Sodium ethylenesulphonate

Biodegradation in water: screening tests

Description of key information

According to the key study (OECD 301 B) the test item can be considered as inherently biodegradable.

The degradation of the test item at the end of the test was 67.4% of ThCO₂ (42 d with considering the IC in the liquid phase, mean of three replicates. After 28 days, the mean degradation was 31.8% of ThCO₂ with individual values varying widely (6.9% — 68.3%).

Therefore, the test item did not reach the criteria for ready biodegradability (60% of ThCO₂ within 28 days and within a 10-day window). However, the test item reached the criterion to be considered non-persistent (60% of ThCO₂ within 60 days).

The pH in the test vessels was 7.0 — 7.5 after 28 days and 7.1 at the end of the test.

The test guideline pass level for ready biodegradability (60 % CO₂ formation) was not reached within 28 days.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Type of water:

freshwater

Additional information

Key study

The degradation of the test item at the end of an OECD 301 B test was 67.4% of ThCO₂ (42 d with considering the IC in the liquid phase, mean of three replicates. After 28 days, the mean degradation was 31.8% of ThCO₂ with individual values varying widely (6.9% — 68.3%).

Therefore, the test item did not reach the criteria for ready biodegradability (60% of ThCO₂ within 28 days and within a 10-day window) and the test duration was extended to 42 days. The test item reached the criterion to be considered non-persistent (60% of ThCO₂ within 60 days). The pH in the test vessels was 7.0 — 7.5 after 28 days and 7.1 at the end of the test.

Supporting studies

The purpose of an OECD 301 E study was to determine the ready biodegradability of sodium vinylsulphonate, but the study report had some deficiencies in documentation. The test item was exposed to activated sludge from the aeration tank of a domestic waste water treatment plant for 28 days. The biodegradation was followed by dissolved organic carbon (DOC) during exposure. Under the test conditions the percentage biodegradation of the test item reached a mean of 56 % after 28 days based on DOC. Therefore, the test item can be considered as inherently biodegradable.

In another supporting study, performed prior to OECD guideline release, sodium vinylsulphonate was assessed for its biodegradability using non-adapted and adapted sludge. The biodegradation was followed by chemical oxygen demand (COD) in a Sapromat. In this study sodium vinylsulphonate was practically non-biodegradable without adaption of the sludge. However, with adapted sludge 90 % biodegradability was observed. Therefore, the test item was considered as inherently biodegradable in this study.

Assessment

In summary, it can be concluded that the substance sodium vinyl sulphonate is biologically degraded but shows a significant lag time before biodegradation begins, thereby exceeding the 28-day window, typically applied in biodegradation studies. The results of the key study however show clearly that with an extended observation period, a high level of biodegradation can be observed (67.4% of ThCO₂ within 42 d). Thus, the substance is considered inherently biodegradable and non-persistent.