Benzenesulfonic acid, 4-C15-16-sec-alkyl derivs.-, compd. with 1-aminopropane-2-ol

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

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:

The exposure to C1516 LAS-MIPA can be thought of as exposure to a combination of C1516 LAS and MIPA as the substance will dissociate at relevant pH’s. Please see attached read across documentation for complete justification.

Reason / purpose for cross-reference:

read-across source

Duration of test (contact time):

d

Key result

Parameter:

% degradation (O2 consumption)

Value:

>= 36.36 - <= 45.88

Sampling time:

28 d

Remarks on result:

other: (test 1, December 2013, 3 concentrations tested)

Key result

Parameter:

% degradation (O2 consumption)

Value:

>= 33.43 - <= 51.75

Sampling time:

28 d

Remarks on result:

other: (test 2, January 2014, 3 concentrations tested)

Key result

Parameter:

% degradation (O2 consumption)

Value:

>= 45.55 - <= 63.08

Sampling time:

42 d

Remarks on result:

other: (test 2, January 2014, 3 concentrations tested)

Key result

Parameter:

COD

Value:

ca. 2.643 other: mg COD/mg sample (test item, test 1 in December 2013)

Key result

Parameter:

COD

Value:

ca. 1.826 other: mg COD/mg sample (sodium benzoate, test 1 in December 2013)

Key result

Parameter:

COD

Value:

ca. 2.695 other: mg COD/mg sample (test item, test 2 in January 2014)

Key result

Parameter:

COD

Value:

ca. 1.752 other: mg COD/mg sample (sodium benzoate, test 2 in January 2014)

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable

Conclusions:

SOLOTERRA® 117H can be classified as “inherently biodegradable”. The second study was extended to 42-days to demonstrate that it can achieve 60% ThOD. The two tests clearly show that there is toxicity/inhibition to the test microbes. This results in considerable deficit for the %ThOD profile curves and likely impedes the ability to demonstrate “ready biodegradable” classification.

Executive summary:

The purpose of these studies was to establish the ready biodegradability of the product SOLOTERRA® 117H (Benzenesulfonic acid, 4-C15-16-sec-alkyl derivs.) as an indication of its environmental fate. Tests of ready biodegradability are by definition stringent tests that provide limited opportunity for acclimation and biodegradation to occur. A positive result in a test of ready biodegradability is an indication the test substance will undergo rapid and ultimate biodegradation in the environment. However, a negative result in a test of ready biodegradability does not necessarily mean that the test substance will not be biodegraded under relevant environmental conditions but that additional testing may be needed. The work involved two studies; the first being conducted as typical; the second attempts to take into account and control toxicity/inhibition as well as extending past the usual 28-day experiment to demonstrate inherent biodegradable status. The two experimental start dates for the study was 12 December 2013 to 2 January 2014 and 16 January to 27 February 2014 (second test was extended to 42-days).

The biodegradation test was performed on SOLOTERRA® 117H in triplicates for test one and quadruplicates in test two using a 20 channel Coordinated Environmental Services (CES) Ltd (Cornwell, UK) aerobic electrolytic respirometer unit following the OECD 301F guideline. A CES electrolytic respirometer unit consists of 20 one-liter vessels fitted with heads containing O2 and CO2 sensors. The system measures the amount of CO2 generated by means of a cuvette filled with 2% sodium hydroxide and a conductivity probe that determines the change in conductivity as CO2 is absorbed from the headspace gases of the test vessel. A differential pressure sensor head is designed to measure the amount of O2 used by respiring microorganisms. It achieves this by detecting the difference in pressure during the uptake of oxygen and generation and caustic scrub of CO2 and then supplying O2 back to the headspace using an electrolytic copper sulfate cell.

The electrolytic cell contains a chamber filled with copper sulfate solution. Oxygen is generated in this chamber by passing an electrical charge (initiated by the test vessel head pressure change sensor) between electrodes. It is connected to the headspace of the sample vessel by a vent. Valves are used to balance the pressure and return generated O2 to the headspace of the test vessel. The data is handled by a PC which continuously records the amount of CO2 (mg) absorbed and O2 (mg) generated.

The 1-liter vessels are placed in the water bath (22±1 degree C) and screwed into the respirometer head/cap. The electrolytic respirometer unit with magnetic stirrer belt system is activated slowly. Once all bottles are in place, the speed of the stirring is adjusted to 300-400 rpm. The instrument undergoes a 60 minute initialization /equalization before data collection begins. CO2 generation and O2 uptake data is recorded by the instrument every six hours.

The blank 1-liter vessels are prepared identical to the samples (i.e. test medium, inoculate, and silica gel when present) except that they did not contain the test substance. To minimize the number of blanks required in the test, the silica gel when present is also included in the benzoate reference 1-liter vessels. The oxygen demand results for SOLOTERRA® 117H and the benzoate reference are determined by blanking out the oxygen demand contribution from the blank inoculate vessels that may or may not contain the added silica gel.

The average biodegradation obtained in the first study for the following test item concentrations of 10 mg/L, 20 mg/L, and 40 mg/L were 36.36%, 45.88%, and 44.75%, respectively, within 28 days.

In the extended second study, the average biodegradation after 28 days of 33.43%, 44.86%, and 51.75% and after 42 days of 45.55%, 57.68%, and 63.08%, for the respective test item concentrations of 10 mg/L, 20 mg/L, and 40 mg/L, were achieved.

The validity of the biodegradation test was confirmed by meeting the following criteria as specified in the OECD 301 F Test Guidelines.

