Bis(2-ethylhexyl)amine

Biodegradation in water: screening tests

Description of key information

The substance is not readily biodegradable.

Additional information

Ready biodegradability assessment

The ready biodegradability of bis(2-ethylhexyl)amine (CAS 106-20-7) was studied in several tests according to OECD TG 301. The studies were performed under GLP conditions. The substance can inhibit the degradation activity of activated sludge according to the results of an OECD TG 209 guideline study (3-h EC50 = 86 mg/L, 3-h EC10 = 18 mg/L; BASF SE, 2012; report no. 08G0454/11G167); therefore, the degradability studies were performed with relatively low test material concentrations to prevent an inhibition of the inoculum. The available data are summarized in the table below.

Reference; Report no/	Guide-line	Enhanced conditions	Inoculum; Source	Degradation	Interpretation
BASF (2022); SE23G0454/11G263 (Key study)	OECD 301D	yes (61 d)	domestic effluent, non-adapted; Lambsheim/Germany	0% ThOD in 61 d	no biodegradation observed under test conditions
BASF SE (2020); 23G0454/11G245 (Supporting study)	OECD 301D	yes (60 d)	domestic effluent, non-adapted; Lambsheim/Germany	2% ThOD in 60 d	no biodegradation observed under test conditions
BASF SE (2023); 27G0454/11G264 (Key study)	OECD 310	yes (60 d)	domestic activated sludge, non-adapted; Lambsheim/Germany	0% ThCO2 in 60 d	no biodegradation observed under test conditions
BASF SE (2022); 22G0454/11G246 (other information)	OECD 301B	yes (60 d)	domestic activated sludge, non-adapted; Lambsheim/Germany	14% ThCO2 in 28 d; 65% ThCO2 in 60 d	biodegradable after adaptation
BASF SE (2012); 22G0454/11X516 (other information)	OECD 301B	yes (60 d)	domestic activated sludge, non-adapted; Werdhoelzli/Switzerland	0.9% ThCO2 in 60 d; 83% DOC removal in 28 d	no biodegradation observed under test conditions; DOC removal most likely due to adsorption
BASF SE (2022); 22G0454/11G248 (other information)	OECD 301B	yes (60 d)	domestic activated sludge; Mannheim/Germany	61% ThCO2 in 28 d; 90% ThCO2 in 60 d	biodegradable after adaptation
BASF SE (2016); 22G0454/11G208 (other information)	OECD 301B	yes (60 d)	domestic activated sludge; Mannheim/Germany	69% ThCO2 in 28 d; 91% ThCO2 in 60 d; 94% DOC removal in 60 d	biodegradable after adaptation

 

The most current studies were a headspace test according to OECD TG 310 (BASF SE, 2023, report no. 27G0454/11G264) and a closed bottle test according to OECD TG 301D as demanded by ECHA in a final decision (communication number SEV-D-2114576354 -43 -01/F; BASF SE, 2023, report no. 2G30454/11G263) with an enhanced incubation period of 61 days. Both studies were performed with inoculum from the wwtp in Lambsheim/Germany, which treats predominately municipal wastewater. Therefore, the inoculum is not pre-adapted to the substance. In addition to monitoring the evolution of CO₂ in the headspace test and oxygen demand in the closed bottle test, substance specific chemical analysis was performed to assess if the substance adsorbs onto the test vessels or the inoculum. The validity criteria were met in the OECD 310 and slightly failed in the OECD 301D (due to a slighty toxic effect of the substance towards the inoculum). No biodegradation was observed under the specific test conditions of OECD TG 310 (0% TIC/TOC) and OECD TG 301D (0% BOD/ThOD).

In the headspace test, adsorption to the test vessels or the sludge was not observed based on the specific chemical analysis of the test substance assays as well as the blank controls with and without activated sludge. The recovery was approximately 100% in all these assays.

 

In the OECD 301D, substance specific analytics conducted in the replicates of the physical chemical control without test system (PC) recovered 102.9% of the applied initial amount of test item (2 mg/L) which corresponds to about 2.1 mg/L test item.
The recovery rate of the replicates of the physical chemical control with test system (PCS) recovered 95.6% (mean value of the sample numbers 194/195/196) of the applied initial amount of test substance (2 mg/L) which corresponds to about 1.9 mg/L test item. In substance specific analytics, 96.1% of the applied initial amount of test item (2 mg/L) was recovered which corresponds to about 1.9 mg/L test item.

 

In both studies, the OECD 301D and the OECD 310, the substance was not readily and not inherently biodegradable.

 

Prior to these two studies, five degradation studies according to OECD TG 301B were performed using different sources for the inoculum and different test concentrations.

In the CO₂ evolution test (OECD TG 301B) using activated sludge from the municipal wwtp of Lambsheim/Germany (BASF SE, 2022; report no. 22G0454/11G246), the substance was degraded to 65±7% CO₂/ThCO₂ (mean + SD of three replicates) after an exposure period of 60 days. After 28 d, the degradation was at 14% CO₂/ThCO₂. The lag phase was 26 days. The degradation curves of the three test substance replicates are sigmoidal; therefore, biodegradation is assumed to have taken place. The validity criteria were met except for the temperature which was slightly below 20 °C throughout the exposure. The impact on the degradation is assumed as not relevant. The results of the abiotic control (96% CO₂/ThCO₂) are not plausible. The abiotic control is invalid. No explanation was found for the evolved CO₂. Although, the substance is biodegradable, the result cannot be used in the persistence assessment as the lag phase was rather long and can be interpreted as an adaptation of the microorganisms according to REACH Guidance document R.7b (v4.0, ECHA, 2017).

