Potassium (E,E)-hexa-2,4-dienoate

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:

17-12-2001 to 18-03-2002

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Guideline study (GLP) The pH values were not reported. However, since the results of both, treatment and controls, are consistent, respectively, and the quality criteria are fulfilled, the non-reporting of pH is considered a minor deficiency that does affect the validity of the study.

Justification for type of information:

Since sorbic acid is the corresponding acid to potassium sorbate, the substance in question, extrapolation of the obtained results is not considered to be restricted.

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

yes

Remarks:

, the test was performed as a limit test, as a consequence of the results of the range-finding test.

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

, the test was performed as a limit test, as a consequence of the results of the range-finding test.

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2000-07-20

Specific details on test material used for the study:

Substance name: Sorbic Acid
Batch number: 0000005562
Chemical name: 2,4-Hexadienoic acid
CAS number: 110-44-1
Formula: C6HsO2
Molecular weight: 112.13 g/mol
Dissociation constant: 4.76
Content: 99.9%
Certificate of analysis: 27/02/2001
Expiry date: 23/02/2004
Appearance / colour: Solid / white - yellowish
Safety precautions:
Storage conditions:
Purity and composition

Analytical monitoring:

no

Details on sampling:

No measurements conducted during the test.

Vehicle:

no

Details on test solutions:

Synthetic sewage as specified by EC method C.11 and OECD guideline 209.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Source: Municipal STP of Pforzheim, Germany
- Preparation of inoculum for exposure: Washed with tap water by centrifugation; resuspended in 4 L of tap water and aerated.
- Pretreatment: No
- Initial biomass concentration: 1.6 g/L suspended solids (test medium)

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Post exposure observation period:

no data

Hardness:

no data

Test temperature:

20 ± 2 °C

pH:

Not provided

Dissolved oxygen:

measured as effect parameter

Salinity:

not applicable

Nominal and measured concentrations:

Main test: 100 mg/L (limit test)

Details on test conditions:

TEST SYSTEM
- Test vessel: BOD flasks, approx. 250–300 mL
- Type (delete if not applicable): open
- Aeration: yes, WISO air pump with activated carbon filter, 0.5–1 L/min
- No. of vessels per concentration (replicates): 6
- No. of vessels per control (replicates): 2
- Suspended solids concentration: 1.6 g/L

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): Respiration inhibition measured as continuous recording of oxygen concentration over 10 min. Measuring equipment: O2-electrode, oxymeter OXI 340, WTW, Weilheim, Germany

TEST CONCENTRATIONS
- Range finding study: yes
- Test concentrations: 0.01–100 mg/L, spaced by a factor of 10.
- Results used to determine the conditions for the definitive study: yes, as suggested by the results of the range-finding test, the main test was conducted in the style of a limit test: 100 mg/L, 6 replicates

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol (DCP), CAS-No.: 591-35-5, 5, 15, and 30 mg/L

Key result

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

Remarks on result:

other: limit test

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: limit test

Details on results:

- Preliminary test: No inhibitory effect found up to the highest test concentration.
- Main test: no inhibitory/toxic effects were observable at the limit test concentration of c = 100 mg/L. After 3 h test duration, sorbic acid showed more of a stimulating effect on microbial activity rather than inhibition.
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: Solubility in water, stability, adsorption behaviour and volatility are unlikely to have impacted the results.
- Effect data: after 30 min: 6.0 ± 3.2 % inhibition (mean ± SD); after 3 h: –8.7 ± 3.5 % inhibition (mean ± SD)

Results with reference substance (positive control):

EC50 is within the critical range of 5–30 mg/L.

Reported statistics and error estimates:

Percent respiration inhibition, as described in OECD guideline 209 and EC method C.11.

Table1: Effect data (respiration inhibition) from the main test; replicates were conducted with a concentration of 100 mg/L sorbic acid.

Replicate no.	RS (mg O2/ L × h)	RC1+ RC2 (mg O2/L ×h)	% inhibition^*)
(a) after 30 min
Test substance
0.0 (Control 1)	39.61	77.52	—
(1)	35.65	77.52	8.0
(2)	36.67	77.52	5.4
(3)	35.17	77.52	9.3
(4)	38.75	77.52	0.5
(5)	36.41	77.52	6.1
(6)	36.48	77.52	5.9
0.0 (Control 2)	37.91	77.52	—
Reference substance
5 mg/L	29.38	77.52	24.2
15 mg/L	16.25	77.52	58.1
30 mg/L	8.11	77.52	79.1
(b) after 3 h
Test substance
0.0 (Control 1)	33.34	69.62	—
(1)	36.83	69.62	–5.8
(2)	36.36	69.62	–4.5
(3)	39.40	69.62	–13.2
(4)	37.95	69.62	–9.0
(5)	39.10	69.62	–12.3
(6)	37.31	69.62	–7.2
0.0 (Control 2)	36.28	69.62	—
Reference substance
5 mg/L	24.39	69.62	29.9
15 mg/L	12.17	69.62	65.0
30 mg/L	4.93	69.62	85.8
^*)negative values indicate stimulating effects

 

Validity criteria fulfilled:

yes

Remarks:

The reference substance showed the expected toxic effect, with an EC50 in the range of 5–30 mg/L. The respiration rates of the controls at the start and the end of the test varied by less than 15 %.

Conclusions:

In the limit test with sorbic acid no effect were detected at 100 mg/L. Thus, the EC50 (3 h) is above 100 mg/L. The test was conducted with sorbic acid, which is the corresponding free acid to potassium sorbate. Since the sorbate anion is the physiologically and environmentally relevant component, the results are considered to be also valid for potassium sorbate without any restrictions.

Executive summary:

The respiration rate of an activated sludge was studied according to the OECD 209 guidelines. Activated sludge was fed with a standard amount of synthetic sewage feed and measured after 30 minutes and 3 hours of contact in the presence of Sorbic Acid. A range-finding test was conducted at 0.01 mg/L to 100 mg/L were tested to determine the final dilution concentrations. Since no inhibitory effects of Sorbic Acid were onserved at any of these test concentration, the main test was performed in a limit test design with 6 replicates of
the highest test concentration of 100 mg/L. In conclusion, no inhibitory effects were found in the main test, therefore, Sorbic Acid was found to be not toxic on sewage treatment.

Description of key information

3-hour EC50 >100 mg/l
3-hour NOEC >100 mg/l

Key value for chemical safety assessment

EC50 for microorganisms:

100 mg/L

EC10 or NOEC for microorganisms:

100 mg/L

Additional information

In an acute toxicity limit test conducted with sorbic acid, both the EC50 and the NOEC were above 100 mg/l.