Neodecanoic acid, iron salt

Endpoint summary

Description of key information

The test item cannot be classified as readily biodegradable.

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 Day 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.