Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Sulfolane is highly mobile in water and not expected to adsorb to sediments or soils. It is not expected to hydrolyse or be readily biodegradable. The weight of evidence assessment appended to Section 13 suggests that if the conditions remain favourable sulfolane will ultimately degrade. Data from non-standard studies suggest that sulfolane can be degraded within the PBT criteria of 40 days for surface waters and 120 days for soils. The overall conclusion for persistence under aerobic conditions is not P or vP.

Sulfolane will be persistent under anaerobic conditions. Sulfolane is not bioaccumulative.

Additional information

Sulfolane is predicted to partition predominantly to water. It does not have a high adsorption capacity to soil or sediment and will be highly mobile (Luther et al 1998; Saint Fort 2006). A Kd for sulfolane of 0.045 L/kg at 22°C for soils/aquifer materials is considered the key result for sulfolane. This was calculated as the average of 3 soils, where the Kds were log transformed before averaging (Luther et al. 1998). For the terrestrial environment sulfolane will be associated with soil and soil pore water but will not adsorb to the soil. Information is available to suggest that under certain conditions (e.g. continuous input to the environment from a sour gas plant) sulfolane will pass through the soil into anaerobic groundwater (Greene et al. 1998). The vapour pressure of sulfolane is 2.22 Pa at 40°C and less than 2.9 E-08 Pa and thus it is expected that the substance will not enter the atmosphere.

Sulfolane will not undergo hydrolysis due to the lack of hydrolysable functional groups. This is supported by an experimental study which showed that hydrolysis did not occur (Kurume 1999).

Sulfolane is not readily biodegradable based on guideline studies and QSAR predicted calculations (CITI 1992;Hill 2006).There is however evidence 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) and in experiments with populations of sulfolane adapted bacteria (Greene et al. 2000). Data from non-standard studies also suggest that sulfolane can be degraded within the PBT criteria of 40 days for surface waters (Greene et al. 1998; Greene et al. 1999) and 120 days for soils (Greene and Fedorak 2001; Saint Fort 2006) at environmentally relevant temperatures between 8-10°C. This data has been considered as part of a weight of evidence assessment which is appended to Section 13 of the CSR. To maximise biodegradation of sulfolane, aerobic, nutrient rich conditions are required. An existing population of sulfolane degrading bacteria (for example due to pre-exposure to the substance) will also accelerate biodegradation by reducing the lag time for degradation. Under aerobic conditions, sulfolane will degrade completely to carbon dioxide, water, biomass and sulphate. Some intermediates of sulfolane degradation under aerobic conditions have been identified but these are expected to undergo rapid mineralisation (Greene et al. 2000). Temperature, test concentration and nutrient content all contribute to the degradation rates for sulfolane and, under certain conditions, the lag time before degradation is such that the criteria for persistence will not be met (Greene et al. 1998; Greene et al. 1999). The evidence from the available information suggests that if the conditions remain favourable sulfolane will ultimately degrade and this conclusion is supported by previous regulatory reviews. The overall conclusion for persistence under aerobic conditions is not P or vP.

Sulfolane will be persistent under anaerobic conditions (Kim et al. 2000; Greene et al. 1998). There is some limited evidence for anaerobic degradation of sulfolane and one potential metabolite, thiolane, may be toxic to microbes, limiting degradation (Kim et al. 2000).

Sulfolane has a very low potential for bioaccumulation, based on the low reported Log Pow (<0 at 20°) and experimental data reporting the BCF to be <1.3 (Kurume 1977).