Neodecanoic acid, iron salt

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

05 April 2017–4 May 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Version / remarks:

Revision 1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Batch number: E01133-065
Purity: 100 %
Date received: 6 March 2017
Retest date: 31 July 2019
Storage conditions: Refrigerated under nitrogen (2-8 °C)

Oxygen conditions:

aerobic

Remarks:

The air used in this study was delivered from a cylinder of CO2-free air (Air Products).

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

A sample of activated sludge was collected from one of the return lines at Burley Menston sewage treatment works (West Yorkshire, UK), which has a predominantly domestic wastewater catchment. The sample was transported in a closed container, but with an adequate headspace, to prevent the sample becoming anaerobic.
On arrival, the sample was aerated by means of a compressed air supply.
The suspended solids concentration of the activated sludge was determined by filtering a subsample (25 mL) through a pre-dried and pre-weighed glass microfibre filter (Whatman GF/C). The filter and retained solids were then dried in an oven (nominally 105 °C) and re-weighed. The weight of the sludge solids was determined from the difference in the weights before and after drying. The concentration of suspended solids was calculated to be 4.2 g/L.
The activated sludge used in this study was not deliberately acclimatised or adapted to the test item before exposure under test conditions.

Duration of test (contact time):

ca. 28 d

Initial conc.:

15 other: 15 mg carbon/L.

Based on:

test mat.

Remarks:

the test item was accurately weighed (35.61 to 35.69 mg) for direct addition to test substance and toxicity control vessels, to give a nominal test substance concentration corresponding to 15 mg carbon/L.

Parameter followed for biodegradation estimation:

CO2 evolution

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (CO2 evolution)

Value:

7

Sampling time:

29 d

Remarks on result:

other: Mean carbon dioxide evolution from the test item was 7 % (day 29) of the theoretical carbon dioxide yield throughout the test.

Remarks:

Mean carbon dioxide evolution from the test item was 7 % (day 29) of the theoretical carbon dioxide yield throughout the test. The level of biodegradation did not meet the requirements for ready biodegradability and the test item hence cannot be classified as readily biodegradable.

Details on results:

All validity criteria were satisfied (inorganic carbon content, degradation of reference material, CO2 production from blank controls) and the results of this study are therefore considered to be valid.
No inhibitory effect was observed on the biodegradation of the reference substance in the presence of the test item.

The inorganic carbon content of the test medium was determined to be 1.89 mg carbon/L, corresponding to 4.2 %.

Carbon dioxide evolution and percentage biodegradation data are presented in the attached Table 2, Table 3 and Figure 1. The mean total carbon dioxide production in the blank control vessels was 47 mg/L (test end), satisfying the validity criterion of less than 70 mg/L.

To be considered readily biodegradable, a test substance must achieve 60 % biodegradation by the end of the test. Additionally, the test substance must biodegrade by at least 60 % within 10 days of having degraded by 10 %.

The test item showed limited biodegradation during the study with a maximum mean biodegradation of 7 % on day 29. The test item hence cannot be considered readily biodegradable.

Percent biodegradation values at each sampling interval, for the two replicates containing the test item did not vary by more than 13 % (day 29), therefore satisfying the validity criterion of less than 20 % difference.

Sodium benzoate (c)

Rapid carbon dioxide generation commenced immediately and declined to a more gradual rate over the period of the incubation as shown in the attached Figure 1. The percentage biodegradation had exceeded 60 % by day 6 (68 %) in reference vessel R1 and by the end of the incubation phase, the biodegradation had reached 96 %. The validity criterion of 60 % biodegradation at 14 days was therefore met.

Assessment of biodegradation in the toxicity control was confined to the sodium benzoate fraction. The rate of biodegradation of the reference substance in the presence of the test item (68 % at day 6, 92 % by the end of the incubation phase on day 28 and 93 % by the end of the test on day 29) was comparable to that of the reference substance alone. This suggests that the test item had no inhibitory effect on the sludge microorganisms under the test conditions and, as the biodegradation still exceeded 60 % by day 6, the test was considered to be valid.

