4-morpholinopropanesulphonic acid

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Justification for type of information:

ANALOGUE APPROACH JUSTIFICATION
Please refer to the attached read-across justification in section 13

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 080 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

1 080 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Key result

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

> 1 080 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Description of key information

In a limit test with the nominal concentration of 1080 mg/L no inhibitory effect of the read-across substance was observed as compared to the blank control after 3 hours of incubation (reference 6.1.7-1).

Key value for chemical safety assessment

EC50 for microorganisms:

1 080 mg/L

EC10 or NOEC for microorganisms:

1 080 mg/L

Additional information

No study data with the test item is available for toxicity to microorganisms. Therefore, a read-across to the read-across substance with a very similar chemical structure and comparable physico-chemical parameters is used to evaluate the potential for toxicity to microorganisms of the test item. 

The purpose of the 3 hour test was to evaluate the influence of the read-across source substance on the activity of the activated sludge by measuring the respiration rate under defined conditions in a study according to OECD TG 209 under GLP conditions. The respiration rates (total, heterotrophic and nitrification oxygen uptake rates) of samples of activated sludge fed with synthetic sewage were measured in an enclosed cell containing an oxygen electrode after a contact time of 3 hours. A preliminary test was performed to estimate the range of concentrations of the test item needed in the definite (main) test for determining the inhibition of oxygen consumption.  In the preliminary test of this study, the test item was investigated at the nominal concentrations of 10.8; 108 and 1080 mg/L. These test item concentrations were chosen taking into account a correction for the water content of the test item. In parallel with the test item treatments 3,5-Dichlorophenol was used as positive reference control; furthermore blank (inoculum) control, nitrification controls and abiotic controls were investigated. Based on the absence of any inhibitory effect in the preliminary experiment, the test item was investigated at the limit concentration of nominal 1080 mg/L in the main test. Similarly to the preliminary test, defined amounts of the test item were added directly into the test vessels. In parallel with the test item treatments, 3,5-Dichlorophenol was used as positive reference control at concentration levels of 2, 7 and 24.5 mg/L; furthermore blank (inoculum) control and nitrification controls were investigated. The definite test was performed without abiotic controls, based on the results of the preliminary test where abiotic controls were tested at the test item concentration of 1080 mg/L and no remarkable abiotic oxygen consumption was noticed. In accordance to the preliminary experiment, the test item does not adversely affect the pH within the test system; therefore, the main test was performed without additional pH adjustment. All validity criteria of the study were met. The observed oxygen consumption rates and consequently the specific respiration rates in the examined test item (limit) concentration remained in the range of the blank controls (the average specific respiration rate at 1080 mg/L: 37.13 mg O₂/gh), no remarkable inhibitory effect of the test item was observed. The obtained 1.17 % inhibition was considered as being within the range of biological variability of the applied test system. The specific respiration rates at the examined test item concentration of 1080 mg/L were compared with the blank control values using 2-Sample T-test (α = 0.05). No statistical significant differences were noticed in the comparison of blank control and test item treated groups. Under the test conditions, the EC₁₀ and EC₅₀ values of test item were determined as higher than 1080 mg/L. Based on the statistical evaluation in this test the NOEC was 1080 mg/L. In conclusion this study demonstrated the absence of inhibition of oxygen consumption by the test item up to and including the limit concentration of 1080 mg/L.