• The delta of the max./min. of replicate %ThOD (COD) values at the plateau of the data, at the end of the test or at the end of the 10-day window, as appropriate, is less than 20%.

• The extent of biodegradation of the benzoate reference compound has reached the pass level of 60% ThOD (COD) on or before day 10-day window.

• The total O2 consumption in inoculum blanks with or without silica did not exceed 60 mg/L in 28 days. The maximum O2 consumed was < 30 mg/L.

• As the combined ThOD exceeded 25%, the test chemical SOLOTERRA® 117H can’t be assumed to be inhibitory based on the guidelines. However, there is an observed lag period, a reduction in respiration as compared to the controls that occurs. This resulted in a negative deficit for the %ThOD. The protocol criterion is not reflective of true inhibition in the case of SOLOTERRA® 117H.

• The sterility controls of similar compounds conducted in earlier studies demonstrated that biodegradation and not chemical oxidation was occurring in this test.

Based on the results of the two performed OECD 301F studies, the test item Benzenesulfonic acid, 4 -C15 -16 -sec-alkyl derivs. can be considered inherently biodegradable.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Duration of test (contact time):

28 d

Parameter:

% degradation (O2 consumption)

Value:

>= 78

Sampling time:

28 d

Details on results:

RS-Freetext:
10-day window reached (60% ThOD): yes, for the test substance the 10% level was reached after 2.6 days and the 60% level after 3.0 days
Mean % biodegradation (based on BOD/ThOD-NH3) corrected for blank at 10.7-12.6 days/28 days (end of 10 day window/end of test):
BENZOATE: 84/91
TEST SUBSTANCE: 129/124*
TOXIC CONTROL: 98/99
* % biodegradation based on oxygen consumption relative to ThOD-NH3 and corrected for partial mineralisation of organic nitrogen to nitrate and nitrite is 105%

Mean % biodegradation after 28 days based on removal of DOC and mineralisation to CO2 gave the following results:
BENZOATE: 99 (DOC) and 72 (CO2)
TEST SUBSTANCE: 83 (DOC) and 78 (CO2)
TOXIC CONTROL: 94 (DOC) and 75 (CO2)

NO2- and NO3- concentrations (mg/L) at start (0 days) and end (28 days):
CONTROL: 0.11 and 0.25 (0 d); 0.15 and 10.19 (28 d)
BENZOATE: 0.11 and 0.39 (0 d); 0.15 and 9.75 (28 d)
TEST SUBSTANCE: 0.14 and 0.25 (0 d); 0.15 and 20.83 (28 d)
TOXIC CONTROL: 0.14 and 0.79 (0 d); 0.15 and 16.33 (28 d)

Interpretation of results:

readily biodegradable

Conclusions:

MIPA exceeded 60% degradation by the end of an OECD 301F study and met the 10 day window criteria resulting in the substance being considered readily biodegradable.

Executive summary:

MIPA was readily biodegradable in an OECD 301F study.

Description of key information

The ready biodegradability of the read across substance Benzenesulfonic acid, 4-C15-16-sec-alkyl derivs. was assessed in various studies.

Based on the observations in an OECD 301B GLP study, two further 301F studies with slight modifications were conducted. The first OECD 301F study being conducted as typical; the second OECD 301F study attempted to take into account and control toxicity/inhibition as well as extending past the usual 28-day experiment to demonstrate inherent biodegradable status.

The initial ready biodegradation study with Benzenesulfonic acid, 4-C15-16-sec-alkyl derivs., carried out according to OECD guideline 301B, resulted in no/negligible biodegradation after 28 days. Although all validation criteria are met in regard to the guideline, based on our experience and experts’ judgment, it can be considered that the obtained result is not reliable. The underlying study shows significant methodological deficiencies, as the substance properties and possible inhibition was not addressed. Hence, the test system is unsuitable.
To address the shortcomings of the first biodegradation study, Benzenesulfonic acid, 4-C15-16-sec-alkyl derivs. was tested subsequently in further biodegradation studies according to OECD 301F guideline at different concentrations and in the latest setup also extended and dispersed on silica gel to reduce toxicity and enable degradation by the microorganisms.

In a OECD 301F study with the second read across substance (Monoisopropanolamine - MIPA), the substance was considered readily biodegradable exceeding 60% degradation by the end of the study and meeting the 10 day window criterium.
Considering all of the available read across studies, Benzenesulfonic acid, 4 -C15 -16 -sec-alkyl derivs. MIPA salt would be expected to induce inhibition to the inoculum, but can be considered inherently biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Additional information

Based on the OECD guidelines, the read across substance Benzenesulfonic acid, 4 -C15 -16 -sec-alkyl derivs. was not considered inhibitory to the inoculum in an OECD 301B assay. In contrast, the negative %ThOD during the first 10 -14 days of the extended OECD 301F study clearly shows that the oxygen uptake in all three concentrations tested is being impacted and hence reduced below the background oxygen uptake. This phenomenon can only occur as a result of some form of microbial toxicity or inhibition. It appears to be lessened in the test where silica gel is present. It is more dramatic/exacerbated in the lower concentrations due to less total mg ThOD. During the second OECD 301F test, in the first 24 hours the % inhibition to respiration is greater than 80% at the 40 mg/L concentration. The EC50 for % inhibition appears to be less than 10 mg/L. In conclusion the silica gel did provide some reduction to the maximum negative %ThOD observed at all test concentrations. Benzenesulfonic acid, 4-C15-16-sec-alkyl derivs. can be considered inherently biodegradable based on the results obtained in an extended OECD 301F test resulting in > 60% biodegradation after 42 days.

The second read across substance (MIPA) was readily biodegradable in an OECD 301F study.