6-[(p-tosyl)amino]hexanoic acid, compound with 2,2',2''-nitrilotriethanol (1:1)

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The following read-across hypothesis is proposed for the registered substance:
The registered substance 6-[(p-tosyl)amino]hexanoic acid, compound with 2,2',2''-nitrilotriethanol (1:1) (target substance) is manufactured directly from 6-[(p-Tosyl)amino]hexanoic acid (source substance) by simple neutralisation with triethanolamine (TEA). Other than ionization of the carboxylic acid group, the 6-[(p-Tosyl)-amino]hexanoic acid remains chemically unchanged upon salt formation. In water, the acid and amine components of the target substance dissociate completely to the source substance and TEA and these two components behave essentially as independent substances. Moreover, it is hypothesised here that TEA is non-hazardous substance and the acid component of the salt that will have a more significant impact on the outcome of any (eco)toxicological or environmental tests. Hence, the toxicity data on the source substance will accurately represent the toxicity of the target substance.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Details are attached in Section 13 of the dataset

3. ANALOGUE APPROACH JUSTIFICATION
Details are attached in section 13 of the dataset

4. DATA MATRIX
Details are attached in section 13 of the dataset

Reason / purpose for cross-reference:

read-across source

Duration of test (contact time):

d

Reference substance:

aniline

Key result

Parameter:

% degradation (CO2 evolution)

Remarks:

based on ThCO2

Value:

64

Sampling time:

28 d

Remarks on result:

other: 45 % degradation after 20 days, 10 day window criterion not fulfilled

Details on results:

Degradation after 28 days:
Based on CO2 Evolution: 64%

Results with reference substance:

60% degradation after 8 d.

Validity criteria fulfilled:

yes

Remarks:

All the test performance criteria were met and the test is valid

Interpretation of results:

other: when applying the 10-day-window, the test item ASCplus® is not readily biodegradable following OECD 301B and EU C.4-C respectively. As degradation reached the pass level of 60% in the course of the test, ASCplus® is considered as ultimately biodegradable

Conclusions:

• The test item ASCplus® (source) is considered as “not readily biodegradable“.
• The degree of biodegradation reached 64 % after 28 days.
• The 10-day-window began on day 9, at its end, 45 % degradation were reached, missing the pass level of 60 % given in the OECD guideline.
• As degradation reached the pass level of 60% in the course of the test, ASCplus® is considered as ultimately biodegradable, within 28 days.
• The abiotic degradation reached 0.7 %.

Executive summary:

The biodegradation potential of the test substance (source item) was determined in accordance with the OECD Guideline for Testing of Chemicals 301B. The test substance was tested for ready biodegradability using activated sludge of a sewage treatment plant receiving predominantly domestic sewage. The test was conducted over a period of 28 days. After 28 days the biodegradation of the test substance was recorded as 64% (based on CO2 evolution).The 10-day-window began on day 9, at its end, 45% degradation were reached, missing the pass level of 60% given in the OECD guideline. As degradation reached the pass level of 60% in the course of the test, ASCplus® is considered as ultimately biodegradable, within 28 days.

The analytical determinations indicate a degradation of the test item ASCPlus® and in parallel an increase of the metabolite 4-aminobutyric acid (ABA). The metabolite 4-N-p-Tosylglycine is produced only in minor concentration toward the end of the test. The measured test item and metabolite concentrations support the CO2 evolution data.

The test substance (source) was the carboxylic acid component of the registered substance (tosyl salt). Read-across between the tosyl salt carboxylic acid (6-[(p-Tosyl)amino]hexanoic acid) and the registered substance is considered justified as the registered substance is manufactured directly from 6-[(p-Tosyl)amino]hexanoic acid by simple neutralisation with triethanolamine (TEA). Other than ionization of the carboxylic acid group, the 6-[(p-Tosyl)amino]hexanoic acid remains chemically unchanged upon salt formation. In water, the acid and amine components of 6-[(p-Tosyl)amino]hexanoic acid, compound with 2,2’,2’’-nitrilotriethanol (1:1) dissociate completely and behave essentially as independent substances. Since TEA can be considered non-hazardous, it is the acid component of the salt that will have a more significant impact on the outcome of any (eco)toxicological or environmental tests. The pKa of the carboxylic acid group in 6-[(p-Tosyl)amino]hexanoic acid (pKa = 4.90) is the same in the free acid as it is in the TEA salt. As a result, 6-[(p-Tosyl)amino]hexanoic acid will respond to changes of pH in the same way whether it is in the salt form or as the parent carboxylic acid and hence it’s bioavailability will be the same (Further justifications for the support of read-across hypothesis are attached in Section 13).

Description of key information

After 28 days the biodegradation of the registered substance was recorded as 64% (based on CO2 evolution). The 10-day-window began on day 9, at its end, 45% degradation were reached, missing the pass level of 60 % given in the OECD guideline. As degradation reached the pass level of 60% in the course of the test, ASCplus® is considered as ultimately biodegradable, within 28 days.

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater

Additional information

The biodegradation potential of the test substance was determined in accordance with the OECD Guideline for Testing of Chemicals 301B. The test substance was tested for ready biodegradability using activated sludge of a sewage treatment plant receiving predominantly domestic sewage. The test was conducted over a period of 28 days. After 28 days the biodegradation of the test substance was recorded as 64% (based on CO2 evolution).The 10-day-window began on day 9, at its end, 45% degradation were reached, missing the pass level of 60% given in the OECD guideline. As degradation reached the pass level of 60% in the course of the test, ASCplus® is considered as ultimately biodegradable, within 28 days.

The analytical determinations indicate a degradation of the test item ASCPlus® and in parallel an increase of the metabolite 4-aminobutyric acid (ABA). The metabolite 4-N-p-Tosylglycine is produced only in minor concentration toward the end of the test. The measured test item and metabolite concentrations support the CO2 evolution data.

An additional study was conducted on a formulated product containing the registered substance to determine the inherent biodegradability of the formulated product. The inherent biodegradability of the test material was determined in accordance with the OECD Guideline for Testing of Chemicals 302B. The biodegradation of the substance was measured by COD analysis. 0.1825 ml/l (equivalent to 142.9 mg/l COD) of test substance was added to test vessels containing 357.1 mg/l of activated sludge. The final 56 day degradation value was determined to be 78.6% at 0.1825 ml/l of test substance. From the results of this study it can be concluded that p-TSA Triethanolamine salt does not meet the criteria for classification as 'inherently biodegradable' according to the OECD 302B method, with >70% biodegradation being achieved within the 56 day test period. The test material shows good potential for ultimate biodegradation under the conditions of this study.