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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Comparable to guideline study, GLP
Justification for type of information:
1. HYPOTHESIS FOR THE ANALOGUE APPROACH


The read-across is an analogue approach based on the hypothesis that the Source substance (Trimethylolpropane (TMP)) and Target substance (Trimethylolethane (TME)) will have similar toxicological and ecotoxicological properties due to their close structural and physicochemical similarities.

The Source substance (which is registered at Annex X) has a comprehensive data set covering the REACH Annex VIII registration band at which the Target substance is being registered. The availability of this data set, along with the Source substances similarity to the Target substance, are considered sufficient for the read-across to be an appropriate adaptation to the standard information requirements of Annex VIII of the REACH regulation for the Target substance in accordance with the provisions of Annex XI, 1.5 of the REACH regulation.


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

The Source substance is very pure (>99.6% w/w) while the technical grade of the Target substance as placed on the EU market contains two impurities; bis-TME (Cas No 63603-72-5) and Di-TME (Cas No 34541-79-2). The concentration of these impurities varies between batches and each impurity can be present at up to 4% w/w per batch.

The impurities in the Target substance are considered not to have any impact on toxicological or physico-chemical profile versus the main component. This is discussed further in the Read-Across Assessment Framework Report.


3. ANALOGUE APPROACH JUSTIFICATION

The Source and Target substances both contain the same 1,1,1-trimetholethyl group unit with the only structural difference being the presence of a methyl group (CH3-) for TMP instead of hydrogen (H-) for TME. Both the Source and Target substances have similar molecular weights of 134.17 and 120.15 respectively.

The physicochemical test results between the Source and Target substance are almost identical although water and logPow values are different as is the melting/freezing point. This divergence is not considered to have any significance to the read-across and is discussed further in the Read-Across Framework Report.

Because the structural and physicochemical profiles of the Source and Target substances are so similar, a read-across between the two substances is considered valid, as they are both expected to have similar toxicological and ecotoxicological profiles.

Further discussion of the similarities between the Source and Target substances is discussed in the Read-Across Assessment Framework Report.

4. DATA MATRIX

See Read-Across Assessment Framework Report
Parameter:
% degradation (DOC removal)
Value:
6
Sampling time:
28 d
Interpretation of results:
not readily biodegradable

Description of key information

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

Assessment is by read-across to the source substance trimethylolpropane (CAS No: 77-99-6).