2,3,3-trimethyl-3H-indole-5-carboxylic acid

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

other information

Study period:

1988

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

ISO 8192 (Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation)

Version / remarks:

in most parts identical with OECD Guideline 209

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

activated sludge of a predominantly industrial sewage

Details on inoculum:

- first, the sludge was settled and the supernatant was decanted
- after centrifuging (20 min at 4000 rpm and 20°C) the supernatant was decanted
- approx. 1 g of the wet sludge was dried in order to calculate the amount of sludge to achieve a concentration of activated sludge of 6 g/L (dry weight) suspended solids
- the calculated amount of sludge was first dissolved in synthetic medium and than filled up to a defined end volume with deionised water
- test concentration of activated sludge: 6 g/L dry weight

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20.5 - 21.5 °C

pH:

7.4 - 7.8

Nominal and measured concentrations:

100, 1000, 10000 mg/L
The test item concentrations were based on nominal concentrations and not confirmed by analytical methods.

Details on test conditions:

250 mL of sludge with test item were incubated for 3 h with permanent aeration (50-100L/h)

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorphenol

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

>= 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

The respiration rate for each concentration was determined graphically from the linear part of the curve of O2-content versus time.
EC50 has been calculated by probit analysis.

Results with reference substance (positive control):

The toxicity of the reference substance 3,5-Dichlorphenol to bacteria was determined to be 4% for 1 mg/L and 75% for 20 mg/L. EC50 was graphically determined to be 8.9 mg/L.

Oxygen content during exposure phase

	Test item concentration [mg/L]	O2 start [mg/L]	O2 end [mg/L]	Time (start-end) [min]	inhibition [%]
Test item	100	4.6	2.0	6.0	0
	1000	4.7	2.9	5.0	10.0
	10000	5.4	3.1	7.0	17.9
Control 1		4.7	2.3	6.0	0
Control 2		3.9	2.3	4.0	0
Autoxidation	10000	9.4	9.4	10.0	0
3,5-Dichloro-phenol	1	4.6	2.3	6.0	4
	20	8.1	7.9	2.0	75

Conclusions:

After 3 h of incubation no effects were visible at 100 and 1000 mg/L for 2,3,3-trimethyl-3H-indole-5 -carboxylic acid. At 10000 mg/L an inhibiton of the respiration of the activated sludge of 18 % was found.

Executive summary:

The study was performed according to ISO 8192:1986/B, which is mostly identical with Guideline OECD 209. After 3 h incubation an EC50 >= 10000 mg/L was determined for 2,3,3-trimethyl-3H-indole-5-carboxylic acid. No effects were visible at 100 and 1000 mg/L. At 10000 mg/L an inhibiton of the respiration of the activated sludge of 18 % was found.

Description of key information

The study was performed according to ISO 8192:1986/B, which is mostly identical with Guideline OECD 209. After 3 h incubation an EC50 >= 10000 mg/L was determined for 2,3,3-trimethyl-3H-indole-5 -carboxylic acid. No effects were visible at 100 and 1000 mg/L. At 10000 mg/L an inhibiton of the respiration of the activated sludge of 18 % was found.

Key value for chemical safety assessment

EC50 for microorganisms:

10 000 mg/L