(c) The Reference vessel (R2) has been excluded from this test as it appeared anomalous and can be scientifically justified to be removed. The Reference vessel (R2) did not meet the validity criterion of 60% biodegradation by Day 14. This appears to be anomalous as the first replicate did meet the criterion by Day 6, R2 will not therefore be used in the mean data.

The test will remain within the specified requirements of the OECD guidelines for one reference vessel, and does not impact the integrity of the study.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

All validity criteria were satisfied (inorganic carbon content, degradation of reference material, CO2 production from blank controls) and the results of this study are therefore considered to be valid.
No inhibitory effect was observed on the biodegradation of the reference substance in the presence of the test item.
Mean carbon dioxide evolution from the test item was 7 % (day 29) of the theoretical carbon dioxide yield throughout the test. The level of biodegradation did not meet the requirements for ready biodegradability and the test item cannot, therefore, be classified as readily biodegradable.

Executive summary:

The ready biodegradability of neodecanoic acid, iron salt, was assessed by measurement of carbon dioxide (CO2) evolution under standard conditions. The procedure followed OECD guideline 301B.

All validity criteria were satisfied (inorganic carbon content, degradation of reference material, CO2 production from blank controls). No inhibitory effect was observed on the biodegradation of the reference substance in the presence of the test item (toxicity control).

The test item showed 5 % mean biodegradation during the incubation and 7 % mean biodegradation at the end of the study. As a result, the test item cannot be considered readily biodegradable.

Description of key information

The test item cannot be classified as readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

The ready biodegradability of the test item was assessed by measurement of carbon dioxide (CO2) evolution under standard conditions. The procedure followed was that of OECD guideline 301B, Ready Biodegradability (Adopted 1981, Revised 1992).

The test substance, was added to the test system as a solid. Buffered mineral salts medium was added to give a test substance concentration equivalent to 15 mg organic carbon/L. The medium was inoculated with microorganisms derived from a sample of activated sludge not previously intentionally exposed to the test substance. Test vessels were incubated in darkness at 22 ± 2 °C for 28 days and their contents continuously sparged with a supply of CO2-free air. The exhaust air from each vessel was passed through a series of traps containing a barium hydroxide solution to trap evolved CO2.

At regular intervals during the incubation, traps were detached and their contents titrated with hydrochloric acid to determine the quantity of CO2 evolved from the respective test vessels. At the end of incubation, 28 days, the test vessel contents were acidified to release any residual CO2 that may have remained in solution. Titration of the traps was performed following overnight aeration.

The procedure and the activity of the inoculum were checked by measuring the CO2 evolved from a reference substance vessel containing sodium benzoate. An additional vessel containing a combination of the test and reference substances served as a toxicity control to assess whether the test substance was inhibitory to biodegradation at the test concentration. Two blank control vessels were also prepared containing inoculated medium only. The results of these vessels were used to check the validity of the test and to correct the evolved CO2 values.

the test item showed = 5 % mean biodegradation during the incubation and = 7 % mean biodegradation at the end of the study. As a result, the test item cannot be considered readily biodegradable.

The mean total CO2 production in the blank control vessels was 47 mg/L at the end of the test, satisfying the validity criterion of < 70 mg/L.

Mean biodegradation of the reference substance vessel (R1) had exceeded 60% by day 6 and had reached 94 % by the end of the incubation phase on day 28 and 96% by the end of the test on day 29. The rate of biodegradation of the reference substance in the presence of the test item(68 % at day 6, 92 % by the end of the incubation phase on say 28 and 93% by the end of the test on day 29) was similar to that of the reference substance alone, suggesting that the test item did not have an inhibitory effect on the sludge microorganisms under the test conditions and the test was considered to be valid. Reference vessel (R2) has been excluded from this test as it appeared anomalous and can scientifically justified to be removed, this allows the test to remain within the specified requirements of the OECD guidelines for one reference vessel, and does not impact the integrity of the study.

The inorganic carbon content of the test medium was determined to be

1.89 mg carbon/L, corresponding to 4.2 % satisfying the validity criterion of < 5 %.

All validity criteria were satisfied, the blank controls and reference vessels performed as expected, and the results of this study are therefore considered to be valid.