Decyl 2-ethylhexanoate

Biodegradation in water: screening tests

Description of key information

Readily biodegradable: 76% in 29 d (CO2 evolution), OECD 301B

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

One study is available investigating the ready biodegradability of Decyl 2-ethylhexanoate (CAS 93777-46-9). This study was conducted according to OECD 301B (GLP) using activated sludge from a municipal sewage treatment plant being exposed to the test substance at a concentration of 16 mg/L, corresponding to 12 mg TOC/L, for 28 days. After 28 days, the test substance reached 76% biodegradation of the test substance in one replicate meeting the 10-day window. The second replicate reached 58% biodegradation after 28 days. Thus, based on the result from one replicate the substance is readily biodegradable according to the OECD criteria.

This result is confirmed by a reliable QSAR calculation using BIOWIN v4.10 and experimental results from two structurally related substances (in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5), which are characterized by a similar ecotoxicological profile and comparable structure. The results give further evidence that the target substance is readily biodegradable.

The read-across was performed using the results from the source substances Hexanoic acid, 2-ethyl-, C16-18 alkyl esters (CAS 90411-68-0) and Fatty acids, C8-16, 2-ethylhexyl esters (CAS 135800-37-2) in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5.. This read-across is justified in detail within the analogue justification in IUCLID Section 13.

The study with the source substance Hexanoic acid, 2-ethyl-, C16-18 alkyl esters (CAS 90411-68-0) was conducted under aerobic conditions according to OECD guideline 301B (GLP) using non-adapted, domestic activated sludge as inoculum. Based on CO2 evolution a mean degradation of 90% was observed after 29 days. According to “OECD Guidelines for the testing of chemicals – Revised introduction to the OECD guidelines for testing of chemicals, Section 3 – Part 1: Principles and strategies related to the testing of degradation of organic chemicals degradation” published by OECD (2006) the ready biodegradability data for mixtures should be evaluated carefully. For substances with different chain lengths the 10-day window should not be used for the interpretation of the results. It is possible that a sequential biodegradation occurred which might have led to a prolonged lag-Phase and therefore a slower biodegradation period. In this case the pass level can be applied at 28 days. Hence, the test substance is determined to be readily biodegradable according to OECD criteria.

The second study with the source substance Fatty acids, C8-16, 2-ethylhexyl esters (CAS 135800-37-2) was tested in an O2-consumption test according to OECD 301D (Closed bottle test) under GLP conditions. The biodegradation of 2 and 5 mg/L test material was monitored for 30 days. After 30 days, 97 and 65% of the initial test substance was degraded, respectively, indicating that the substance is readily biodegradable.

Based on the available results from the target substance, QSAR calculation and structurally related source substances (in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5), it can be concluded that Decyl 2-ethylhexanoate (CAS 93777-46-9) is expected to be readily biodegradable according to the OECD guideline criteria.