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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

The available data from standard studies suggest that sulfolane is not readily biodegradable under either aerobic or anaerobic conditions. Non-standard studies suggest that sulfolane will inherently biodegrade in the presence of a population of sulfolane degrading bacteria under aerobic conditions and these are discussed in more detail in a weight of evidence assessment for degradation of sulfolane appended to IUCLID Section 13 or Annex 3 of the CSR.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable, not fulfilling specific criteria

Additional information

The available data from standard studies suggest that sulfolane is not readily biodegradable under either aerobic or anaerobic conditions. An OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I) (CITI 1992) reported 10.1 % of the substance degraded within 2 weeks and QSAR predictions with Biowin V4.1 do not predict the substance to be readily biodegradable. Non-standard studies suggest that sulfolane will biodegrade in bioreactors in the presence of a population of sulfolane degrading bacteria under aerobic conditions (Chou and Swatloski 1983; Ying et al. 1994). The oxidation of sulfolane is given in the following equation C4H8O2S + 6.5O24CO2+ 3H2O + 2H++ SO42-(Chou and Swatloski 1983). Greene et al. (2000) demonstrated that a mixed population of bacteria has greater capacity for complete mineralisation of sulfolane than some isolated bacterial populations. They identified n-butanol and butyrate as temporary intermediates in sulfolane degradation. There is often a lag period as number of competent degraders capable of cleaving the heteroatomic rings of sulfolane increase but once degradation commences it usually degrades rapidly to CO2, biomass, soluble organic carbon, water and sulphate (Greene et al. 2000).

Sulfolane will not readily biodegrade under anaerobic conditions (Kim et al. 2000).

In summary, sulfolane is not readily biodegradable but is expected to be degraded rapidly by populations of adapted sulfolane degrading bacteria, and if optimal conditions are provided. A weight of evidence assessment for degradation of sulfolane is appended to Section 13.