2,2'-butyliminodiethanol

Bioaccumulation: aquatic / sediment

Link to relevant study record(s)

Reference

Endpoint:

bioaccumulation in aquatic species: fish

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH
In this justification, the read-across (bridging) concept is applied, based on the chemical structure of the potential analogues, their toxicokinetic behaviour and other available (eco-)toxicological data.
Please refer to a full version of Read-across statement attached in the section 13 "Assessment reports".

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The underlying hypothesis for the read-across is that the target and the source substance have similar ecotoxicological properties due to their structural similarity, resemblance to their chemical reactivity, and biotransformation products in environmental compartments. The substances share the same ethanolamine moiety and can be considered as derivatives of mono-ethanolamine (CAS 141-43-5).
The target substance BDEA (CAS 102-79-4), as well as the source substance DBEA (CAS 102-81-8) belong to the category of the “Aliphatic amines” according to the profiler “US EPA New Chemical Categories” in the OECD QSAR Toolbox v4.1. Within this category the aquatic toxicity of aliphatic amines follows a regular pattern with regard to the carbon chain length. Furthermore, the chemicals are characterized by a common Mode Of Action (MOA) in detail as “narcotic amines” according to Acute aquatic toxicity MOA by OASIS in the OECD QSAR Toolbox v4.1.
The use of toxicological data between tertiary butyl amine derivatives for the read-across purpose of ecotoxicological endpoints was also discussed at the CoCAM 6 (Paris, 2014) and approved (based on the following arguments: similar chemical structure with a central nitrogen atom bearing an unshared pair of electrons that underlies their similar chemical behaviour; similar physico-chemical properties, acute aquatic toxicity classification of OASIS as “narcotic amines”).

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)

source substance: 2-Dibutylethanolamine (or 2-Dibutylaminoethanol)
structural formula: C10H23NO
Smiles: CCCCN(CCCC)CCO
Molecular weight: 173.30
CAS 102-81-8
EC No 203-057-1
purity: not specified

target substance: Butyldiethanolamine
structural formula: C8H19NO2
Smiles: CCCCN(CCO)CCO
Molecular weight: 161.24
CAS 102-79-4
EC No 203-055-0
purity: not specified
No additional information is available on purity of the source and the target substances. Both substances are normally of high purity, containing only minor amounts of impurities that do not influence the read-across validity.

3. ANALOGUE APPROACH JUSTIFICATION
BDEA is a tertiary amino alcohol but can also be regarded as a tertiary amine. It has one N-alkyl chain (in this case butyl) and two aliphatic alcohol groups (ethanol). Dibutylethanolamine (DBEA) is also a tertiary amine with two butyl rests but one ethanol group. They are linked by the common functionality of nitrogen atom which bears an unshared pair of electrons and tends to share these electrons determining a similar chemical behaviour.
According to the inclusion rules of the category of “Aliphatic Amines”, environmental toxicity of amines is related to the length of the hydrophobic carbon chains: the longer (or greater the number of carbons) the chain the more toxic to aquatic organisms when the number of amines is constant; and the greater the number of amines, the greater the toxicity given a constant carbon chain length (Explanation tool of profiler “US EPA New Chemical Categories” in the OECD QSAR Toolbox v4.1).
BDEA and DBEA have an identical number of amines. However, they distinguish in the number of carbon atoms: the target substance BDEA has 8 carbon atoms and DBEA has 10 carbon atoms. Given the explanation of "Aliphatic Amines", stating that the toxicity of aliphatic amines grows with the number of carbons, the toxicity to aquatic organisms of BDEA is expected to be lower than the toxicity of DBEA. Indeed, an increasing toxicity potential of butyl alkanolamines was observed in the experimental studies following order BDEA < BEA < DBEA (BEA is a Butylethanolamine, another supporting source butyl ethanolamine).
Butyl alkanolamines are also similar in their environmental fate endpoints. The substances are considered to be hydrolytically stable as they contain no chemical groups liable to hydrolysis. Referring to biodegradation, the same trend can be identified, showing an increasing biodegradation potential with BDEA < BEA < DBEA. The log Koc values (especially for BDEA and DBEA) are relatively close and support the read-across approach. Furthermore, the results show that the substances do not have a significant potential for persistence (not P not vP). Butyl alkanolamines are not expected to evaporate from the water surface to the atmosphere (HLC > 1 Pa*m /mol).
Concerning specifically bioaccumulation behaviour of butyl alanolamines, based on their log Kow, bioaccumulation is not likely for BDEA (log Kow = 0.58, meas.) and BEA (log Kow = 0.64, meas.) and is also not expected for DBEA (log Kow = 1.86, meas.). In addition, the BCF was also estimated using the QSAR model BCFBAF (v3.01) by EPIWIN (EPI Suite v4.11) as supporting information. This QSAR model provides a scientifically accepted calculation method and its estimate is applicable to the uncharged substance. While the results of the BCFBAF v3.01 model (Meylan et al., 1997/1999) differ by a factor of approximately 2 (regression based estimates for BDEA: BCF of 3.16 L/kg ww; BEA: BCF of 3.162 L/kg ww; DBEA: BCF of 7.84 L/kg ww).
It can be concluded that all three substances lack a significant bioaccumulation potential in organisms (not B not vB).

