2,2'-butyliminodiethanol

Long-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

long-term toxicity to aquatic invertebrates

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 specifiedNo 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 in "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 aquatic toxicity fish, invertebrates and algae studies following order BDEA < BEA < DBEA (BEA is a Butylethanolamine, another supporting source butyl ethanolamine). In details, the target substance BDEA was not acutely harmful/toxic to fish Leucisdus idus with LC50 > 316.0 - < 464.0 mg/L (not neutralised) and < 464.0 mg/L (neutralised). For BEA, a LC50(96h) of greater than 100 mg/L was established in an acute toxicity study to fish (Golden orfe). DBEA is considered to be acutely harmful to fish at unadjusted pH, due to its LC50 < 100 mg/L (however, no classification is warranted). The nominal 96-h LC50 was determined to be 31.6 mg/L using Leuciscus idus as test species. However, since DBEA is the substance with the highest basicity, its toxicity was significantly reduced after pH-adjustment (96-h LC50 > 100 to < 500 mg/L). Furthermore, this result is supported by a guideline study according to OECD 203 with a nominal and analytically verified 96-h LC50 of 29.2 mg/L in Oryzias latipes. In the aquatic toxicity studies to invertebrates, 48-h EC50 values were higher than 100 mg/l for the target substance BDEA and the source substance BEA, and EC50 of 81.7 mg/L was established for DBEA. DBEA revealed the highest toxicity also regarding the endpoint “toxicity to aquatic algae”, when compared to BEA and BDEA. The results of these studies are in accordance with the regular pattern found in the read-across category of “Aliphatic amines”. DBEA revealing the highest toxicity of the three query substances, has the highest number of carbon atoms.

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). All three substances lack a significant bioaccumulation potential in organisms (not B not vB).

In conclusion, DBEA is predicted to have the highest aquatic toxicity according to the regular pattern found in the category of “Aliphatic amines”. This has also been observed in the given data on short-term toxicity. Therefore, using long-term toxicity data on DBEA as read-across source for BDEA can be regarded as a worst-case approach. This leads to the conclusion that BDEA is also considered to be not chronically toxic to aquatic invertebrates.

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

Reason / purpose for cross-reference:

read-across source

Key result

Duration:

21 d

Dose descriptor:

NOEC

Effect conc.:

4.4 mg/L

Nominal / measured:

not specified

Conc. based on:

not specified

Basis for effect:

reproduction

Key result

Duration:

21 d

Dose descriptor:

EC50

Effect conc.:

9 mg/L

Nominal / measured:

not specified

Conc. based on:

not specified

Basis for effect:

reproduction

Validity criteria fulfilled:

not specified

Conclusions:

NOEC (21 days) = 4.4 mg/L. 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 long-term toxicity to aquatic invertebrates than DBEA.

Executive summary:

The long-term toxicity towards Daphnia magna has been investigated according to OECD 211 for the read-across substance 2-dibutylaminoethanol (CAS 102-81-8). Test organisms were exposed to the test substance for 21 days resulting in a NOEC of 4.4 mg/L (based on reproduction) and an EC50 of 9 mg/L (based on reproduction).

Description of key information

RA (CAS 102-81-8)_OECD 211: EC50 (21 d) = 9 mg/L; NOEC (21 d) = 4.4 mg/L

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

NOEC

Effect concentration:

4.4 mg/L

Additional information

There are no studies regarding long-term toxicity to aquatic invertebrates 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 long-term toxicity towards Daphnia magna has been investigated according to OECD 211 for the read-across substance 2-dibutylaminoethanol (CAS 102-81-8; NITE, 2011). Test organisms were exposed to the test substance for 21 days resulting in a NOEC of 4.4 mg/L (based on reproduction) and an EC50 of 9 mg/L (based on reproduction).