3-methyltetrahydrothiophene 1,1-dioxide

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

According to Annex VII, 9.2.1.1 of the REACh Regulation (EC) No 1907/2006, Ready biodegradability is standard information required for the registration of substances manufactured or imported in quantities of one tonne per year or more. However, according to Annex XI, 1.5 of the REACH Regulation, Read-across and grouping approaches can be used to adapt the standard testing regime. This read-across study report follows notably the recommendations made by the European Chemicals Agency in its “Guidance on information requirements and chemical safety assessment Chapter R.6 – QSARs and grouping of chemicals” (ECHA, 2008) and in its document “Read-Across Assessment Framework (RAAF)” (ECHA, 2017).

A read-across approach appears appropriate to predict the endpoint “Ready biodegradability” for the substance 3-methyl sulfolane (3MSL) because:
- A ready biodegradability screening study, according to OECD test guideline 301 (1992), is available for the substance sulfolane (SL), which structure is very similar. Both Source and Target are mono-constituent substances built with a heterocyclic function “thiophene 1,1-dioxide” and the only difference is an additional methyl group at position 3 in the Target substance. As for now it should be underlined that the influence of this additional group on the biodegradability kinetic cannot be predicted, and therefore, this read-across assessment intends only to conclude about the absence of ready biodegradability.
- Analysis of literature and data available for these substances and others tends to confirm that variations in the structure do not significantly influence the biodegradability, that in lab test conditions no readily biodegradability is observed, but that lab or field preconditioning conditions may allow the biodegradation of the sulfolane chemical structure.
- To conclude on the CLP classification and the first-tier risk assessment, it is only needed a categorisation as “readily biodegradable”, or as “inherently biodegradable fulfilling certain criteria”; or as “inherent inherently biodegradable not fulfilling certain criteria”, or as “not readily biodegradable”; this read-across prediction thus complies with the REACh regulatory requirements.

The attached report follows the RAAF method and so presents:
1) The hypothesis: analogue read-across approach, based on the similarity of the structures and the aerobic degradation of these types of structures by microorganisms;
2) The scientific justifications (“Assessment Elements”) and their evaluation (“Assessment Options”); which demonstrate the confidence that can be put in this prediction.
3) The conclusions, usable for classification assessment or risk assessment, which are summarised hereafter.

The conclusion of the read-across assessment from the source Sulfolane (SL) to the target substance 3-methyl sulfolane (3MSL) is: Substance 3-methyl sulfolane (3MSL) is not readily biodegradable.

Reason / purpose for cross-reference:

read-across source

Oxygen conditions:

aerobic

Key result

Parameter:

% degradation (O2 consumption)

Value:

10.1

Sampling time:

14 d

Parameter:

% degradation (TOC removal)

Value:

0

Sampling time:

14 d

Details on results:

The percentage biodegradation of the test material was apparently 10.1 % in the indirect determination, but this is attributable to the low volume of basal respiration. The test material showed no biodegradability in the direct determination.

A reliability score of 1 for this study was provided in the 'SIDS Initial Assessment Report', which strongly suggests that the validation criteria were taken into account.

Results with reference substance:

Not specified

Validity criteria fulfilled:

not applicable

Remarks:

Read across entry. A reliability score of 1 for the source study was provided in the 'SIDS Initial Assessment Report', which strongly suggests that the validation criteria were taken into account

Interpretation of results:

not readily biodegradable

Conclusions:

Based on the read across approach using data on the structural analogue Sulfolane, which was biodegraded by 10.1 % , based on BOD after 14 days, it is concluded that 3-Methyl Sulfolane should be classified as not readily biodegradable.

Executive summary:

Biodegradability of 3-Methyl Sulfolane is read across from data on Sulfolane. The ready biodegradability of Sulfolane was determined in a MITI (I) test (OECD TG 301C) conducted by METI Japan in 1975. The study is in accordance with generally accepted principles, despite the limited details, and is deemed reliable. The percentage biodegradation of the test material was apparently 10.1 % in the indirect determination, but this is attributable to the low volume of basal respiration. The test material showed no biodegradability in the direct determination. Sulfolane should therefore be classified as not readily biodegradable.

Description of key information

Based on the read across approach using data on the structural analogue Sulfolane, which was biodegraded by 10.1 % , based on BOD after 14 days, it is concluded that 3-Methyl Sulfolane should  be classified as not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater