sludge micro-organisms by measuring the respiration rate, under defined conditions, in the presence of different concentrations of the test substance. The method is based on that described in OECD test guideline 209 in which activated sludge, freshly obtained from a sewage treatment plant receiving largely domestic sewage, is used as the microbial source. The purpose of the study is to assess the possible effect of the test substance on aerobic microbial treatment plants and to indicate suitable non-inhibitory concentrations of the test substance for biodegradability tests.   

Two controls, without test substance, were included in the study to determine the degree of experimental variation. The sensitivity of the activated sludge was estimated using three concentrations of the reference substance 3,5-dichlorophenol (3,5-DCP).

Between 3.2 and 100 mg/l of the test substance there was no apparent dose related response. However, for 320 mg/l and 1000 mg/l a response was observed with 18 and 63% inhibition respectively. The data clearly indicates that the EC50 lies between 320 mg/l and 1000 mg/l although an exact value could not be calculated with so few data.

The EC50 for the reference substance 3,5-DCP was 5.62 mg/l, satisfying the OECD validity condition that the EC50 for this substance be in the range 5 to 30 mg/l. The second validty conition, given in OECD 209, that the two control flasks had respiration rates within 15% of each other was also satisfied in this test.

Description of key information

ASRIT NOEC = 100 mg/L; OECD 209; Chemex (2001)

Key value for chemical safety assessment

EC50 for microorganisms:

320 mg/L

EC10 or NOEC for microorganisms:

100 mg/L

Additional information

In an activated sludge respiration inhibition test conducted in accordance with OECD 209, no effect was seen on 3h respiration inhibition between 3.2 and 100 mg/l, resulting in a NOEC of 100 mg/L.. Inhibition of respiration was observed between 320 mg/l and 1000 mg/l ashowing 18 and 63% inhibition respectively. The report defined the EC50 between 320 mg/l and 1000 mg/l.