Isopropylamine

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:

1996

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Only 30 min exposure time; only 2 concentrations tested; however, supported by tests on ready and inherent biodegradability (no microorganism toxicity observed.

Justification for type of information:

Exposure time in this test was limited to 30 minutes. However, available biodegradation screening tests (see cross-references) support this study with regard to long-term exposure of microorganisms: neither at 100 mg/L nor at 656 mg/L initial test item concentration was any relevant microorganism toxicity observed (fast and thorough mineralisation).

Reason / purpose for cross-reference:

reference to other study

Remarks:

Ready biodegradability

Reason / purpose for cross-reference:

reference to other study

Remarks:

Inherent biodegradability (oxygen consumption)

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Version / remarks:

adopted in April 1984

Deviations:

yes

Remarks:

only 2 concentrations tested

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

Based on a relative density of 0.69, 181 µL and 362 µl were directly added to the test medium to arrive at test item concentrations of 500 and 1000 mg/L (250 mL total volume).

Test organisms (species):

activated sludge, domestic

Details on inoculum:

Activated sludge from a laboratory wastewater plant treating municipal and artificial sewage. Concentration of dry substance 1 g/L .

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

30 min

Hardness:

no data

Test temperature:

20 ± 2 °C

pH:

According to the report, pH was adapted to pH 7.0 to 8.0 before inoculum was added.
However, in the results table, pH values of 10.9 (500 mg/L) and 11.2 (1000 mg/L) are given (see attached illustration). This is contradictory and it is not clear what actual pH prevailed during the study.

Dissolved oxygen:

no data

Salinity:

fresh water

Nominal and measured concentrations:

500 and 1000 mg/L (nominal)

Details on test conditions:

Incubation temperature: 20 +/-2 °C;
Synthetic medium: 100x concentrated OECD medium, 8 mL per sample (final volume 250 mL);

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Key result

Duration:

30 min

Dose descriptor:

other: EC20

Effect conc.:

ca. 600 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

30 min

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth inhibition

Duration:

30 min

Dose descriptor:

other: EC80

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth inhibition

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Relevant effect levels: EC20 approx. 1.5 mg/L, EC50 approx. 10 mg/L, EC80 approx. 80 mg/L

Validity criteria fulfilled:

yes

Remarks:

according to OECD 209 (1984)

Conclusions:

In a valid (RL 2) activated sludge respiration inhibition test (OECD 209, 1984) performed compliant to GLP the following results were obtained:
EC20 (30 min) ca. 600 mg/L;
EC50 (30 min) > 1000 mg/L (27 % inhibition observed relative to control).
The study is supported regarding long-term microorganism toxicity by available biodegradation screening tests, where no microorganism toxicity was observed up to 656 mg/L test item (fast and thorough mineralisation).

Executive summary:

In a valid (RL 2) activated sludge respiration inhibition test (OECD 209, 1984) performed compliant to GLP the following results were obtained:

EC20 (30 min) ca. 600 mg/L;

EC50 (30 min) > 1000 mg/L (27 % inhibition observed relative to control).

Contradictory information is given in the report with regard to the pH prevailing during the test. While the text section states that neutralization were performed before addition of inoculum, the results table gives pH values of 10.9 (500 mg/L) and 11.2 (1000 mg/L) which would make pH induced toxicity probable.

While the exposure time was limited to 30 minutes instead of 3 hours demanded today as the minimum exposure time, the study is supported regarding long-term microorganism toxicity by available biodegradation screening tests, where no microorganism toxicity was observed up to 656 mg/L test item (fast and thorough mineralisation).

Altogether, the data allow to reliably conclude on a rather low STP microorganism toxicity, which may have been induced solely due to the alkaline pH produced by isopropylamine (pKa 10.8 for alkaline functionality). Accordingly, an approximate EC10 of 300 mg/L is derived from the data and is taken as the relevant key value for chemical safety assessment.

Description of key information

In a valid (RL 2) activated sludge respiration inhibition test (OECD 209, 1984) performed compliant to GLP the following results were obtained:

EC20 (30 min) ca. 600 mg/L;

EC50 (30 min) > 1000 mg/L (27 % inhibition observed relative to control).

The study is supported regarding long-term microorganism toxicity by available biodegradation screening tests, where no microorganism toxicity was observed up to 656 mg/L test item (fast

and thorough mineralisation).

Accordingly, an approximate EC10 of 300 mg/L is derived from the data on respiration inhibition and is taken as the relevant key value for chemical safety assessment.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

300 mg/L

Additional information

In a valid (RL 2) activated sludge respiration inhibition test (OECD 209, 1984) performed compliant to GLP the following results were obtained:

EC20 (30 min) ca. 600 mg/L;

EC50 (30 min) > 1000 mg/L (27 % inhibition observed relative to control).

Contradictory information is given in the report with regard to the pH prevailing during the test. While the text section states that neutralization were performed before addition of inoculum, the results table gives pH values of 10.9 (500 mg/L) and 11.2 (1000 mg/L) which would make pH induced toxicity probable.

While the exposure time was limited to 30 minutes instead of 3 hours demanded today as the minimum exposure time, the study is supported regarding long-term microorganism toxicity by available biodegradation screening tests, where no microorganism toxicity was observed up to 656 mg/L test item (fast and thorough mineralisation).

Altogether, the data allow to reliably conclude on a rather low STP microorganism toxicity, which may have been induced solely due to the alkaline pH produced by isopropylamine (pKa 10.8 for alkaline functionality). Accordingly, an approximate EC10 of 300 mg/L is derived from the data on respiration inhibition and is taken as the relevant key value for chemical safety assessment.