4. DATA MATRIX
Please refer to the full version of the read-across statement.

Reason / purpose for cross-reference:

read-across source

Vehicle:

not specified

Lipid content:

4.5 %

Time point:

start of exposure

Lipid content:

4.8 %

Time point:

end of exposure

Type:

BCF

Value:

< 5

Basis:

other: Concentration of test substance in fish, no further data available.

Calculation basis:

steady state

Remarks on result:

other: Conc.in environment / dose:0.2

Type:

BCF

Value:

< 39

Basis:

other: Concentration of test substance in fish, no further data available.

Calculation basis:

steady state

Remarks on result:

other: Conc.in environment / dose:0.02

Validity criteria fulfilled:

not applicable

Remarks:

Since a detailed study documentation is missing, it cannot be guaranteed that all validity criteria are sufficiently fulfilled.

Conclusions:

A steady-state BCF of < 39 has been determined for the read-across substance Dibutylethanolamine. Based on the read-across justification, the source substance DBEA is predicted to have the highest aquatic toxicity according to the regular pattern found in the category of “Aliphatic amines”. Therefore, the result established in this study is considered to represent a worst-case for the target substance BDEA. Thus, the target substance BDEA is predicted to have even lower bioaccumulation potential than DBEA.

Executive summary:

The bioaccumulation in fish for the read-across substance Dibutylethanolamine (CAS 102-81-8) was experimentally determined according to OECD Guideline 305 C (NITE, 2011). The test organisms (Cyprinus carpio) were exposed to the test substance in nominal concentrations of 0.2 and 0.02 mg/L for 28 days, respectively. In this freshwater flow-through test, a renewal rate of 200-800 mL/min for the test solution was assured in the test vessels (glass tanks of 100 liters in volume). 15 - 20 test organisms were exposed to the test substance per vessel. The lipid content of the organisms was measured at the beginning (4.5 %) and the end of exposure (4.8 %).

For the test concentration of 0.2 mg/L, a steady-state BCF of < 5 was determined. The substance concentration of 0.02 mg/L resulted in a steady-state BCF of < 39.

Description of key information

RA (CAS 102-81-8)_NITE-2002_OECD 305C: BCF > 39

Key value for chemical safety assessment

BCF (aquatic species):

39 dimensionless

Additional information

There are no studies on bioaccumulation available for Butyldiethanolamine. Therefore, the data on its structural analogue Dibutylethanolamine (DBEA, CAS 102-81-8) is taken to evaluate this endpoint (please refer also to read-across statement attached in IUCLID Section 13).

 

The bioaccumulation in fish for the read-across substance Dibutylethanolamine (CAS 102-81-8) was experimentally determined according to OECD Guideline 305 C (NITE, 2011). The test organisms (Cyprinus carpio) were exposed to the test substance in nominal concentrations of 0.2 and 0.02 mg/L for 28 days, respectively. In this freshwater flow-through test, a renewal rate of 200-800 mL/min for the test solution was assured in the test vessels (glass tanks of 100 liters in volume). 15 - 20 test organisms were exposed to the test substance per vessel. The lipid content of the organisms was measured at the beginning (4.5 %) and the end of exposure (4.8 %). For the test concentration of 0.2 mg/L, a steady-state BCF of < 5 was determined. The substance concentration of 0.02 mg/L resulted in a steady-state BCF of < 39.

 

In addition, the aquatic bioaccumulation of Butyldiethanolamine was estimated based on software tool EPIWIN (BCFBAF, v.3.02) of US-EPA (Chemservice S.A., 2015, update 2022). The calculated BCF of 3.16 L/kg wet-wt confirms the lack of bioaccumulation potential.