In the CO₂ evolution test (OECD TG 301B) using activated sludge from the municipal wwtp of Werdhoelzli/Switzerland (BASF SE, 2012; report no. 22G0454/11X516), no biodegradation was observed based on CO₂ evolution (0.9% CO₂/ThCO₂ after 60 d). In this study, adsorption to the test vessel and/or activated sludge was assumed as the DOC removal was 83% in 60 days without observed mineralization. The study is valid as all criteria of the guideline were fulfilled.

Two enhanced ready biodegradability studies were performed according to OECD TG 301B using activated sludge from the wwtp from Mannheim/Germany. The municipal wwtp treats municipal and industrial wastewater; therefore, the activated sludge is not accepted as non-adapted inoculum. In both studies the ready biodegradability criterion of ≥ 60% CO₂/ThCO₂ was met after the prolonged incubation period of 60 days. The substance is biodegradable.

In the study BASF SE (2022; report no. 22G0454/11G248), the substance was degraded to 61±1% in 28 d and to 90% in 60 days. The 10-day window was failed. The degradation curve is sigmoidal. The substance is biodegradable. The validity criteria are met with a slight failure of the DIC content in the blank control. In addition, the deviation between the highest and lowest degree of biodegradation among three replicates were >20%. Therefore, only those replicates with deviation less than 20% (TS1 and TS2) and comparable biodegradation rates were considered for final evaluation. TS3 is omitted from the mean value calculation as the degradation was slower compared to the others and resulted in a deviation > 20%.

The study BASF SE (2016; report no. 22G0454/11G208) resulted in similar degradation values: 60-70% in 28 d and to 90-100% in 60 days. The 10-day window was slightly failed (approximately 58% at the end of the 10-d window). The validity criteria were met except for the DIC in the blank control; however, an influence on the test result can be excluded.

Based on the available data, it can be concluded that the substance is not readily biodegradable according to OECD criteria. However, adapted inoculum is capable of biodegrading the substance.

 

Assessment of metabolites

QSAR-disclaimer

In Article 13 of Regulation (EC) No 1907/2006, it is laid down that information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI (of the same Regulation) are met.

According to Annex XI of Regulation (EC) No 1907/2006 (Q)SAR results can be used if (1) the scientific validity of the (Q)SAR model has been established, (2) the substance falls within the applicability domain of the (Q)SAR model, (3) the results are adequate for the purpose of classification and labeling and/or risk assessment and (4) adequate and reliable documentation of the applied method is provided.

The criteria listed in Annex XI of Regulation (EC) No 1907/2006 are considered to be adequately fulfilled and, therefore, the endpoint(s) sufficiently covered and suitable for risk assessment.

 

Metabolites

As the substance is not readily biodegradable, the assessment of bioaccumulation/bioconcentration and biodegradation of the predicted metabolites from the QSAR estimation model with an estimated quantity of ≥ 0.1% was performed as a worst-case consideration.

The model CATABOL 301C v02.08 (OASIS Catalogic v5.15.2.14) predicted five relevant metabolites in terms of the PBT/vPvB assessment, with an estimated quantity of ≥ 0.1% (equivalent to a quantity setting in OASIS CATALOGIC of ≥0.001 mol/mol parent). Four metabolites were calculated to be readily biodegradable (≥ 60% after 28 days, based on BOD; individual biodegradation ranging from 63 to 89%), thereby not fulfilling the screening criteria as potentially P/vP as laid down in Section 3.1 of REACH Annex XIII. One metabolite (#1.3) was calculated to be not readily biodegradable (< 60% after 28 days, based on BOD).

Three of the metabolites were not completely in the applicability domain of the BOD model due to fragments which were not present in the chemicals of the training set. In case of metabolites #1.4 and #1.7, the fraction of the unknown fragments is low (≤ 10%); therefore, the result is sufficiently reliable. The biodegradability prediction of metabolite #1.5 is not reliable as 70% of the fragments are not present in chemicals of the training set.

Therefore, the bioaccumulation potential is also assessed. All five metabolites have a log Kow ≤ 4.5 (ranging from 0.91 to 2.96), thereby not fulfilling the screening criteria for bioaccumulation (B/vB) as laid down in Section 3.1 of REACH Annex XIII.

As none of the relevant degradation products fulfill the screening criteria for P/vP and B/vB properties, no further assessment of their toxicity (T) is needed in accordance with Section 2.1 of Annex XIII of REACH. It can be concluded that the relevant degradation products are neither PBT nor vPvB substances.

The ECHA disseminated database lists metabolites #1.3 and #1.4 also as not PBT/vPvB; therefore, supporting the assessment of these substances (for details see ‘Attached background material’ of the respective Endpoint Study Record).

Based on modeled data relevant degradation products present in concentration of ≥ 0.1% (equivalent to quantity setting in OASIS CATALOGIC: ≥0.001 [mol/mol parent]) do neither fulfill the PBT criteria (not PBT) nor the vPvB criteria (not vPvB).